Intensity-Modulated Radiation Therapy vs. 3D Conformal Radiation Therapy for Squamous Cell Carcinoma of the Anal Canal.

Purpose: We compared our institutional experience using 3D conformal radiation therapy (3DCRT) vs. IMRT (intensity-modulated radiation therapy) for anal cancer.

Methods: We performed a single-institution retrospective review of all patients with squamous cell carcinoma anal cancer treated from September 2000 through September 2011, using definitive chemoradiation with curative intent.

Results: This study included 89 consecutive patients (37 3DCRT, 52 IMRT). Median follow-up for all patients, IMRT patients alone, and CRT patients alone was 26.5 months (range, 3.5-133.6), 20 months (range, 3.5-125.5), and 61.9 months (range, 7.6-133.6), respectively. Three-year overall survival (OS), progression-free survival (PFS), locoregional control (LRC), and colostomy-free survival (CFS) were 91.1%, 82.3%, 90.8%, and 91.3% in the IMRT cohort and 86.1%, 72.5%, 91.9%, and 93.7% in the 3DCRT group (all P > .1). More patients in the 3DCRT group required a treatment break (11 vs. 4; P = .006), although the difference in median treatment break duration was not significant (12.2 vs. 8.0 days; P = .35). Survival did not differ based on whether a treatment break was needed (all P > .1). Acute grade ≥3 nonhematologic toxicity was decreased in the IMRT cohort (21.1 vs. 59.5%; P < .0001). Acute grade ≥3 skin toxicity was worse in the 3DCRT group (P < .0001), whereas an improvement in late grade ≥3 gastrointestinal (GI) toxicity was observed in the IMRT patients (P = .012).

Conclusions: This study is the largest thus far to compare 3DCRT and IMRT for definitive treatment of anal cancer. Although long-term outcomes did not significantly differ based on RT technique, a marked decrease in adverse effects and the need for a treatment break was achieved with IMRT.