Development of flat adenoma and superficial rectal cancer after pelvic radiation.

Little is known about the early development of rectal cancer in patients with radiation-induced colitis. We describe two patients with a history of radiation colitis who developed rectal cancer. The macroscopic appearance of these lesions suggested that they arose de novo, but the histologic findings were more consistent with progression along the adenoma-to-carcinoma sequence, a hybrid of de novo lesion and adenoma. Early rectal cancer associated with chronic inflammation should be considered if a nonpolypoid adenomatous lesion is detected in a patient who has received pelvic radiation.