Intensity-modulated radiation therapy versus 3D conformal radiation therapy for squamous cell carcinoma of the anal canal.

Abstract

494 Background: The emergence of intensity-modulated radiation therapy (IMRT) in the treatment of anal cancer has dramatically lowered the incidence of severe toxicity while maintaining excellent long-term outcomes. We compared our institutional experience using 3D conformal radiation therapy (3DCRT) versus IMRT for anal cancer. Methods: We performed a single-institution retrospective review of all non-metastatic squamous cell carcinoma anal cancer patients treated between 2000-2011 using definitive chemoradiation with curative intent. Results: This study included 89 consecutive anal cancer 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% for the 3DCRT patients (all p>0.1). More patients in the 3DCRT group required a treatment break (11 vs. 4; p=0.006), although the difference in median treatment break duration was not significant (12.2 vs. 8.0 days; p=0.35). Survival outcomes did not differ based on whether a treatment break was required (all p>0.1). Acute grade ≥3 non-hematologic toxicity was significantly decreased in the IMRT cohort (21.1 vs. 59.5%; p<0.0001). Acute grade ≥3 skin toxicity was significantly worse in the 3DCRT group (p<0.0001) while an improvement in late grade ≥3 GI toxicity was observed in the IMRT patients (p=0.012). Conclusions: This is the largest retrospective review comparing 3DCRT and IMRT for definitive treatment of anal cancer. In contrast to previously published data, this study demonstrates that while long-term outcomes do not significantly differ based on RT technique, a marked decrease in adverse effects and the need for a treatment break can be achieved using IMRT.