Intensity-modulated Radiation Therapy for Anal Cancer: Results From a Multi-Institutional Retrospective Cohort Study

Objectives: To assess toxicity and efficacy of intensity-modulated radiation therapy (IMRT) for anal cancer.

Methods: Records of 152 patients were reviewed retrospectively from multiple institutions. Data on disease control and toxicity were collected as well as patient and treatment characteristics. Acute (<6 mo) and late (≥6 mo) severe toxicity (grade ≥3) were graded. Four patients were excluded due to the presence of metastatic disease or stage TX. Late toxicity data were available for 120 patients.

Results: Median cumulative IMRT dose was 51.25 Gy (median, 28 fractions). All but 2 patients received chemotherapy. With median follow-up of 26.8 months, local control at 3 years was 87%, worse for patients with T3-T4 than T1-T2 disease on univariate analysis (79% vs. 90%; P=0.04). Regional control, distant control, and overall survival were 97%, 91%, and 87%, respectively, at 3 years. Nodal status was associated with regional control, distant control, and overall survival (P<0.01 for each). Most common severe acute toxicity was hematologic (41%), skin (20%), and gastrointestinal tract (11%). Two grade 5 toxicities occurred (hematologic and gastrointestinal tract). Severe late toxicity affected skin (1%) and gastrointestinal tract (3%).

Conclusions: IMRT with chemotherapy resulted in excellent local control. Although T stage predicted worse local control, most T3-T4 disease was controlled with IMRT. Nodal status predicted regional and distant control and overall survival. Severe toxicity was acceptable.