Effects of Radiation Therapy on the Female Reproductive Tract in Childhood Cancer Survivors: A PENTEC Comprehensive Review.

PURPOSE: The PENTEC (Pediatric Normal Tissue Effects in the Clinic) task force aimed to quantify effects of radiation therapy (RT) dose to the female reproductive organs after treatment for childhood cancer.

METHODS AND MATERIALS: Relevant studies published 1970 to 2017 were identified systematically through PubMed, Medline, and Cochrane databases with additional articles before 2021 identified by the group. Two large studies reported sufficient data to allow modeling of acute ovarian failure (AOF; loss of function ≤5 year from diagnosis) and premature ovarian insufficiency (POI; loss of function at attained age <40 years) based on maximum dose to least affected ovary. Although normal tissue complication probability modeling was not feasible for the uterus due to limited data, the relationship between ultrasound-measured uterine volume and estimated amount of RT was plotted. Limited data regarding vaginal toxicity were available.

RESULTS: The risk of AOF increases with RT dose to least affected ovary, alkylating agent cumulative dose (cyclophosphamide equivalent dose [CED] in g/m2 ), age at RT, and stem cell transplantation: Two Gy to the least affected ovary resulted in AOF risk of 1% to 5% (CED = 0, risk increasing with age), 4% to 7% (CED = 10 g/m2 , risk increasing with age), and 6% to 13% (CED = 30 g/m2 , risk increasing with age). For patients aged 1 and 20 years at time of RT, AOF risk was ≥50% at doses of 24 Gy and 20 Gy with no alkylating chemotherapy, 22.5 Gy and 17 Gy with intermediate alkylator dose (10 g/m2 ), and 17 Gy and 13 Gy with high alkylator dose (30 g/m2 ). Risk of POI increases with survivor (attained) age (rather than age at time of RT), radiation dose to least affected ovary, and alkylator dose. Data review suggested that higher radiation doses to the uterus are associated with uterine toxicity, with uterine size considerably restricted after 12 Gy. Vaginal radiation in children is associated with high toxicity risk, although dose-volume data are not available for quantification.

CONCLUSIONS: Risk of AOF increases with age at RT, CED exposure, and RT dose; risk of POI likewise increases with RT dose, CED exposure, and survivor age. Both AOF and POI are expected to affect fertility and estrogen production. Data suggest that RT uterine dose >12 Gy may be associated with uterine size restriction. Adult literature suggests that maintaining vaginal dose <5 Gy may limit toxicity. Treatment of life-threatening malignancy remains a priority over reproductive preservation; however, when possible, radiation and surgical techniques should be considered to minimize dose to least affected ovary, uterus, and vagina. Survivors should receive endocrine and gynecologic support; those desiring pregnancy should be counseled early to maximize reproductive options.