Ovarian Tissue Freezing: A Fertility Preservation Option for Young Cancer Patients

Table of Contents

• Introduction: Why This Matters for Young Patients
• How Cancer Treatment Affects Fertility
• What Is Ovarian Tissue Cryopreservation?
• Who Qualifies for Ovarian Tissue Freezing?
• Specific Criteria for Patient Selection
• Freezing Techniques: Slow Freezing vs. Vitrification
• Transplantation Methods: Orthotopic vs. Heterotopic
• Important Risks and Safety Considerations
• Conclusion and Key Takeaways
• Source Information

Introduction: Why This Matters for Young Patients

Childhood and adolescent cancer remains a significant health concern, affecting a substantial portion of this age group. While modern treatments have dramatically improved survival rates—reaching up to 90% for certain cancers—these advancements come with a cost: damaging effects on reproductive health.

It's estimated that 1 in 530 adults aged 20-39 years old has survived childhood cancer. As survival rates have increased, particularly in North America and Western Europe, the population of childhood cancer survivors has grown substantially. This makes fertility preservation an increasingly important consideration for young patients and their families.

Cancer treatments, including chemotherapy and radiotherapy, often have gonadotoxic effects that can lead to ovarian failure and infertility. The resulting decrease in hormone production may also increase risks of hypertension, cardiovascular disease, osteoporosis, and menopausal symptoms, significantly impacting quality of life.

How Cancer Treatment Affects Fertility

Ovaries are particularly vulnerable to cytotoxic chemotherapy agents, which act progressively and with irreversible effects. These drugs cause apoptosis (programmed cell death) of primordial follicles while simultaneously decreasing anti-Müllerian hormone levels. This process activates remaining intact follicles, ultimately leading to exhaustion of ovarian content.

The final effects on reproductive ability depend on several factors:

• Drug dosage and duration of chemotherapy
• Specific drug type
• Patient age during treatment

Chemotherapy drugs are classified into three risk categories based on their ovarian toxicity:

High-Risk Drugs: Cyclophosphamide, Ifosfamide, Chlorambucil, Melphalan, Busulfan, Nitrogen mustard, Procarbazine, Nitrosoureas

Intermediate-Risk Drugs: Cisplatin, Carboplatin, Adriamycin, Doxorubicin, Actinomycin D

Low-Risk Drugs: Methotrexate, 5-Fluorouracil, Vincristine, Vinblastine, Bleomycin, Mercaptopurine

Radiation therapy has particularly devastating effects on primordial follicles, leading to early ovarian failure, decreased hormone production, and uterine abnormalities. When the pelvis or abdomen is within irradiation limits, follicular damage may appear when radiation dose reaches ≥10Gy in post-pubertal and ≥15Gy in pre-pubertal girls.

According to the Children's Oncology Group guidelines, higher cumulative doses of alkylating agents or combinations of alkylators, especially when combined with radiation to abdomen/pelvis or brain/cranium, significantly increase risk for ovarian hormone deficiencies and infertility.

What Is Ovarian Tissue Cryopreservation?

Ovarian tissue cryopreservation (OTC) involves surgically removing either strips of ovarian tissue or the entire ovarian cortex before beginning cancer treatments. This method offers several distinct advantages, especially for prepubertal patients.

Unlike other fertility preservation methods, OTC doesn't require ovarian stimulation, allowing immediate administration of anti-cancer treatment. This avoids potential risks of stimulating estrogen-sensitive cancers and represents the only viable option for prepubertal girls with cancer.

The procedure preserves primordial follicles in the ovarian cortex, which show better resistance to cryoinjury compared to mature oocytes. This method also captures a larger number of primordial follicles, increasing fertility possibilities throughout the graft's lifetime and reducing the need for multiple IVF attempts.

The historical timeline of OTC is noteworthy. The concept was first described in rats in 1954, but the first human ovarian transplantation with previously preserved tissue wasn't performed until 1999 by Dr. Kutluk Oktay. The first live human birth from cryopreserved ovarian tissue using slow freeze technique was reported in 2004 by Donnez et al.

As of 2018, 360 autotransplantations have been performed with successful pregnancies reaching 30%. More than 130 live births after ovarian tissue cryopreservation and autotransplantation have been reported, with numbers exceeding 200 by 2020. Recent literature shows pregnancy and live birth rates reaching 50% and 41% respectively in a series of 60 women across three clinical centers.

Who Qualifies for Ovarian Tissue Freezing?

OTC is essentially the only fertility preservation option for girls before puberty and adolescents who will undergo gonadotoxic cancer treatment. The indications have expanded significantly since the first reported cases in 2007 involving only girls with cancer.

The most common indications include:

• Treatment with alkylating agents
• Pre-allograft and autologous hematopoietic stem cell conditioning
• Ovarian-focused radiotherapy
• Gonadectomy
• Hematological malignancies (leukemia, myelodysplastic syndromes)
• Lymphomas
• Bone tumors
• Neurological neoplasms (neuroblastoma, central nervous system cancer)
• Sarcomas
• Turner syndrome
• Benign hemoglobinopathies

The relative frequency of malignancies as indication for cryopreservation ranges from 67% to 95%. For non-malignant diseases, Turner syndrome and benign hemoglobinopathies are the most common indications.

Although not yet covered by general guidelines, OTC may benefit young girls with metabolic diseases causing ovarian degeneration, such as galactosemia. These patients maintain healthy follicles in early age but require further evaluation of fertility rates from preserved tissue, making this approach experimental for this patient group.

Specific Criteria for Patient Selection

While OTC offers significant advantages, specific suitability criteria must be considered before recommending this procedure. The risk of premature ovarian insufficiency should exceed 50%, estimated based on remaining ovarian tissue quantity and quality plus the type of anti-cancer therapy planned.

Although literature suggests 15 years as a suitable age cutoff for OTC before anti-cancer treatment, some studies show that exposure to therapy before cryopreservation doesn't necessarily harm final outcomes, even in cases like acute leukemia where immediate treatment is necessary.

Pelvic radiotherapy requires special consideration. The reproductive system is highly sensitive to direct radiation >25Gy during childhood, often leading to infertility. Live births after pelvic radiotherapy are highly unlikely due to local irradiation effects and potential rejection of transplanted tissue from radiation-induced fibrous tissue development.

Patient age at transplantation is crucial, with age being inversely associated with successful outcomes. Thirty-five years is generally considered the upper limit for cryopreservation techniques due to reduced primordial follicle quantity as women age.

Additional suitability criteria include:

• Expected survival exceeding 5 years
• Absence of metastases
• No contraindications for surgery

Freezing Techniques: Slow Freezing vs. Vitrification

OTC involves surgical removal of either ovarian tissue strips or the entire ovarian cortex. The quantity of removed tissue relates to ovary size and premature ovarian insufficiency risk. While removing both ovaries is an option, ovarian biopsies often suffice for fertility retention.

Three main techniques are used for ovarian tissue cryopreservation:

Vitrification: First reported in 1985, this technique solidifies cells in a glass-type form without ice crystallization using high concentrations of cryoprotectant agents and rapid cooling rates reaching 5000°C/min. While effective, it requires higher cryoprotectant concentrations increasing cellular toxicity risk.

Ultra-Rapid Freezing: This technique involves direct exposure of sample containers to liquid nitrogen using lower cryoprotectant quantities than vitrification. It's mainly used for oocyte and embryo freezing rather than ovarian tissue preservation.

Slow-Freezing Technique: Introduced in 1966, this method uses programmable freezers with controlled cooling rates of 1.5°C/min and lower cryoprotectant concentrations compared to vitrification. The procedure requires many hours but represents the most commonly used and successful method for OTC.

Slow freezing remains the preferred technique worldwide for successful ovarian follicle preservation and live births after transplantation. As of current data, 131 pregnancies and 75 live births are reported after slow freezing and transplantation, compared to only 4 births following vitrification techniques. Slow freezing also successfully restores endocrine function within 1-20 months after transplantation (mean time: 3-5 months).

Transplantation Methods: Orthotopic vs. Heterotopic

Reimplantation of ovarian tissue can be achieved through two primary methods, each with distinct advantages and considerations.

Orthotopic Transplantation: This involves implanting ovarian tissue inside the peritoneal cavity into the remaining ovary, ovarian fossa, or broad peritoneal ligament. The significant advantage is the possibility of spontaneous pregnancy leading to live births. Endocrine function recovery occurs in over 95% of cases, beginning 2-9 months after grafting and maintaining functionality for up to 7 years.

Live birth rates reach up to 41.6% with this technique. However, as a surgical procedure, complication rates range from 2 to 7.1 per 1000 cases. Currently, orthotopic transplantation remains the method of choice when live birth is the primary goal.

Heterotopic Transplantation: This method implants ovarian tissue in locations outside the peritoneal cavity, such as the subcutaneous abdominal wall, beneath the peritoneum, the rectus muscle, or the forearm. Advantages include simplicity, cost-effectiveness, less invasive procedure, and feasibility when pelvic adhesions prevent orthotopic transplantation.

The main limitation is that spontaneous pregnancy isn't possible, and though IVF remains an option, experience is very limited. Heterotopic transplantation is preferred when recovery of natural endocrine function is the primary treatment goal.

OTC through heterotopic transplantation has been successfully described, resulting in recovery of endocrine function and puberty when tissue was cryopreserved at 10 years of age. While experience remains limited, rates of ovarian functionality, successful pregnancy, and live births appear close to documented rates in adult patients.

Important Risks and Safety Considerations

Like any invasive medical procedure, ovarian tissue cryopreservation carries specific risks and potential complications that patients and families must understand.

The most significant risk is potential reimplantation of malignant cells along with ovarian tissue. This risk is particularly relevant since most patients undergo cryopreservation before beginning anti-cancer treatment. Risk levels vary considerably by cancer type and ovarian involvement.

Low-Risk Malignancies (<0.2% risk): Early-stage breast cancer (Stage I-III), squamous cell carcinoma of the cervix, Hodgkin lymphoma, and Wilms' tumor.

Moderate-Risk Malignancies (0.2-11% risk): Stage IV breast cancer, Ewing sarcoma, cervical adenocarcinoma, and non-Hodgkin lymphoma.

High-Risk Malignancies (>11% risk): Leukemia, neuroblastoma, and Burkitt lymphoma. Patients with acute leukemia present particular concern since malignant cells can be traced in the blood, raising reimplantation risk during grafting.

Patients considered high-risk for malignant cell reimplantation typically should not undergo OTC and subsequent transplantation. Alternatively, ovarian tissue might be resected after multiple chemotherapy cycles to reduce malignant cell presence in ovaries.

Though four live births have been described in patients with ovarian tissue collected after chemotherapy for leukemia, the risk of chemotherapy damaging ovarian tissue exists and may negatively affect graft quality and longevity. Thorough histological analysis of ovarian tissue before cryopreservation and before reimplantation is essential to avoid transplanting cancer cells.

Current detection methods include histological analyses, immunohistochemical testing for disease-specific markers, fluorescence in situ hybridization, and molecular methods. However, even with patients theoretically in total remission, the risk—though low—cannot be completely eliminated.

Conclusion and Key Takeaways

Ovarian tissue cryopreservation represents a significant advancement in fertility preservation for young cancer patients, particularly prepubertal girls who cannot undergo conventional egg freezing methods. The procedure offers distinct advantages including no need for ovarian stimulation, preservation of numerous primordial follicles, and potential restoration of both fertility and endocrine function.

With over 200 successful live births reported worldwide and pregnancy rates reaching 50% in some studies, OTC has proven clinically effective. The American Society for Reproductive Medicine has recognized this method as safe and clinically accepted since 2019.

Patient selection remains crucial, with considerations including cancer type, planned treatments, age, and specific risk factors. While reimplantation of malignant cells represents the most significant concern, careful screening and advancing detection methods continue to improve safety profiles.

As cancer survival rates continue to improve for childhood and adolescent patients, fertility preservation options like ovarian tissue cryopreservation will play an increasingly important role in comprehensive cancer care and quality of life for survivors.

Source Information

Original Article Title: Ovarian Tissue Cryopreservation in Children and Adolescents

Authors: Angeliki Arapaki, Panagiotis Christopoulos, Emmanouil Kalampokas, Olga Triantafyllidou, Alkis Matsas, Nikolaos F. Vlahos

Publication: Children 2022, 9(8), 1256

Affiliation: Second Department of Obstetrics and Gynecology, "Aretaieion" Hospital, Faculty of Medicine, National and Kapodistrian University of Athens, Greece

This patient-friendly article is based on peer-reviewed research and maintains all significant findings, data points, and clinical recommendations from the original scientific publication.