Chemotherapy use in early-stage anal canal squamous cell carcinoma and its impact on outcome.

Abstract

2 Background: The standard of care for non-metastatic squamous cell carcinoma of the anal canal (SCCA) is concurrent chemoradiotherapy with high rates of local control. There is some thought that perhaps chemotherapy can be omitted for the earliest stages without worse outcomes. We used the National Cancer Database (NCDB) to identify predictors of chemotherapy receipt or omission to assess the impact on outcomes. Methods: We queried the NCDB from 2004-2016 for patients with cT1N0M0 SCCA treated non-operatively with radiation with and without chemotherapy and at least 2 months of follow-up. Logistic regression was used to generate predictors of chemotherapy use. Cox regression identified predictors of survival. Propensity matching was done to help account for indication bias. Results: We identified 2,959 patients meeting eligibility, of which 8% (n = 237) were treated without chemotherapy. The vast majority (n = 2722, 92%) were recorded as having multi-agent chemotherapy. Median radiation dose was 50.4 Gy (IQR 45-54) in 28 fractions (IQR 49.4-59.4) with chemotherapy and 54.0 Gy (IQR 49.4-59.4) in 30 fractions (IQR 25-33) in those who had chemotherapy omitted. Predictors of omission of chemotherapy were older age (OR 0.66, 95% CI [0.49-0.90], P = 0.0087), higher comorbidity score (OR 0.62, 95% CI [0.38-0.99], P = 0.0442), African American race (OR 0.57, 95% CI [0.36-0.90], P = 0.0156) and more remote year of treatment (OR 1 1 for years 2004-2006). Predictors of survival were younger age (HR 1.73 for age > 58 years, 95% CI [1.41-2.11], P < 0.001), multi-agent chemotherapy use (HR 0.48, 95% CI [0.38-0.62], P < 0.0001), higher income (HR 0.57, 95% CI [0.40-0.81], P = 0.0016), female gender (HR 0.68, 95% CI [0.57-0.82], P = 0.0016), and private insurance (HR 0.54, 95% CI [0.34-0.87], P = 0.0104). After propensity matching, overall survival at 120 months for patients treated with and without chemotherapy was 86% and 65%, respectively (p < 0.0001). Conclusions: Chemotherapy is utilized the majority of the time in early stage SCCA. Being mindful of the limitations of a retrospective database analysis, our results suggest an association with worse survival outcomes when chemotherapy is omitted.