Colorectal cancer after irradiation for cervical cancer--case reports.

Three patients with colorectal cancer after irradiation for cervical cancer are described. One patient had two colorectal cancers. Three of the four cancers in these patients were located in the rectum and one in the sigmoid colon; all were within the irradiation field. Microscopic radiation proctocolitis was observed in all specimens. The interval between irradiation and the diagnosis of colorectal cancer was 20-24 years. It is important to consider patients who have undergone pelvic irradiation as being in a high risk group for the development of colorectal cancer. Close and long-term surveillance may be useful in these patients.