Fertility Preservation in Pediatric Oncology: A 10-Year Single-Center Experience in Northern Spain.

: The aim of this study is to describe fertility preservation (FP) techniques performed over the last 10 years at a tertiary hospital in northern Spain in patients under 18 diagnosed with cancer. : A retrospective medical record review was conducted for patients aged 0 to 18 years diagnosed between January 2014 and December 2023 in the Pediatric Oncology Unit at a university hospital. We evaluated patient characteristics, the timing of FP procedures, and potential risk factors for ovarian insufficiency and early azoospermia. Additionally, we assessed the agreement between two gonadotoxicity risk classifications. : In our center, FP is more frequently offered to pubertal patients (12 to 16 years old), prior to treatment in those at high risk of subsequent gonadotoxicity (>80%), and after treatment in those at low risk (<20%). Additionally, the increased provision of FP over the last five years of the study suggests improved clinician uptake of this long-term effect of cancer treatment. Our study found weak agreement between available gonadotoxicity risk classifications, complicating the identification of FP candidates. Long-term follow-up of survivors allowed for the detection of ovarian insufficiency (1.2%) and early azoospermia (0.7%), enabling hormone replacement therapy when necessary. Hematopoietic stem cell transplantation (HSCT) emerged as a predictor of early infertility. : Our study highlights the prevalence of gonadotoxicity in pediatric cancer patients at our center and the increasing access to FP techniques. The findings emphasize the importance of personalized medicine, tailored FP strategies based on individual risk, and long-term follow-up to assess fertility status.