Zhu Z, et al. - Using the Medline (PubMed), EMBASE, and the Cochrane Library, a systematic literature search was conducted to examine whether radiotherapy for prostate cancer increases the risk of therapy-related rectal cancer and colon cancer. Using unadjusted odds ratio and adjusted hazard ratio with their 95% confidence interval, the risk of second colorectal cancer after radiotherapy was summarized. Compared with patients unexposed to radiation, radiotherapy was correlated with an increased risk of subsequent rectal cancer. However, the colon might be free from the damage of radiation. It was noted that brachytherapy had no connection with second rectal cancer or colon cancer.