Elective inguinal node irradiation in early-stage T2N0 anal cancer: prognostic impact on locoregional control.

PURPOSE: To evaluate the influence of elective inguinal node radiation therapy (INRT) on locoregional control (LRC) in patients with early-stage T2N0 anal cancer treated conservatively with primary RT.

METHODS AND MATERIALS: Between 1976 and 2008, 116 patients with T2 node-negative anal cancer were treated curatively with RT alone (n=48) or by combined chemoradiation therapy (CRT) (n=68) incorporating mitomycin C and 5-fluorouracil. Sixty-four percent of the patients (n=74) received elective INRT.

RESULTS: Over a median follow-up of 69 months (range, 4-243 months), 97 (84%) and 95 patients (82%) were locally and locoregionally controlled, respectively. Rates for 5-year actuarial local control, LRC, cancer-specific, and overall survival for the entire population were 81.7% ± 3.8%, 79.2% ± 4.1%, 91.1% ± 3.0%, and 72.1% ± 4.5%, respectively. The overall 5-year inguinal relapse-free survival was 92.3% ± 2.9%. Isolated inguinal recurrence occurred in 2 patients (4.7%) treated without INRT, whereas no groin relapse was observed in those treated with INRT. The 5-year LRC rates for patients treated with and without INRT and with RT alone versus combined CRT were 80.1% ± 5.0% versus 77.8% ± 7.0% (P=.967) and 71.0% ± 7.2% versus 85.4% ± 4.5% (P=.147), respectively. A trend toward a higher rate of grade ≥3 acute toxicity was observed in patients treated with INRT (53% vs 31%, P=.076).

CONCLUSIONS: In cases of node-negative T2 anal cancer, the inguinal relapse rate remains relatively low with or without INRT. The role of INRT in the treatment of early-stage anal carcinoma needs to be investigated in future prospective trials.