Longitudinal trends in testicular volume z scores from puberty to adulthood, sperm quality, and paternity outcomes after childhood cancer.

Background: Childhood cancer therapy may cause subfertility. This study correlated cancer therapy exposures with testicular volumes from puberty to adulthood, spermatogenesis, and paternity outcomes in adulthood.

Methods: The study population comprised 255 male childhood cancer survivors (CCS) (survival ≥5 years, diagnosed in 1964-2000 at the Helsinki Children's Hospital) whose testicular volume was measured at ages 12 years (n = 38), 14 years (n = 57), 16 years (n = 63), 18 years (n = 105), and in adulthood (n = 43; median age, 27 years). Testicular volumes were converted to age-specific z scores. In addition, 92 CCS provided semen sample in adulthood (median age, 25.2 years); and paternity was evaluated through national register data (mean age at assessment, 37.6 years; n = 252).

Results: Compared with age-specific reference values, CCS generally exhibited low testicular volume z scores at ages 12-18 years. Testicular volume z scores in CCS treated exclusively with chemotherapy returned to the reference range in adulthood. In contrast, patients exposed to testicular radiation ≥1 gray (Gy) (median dose, 12 Gy) showed no late recovery in testicular size. Testicular radiation ≥1 Gy and a cyclophosphamide equivalent dose ≥12 g/m² were identified as risk factors for azoospermia in adulthood. Patients exposed to testicular radiation ≥1 Gy and a cyclophosphamide equivalent dose ≥4 g/m² had lower paternity rates.

Conclusions: Testicular volume growth after prolonged follow-up suggests a potential late recovery of spermatogenesis in CCS treated exclusively with chemotherapy. However, alkylating agents increased the risk of having prolonged azoospermia and nonpaternity. High-dose testicular radiation causes long-term depletion of spermatogonia and was the strongest risk factor for azoospermia and nonpaternity.