The effect of dose escalation for large squamous cell carcinomas of the anal canal.

Abstract

Chemoradiation allows for organ preservation in patients with anal cancer, but patients with large tumors (> 5cm) have elevated rates of locoregional recurrence. With conformal radiation techniques, there is interest in dose escalation to decrease local recurrence in patients with large tumor size. The National Cancer Database (NCDB) was used to identify patients with anal cancer from 2004 to 2013 with tumors > 5cm. Adult patients who received definitive chemoradiation were included. Patients with prior resection were excluded. High dose was defined as greater than or equal to 5940cGy. Statistical analyses were performed using logistic regression, Kaplan-Meier, and Cox proportional hazards for overall survival (OS). In total, 1349 patients were analyzed with 412 (30.5%) receiving high-dose radiation therapy (RT). 5-year OS was 58 and 60% for high and standard dose RT, respectively (p = 0.9887). On univariate analysis, high-dose RT was not associated with improved OS (HR = 0.998, CI 0.805-1.239, p = 0.9887). On multivariate analysis, high-dose RT (HR = 0.948, CI 0.757-1.187, p = 0.6420) was not associated with improved OS but older age (HR = 1.535, CI 1.233-1.911, p = 0.0001), male sex (HR = 1.695, CI 1.382-2.080, p < 0.0001), comorbidities (HR = 1.389, CI 1.097-1.759, p = 0.0064), and long RT (HR = 1.299, CI 1.047-1.611, p = 0.0173) were significantly associated with decreased OS. There was no observed difference in OS for dose escalation of anal cancers > 5cm in this population-based analysis. Differences in local control and salvage therapy cannot be assessed through the NCDB. Whether dose escalation of large tumors may improve local control and colostomy-free survival remains an important question and is the subject of ongoing trials.