Semen quality in men with cancer: comparison with a healthy Swiss reference population

Abstract This study aimed to investigate the impact of cancer and its treatment on semen quality and to examine the differences according to cancer type and stage. In this monocentric retrospective cohort study, men aged 12 to 50 years who underwent semen analysis for fertility preservation prior to cancer treatment between 2005 and 2024 at a public hospital in Central Switzerland were eligible. Semen parameters of 373 cancer patients were compared with those of a healthy Swiss reference population (2871 military recruits) with adjustment for potential confounders. Subgroup analyses were performed by cancer type and stage, while paired analyses evaluated changes in semen quality before and after treatment. Before treatment, cancer patients had lower sperm concentration, total sperm count and total motile sperm count compared with the reference population. After adjustment, these differences remained significant only in men with testicular cancer. Following treatment, the proportion of men with azoospermia increased across all cancer types. While partial recovery was observed in patients with testicular cancer, patients with haematological and other solid cancer demonstrated a clear deterioration in semen quality, consistent with the higher gonadotoxicity of their treatments. In conclusion, semen quality may already be compromised in men with cancer prior to treatment, especially in testicular cancer. The extent of treatment-related impairment varies by cancer type and treatment. These findings highlight the importance of individualised and timely fertility counselling, sperm cryopreservation prior to treatment and the need for structured long-term follow-up of reproductive health in cancer survivors. Lay Summary Cancer and its treatment can reduce fertility in men of reproductive age and can affect the ability to have children. It is still unclear how much of this effect is caused by the disease itself and how much by the treatment. In this study, we compared semen quality in men with cancer before and after treatment with that of healthy Swiss men. We found that some patients, especially those with testicular cancer, already had lower semen quality before starting the treatment. After treatment, semen quality often further decreased and more men had no sperm in their ejaculate. This was particularly seen in patients who received treatments known to strongly affect fertility. These findings show that both cancer and cancer treatment can impair male fertility. This highlights the importance of early counselling and offering sperm freezing before treatment, as well as providing long-term reproductive follow-up after cancer care.