Abstract
Background/Objectives: 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.

Methods: 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.

Results: 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.

Conclusions: 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.