Men with rectal cancer stage I to III planned for resection was included in the study. Men treated with preoperative RT were assigned to the exposed group and men treated with surgery alone were assigned to the unexposed group. Eighteen months after start of inclusion, less than 10% of the participants were treated with surgery alone. To increase the sample size of the unexposed group, men with prostate cancer stage I to III and scheduled for robot-assisted prostatectomy were also included.
Participants with rectal cancer were enrolled at two centres in Stockholm (Karolinska University Hospital and Ersta Hospital) between 2010 and 2014. Participants with prostate cancer were enrolled at the Urology department of the Karolinska University Hospital in Stockholm between 2012 and 2013.
Patient data, fasting venous blood samples, semen samples and questionnaires regarding sexual function and well being were collected before start of oncological treatment (baseline), 1 and 2 years after surgery. Men treated with preoperative RT for rectal cancer had an additional venous blood sample during the week before surgery. Men with rectal cancer under 55 years of age were offered semen cryopreservation.
Participants could choose if they wanted to participate in one, two or three of the following parts; hormone analysis, semen analysis and/ or questionnaires regarding sexual function and well being. Semen sampling and cryopreservation was not performed in men with prostate cancer.
Changes in hormone levels, semen measurements and sexual function during follow-up were assessed, and compared between exposed and unexposed participants.