Patterns of care and outcomes of intensity modulated radiation therapy versus three-dimensional conformal radiation therapy for anal cancer.

BACKGROUND: Definitive chemoradiation is the standard of care for anal squamous cell carcinoma. Compared to three-dimensional conformal radiation therapy (3DCRT), intensity modulated radiation therapy (IMRT) is increasingly becoming the preferred technique in order to reduce treatment related toxicity. The objective of this study is to evaluate practice patterns and total radiation treatment times of two radiation modalities. METHODS: A total of 6,966 patients with non-metastatic squamous cell carcinoma of the anus who received definitive chemoradiation were queried from the National Cancer Database (NCDB) from 2004-2013. Logistic regression was performed to assess for predictors of IMRT receipt. The Kaplan-Meier method and multivariable Cox regression analysis was used to assess overall survival (OS). RESULTS: In total, 3,868 (55.5%) received 3DCRT and 3,098 (44.5%) received IMRT. Total radiation treatment time was <7 weeks for 54.3% of patients treated with 3DCRT versus 63.8% of patients treated with IMRT. On multivariable logistic regression, positive clinical nodes (OR =1.20, P=0.001) and treatment at an academic facility (OR =1.23, P<0.001) were associated with increased likelihood of receiving IMRT. The 5-year OS was 73.0% for 3DCRT and 73.9% for IMRT (P=0.315). On multivariable analysis, total radiation treatment time ≥7 weeks (HR =1.33, P<0.001) was associated with worse survival while radiation modality (3DCRT vs. IMRT) did not impact survival (HR =0.98, P=0.763). CONCLUSIONS: IMRT has dramatically increased in utilization from 2% to 65% during the study time period. IMRT was less likely than 3DCRT to have prolonged radiation treatment times, which was associated with worse survival.