Testicular function after radiotherapy for rectal cancer--a review

Eighty percent of all male rectal cancer patients are sexually active at the time of diagnosis. Because of modern multimodal therapy many can expect long-term survival. The testes can be exposed to scattered or direct radiation during radiotherapy, depending on their position in relation to the targeted volume.

This review analyzes the current literature providing data on testicular exposure to radiation during radiotherapy for rectal cancer and the consequences on testicular function.

A systematic search was conducted in PubMed, Embase, and Cochrane. Ten original articles providing data on testicular exposure to radiation and testicular function in men with primary rectal cancer were included for qualitative synthesis.

Data on testicular exposure to radiation and testosterone levels in men with rectal cancer are reported.

On average, the testes were exposed to 0.24-8.4 Gy during long-course radiotherapy for rectal cancer. Testosterone levels after radiation were significantly lower compared with pretreatment levels or compared with patients treated with surgery alone. After radiotherapy, the absolute risk increase was 0.17-0.30 for posttreatment testosterone levels below 8 nmol/L. In the largest study, the relative risk was 2.7 for testosterone levels below 8 nmol/L for men treated with radiotherapy compared with men treated with surgery alone.

Current data generate three hypotheses: (i) during long-course radiotherapy for rectal cancer, the testes can be exposed to direct and/or scattered radiation; (ii) men treated with radiotherapy seem at risk to develop testicular dysfunction with decreased serum testosterone levels compared with both pretreatment values and men treated with surgery alone; and (iii) a decrease in testosterone levels (<8 nmol/L) may precipitate specific symptoms caused by testosterone deficiency such as impaired physical, psychological, and sexual function after treatment.