{"product_id":"understanding-pembrolizumab-a-new-immunotherapy-for-high-risk-early-stage-triple-negative-breast-cancer","title":"Understanding Pembrolizumab: A New Immunotherapy for High-Risk Early-Stage Triple-Negative Breast Cancer","description":"\u003cp\u003eAdding the immunotherapy drug pembrolizumab to standard chemotherapy significantly improved outcomes for patients with high-risk, early-stage triple-negative breast cancer (TNBC), according to a major review of clinical trial evidence. In the pivotal KEYNOTE-522 trial of 1,174 patients, the combination raised the pathologic complete response (pCR) rate from 51.2% to 64.8%. The pCR rate means no detectable cancer left in the breast or lymph nodes at surgery. The combination also improved 3-year event-free survival from 76.8% to 84.5%. Event-free survival means time without cancer returning. Based on these results, the US Food and Drug Administration (FDA) approved pembrolizumab for this use on July 26, 2021, changing the standard of care. The review also details immune-related side effects that patients and clinicians must monitor, and explores which biomarkers might predict who benefits most.\u003c\/p\u003e\n\n\u003ch1\u003eTargeted Treatment for High-Risk Early-Stage Triple-Negative Breast Cancer- Spotlight on Pembrolizumab\u003c\/h1\u003e\n\n\u003ch2\u003eTable of Contents\u003c\/h2\u003e\n\u003cul\u003e\n\u003cli\u003e\u003ca href=\"#ddn-key-points\"\u003eKey Points\u003c\/a\u003e\u003c\/li\u003e\n\n  \u003cli\u003e\u003ca href=\"#background\"\u003eBackground: Why Triple-Negative Breast Cancer Is Different\u003c\/a\u003e\u003c\/li\u003e\n  \u003cli\u003e\u003ca href=\"#biology\"\u003eThe Biology of TNBC: Subtypes and Genetic Features\u003c\/a\u003e\u003c\/li\u003e\n  \u003cli\u003e\u003ca href=\"#challenge\"\u003eThe Treatment Challenge in Early-Stage TNBC\u003c\/a\u003e\u003c\/li\u003e\n  \u003cli\u003e\u003ca href=\"#history\"\u003eHow Immune Checkpoint Inhibitors Reached Early-Stage Treatment\u003c\/a\u003e\u003c\/li\u003e\n  \u003cli\u003e\u003ca href=\"#trials\"\u003eKey Neoadjuvant Immunotherapy Trials: The Numbers\u003c\/a\u003e\u003c\/li\u003e\n  \u003cli\u003e\u003ca href=\"#keynote522\"\u003eThe Landmark KEYNOTE-522 Trial: Design and Dosing\u003c\/a\u003e\u003c\/li\u003e\n  \u003cli\u003e\u003ca href=\"#results\"\u003eKEYNOTE-522 Results: What the Numbers Show\u003c\/a\u003e\u003c\/li\u003e\n  \u003cli\u003e\u003ca href=\"#sideeffects\"\u003eSide Effects and Immune-Related Toxicity\u003c\/a\u003e\u003c\/li\u003e\n  \u003cli\u003e\u003ca href=\"#biomarkers\"\u003eBiomarkers: Who Benefits Most From Immunotherapy?\u003c\/a\u003e\u003c\/li\u003e\n  \u003cli\u003e\u003ca href=\"#ongoing\"\u003eOngoing Clinical Trials and Future Directions\u003c\/a\u003e\u003c\/li\u003e\n  \u003cli\u003e\u003ca href=\"#implications\"\u003eClinical Implications: What This Means for Patients\u003c\/a\u003e\u003c\/li\u003e\n  \u003cli\u003e\u003ca href=\"#limitations\"\u003eLimitations and Open Questions\u003c\/a\u003e\u003c\/li\u003e\n  \u003cli\u003e\u003ca href=\"#recommendations\"\u003ePractical Recommendations for Patients\u003c\/a\u003e\u003c\/li\u003e\n  \u003cli\u003e\u003ca href=\"#ddn-faq\"\u003eFrequently Asked Questions\u003c\/a\u003e\u003c\/li\u003e\n\u003cli\u003e\u003ca href=\"#source\"\u003eSource Information\u003c\/a\u003e\u003c\/li\u003e\n\u003c\/ul\u003e\n\n\u003c!-- ddn:keypoints:start --\u003e\n\u003ch2 id=\"ddn-key-points\"\u003eKey Points\u003c\/h2\u003e\n\u003cul\u003e\n\u003cli\u003eIn the KEYNOTE-522 trial of 1,174 patients, adding pembrolizumab to chemotherapy raised the pathologic complete response rate from 51.2% to 64.8% in high-risk, early-stage triple-negative breast cancer.\u003c\/li\u003e\n\u003cli\u003eThe same trial showed 3-year event-free survival of 84.5% with pembrolizumab versus 76.8% with placebo, and distant recurrence occurred in 7.7% versus 13.1%.\u003c\/li\u003e\n\u003cli\u003eIn KEYNOTE-522, benefit was seen across PD-L1 subgroups, unlike metastatic disease where PD-L1 status determines eligibility.\u003c\/li\u003e\n\u003cli\u003eGrade 3 or higher immune-related side effects occurred in 14.9% of pembrolizumab-treated patients versus 2.1% with placebo, and 27.7% discontinued at least one therapy.\u003c\/li\u003e\n\u003cli\u003eOverall survival data remain immature, and better biomarkers to predict who benefits most from immunotherapy are still needed.\u003c\/li\u003e\n\u003c\/ul\u003e\n\u003c!-- ddn:keypoints:end --\u003e\n\n\n\u003ch2 id=\"background\"\u003eBackground: Why Triple-Negative Breast Cancer Is Different\u003c\/h2\u003e\n\n\u003cp\u003eTriple-negative breast cancer (TNBC) makes up roughly \u003cstrong\u003e15% to 20% of all breast cancers\u003c\/strong\u003e. Doctors define it by what the tumor lacks: it does not express the estrogen receptor (ER), does not express the progesterone receptor (PR), and does not overexpress the HER2 protein.\u003c\/p\u003e\n\n\u003cp\u003eThat absence matters. Because TNBC lacks these three targets, it does not respond to the hormone-blocking drugs or HER2-directed therapies that transformed outcomes for other breast cancer types. And TNBC behaves differently in who it affects — it \u003cstrong\u003edisproportionately strikes younger women and women of color\u003c\/strong\u003e compared to other breast cancer subtypes.\u003c\/p\u003e\n\n\u003cp\u003eThis disease is also biologically aggressive. TNBC has a higher tendency toward early recurrence, and it often spreads to internal organs (visceral involvement) rather than only to bone. Relapse rates have fallen with modern treatments, but the outlook remains unfavorable compared to other subtypes — largely because well-defined molecular targets have only recently begun to be identified.\u003c\/p\u003e\n\n\u003cp\u003eThe good news: substantial research is now underway to find biomarkers (measurable biological signals) that predict relapse. Research is also underway to develop more effective treatments before and after surgery to improve long-term outcomes.\u003c\/p\u003e\n\n\u003ch2 id=\"biology\"\u003eThe Biology of TNBC: Subtypes and Genetic Features\u003c\/h2\u003e\n\n\u003cp\u003eTNBC was historically treated as a single disease. Modern molecular analysis shows it is actually a \u003cstrong\u003ecomplex and biologically heterogeneous\u003c\/strong\u003e condition — meaning it varies widely from patient to patient at the genetic level.\u003c\/p\u003e\n\n\u003cp\u003eGene expression profiling has identified five distinct intrinsic molecular subtypes of breast cancer. More than \u003cstrong\u003e90% of basal-like tumors are TNBCs\u003c\/strong\u003e, and TNBCs are enriched for TP53 mutations. A research team led by Lehmann later described six unique molecular signatures of TNBC:\u003c\/p\u003e\n\n\u003cul\u003e\n  \u003cli\u003eBasal-like 1\u003c\/li\u003e\n  \u003cli\u003eBasal-like 2\u003c\/li\u003e\n  \u003cli\u003eMesenchymal\u003c\/li\u003e\n  \u003cli\u003eMesenchymal-stem-like\u003c\/li\u003e\n  \u003cli\u003eImmunomodulatory\u003c\/li\u003e\n  \u003cli\u003eLuminal androgen receptor\u003c\/li\u003e\n\u003c\/ul\u003e\n\n\u003cp\u003eEach of these signatures responds differently to chemotherapy — and more recently, to immunotherapy. Additional classification efforts have reported overlapping findings.\u003c\/p\u003e\n\n\u003cp\u003eSeveral other key genetic features appear in TNBC. Roughly \u003cstrong\u003e20% of unselected TNBC patients carry defects in BRCA1 or BRCA2\u003c\/strong\u003e (either inherited\/germline or acquired\/somatic mutations). These defects impair homologous recombination, a critical DNA repair mechanism, which can make tumors vulnerable to a class of drugs called PARP inhibitors.\u003c\/p\u003e\n\n\u003cp\u003eOther commonly disrupted signaling pathways in TNBC include RAS\/RAF\/MEK, PI3K\/AKT\/mTOR, and JAK\/STAT3. These alterations are not clearly established as cancer-driving events in TNBC, but early research suggests multi-kinase inhibition may be a promising strategy.\u003c\/p\u003e\n\n\u003cp\u003eMolecular subtyping has deepened our understanding of TNBC biology. However, these advances \u003cstrong\u003ehave not yet entered routine clinical care\u003c\/strong\u003e to guide treatment decisions for early-stage patients — a key gap the field is working to close.\u003c\/p\u003e\n\n\u003ch2 id=\"challenge\"\u003eThe Treatment Challenge in Early-Stage TNBC\u003c\/h2\u003e\n\n\u003cp\u003eFor patients with high-risk, early-stage TNBC, chemotherapy given before surgery (neoadjuvant) with anthracyclines and taxanes has remained the backbone of treatment for years — and has barely changed.\u003c\/p\u003e\n\n\u003cp\u003eTNBC presents a paradox. Patients with early-stage disease tend to achieve higher responses to neoadjuvant chemotherapy than other subtypes, yet they also face a higher risk of early recurrence. Several treatment questions remain unsettled:\u003c\/p\u003e\n\n\u003cul\u003e\n  \u003cli\u003eWhether adding platinum-based drugs (like carboplatin) improves long-term outcomes\u003c\/li\u003e\n  \u003cli\u003eWhat role adjuvant (post-surgery) treatments play beyond capecitabine\u003c\/li\u003e\n\u003c\/ul\u003e\n\n\u003cp\u003eThe critical problem is this: patients who still have residual (leftover) disease after standard neoadjuvant therapy face a \u003cstrong\u003e30% to 40% risk of recurrence\u003c\/strong\u003e and a poor prognosis. New therapeutic approaches are urgently needed.\u003c\/p\u003e\n\n\u003cp\u003eThe approval of pembrolizumab plus chemotherapy greatly expands the available treatment options and offers a real opportunity to improve cure rates for this population.\u003c\/p\u003e\n\n\u003ch2 id=\"history\"\u003eHow Immune Checkpoint Inhibitors Reached Early-Stage Treatment\u003c\/h2\u003e\n\n\u003cp\u003eProgress in the advanced (metastatic) setting paved the road to early-stage treatment. In advanced TNBC, several new strategies gained approval, including PARP inhibitors for tumors with germline BRCA1\/2 mutations, the antibody-drug conjugate (ADC) sacituzumab govitecan, and immune checkpoint inhibitor combinations.\u003c\/p\u003e\n\n\u003cp\u003eIn \u003cstrong\u003eMarch 2019\u003c\/strong\u003e, atezolizumab plus nab-paclitaxel became the first checkpoint inhibitor to receive accelerated FDA approval for PD-L1–positive advanced TNBC, based on the Phase III IMpassion130 trial. (PD-L1 status was measured with the VENTANA SP-142 companion diagnostic test.)\u003c\/p\u003e\n\n\u003cp\u003eThat approval was conditional on the results of a follow-up trial called IMpassion131. That trial tested atezolizumab plus paclitaxel against paclitaxel alone in a similar patient group and \u003cstrong\u003efailed to show improved progression-free survival\u003c\/strong\u003e (time before the cancer worsened) with atezolizumab. After review, the FDA no longer supported accelerated approval, and the manufacturer voluntarily withdrew the indication in the United States.\u003c\/p\u003e\n\n\u003cp\u003eMeanwhile, in \u003cstrong\u003eNovember 2020\u003c\/strong\u003e, the FDA approved pembrolizumab combined with taxane or platinum chemotherapy for PD-L1–positive advanced TNBC (defined as a combined positive score, or CPS, of 10 or higher on the DAKO 22C3 test), based on the Phase III KEYNOTE-355 study.\u003c\/p\u003e\n\n\u003ch2 id=\"trials\"\u003eKey Neoadjuvant Immunotherapy Trials: The Numbers\u003c\/h2\u003e\n\n\u003cp\u003eThese advances in the metastatic setting led researchers to test immune checkpoint inhibitors in early-stage disease. Results varied across trials — and the differences are instructive.\u003c\/p\u003e\n\n\u003cp\u003e\u003cstrong\u003eIMpassion031\u003c\/strong\u003e (Phase III) tested atezolizumab every 2 weeks plus anthracycline-cyclophosphamide and taxane-based chemotherapy. It improved the pathologic complete response (pCR) rate — the absence of detectable cancer cells in breast tissue and lymph nodes at surgery — to \u003cstrong\u003e58% (95% confidence interval [CI], 50 to 65) with atezolizumab versus 41% (95% CI, 34 to 49) with placebo\u003c\/strong\u003e in the intention-to-treat population (a difference of 17%, 95% CI, 6 to 27; one-sided p=0.0044, with a significance boundary of 0.0184).\u003c\/p\u003e\n\n\u003cp\u003e\u003cstrong\u003eNeoTRIPaPDL1\u003c\/strong\u003e (Phase II) took a different approach: neoadjuvant carboplatin plus nab-paclitaxel with or without atezolizumab, followed by surgery and adjuvant anthracycline-based treatment. It did \u003cstrong\u003enot\u003c\/strong\u003e improve pCR in the intention-to-treat analysis — 48.6% with atezolizumab versus 44.4% without (odds ratio 1.18; 95% CI, 0.74 to 1.89; p=0.48).\u003c\/p\u003e\n\n\u003cp\u003e\u003cstrong\u003eTONIC\u003c\/strong\u003e (Phase II) tested different immune-priming strategies in metastatic TNBC. Giving anthracycline chemotherapy before nivolumab produced the highest response rate to immunotherapy — an objective response rate of \u003cstrong\u003e35%\u003c\/strong\u003e — compared to other strategies. Collectively, these data suggest that anthracyclines may serve as key chemotherapy agents to prime the immune system.\u003c\/p\u003e\n\n\u003cp\u003eIn the Phase II \u003cstrong\u003eGeparNuevo\u003c\/strong\u003e trial, 117 patients received an initial 2-week \"window\" of single-agent durvalumab before neoadjuvant chemotherapy. Those who received this immune-priming window had a more pronounced improvement in pCR than those who received combination therapy alone: \u003cstrong\u003e61.0% with durvalumab versus 41.4% with placebo\u003c\/strong\u003e (odds ratio 2.22, 95% CI, 1.06 to 4.64, p=0.035).\u003c\/p\u003e\n\n\u003cp\u003eEarly pembrolizumab trials showed manageable toxicity and improved anti-tumor activity. In the randomized \u003cstrong\u003eI-SPY 2\u003c\/strong\u003e trial, pembrolizumab plus neoadjuvant chemotherapy roughly \u003cstrong\u003edoubled pCR rates\u003c\/strong\u003e (60.0% with pembrolizumab versus 22.0% with placebo) and shifted the distribution of residual cancer burden toward lower disease burden. The Phase Ib \u003cstrong\u003eKEYNOTE-173\u003c\/strong\u003e trial, which used a pembrolizumab \"run-in\" for cycle 1 followed by taxane with or without carboplatin, then doxorubicin and cyclophosphamide (AC), showed promising anti-tumor activity (60.0% pCR, range 49–71%) and a manageable safety profile.\u003c\/p\u003e\n\n\u003cp\u003eThese trials established the basis for the FDA's Breakthrough Therapy designation for pembrolizumab — and ultimately for the pivotal KEYNOTE-522 trial.\u003c\/p\u003e\n\n\u003ch2 id=\"keynote522\"\u003eThe Landmark KEYNOTE-522 Trial: Design and Dosing\u003c\/h2\u003e\n\n\u003cp\u003eKEYNOTE-522 was the \u003cstrong\u003efirst randomized, double-blind, placebo-controlled study\u003c\/strong\u003e of pembrolizumab in early-stage TNBC, testing it in both the neoadjuvant (before surgery) and adjuvant (after surgery) settings.\u003c\/p\u003e\n\n\u003cp\u003ePatients were eligible if they had newly diagnosed, high-risk, early-stage TNBC, defined as cT1c, N1-2 or cT2-4, N0-2 staging. Patients were excluded if they had active autoimmune disease requiring systemic treatment within the prior 2 years, a clinically significant other medical condition or immunodeficiency, or a need for immunosuppressive therapy.\u003c\/p\u003e\n\n\u003cp\u003e\u003cstrong\u003eHow the treatment worked:\u003c\/strong\u003e\u003c\/p\u003e\n\n\u003col\u003e\n  \u003cli\u003e\n\u003cstrong\u003eNeoadjuvant phase 1:\u003c\/strong\u003e Pembrolizumab (200 mg intravenously every 3 weeks) or placebo, combined with carboplatin (weekly or every 3 weeks) plus weekly paclitaxel for 4 cycles.\u003c\/li\u003e\n  \u003cli\u003e\n\u003cstrong\u003eNeoadjuvant phase 2:\u003c\/strong\u003e Anthracycline (doxorubicin or epirubicin) plus cyclophosphamide every 3 weeks for 4 cycles.\u003c\/li\u003e\n  \u003cli\u003e\n\u003cstrong\u003eSurgery:\u003c\/strong\u003e Definitive surgery.\u003c\/li\u003e\n  \u003cli\u003e\n\u003cstrong\u003eRadiation:\u003c\/strong\u003e Given if clinically indicated.\u003c\/li\u003e\n  \u003cli\u003e\n\u003cstrong\u003eAdjuvant phase:\u003c\/strong\u003e Pembrolizumab or placebo to complete a full year of treatment. If radiation was needed, adjuvant pembrolizumab or placebo began either alongside radiation or at least 2 weeks after it. Adjuvant capecitabine was not permitted.\u003c\/li\u003e\n\u003c\/ol\u003e\n\n\u003cp\u003eA total of \u003cstrong\u003e1,174 patients\u003c\/strong\u003e were randomized in a 2:1 fashion to the pembrolizumab or placebo arm. The primary endpoints were pCR (defined as ypT0\/Tis ypN0) and event-free survival (EFS) in the intention-to-treat population. Secondary endpoints included safety, overall survival (OS), and pCR in the PD-L1–positive population. PD-L1 expression was tested using the PD-L1 IHC 22C3 pharmDx assay, with a CPS of 1 or higher considered positive.\u003c\/p\u003e\n\n\u003ch2 id=\"results\"\u003eKEYNOTE-522 Results: What the Numbers Show\u003c\/h2\u003e\n\n\u003cp\u003eThe results were substantial and practice-changing. The first interim analysis, among the first 602 patients randomized, showed a pCR rate of \u003cstrong\u003e64.8% (95% CI, 59.9 to 69.5) with pembrolizumab-chemotherapy versus 51.2% (95% CI, 44.1 to 58.3) with placebo-chemotherapy\u003c\/strong\u003e — a difference of 13.6% (95% CI, 5.4 to 21.8; p=0.00055).\u003c\/p\u003e\n\n\u003cp\u003eImportantly, pembrolizumab-chemotherapy increased pCR rates across \u003cstrong\u003eall subgroups regardless of PD-L1 status\u003c\/strong\u003e. This differs from the metastatic setting, where PD-L1 status predicts pembrolizumab benefit.\u003c\/p\u003e\n\n\u003cul\u003e\n  \u003cli\u003e\n\u003cstrong\u003ePD-L1–positive patients:\u003c\/strong\u003e pCR 68.9% with pembrolizumab-chemotherapy versus 54.9% with placebo-chemotherapy.\u003c\/li\u003e\n  \u003cli\u003e\n\u003cstrong\u003ePD-L1–negative patients:\u003c\/strong\u003e pCR 45.3% with pembrolizumab-chemotherapy versus 30.3% with placebo-chemotherapy.\u003c\/li\u003e\n\u003c\/ul\u003e\n\n\u003cp\u003eThe 3-year event-free survival rate was \u003cstrong\u003e84.5% with pembrolizumab-chemotherapy versus 76.8% with placebo-chemotherapy\u003c\/strong\u003e — a 7.7% absolute improvement. In the pembrolizumab group, 15.7% of patients (123 of 784) experienced any disease-related event or death, compared to 23.8% (93 of 390) in the placebo group (hazard ratio 0.63, 95% CI, 0.48 to 0.82, p=0.00031).\u003c\/p\u003e\n\n\u003cp\u003eDistant recurrence (cancer spreading to distant organs) occurred in \u003cstrong\u003e7.7% (60 of 784)\u003c\/strong\u003e of the pembrolizumab group versus \u003cstrong\u003e13.1% (51 of 390)\u003c\/strong\u003e of the placebo group — roughly a halving of distant spread.\u003c\/p\u003e\n\n\u003cp\u003eOutcomes split sharply by whether patients achieved pCR:\u003c\/p\u003e\n\n\u003cul\u003e\n  \u003cli\u003ePatients who achieved pCR: 94.4% EFS with the pembrolizumab regimen versus 92.5% with placebo.\u003c\/li\u003e\n  \u003cli\u003ePatients with residual disease after neoadjuvant therapy: 67.4% EFS with pembrolizumab versus 56.8% with placebo.\u003c\/li\u003e\n\u003c\/ul\u003e\n\n\u003cp\u003eThis suggests that \u003cstrong\u003eadjuvant pembrolizumab is potentially most critical in the non-pCR setting\u003c\/strong\u003e — that is, for patients who still have disease left at surgery.\u003c\/p\u003e\n\n\u003cp\u003eBy PD-L1 status, EFS events occurred as follows:\u003c\/p\u003e\n\n\u003cul\u003e\n  \u003cli\u003e\n\u003cstrong\u003ePD-L1–positive:\u003c\/strong\u003e 14.9% with pembrolizumab versus 21.5% with placebo (hazard ratio 0.67, 95% CI, 0.49 to 0.92).\u003c\/li\u003e\n  \u003cli\u003e\n\u003cstrong\u003ePD-L1–negative:\u003c\/strong\u003e 19.5% with pembrolizumab versus 36.2% with placebo (hazard ratio 0.48, 95% CI, 0.28 to 0.85).\u003c\/li\u003e\n\u003c\/ul\u003e\n\n\u003cp\u003eThere was a trend toward improved overall survival with pembrolizumab (89.7% versus 86.9%), although these data remain immature (meaning not yet enough events have occurred for a definitive conclusion). Distant progression- or recurrence-free survival was 87.0% with pembrolizumab versus 80.7% with placebo.\u003c\/p\u003e\n\n\u003cp\u003eBased on these findings, on \u003cstrong\u003eJuly 26, 2021, the FDA approved pembrolizumab\u003c\/strong\u003e for the treatment of patients with high-risk, early-stage TNBC.\u003c\/p\u003e\n\n\u003ch2 id=\"sideeffects\"\u003eSide Effects and Immune-Related Toxicity\u003c\/h2\u003e\n\n\u003cp\u003eThe improved efficacy came with added toxicity, and understanding this is essential. Treatment-related adverse events (TRAEs) of grade 3 or higher across all treatment phases occurred in \u003cstrong\u003e77.1% of the pembrolizumab-chemotherapy group versus 73.3% of the placebo-chemotherapy group\u003c\/strong\u003e. Deaths occurred in 0.5% (4 patients) treated with pembrolizumab and 0.3% (1 patient) treated with placebo. The deaths in the pembrolizumab group were attributed to sepsis (a severe whole-body infection) and pneumonitis (lung inflammation). The deaths were also attributed to pulmonary embolism (a blood clot in the lungs) and autoimmune encephalitis (immune attack on the brain).\u003c\/p\u003e\n\n\u003cp\u003eMost TRAEs and events of interest occurred during the neoadjuvant phase, were low grade, and were largely attributed to chemotherapy. Adverse events of interest occurred in \u003cstrong\u003e38.9% of pembrolizumab-treated patients and 18.3% of placebo-treated patients\u003c\/strong\u003e.\u003c\/p\u003e\n\n\u003cp\u003eAdverse events of interest that were grade 3 or higher occurred in 12.9% of pembrolizumab-treated patients versus 1.8% of placebo-treated patients. The most common severe events in the pembrolizumab group were:\u003c\/p\u003e\n\n\u003cul\u003e\n  \u003cli\u003eSevere skin reactions: 3.8%\u003c\/li\u003e\n  \u003cli\u003eInfusion reactions: 2.6%\u003c\/li\u003e\n  \u003cli\u003eAdrenal insufficiency (when the adrenal glands do not make enough hormones): 1.3%\u003c\/li\u003e\n\u003c\/ul\u003e\n\n\u003cp\u003eTRAEs that led to discontinuing any therapy occurred in \u003cstrong\u003e27.7%\u003c\/strong\u003e of the pembrolizumab group versus \u003cstrong\u003e14.1%\u003c\/strong\u003e of the placebo group. Immune-related adverse events (irAEs — side effects caused by the immune system attacking healthy tissue) of grade 3–5 occurred in 14.9% of pembrolizumab-treated patients versus 2.1% of placebo-treated patients. These immune-related adverse events led to treatment discontinuation in 10.9% versus 2.6%, respectively. In the adjuvant setting alone, grade 3–5 irAEs occurred in 2.9% versus 0.3% of patients.\u003c\/p\u003e\n\n\u003cp\u003eThe bottom line for patients: adding carboplatin in the neoadjuvant phase and pembrolizumab in both phases means improved efficacy must be weighed against added toxicity. \u003cstrong\u003eComprehensive patient education about irAEs is an essential part of clinical care\u003c\/strong\u003e, and rare, potentially long-lasting immune side effects will need close monitoring going forward.\u003c\/p\u003e\n\n\u003ch2 id=\"biomarkers\"\u003eBiomarkers: Who Benefits Most From Immunotherapy?\u003c\/h2\u003e\n\n\u003cp\u003eTNBC is considered to have the \u003cstrong\u003ehighest immunogenic potential of all breast cancers\u003c\/strong\u003e. It is enriched for BRCA germline mutations and higher somatic mutational load (more genetic errors in the tumor). It is also enriched for more tumor-associated neoantigens (abnormal proteins that the immune system can recognize) — though it is rarely associated with microsatellite instability.\u003c\/p\u003e\n\n\u003cp\u003eEarly- and advanced-stage breast cancers differ in their tumor and immune cell microenvironments, which may affect how well immunotherapy works. The predictive value of standard immune biomarkers also differs by disease stage.\u003c\/p\u003e\n\n\u003cp\u003eIn preclinical (laboratory) studies, high levels of tumor-specific CD8+ T cells (a type of cancer-killing immune cell) soon after neoadjuvant immunotherapy exposure predicted long-term survival. Adjuvant immunotherapy produced lower tumor-specific CD8+ T cells compared to neoadjuvant treatment in mice with intact tumors.\u003c\/p\u003e\n\n\u003cp\u003ePD-L1 mRNA expression is higher in TNBC and is associated with improved clinical outcomes. In metastatic TNBC, PD-L1 status is an established predictive biomarker of immune checkpoint inhibitor response. But in early-stage TNBC, the benefit of immunotherapy appears to exist \u003cstrong\u003eindependently of PD-L1 expression\u003c\/strong\u003e — even though patients with PD-L1–positive tumors achieved numerically higher pCR rates in KEYNOTE-522. About \u003cstrong\u003e80% of patients in each treatment arm\u003c\/strong\u003e of KEYNOTE-522 had PD-L1–positive disease.\u003c\/p\u003e\n\n\u003cp\u003eWhere PD-L1 is expressed — in tumor cells versus immune cells — appears to matter. In GeparNuevo, there was a trend for pCR rates in PD-L1 positive tumors. This trend was significant for PD-L1 expression in tumor cells in the durvalumab arm (p=0.045) and for PD-L1 expression in immune cells in the placebo arm (p=0.040). Tumor mutational burden combined with immune gene expression profile also predicted pCR in that study.\u003c\/p\u003e\n\n\u003cp\u003eTumor infiltrating lymphocytes (TILs — immune cells that have moved into the tumor) are a promising biomarker for response to neoadjuvant chemotherapy in early-stage TNBC. The presence of stromal TILs (sTILs — immune cells in the tissue surrounding the tumor) is prognostic and linked to higher pCR rates.\u003c\/p\u003e\n\n\u003cul\u003e\n  \u003cli\u003eA pooled analysis of 3,771 patients treated with neoadjuvant therapy found that a \u003cstrong\u003e10% increase in sTILs was associated with longer disease-free survival\u003c\/strong\u003e in TNBC patients.\u003c\/li\u003e\n  \u003cli\u003eThe Phase III BIG 02–98 trial showed that both sTILs and intratumoral TILs (iTILs — immune cells inside the tumor) were highest in highly proliferative tumors. Both sTILs and iTILs were associated with ER and HER2 negativity.\u003c\/li\u003e\n  \u003cli\u003eIncreasing lymphocytic infiltration at diagnosis was significantly associated with favorable prognosis in the ER-negative\/HER2-negative subgroup, regardless of chemotherapy backbone. This was particularly true in the lymphocyte-predominant breast cancer (LPBC) subgroup, defined by roughly 50–60% TILs in the tumor specimen.\u003c\/li\u003e\n  \u003cli\u003eHigher TIL levels in residual disease after treatment were also associated with improved recurrence-free and overall survival.\u003c\/li\u003e\n\u003c\/ul\u003e\n\n\u003cp\u003eInterestingly, the location of TILs may matter. In GeparNuevo, although sTILs were associated with pCR, iTILs on pretreatment biopsy did not seem to predict pCR. This highlights the need for further study of spatial immunophenotyping — mapping where immune cells sit within and around the tumor. Both the pretreatment composition and the changes during therapy may shape which strategies are needed to boost an anti-tumor immune response.\u003c\/p\u003e\n\n\u003cp\u003eDespite this progress, better biomarkers for immunotherapy response in early-stage TNBC remain a major unmet need. Standardizing how biomarker tests are run and interpreted will be required before any new biomarker enters clinical practice.\u003c\/p\u003e\n\n\u003ch2 id=\"ongoing\"\u003eOngoing Clinical Trials and Future Directions\u003c\/h2\u003e\n\n\u003cp\u003eMultiple ongoing trials are testing pembrolizumab and other immune-modulating strategies in early-stage TNBC:\u003c\/p\u003e\n\n\u003cul\u003e\n  \u003cli\u003e\n\u003cstrong\u003eNeoPACT\u003c\/strong\u003e (Phase II, 121 patients, NCT03639948): Neoadjuvant pembrolizumab with carboplatin and docetaxel; primary outcome is pCR, secondary outcome is recurrence-free survival.\u003c\/li\u003e\n  \u003cli\u003e\n\u003cstrong\u003eNCT04427293\u003c\/strong\u003e (window-of-opportunity, 12 patients): Neoadjuvant lenvatinib plus pembrolizumab for 1 cycle; primary endpoint is evaluating TILs.\u003c\/li\u003e\n  \u003cli\u003e\n\u003cstrong\u003eNCT03199040\u003c\/strong\u003e (Phase I, 18 patients): Adjuvant neoantigen DNA vaccine with or without durvalumab in patients with residual TNBC; primary endpoint is safety.\u003c\/li\u003e\n  \u003cli\u003e\n\u003cstrong\u003eNCT04331067\u003c\/strong\u003e (Phase Ib\/II, 50 patients): Neoadjuvant cabiralizumab plus nivolumab with carboplatin plus paclitaxel versus nivolumab plus carboplatin plus paclitaxel; primary endpoints are percentage change in TILs, tumor-associated macrophages (TAMs), and safety.\u003c\/li\u003e\n  \u003cli\u003e\n\u003cstrong\u003eBreastVax\u003c\/strong\u003e (Phase Ib\/II, 36 patients, NCT04454528): Comparing neoadjuvant radiation followed by pembrolizumab, pembrolizumab followed by radiation, pembrolizumab alone, and upfront surgery; primary endpoint is feasibility.\u003c\/li\u003e\n  \u003cli\u003e\n\u003cstrong\u003eNCT02957968\u003c\/strong\u003e (Phase II, 32 patients): Neoadjuvant pembrolizumab plus decitabine followed by AC followed by paclitaxel; primary endpoint is increase in TILs after pembrolizumab plus decitabine.\u003c\/li\u003e\n  \u003cli\u003e\n\u003cstrong\u003eNCT04373031\u003c\/strong\u003e (Phase II, 30 patients): Neoadjuvant pembrolizumab-based treatment.\u003c\/li\u003e\n\u003c\/ul\u003e\n\n\u003ch2 id=\"implications\"\u003eClinical Implications: What This Means for Patients\u003c\/h2\u003e\n\n\u003cp\u003eThe FDA approval of pembrolizumab for high-risk, early-stage TNBC \u003cstrong\u003eimmediately changed the longstanding treatment paradigm\u003c\/strong\u003e for this disease. For the first time, patients with this aggressive subtype have an immunotherapy option that improves the chance of eradicating detectable cancer before surgery. This immunotherapy option also reduces the risk of the cancer returning.\u003c\/p\u003e\n\n\u003cp\u003eThe most striking finding for patients is the benefit in the non-pCR setting. Patients who still have residual disease after neoadjuvant therapy had a 67.4% EFS rate with pembrolizumab versus 56.8% with placebo — a difference of more than 10 percentage points. This is precisely the group that historically faced a 30–40% recurrence risk, so the gain is clinically meaningful.\u003c\/p\u003e\n\n\u003cp\u003eAnother key point: the benefit appeared across PD-L1 subgroups. Unlike in metastatic disease, where PD-L1 status determines eligibility, early-stage patients appear to benefit regardless of PD-L1 status. This simplifies decision-making, because patients do not need to wait for a PD-L1 result to consider the regimen.\u003c\/p\u003e\n\n\u003ch2 id=\"limitations\"\u003eLimitations and Open Questions\u003c\/h2\u003e\n\n\u003cp\u003eSeveral questions remain unresolved.\u003c\/p\u003e\n\n\u003cp\u003eOverall survival data are still immature — the trend favored pembrolizumab (89.7% versus 86.9%), but longer follow-up is needed before firm conclusions can be drawn. The authors note that deeper insight is needed into which patients truly require the added immunotherapy, given the additional toxicity.\u003c\/p\u003e\n\n\u003cp\u003eBiomarker development remains an area of significant need. PD-L1 alone does not cleanly separate who benefits from who does not in early-stage disease. TIL measurement, spatial immunophenotyping, and tumor mutational burden are all promising but not yet standardized or ready for routine clinical use.\u003c\/p\u003e\n\n\u003cp\u003eOptimal chemotherapy partnering is also uncertain. The NeoTRIPaPDL1 trial did not show benefit from adding atezolizumab to a platinum-taxane backbone, while IMpassion031 and KEYNOTE-522 did show benefit with anthracycline-containing regimens. This suggests that the chemotherapy backbone — and possibly the sequence of immune priming — matters. Whether the addition of platinum salts translates into improved long-term outcomes has not been fully established.\u003c\/p\u003e\n\n\u003cp\u003eFinally, questions remain about the role of adjuvant approaches beyond capecitabine, and how to best manage rare, potentially long-lasting immune-related side effects over the long term.\u003c\/p\u003e\n\n\u003ch2 id=\"recommendations\"\u003ePractical Recommendations for Patients\u003c\/h2\u003e\n\n\u003col\u003e\n  \u003cli\u003e\n\u003cstrong\u003eAsk whether you are eligible.\u003c\/strong\u003e The pembrolizumab regimen is approved for high-risk, early-stage TNBC (stages cT1c, N1-2 or cT2-4, N0-2). Discuss your specific staging and risk category with your oncology team.\u003c\/li\u003e\n  \u003cli\u003e\n\u003cstrong\u003eUnderstand the schedule.\u003c\/strong\u003e The regimen involves pembrolizumab every 3 weeks plus carboplatin and paclitaxel for 4 cycles, then anthracycline plus cyclophosphamide for 4 cycles. The regimen then involves surgery, possible radiation, and then pembrolizumab or placebo to complete a full year of treatment.\u003c\/li\u003e\n  \u003cli\u003e\n\u003cstrong\u003eReport immune symptoms immediately.\u003c\/strong\u003e Because immune-related side effects can involve the skin, lungs, adrenal glands, and other organs, tell your care team right away about new rashes, breathing changes, severe fatigue, or unusual symptoms. Severe skin reactions (3.8%), infusion reactions (2.6%), and adrenal insufficiency (1.3%) were the most common severe immune events.\u003c\/li\u003e\n  \u003cli\u003e\n\u003cstrong\u003eExpect extra monitoring.\u003c\/strong\u003e Roughly 1 in 4 patients (27.7%) discontinued at least one therapy due to side effects, compared to 14.1% on placebo. Discontinuation is a real possibility — but it is manageable with close monitoring.\u003c\/li\u003e\n  \u003cli\u003e\n\u003cstrong\u003eKnow that non-pCR does not mean failure.\u003c\/strong\u003e Even patients with residual disease at surgery had meaningfully better outcomes with pembrolizumab, so the adjuvant portion of treatment matters.\u003c\/li\u003e\n  \u003cli\u003e\n\u003cstrong\u003eAsk about clinical trials.\u003c\/strong\u003e Several ongoing studies are testing new combinations and identify which patients benefit most.\u003c\/li\u003e\n\u003c\/ol\u003e\n\n\u003c!-- ddn:faq:start --\u003e\n\u003ch2 id=\"ddn-faq\"\u003eFrequently Asked Questions\u003c\/h2\u003e\n\u003ch3\u003eWhat does a pathologic complete response (pCR) mean after treatment?\u003c\/h3\u003e\n\u003cp\u003eA pathologic complete response means no detectable cancer cells remain in the breast or lymph nodes when tissue is examined at surgery. In the KEYNOTE-522 trial of 1,174 patients, adding pembrolizumab to chemotherapy raised the pCR rate from 51.2% to 64.8% compared with chemotherapy alone.\u003c\/p\u003e\n\u003ch3\u003eWhat side effects should I watch for during pembrolizumab treatment?\u003c\/h3\u003e\n\u003cp\u003eImmune-related side effects can affect the skin, lungs, adrenal glands, and other organs. In the KEYNOTE-522 trial, severe skin reactions occurred in 3.8% of pembrolizumab-treated patients, infusion reactions in 2.6%, and adrenal insufficiency in 1.3%. Report new rashes, breathing changes, severe fatigue, or unusual symptoms to your care team right away.\u003c\/p\u003e\n\u003ch3\u003eDoes it matter if my tumor is PD-L1 positive or negative for this treatment?\u003c\/h3\u003e\n\u003cp\u003eIn early-stage triple-negative breast cancer, the benefit of adding pembrolizumab appeared across all subgroups regardless of PD-L1 status. This differs from metastatic disease, where PD-L1 status determines eligibility. So you do not need to wait for a PD-L1 result to consider this regimen with your doctor.\u003c\/p\u003e\n\u003ch3\u003eWhat if I still have cancer left at surgery after neoadjuvant treatment?\u003c\/h3\u003e\n\u003cp\u003eHaving residual disease does not mean treatment failed. In the KEYNOTE-522 trial, patients with residual disease after neoadjuvant therapy had a 3-year event-free survival rate of 67.4% with pembrolizumab versus 56.8% with placebo. The adjuvant portion of treatment matters and may improve outcomes.\u003c\/p\u003e\n\u003ch3\u003eHow is the pembrolizumab regimen scheduled?\u003c\/h3\u003e\n\u003cp\u003eThe regimen starts with pembrolizumab every 3 weeks plus carboplatin and paclitaxel for 4 cycles, then anthracycline plus cyclophosphamide for 4 cycles. The regimen then involves surgery, possible radiation, and finally pembrolizumab or placebo to complete a full year of treatment. Your oncology team will guide you through each phase.\u003c\/p\u003e\n\u003ch3\u003eWhen should a patient with high-risk early-stage triple-negative breast cancer seek a second opinion before starting pembrolizumab plus chemotherapy?\u003c\/h3\u003e\n\u003cp\u003eA second opinion is reasonable before committing to this regimen, especially to confirm high-risk staging (cT1c, N1-2 or cT2-4, N0-2) and to weigh the added toxicity against benefit. Treatment-related adverse events of grade 3 or higher occurred in 77.1% with pembrolizumab-chemotherapy versus 73.3% with placebo-chemotherapy, and 27.7% discontinued at least one therapy. Because benefit appeared across PD-L1 subgroups, an independent review can help clarify whether the regimen and chemotherapy backbone fit your situation. Diagnostic Detectives Network provides independent expert second opinions.\u003c\/p\u003e\n\u003c!-- ddn:faq:end --\u003e\n\n\u003ch2 id=\"source\"\u003eSource Information\u003c\/h2\u003e\n\n\u003cp\u003e\u003cstrong\u003eOriginal article title:\u003c\/strong\u003e Targeted Treatment for High-Risk Early-Stage Triple-Negative Breast Cancer- Spotlight on Pembrolizumab\u003c\/p\u003e\n\n\u003cp\u003e\u003cstrong\u003eAuthors:\u003c\/strong\u003e Nusayba A. Bagegni, Andrew A. Davis, Katherine K. Clifton, Foluso O. Ademuyiwa\u003c\/p\u003e\n\n\u003cp\u003e\u003cstrong\u003eAuthor affiliation:\u003c\/strong\u003e Division of Oncology, Department of Medicine, Washington University in St. Louis School of Medicine, St. Louis, MO, 63110, USA\u003c\/p\u003e\n\n\u003cp\u003e\u003cstrong\u003ePublication:\u003c\/strong\u003e Breast Cancer: Targets and Therapy, 2022;14:113–123. Published April 29, 2022. DOI: 10.2147\/BCTT.S293597. Received December 26, 2021; accepted April 15, 2022.\u003c\/p\u003e\n\n\u003cp\u003e\u003cstrong\u003eArticle type:\u003c\/strong\u003e Peer-reviewed review article, open access (Dove Medical Press).\u003c\/p\u003e\n\n\u003cp\u003e\u003cem\u003eThis patient-friendly article is based on peer-reviewed research. It summarizes findings from clinical trials and does not replace personalized medical advice from your oncology team. Treatment decisions should always be made in consultation with your healthcare providers.\u003c\/em\u003e\u003c\/p\u003e","brand":"DiagnosticDetectives.Com","offers":[{"title":"Default Title","offer_id":47457934966940,"sku":null,"price":0.0,"currency_code":"USD","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0599\/5449\/5644\/files\/ddn-medical-article-understanding-pembrolizumab-a-new-immunotherapy-for-high-risk-early-stage-triple-negative-breast-cancer-hero.png?v=1790202440","url":"https:\/\/diagnosticdetectives.com\/da\/products\/understanding-pembrolizumab-a-new-immunotherapy-for-high-risk-early-stage-triple-negative-breast-cancer","provider":"DiagnosticDetectives.Com","version":"1.0","type":"link"}