# Breast Cancer During Pregnancy: A Patient's Guide to Treatment Options, Safety, and What Research Shows

Breast cancer during pregnancy (referred to medically as **PrBC**) is the most common type of cancer diagnosed during or shortly after pregnancy, yet it presents unique and complex challenges because treatment must protect both the mother and the developing fetus. Research shows that chemotherapy can be safely given after the first trimester without dose reductions, but several important medications—including hormone therapy, HER2-targeted drugs, immunotherapy, and CDK4/6 inhibitors—must be avoided during pregnancy because of risks to the fetus. This expert commentary from oncologists at the Karolinska Institutet in Stockholm highlights that the management of pregnancy-related breast cancer requires a carefully coordinated, multidisciplinary approach involving oncologists, maternal-fetal medicine specialists, and surgeons to maximize the chance of curing the mother while achieving a full-term, healthy delivery.

# Breast Cancer During Pregnancy: A Patient's Guide to Treatment Options, Safety, and What Research Shows

## Table of Contents

- Key Points
- What Is Breast Cancer During Pregnancy (PrBC)?
- Why Diagnosis Is Often Delayed: The Challenge of Recognizing Symptoms
- The Clinical Trial Gap: Why Pregnant Patients Are Left Out
- Local Treatment: Surgery and Radiation Therapy Options
- How Targeted Therapies May Affect the Fetus
- Chemotherapy During Pregnancy: What Is Safe and When
- Gene Expression Testing: A Complex Tool in PrBC
- Managing HER2-Positive and Triple-Negative Disease After Chemotherapy
- Metastatic Breast Cancer During Pregnancy: The Most Difficult Scenario
- Key Recommendations at a Glance
- What This Means for Patients: Key Takeaways
- What This Study Could Not Prove: Limitations
- Frequently Asked Questions
- Source Information

## Key Points

- Breast cancer during pregnancy is treated with curative intent; avoid harmful treatment delays and dose reductions.
- Chemotherapy after the first trimester is safe, including anthracyclines, cyclophosphamide, taxanes, and carboplatin.
- Endocrine therapy, HER2-targeted agents, immunotherapy, and CDK4/6 inhibitors must be avoided during pregnancy.
- Multidisciplinary care involving oncology and maternal-fetal medicine specialists is essential for optimal management.
- Pregnant patients are often excluded from clinical trials, so expert consensus guidelines guide treatment decisions.

## What Is Breast Cancer During Pregnancy (PrBC)?

Breast cancer is the most common malignancy diagnosed during pregnancy or in the period directly after childbirth. However, despite being the most frequent cancer type in pregnant women, it is still a relatively uncommon event overall. The incidence of breast cancer during pregnancy is rising, largely because more women are choosing to have children later in life—and the risk of breast cancer increases with advancing maternal age.

Medical researchers have identified two distinct patient groups that behave differently:

-
**Breast cancer diagnosed during pregnancy (PrBC)**: The cancer is found while the woman is pregnant.
-
**Postpartum breast cancer**: The cancer is found after delivery and, for reasons that are not completely understood, is associated with worse outcomes compared with breast cancer in non-pregnant women.

This worse prognosis for postpartum breast cancer extends for a prolonged period following delivery. The reasons remain unclear, but this distinction matters for treatment planning and research.

According to a meta-analysis of 30 studies by Azim and colleagues (2012), pregnancy-associated breast cancer has distinct prognostic features. A separate meta-analysis by Shao and colleagues (2020) also confirmed worse outcomes for the postpartum group. These findings highlight that pregnancy-related breast cancer should not be treated as a single category, but rather as two separate disease entities with different clinical behaviors.

## Why Diagnosis Is Often Delayed: The Challenge of Recognizing Symptoms

One of the most significant problems in pregnancy-related breast cancer is **delayed diagnosis**. There are several reasons for this delay, and understanding them can help patients advocate for themselves.

First, the natural physiologic changes of the breast during pregnancy can mask symptoms. As breast tissue becomes denser, enlarged, and more nodular due to hormonal changes, a suspicious lump may be harder to feel or may be dismissed as a normal pregnancy-related change. This makes physical examination considerably more challenging for both patients and doctors.

Second, safety concerns about radiation exposure to the fetus—while well-motivated—can lead to suboptimal diagnostic strategies. Some physicians may hesitate to order necessary imaging tests, worried about harming the developing baby. This caution can result in diagnostic delays, which in turn lead to more advanced stage at diagnosis and a worse prognosis compared with non-pregnant patients. The authors call for a **high index of suspicion** when evaluating any pregnant patient who presents with a breast mass.

Interestingly, the increased use of **non-invasive prenatal testing (NIPT)** has created a new diagnostic pathway. In some cases, these routine prenatal blood tests have incidentally revealed signs of maternal malignancies, including breast cancer, prompting earlier detection than might otherwise have occurred. A nationwide genetic and clinical follow-up study by Heesterbeek and colleagues (2022) documented this phenomenon.

The authors strongly recommend that well-established routines be developed for the diagnostic approach to breast masses in pregnant women. A more streamlined and timely evaluation should include **early multidisciplinary collaboration with maternal/fetal specialists**, so that specialists in both oncology and high-risk obstetrics work together from the very beginning.

## The Clinical Trial Gap: Why Pregnant Patients Are Left Out

One of the most troubling findings discussed in this commentary is the systematic exclusion of pregnant and lactating patients from clinical research. The authors cite a recent systematic review of breast cancer trials that revealed striking statistics:

- Only **0.2%** of breast cancer trials specifically enrolled pregnant and lactating patients
- More than **80%** of clinical trials evaluating drugs listed pregnancy as an exclusion criterion
- Almost **one-fourth (25%)** of behavioral studies also excluded patients with PrBC

This exclusion creates what the authors call an "unfortunate knowledge gap." Because pregnant patients are systematically left out of research, there is a lack of evidence on critical issues such as:

- The optimal timing of chemotherapy during pregnancy
- How pregnancy affects drug metabolism (pharmacokinetics)
- Whether modern radiation techniques are harmful to the fetus
- The safety of certain cytotoxic drugs and novel targeted agents

As a result, the management of breast cancer during pregnancy is not guided by robust, evidence-based clinical trials. Instead, doctors rely on **expert consensus statements**, such as the one recently published by the European Society for Medical Oncology (ESMO) in 2023 (Loibl and colleagues). While these expert guidelines are valuable, the authors emphasize they are a substitute for—not a replacement of—high-quality clinical trial data.

## Local Treatment: Surgery and Radiation Therapy Options

When it comes to treating the tumor itself, the authors emphasize that optimal treatment of PrBC should be **multimodal**—meaning it combines multiple treatment approaches—and should follow the same well-established principles used for non-pregnant patients with breast cancer. However, the welfare of the fetus must always be considered when making decisions about surgery.

**Mastectomy (complete removal of the breast)** may be chosen in cases where the patient will likely not need—or is not suitable for—adjuvant chemotherapy. The reasoning is that by removing the entire breast, the need for adjuvant radiation therapy can be avoided entirely, eliminating the radiation exposure concern during pregnancy.

**Breast-conserving surgery (lumpectomy)**, on the other hand, could be an appropriate option in cases where radiation therapy can be safely delayed until after the baby is born. This allows the patient to keep more of her breast tissue while still receiving comprehensive treatment.

**Radiation therapy** during pregnancy is generally avoided, although the authors note it is not strictly contraindicated. In highly selected cases where postponing radiotherapy until after delivery would be detrimental to the patient's prognosis, radiation can be delivered during the first and part of the second trimester. This requires careful consideration of several factors:

- Gestational age of the fetus
- Adequate shielding to protect the fetus
- The required radiation dose
- Fractionation (how the dose is divided over time)

A recent development that offers promise is **proton radiotherapy**, a form of radiation that allows a considerable reduction in fetal exposure compared with conventional radiation techniques. However, the authors note that standardization of this approach is still needed before it can be widely recommended. Research by Blommaert and colleagues (2023) is currently exploring the challenges and opportunities for proton therapy during pregnancy.

For **sentinel node biopsy** (the procedure to check whether cancer has spread to the lymph nodes), the authors offer a specific recommendation: avoid the use of blue dye. Instead, low-dose technetium-labeled albumin nanocolloid is a feasible and safer alternative for pregnant patients.

## How Targeted Therapies May Affect the Fetus

Several systemic therapies commonly used in breast cancer treatment carry significant risks to the developing fetus, and understanding these risks is crucial for patients making treatment decisions.

**Endocrine (hormone) therapy**: Drugs like tamoxifen must be deferred until after delivery because of their known **teratogenic effect**—meaning they can cause birth defects. A systematic review by Buonomo and colleagues (2020) documented cases of tamoxifen exposure during pregnancy and its associated risks.

**Trastuzumab (Herceptin) and other HER2-targeted agents**: These medications cross the placenta after the first trimester of gestation and are associated with an increased risk for:

- Oligohydramnios (low amniotic fluid)
- Fetal abnormalities
- Pulmonary hypoplasia (underdeveloped lungs)
- Fetal death

A systematic review and meta-analysis by Zagouri and colleagues (2013) confirmed these serious risks. For this reason, HER2-targeted agents are strictly avoided during pregnancy.

**Immune checkpoint inhibitors** (immunotherapy drugs): Evidence on their use during pregnancy is very limited, but consensus guidelines recommend avoiding them during neoadjuvant treatment of triple-negative breast cancer. This recommendation is based on two factors:

- A biological rationale: the PD-1/PD-L1 axis (programmed cell death protein 1 and its ligand) plays a critical role in maternal immune tolerance against the fetus (Guleria and colleagues, 2005)
- Small case series that have shown an increased incidence of pregnancy complications (Andrikopoulou and colleagues, 2021; Borgers and colleagues, 2021)

**Cyclin-dependent kinase 4/6 inhibitors (CDK4/6 inhibitors)**: These newer targeted drugs, used primarily for hormone-receptor-positive breast cancer, should also be avoided during pregnancy. The reasons are twofold: they require concomitant endocrine therapy (which is itself contraindicated), and animal studies have shown fetal harm following exposure. A study by Kelleher and colleagues (2021) demonstrated that deficiency of PARP-1 and PARP-2 in the mouse uterus resulted in decidualization failure and pregnancy loss, providing additional biological evidence of risk for this drug class.

## Chemotherapy During Pregnancy: What Is Safe and When

Given the limitations on targeted agents, chemotherapy remains a cornerstone of treatment for breast cancer during pregnancy. The authors emphasize that the decision to administer chemotherapy—and which regimen to use—is an **oncologic priority** that requires careful thought.

**When can chemotherapy be given?** Chemotherapy can only be administered after the **first trimester** is complete. During the first trimester, cytotoxic drugs may interfere with organogenesis (the formation of the baby's organs), so this period is off-limits. After the first trimester, several key chemotherapy agents can be safely given to pregnant patients with no apparent increase in neonatal complications.

**Which drugs are safe?** The authors identify these agents as safe to administer to pregnant patients after the first trimester:

- Anthracyclines (such as doxorubicin and epirubicin)
- Cyclophosphamide
- Taxanes (such as paclitaxel and docetaxel) — likely safe
- Carboplatin — likely safe

These conclusions are based on several studies. A large 20-year international cohort study by de Haan and colleagues (2018) followed **1,170 patients** diagnosed with cancer during pregnancy and evaluated both oncologic management and obstetric/neonatal outcomes. Systematic reviews by Jiang and colleagues (2021), Mir and colleagues (2010), and Murthy and colleagues (2014) also supported the safety of these agents. However, the authors caution that most of these studies are retrospective case series, where small sample sizes and publication bias may affect the generalizability of the conclusions.

**Dose intensity matters.** One of the strongest recommendations in this commentary is that **a priori dose reduction or omission of drugs is strongly discouraged**. Retaining dose intensity and density is clearly associated with improved outcomes in early breast cancer. This recommendation is supported by:

- Two meta-analyses from the Early Breast Cancer Trialists' Collaborative Group (EBCTCG): one involving **100,000 women across 86 randomized trials** (2023) showing that anthracycline- and taxane-containing chemotherapy is most effective, and another involving **37,298 women across 26 randomized trials** (2019) showing that more frequent administration improves outcomes
- An earlier EBCTCG meta-analysis (2012) of **100,000 women in 123 randomized trials** comparing different polychemotherapy regimens
- A study by Matikas and colleagues (2017) on dose-intense and dose-dense adjuvant chemotherapy for early breast cancer

**Supporting the immune system.** **Granulocyte colony-stimulating factors (G-CSF)** play a critical role in maintaining dose intensity by helping to prevent or manage neutropenia (low white blood cell counts). Available evidence suggests that their administration during pregnancy is likely safe, although the authors acknowledge that rare adverse events from in utero exposure cannot be completely ruled out (Berends and colleagues, 2021; Papakonstantinou and colleagues, 2020).

**When to stop chemotherapy.** Chemotherapy should be discontinued around **week 35 of gestation at the latest** to avoid myelosuppression (suppression of bone marrow function) at the time of delivery. Delivery is often timed to facilitate the planning of further oncologic treatment. The recommendation from the ESMO guidelines is to discontinue chemotherapy **at least 3 weeks before the planned delivery date** to allow the mother's blood counts to recover.

## Gene Expression Testing: A Complex Tool in PrBC

Gene expression profiling (also known as genomic testing) helps refine prognostication in luminal (hormone-receptor-positive) breast cancer. Commercial gene signatures—such as the 70-gene assay (MammaPrint) and the genomic grade index—are widely used to guide treatment decisions in non-pregnant patients.

However, interpreting these tools in pregnant patients is challenging. The authors note that there are genomic and transcriptomic differences between very young-onset breast cancer, PrBC, and older premenopausal non-pregnant breast cancer patients. Research by Nguyen and colleagues (2018) found that breast cancer diagnosed during pregnancy is associated with enrichment of non-silent mutations, mismatch repair deficiency signature, and mucin mutations. Luen and colleagues (2023) characterized the genomic features of hormone-receptor-positive breast cancer in very young women.

Importantly, only **one small study** (Azim and colleagues, 2014) has directly compared gene signatures between pregnant and non-pregnant patients with breast cancer, and it showed **no differences** in the two prognostic signatures evaluated (the 70-gene assay and the genomic grade index). While this is reassuring, the authors caution that the evidence base is very thin, and more research is needed before these tools can be confidently applied to decision-making in pregnant patients.

In practice, the decision to administer chemotherapy in PrBC is based on the expected absolute reduction of recurrence and mortality—which is a function of the patient's absolute risk and the constant relative risk reduction conferred by chemotherapy. Although no specific thresholds are validated and recommended, the absolute benefit should generally exceed the risk for long-term morbidity and mortality caused by cytotoxic agents, while also considering potential fetal toxicity.

## Managing HER2-Positive and Triple-Negative Disease After Chemotherapy

Following neoadjuvant or adjuvant chemotherapy, the next management decisions depend on tumor biology, the need for further treatment, patient preferences, and the risks to the fetus.

**HER2-positive breast cancer:** HER2-targeting agents are highly effective (a network meta-analysis by Villacampa and colleagues, 2023, confirmed their benefit), but they are contraindicated during pregnancy. For patients with HER2-positive disease, one potential option is **iatrogenic preterm delivery** to hasten the start of trastuzumab. However, the authors emphasize that the effect of prematurity on cognitive development—documented in a landmark study by Amant and colleagues in the *New England Journal of Medicine* (2015)—must be weighed carefully against the relatively small benefit of starting trastuzumab a few weeks earlier. Chemotherapy can serve as a "bridge therapy" until delivery, at which point adjuvant trastuzumab can be started.

**Triple-negative breast cancer:** For triple-negative disease, the addition of **carboplatin** to neoadjuvant chemotherapy is associated with improved pathologic complete response rates and event-free survival, making it the standard of care in this setting (Poggio and colleagues, 2022). However, the authors note that we currently lack data on the use of adjuvant immune checkpoint inhibition alone (without neoadjuvant immunotherapy) in pregnancy-related triple-negative breast cancer.

## Metastatic Breast Cancer During Pregnancy: The Most Difficult Scenario

Managing pregnant patients with **metastatic breast cancer** (cancer that has spread beyond the breast) is highly complicated. The authors identify several compounding challenges:

- The need for continuous, ongoing therapy
- The fact that several drug classes are contraindicated during pregnancy
- The complete lack of prospective data
- The difficulty of balancing benefit and detriment to both the mother and the fetus

In this scenario, the authors strongly encourage **open discussions about terminating or continuing the pregnancy**, the available treatment options, and the prognostic implications of each choice. These conversations should enable an informed shared decision between the patient, her family, and her medical team, coupled with emotional and psychological support.

Importantly, the standard first-line therapies recommended for all three breast cancer subtypes in non-pregnant patients are **not appropriate** for patients with metastatic PrBC who do not wish to terminate the pregnancy:

- CDK4/6 inhibitors plus endocrine therapy (for luminal/HER2-negative disease)
- Dual HER2 blockade (for HER2-positive disease)
- Combined chemoimmunotherapy (for triple-negative, PD-L1-positive disease)

In metastatic PrBC, management is truly individualized, with the twofold goal of maximizing the chance for cure and achieving a full-term delivery.

## Key Recommendations at a Glance

The authors provide a clear summary table of recommendations for managing breast cancer during pregnancy. Here is the patient-friendly version:

1.
**Breast surgery**: Both mastectomy and breast-conserving surgery are appropriate options, depending on the individual case and whether radiation can be safely delayed.
1.
**Sentinel node biopsy**: Avoid blue dye. Low-dose technetium-labeled albumin nanocolloid is a feasible and safe alternative.
1.
**Radiation therapy**: Can be considered only in highly selected cases, and requires careful planning with shielding and dose considerations.
1.
**Chemotherapy**: Can be administered only after the first trimester. Must be discontinued at least 3 weeks before the planned delivery date (around week 35 of gestation).
1.
**Supportive medications**: Granulocyte colony-stimulating factor (G-CSF) and ondansetron (an anti-nausea medication) can be safely administered. Methylprednisolone or prednisolone are the preferred steroids.
1.
**Endocrine therapy**: Avoid during pregnancy (teratogenic risk).
1.
**Trastuzumab and other HER2-targeted agents**: Avoid during pregnancy (risk of oligohydramnios, fetal abnormalities, pulmonary hypoplasia, and fetal death).
1.
**Immune checkpoint inhibitors**: Avoid during pregnancy (PD-1/PD-L1 axis plays a role in maternal-fetal immune tolerance).
1.
**Cyclin-dependent kinase 4/6 inhibitors**: Avoid during pregnancy (require concomitant endocrine therapy and animal studies show fetal harm).

## What This Means for Patients: Key Takeaways

Being diagnosed with breast cancer during pregnancy is an overwhelming and frightening experience, but this commentary offers several important messages of hope and guidance.

**First, treatment is delivered with curative intent.** The authors are clear that harmful delays in therapy initiation, unnecessary therapy de-escalation, and chemotherapy dose modifications should all be avoided. Pregnant patients with breast cancer deserve—and can receive—treatment that is as close to the standard of care for non-pregnant patients as possible.

**Second, chemotherapy is an option.** After the first trimester, several effective chemotherapy agents (anthracyclines, cyclophosphamide, taxanes, and carboplatin) can be safely administered without apparent increases in neonatal complications. Dose-dense schedules using both anthracyclines and taxanes are the most effective options, and G-CSF can be used to maintain dose intensity.

**Third, some medications must wait.** Endocrine therapy, HER2-targeted agents, immunotherapy, and CDK4/6 inhibitors are not safe during pregnancy. This means that some treatments that would be first-line in a non-pregnant patient must be deferred until after delivery. This underscores the need for individualized treatment planning that carefully sequences therapy around the pregnancy.

**Fourth, multidisciplinary care is essential.** The authors describe the management of pregnancy-related breast cancer as having a twofold goal: to maximize the chance for cure and to achieve full-term delivery. This requires close collaboration between medical oncologists, surgeons, radiation oncologists, maternal-fetal medicine specialists, and pathologists—all working together as one team.

The authors advocate strongly for establishing **institutional guidelines and routines based on recommendations from scientific societies such as ESMO**. If you are facing this diagnosis, asking your care team about these guidelines can help ensure you receive optimal, evidence-informed care.

## What This Study Could Not Prove: Limitations

As a commentary article, this piece does not present new original research data. Instead, it reviews and synthesizes existing evidence, and the authors are transparent about the limitations of the current knowledge base.

The most significant limitation is the **paucity of prospective studies** in pregnancy-related breast cancer. As noted earlier, pregnant patients are routinely excluded from clinical trials, creating a knowledge gap on essential questions such as the optimal timing of chemotherapy, the effect of pregnancy on drug metabolism, and the safety of newer targeted agents.

Many of the safety conclusions about chemotherapy during pregnancy come from **retrospective case series**, where small sample sizes and publication bias might affect the reliability of the findings. The authors acknowledge this explicitly, noting that generalizability may be limited.

The recommendation to avoid immune checkpoint inhibitors is based largely on biological rationale and small case series, not large clinical trials. Similarly, the data on gene expression profiling in pregnant patients comes from just one small study, which limits confidence in applying these tools to this population.

Finally, the long-term effects of in utero exposure to chemotherapy on the child's development are still being studied. While the landmark study by Amant and colleagues (2015) found that maternal cancer treatment during pregnancy did not adversely affect cognitive development (a reassuring finding), the authors note that the effect of prematurity on cognitive development must be carefully weighed in decisions about early delivery.

## Frequently Asked Questions

### What is breast cancer during pregnancy (PrBC)?

Breast cancer during pregnancy is the most common cancer diagnosed during or shortly after pregnancy, but it is still uncommon overall. It includes cancers found while pregnant and those found after delivery. The postpartum group tends to have worse outcomes. Treatment must protect both the mother and the developing fetus.

### Why is breast cancer during pregnancy often diagnosed late?

Diagnosis is often delayed because normal pregnancy changes make breasts denser and more nodular, which can hide a lump. Also, doctors may avoid necessary imaging tests due to radiation fears. This can lead to more advanced cancer at diagnosis. A high suspicion and early multidisciplinary evaluation are recommended.

### Is chemotherapy safe during pregnancy?

Yes, chemotherapy can be given after the first trimester. Drugs considered safe include anthracyclines, cyclophosphamide, taxanes, and carboplatin. Dose reductions are strongly discouraged. Chemotherapy should stop at around week 35 of gestation, or at least 3 weeks before planned delivery, to allow blood counts to recover.

### Which breast cancer medications must be avoided during pregnancy?

Several drug classes are strictly avoided during pregnancy because they can harm the fetus. These include endocrine therapy such as tamoxifen, HER2-targeted agents like trastuzumab, immune checkpoint inhibitors, and CDK4/6 inhibitors. They may cause birth defects, low amniotic fluid, fetal abnormalities, or pregnancy loss.

### What surgery and radiation options are available for pregnant patients?

Both mastectomy and breast-conserving surgery are possible, depending on whether radiation can be safely delayed. Radiation is generally avoided but may be considered in selected cases with careful shielding. Proton therapy is promising but not yet standard. For lymph node biopsy, low-dose technetium is safer than blue dye.

### What are the risks to the baby from breast cancer treatment?

Chemotherapy after the first trimester does not appear to increase neonatal complications. A landmark study found no adverse effect on cognitive development, but prematurity can affect development. Targeted therapies and hormone therapy are dangerous to the fetus, causing birth defects, low amniotic fluid, and other serious problems.

### How is a treatment plan decided for breast cancer during pregnancy?

A multidisciplinary team—including medical oncologists, surgeons, radiation oncologists, and maternal-fetal specialists—works together. The goal is to maximize the chance of curing the mother while achieving a full-term healthy delivery. Treatment is individualized based on tumor biology, gestational age, and patient preferences.

## Source Information

This patient-friendly article is based on peer-reviewed research published as a commentary in the scientific journal *Acta Obstetricia et Gynecologica Scandinavica*.

**Original article title:** Acta Obstet Gynecol Scand - 2023 - Matikas - Breast cancer during pregnancy The oncologist s point of view

**Authors:** Alexios Matikas and Jonas Bergh

**Affiliations:** Oncology/Pathology Department, Karolinska Institutet, and Breast Center, Karolinska Comprehensive Breast Cancer Center and Karolinska University Hospital, Stockholm, Sweden

**Journal:** Acta Obstetricia et Gynecologica Scandinavica, 2024; Volume 103, pages 775–778

**DOI:** 10.1111/aogs.14729

**Funding:** Alexios Matikas is supported by the Swedish Cancer Society (Cancerfonden) Junior Clinical Investigator award, the Research Funds at Radiumhemmet, and the Swedish Breast Cancer Society (Bröstcancerförbundet). Jonas Bergh's Research Group is funded by the Swedish Cancer Society, the Research Funds at Radiumhemmet, the Stockholm Region, and the Knut and Alice Wallenberg Foundation.

**Conflict of interest disclosure:** The authors reported research funding and consultancy relationships with pharmaceutical companies including Amgen, AstraZeneca, Bayer, Merck, MSD, Novartis, Pfizer, Roche, Sanofi, Seagen, and Veracyte, as well as honoraria and stock holdings as detailed in the original publication.

*Note: This patient-friendly article is based on peer-reviewed research and is intended for educational purposes. It does not constitute medical advice. Patients facing a breast cancer diagnosis during pregnancy should discuss their individual situation with their oncology and obstetrics care team.*


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