Background: The incidence of colorectal cancer (CRC) is increasing in the population under 50 years of age, with more than 10% of cases occurring in young adults. Fertility preservation counseling has therefore received increased attention in this younger patient population. The treatment of CRC is often based on multimodal therapies, including surgery, radiotherapy, chemotherapy, and, more recently, immunotherapy, which makes it difficult to estimate the expected effect of treatment on fertility. We, therefore, systematically analyzed the published literature on the gonadotoxic effects of CRC treatments to better advise patients on the risk of infertility and the need for fertility preservation measures. This systematic review and meta-analysis are part of the FertiTOX project, which aims to reduce the data gap regarding the gonadotoxicity of oncological therapies. Objectives: The aim of this review and meta-analysis is to evaluate the potential impact of CRC therapies on gonadal function to allow more accurate counseling regarding the risk of clinically relevant gonadotoxicity and the need for fertility preservation measures before oncological treatment. Materials and Methods: A systematic literature search was conducted in Medline, Embase, the Cochrane database of systematic reviews, and CENTRAL in March 2024. A total of 22 out of 4420 studies were included in the review. Outcomes were defined as clinically relevant gonadotoxicity, indicated by elevated follicle-stimulating hormone (FSH) and/or undetectable anti-Müllerian hormone (AMH) levels and/or the need for hormone replacement therapy in women and azoo-/oligozoospermia and/or low inhibin B levels in men. Studies with fewer than nine patients were excluded from the meta-analysis. Results: The qualitative analysis included 22 studies with 1634 subjects (775 women, 859 men). Treatment consisted of active surveillance after surgery (37.7%), chemotherapy (12.7%), radiation (0.2%), or radiochemotherapy (53.9%). In 0.5%, the therapy was not clearly described. The meta-analysis included ten studies and showed an overall prevalence of clinically relevant gonadotoxicity of 23% (95% CI: 13–37%). In women, the prevalence was 27% (95% CI: 11–54%), and in men, 18% (95% CI: 13–26%). A subanalysis by type of CRC was only possible for rectal cancer, with a prevalence of relevant gonadotoxicity of 39% (95% CI: 20–64%). In patients undergoing chemotherapy exclusively, the prevalence was 4% (95% CI: 2–10%). In those receiving only radiotherapy, the prevalence was 23% (95% CI: 10–44%); in contrast, it reached 68% (95% CI: 40–87%) in patients who received radiochemotherapy. Conclusions: This first meta-analysis of the clinically relevant gonadotoxicity of CRC therapies provides a basis for counseling on the risk of infertility and the need for fertility preservation measures. Despite the low prevalence of gonadotoxicity in cases receiving chemotherapy alone, fertility preservation is still recommended due to the uncertainty of subsequent therapy and the lack of large longitudinal data on individual treatment effects. Further prospective studies are needed to investigate the impact of CRC treatment on gonadal function and estimate the effect of new treatment modalities, such as immunotherapies.
