Elective groin irradiation is not indicated for patients with adenocarcinoma of the rectum extending to the anal canal.

Abstract Purpose: To evaluate the inguinal nodal failure rate in patients with locally advanced rectal cancer with anal canal involvement (ACI) treated with pelvic chemoradiation without elective inguinal irradiation. Methods and Materials: From 1990 and 1998, 536 patients received preoperative or postoperative chemoradiation for rectal cancer with curative intent; 186 patients had ACI ( 2 /d). The inguinal region was specifically irradiated in only 2 patients who had documented inguinal nodal disease. Results: The median follow-up was 50 months. Only 6 of 184 ACI patients who had clinically negative inguinal nodes at presentation developed inguinal nodal recurrence (5-year actuarial rate 4%); 4 of the 6 cases were isolated. Two patients underwent successful salvage. Only 1 died of uncontrolled groin disease. Local control was achieved in both patients with inguinal nodal disease at presentation, but both died of metastatic disease. Only 3 patients with tumors >4 cm from the verge developed inguinal recurrence (5-year actuarial rate Conclusions: Inguinal nodal failure in rectal cancer patients with ACI treated with neoadjuvant or adjuvant chemoradiation is not high enough to justify routine elective groin irradiation.