Utilization of intensity modulated radiation therapy for anal cancer in the United States.

Background: Chemoradiotherapy for anal cancer (AC) can incur substantial treatment-related toxicities. Whereas radiotherapy (RT) for AC has historically been delivered with two- or three-dimensional conformal RT (2D/3DCRT) techniques, intensity-modulated RT (IMRT) is associated with improved target conformality and lower doses to organs-at-risk (OARs). This is the first investigation to date evaluating trends of IMRT utilization in the United States.

Methods: The National Cancer Data Base (NCDB) was queried [2004-2015] for AC patients receiving definitive chemoradiotherapy with a defined RT technique (3DCRT versus IMRT). Following analysis based on temporal trends, multivariate logistic regression determined factors associated with receipt of IMRT. Secondarily, Kaplan-Meier analysis compared OS between the 3DCRT and IMRT groups, and Cox proportional hazards modeling determined variables associated with OS.

Results: Altogether, 11,396 patients met study criteria; 1,288 (11%) were treated with 3DCRT and 10,108 (89%) with IMRT. Temporally, utilization of IMRT rose significantly, from 28% in 2004 to 96% in 2015, corresponding with a progressive decrease in 3DCRT usage. IMRT was more likely delivered in node-positive disease, at academic centers, and in southern/western regions (P<0.05 for all). T3-4 disease was less likely to receive IMRT (P<0.05). As expected, there were no OS differences based on RT technique (P=0.402). Predictors of worse OS included advancing age, male gender, increasing comorbidities, advanced T-stage, and nodal positivity (P<0.05 for all). In addition to racial- and insurance-related factors, receipt of therapy at academic centers independently predicted for improved OS (P<0.05 for all).

Conclusions: Based on findings from this large, contemporary dataset, IMRT is now the most widely utilized RT technique for AC, and 3DCRT is used in a very small minority of patients. IMRT utilization is impacted by multiple characteristics, such as disease- and regional-related factors. These observations have implications for payers and insurance coverage; improved survival at academic centers has ramifications for patient counseling.