Existing and Emerging Options for Pediatric Oncofertility Patients: Pediatric...

In the United States, approximately 85% of pediatric cancer patients now survive their initial disease, up from much lower rates in the 1970s, due to earlier diagnostics, improved chemotherapy, biologics, and changes in radiation.

Approximately 1.4–1.5 million people are newly diagnosed with cancer annually in the US; globally there are ~10 million new cases per year. About 10% of US cases occur in patients aged ≤45, and 11% of breast cancers are diagnosed before age 40, totaling roughly 200,000 young patients annually.

Pediatric cancer survivors are significantly more likely to be infertile than their siblings.

Fertility concerns extend beyond cancer to rheumatologic diseases (often female, treated with cytotoxic drugs), beta-thalassemia patients receiving stem-cell transplant with sterilizing whole-body radiation, Turner syndrome (mosaic cases with early ovarian failure), BRCA or other cancer-predisposition mutations, and disorders of sex development or gender transition where the biological gamete may be at risk.

Sperm banking has been available for pubertal boys and men for many years at relatively low cost, but navigation to these services was historically poor.

Young women historically had fewer fertility-preservation options than men due to three gaps: information (providers unaware of long-term infertility risk), data (inability to predict individual outcomes), and options (lack of techniques for prepubertal or young patients).

It remains difficult to predict on an individual basis which patients will recover gonadal function after gonadotoxic treatment and which will be permanently sterile.

The Oncofertility Consortium adopted an interdisciplinary framework requiring investment in basic follicle biology, creation of 'silo spanners' (patient navigators bridging oncology, reproductive endocrinology, surgery, genetics, and radiation oncology), training of new scholars in interdisciplinary thinking, and 360° patient support (legal, ethical, insurance, religious counseling).

For women aged ≥18, embryo or egg banking is an established option; the Oncofertility Consortium lowered the recommended age threshold from 18 to 16 two years ago, but use below age 16 should occur only under IRB approval.

Across Oncofertility Consortium sites, the average wait time for controlled ovarian stimulation and egg retrieval is 12 days.

Tamoxifen holidays allow hormone-receptor-positive breast cancer survivors to become pregnant with good outcomes and may improve long-term compliance with adjuvant endocrine therapy.

For prepubertal and adolescent patients up to age 16, ovarian tissue cryopreservation (removal of an entire ovary or cortical biopsy under IRB-approved consent) is the only available fertility-preservation option.

Ovarian cortical tissue is dissected into small strips containing primordial through antral follicles and cryopreserved; tissue may need to remain frozen for 20–30 years if the patient is 5 or 6 years old at diagnosis.

Oocytes that are released adventitiously during ovarian-tissue dissection are often allocated to research in pediatric cases (rather than cryopreserved for the patient) because oocyte quality and aneuploidy rates in patients under 18 are not well characterized; aneuploidy is known to rise both above age 35 and below age 18.

Eighty-six live human births have been documented worldwide from autotransplantation of cryopreserved ovarian tissue, demonstrating that current cryopreservation methods maintain tissue function.

The denominator for ovarian-tissue transplants (total number attempted) and cancer-recurrence rates are not known globally, limiting assessment of efficacy and safety.

Pediatric ovarian cortex contains more primordial follicles than adult tissue (follicles are formed in utero between the second and third trimester), but may also harbor circulating cancer cells; transplanting such tissue risks reintroducing malignancy.

Histologic staining of a 4-year-old patient's ovarian cortex revealed both abundant primordial follicles and circulating cancer cells, illustrating the contamination risk.

Follicles cultured on flat plastic do not maintain three-dimensional architecture; mouse follicles form follicle-like structures but oocytes mature poorly, and human follicles simply flatten out.

Encapsulating isolated follicles in alginate hydrogel maintains three-dimensional architecture, permits follicle expansion and granulosa-cell differentiation into theca cells, and supports estrogen production over time in both mouse and human follicles.

Alginate-encapsulated mouse follicles undergo in-vitro ovulation (antrum formation, oocyte migration to one pole, rupture, and cumulus–oocyte-complex release) and yield live healthy mouse pups after fertilization.

A microfluidic 'organ-on-chip' system (Evatar) linking mouse ovary with human fallopian tube, uterus, cervix, and liver has reproduced a full 28-day menstrual cycle in vitro, including follicular-phase estradiol rise, mid-cycle HCG-triggered ovulation, and luteal-phase progesterone, and can model early pregnancy by maintaining progesterone.

Human ovarian follicles have been grown in alginate for 30–40 days; after 40 days, germinal-vesicle-intact oocytes can be recovered and matured in vitro.

In 2015, Woodruff's group reported the first human metaphase-II eggs matured entirely in vitro from encapsulated follicles, a milestone for fertility preservation without tissue transplantation.

Mature human and mouse oocytes release a 'zinc spark'—a burst of zinc fluorescence—at fertilization; immature oocytes do not. This assay may serve as a non-invasive marker of oocyte developmental competence.

Decellularized ovarian scaffolds ('ovary paper') can be repopulated with follicles and sutured to soft tissue; when transplanted into ovariectomized prepubertal mice, 100% of recipients underwent puberty.

Three-dimensional-printed gelatin scaffolds seeded with GFP-labeled prepubertal mouse follicles become vascularized after transplant and yield live GFP-positive pups, representing the first soft-organ transplant with fully 3D-printed bio-inspired tissue.

Woodruff's group is translating bioprosthetic ovary work to minipigs and plans to transplant small scaffold pieces subcutaneously in consenting human recipients to assess biocompatibility.

Dr. Soo Yung Kim is developing next-generation neoadjuvant fertoprotective drugs with the goal of eliminating the need for ovarian-tissue removal in future cancer patients.

In a one-year National Physicians Cooperative study, 44 pediatric patients (ages 1 month to 15 years) contributed fresh (not cryopreserved) ovarian tissue; 44 follicles were isolated, approximately 20 formed antra, and 4 yielded metaphase-II eggs (the remainder were germinal-vesicle stage). Results were published in Scientific Reports 2015.

A 2016 analysis of NPC pediatric cases (ICD-10 codes) confirmed that clinicians appropriately selected patients at high risk for gonadotoxicity; this work was presented at the 2016 Oncofertility meeting and is pending publication.

For males, sperm banking is recommended regardless of risk level if the family is concerned, because it is non-operative and relatively inexpensive (though it costs money and ~6 hours). For females, ovarian-tissue cryopreservation is a surgical intervention and should be reserved for high-risk cases identified by oncologists using established criteria.

At the beginning of the Oncofertility Consortium, all tissue-banking cases were adults with breast cancer; today nearly no adults participate in the NPC tissue program because they have other options (egg/embryo banking), and the program focuses on pediatric patients.