Anal Squamous Cell Carcinoma: Radiation Therapy Alone Must Be Avoided

Anal squamous cell carcinoma (ASCC) is the most common histological subtype of anal cancer. Rates have been observed to increase in recent years. Combined chemoradiotherapy (CCRT) is currently the gold standard of treatment. The aim of this study is to assess ASCC prevalence, treatment trends, and overall survival (OS) in the United States.

Patients diagnosed with stage I-IV ASCC were identified from the National Cancer Database from 2004 to 2015. The primary outcome was 5-year OS, which was analyzed using Kaplan-Meier survival curves, log-rank test, and Cox proportional hazards models.

34,613 cases were included (stage I: 21.45%; II: 41.00%; III: 31.62%; IV: 5.94%), with an increasing trend in prevalence. CCRT was the most used treatment. Multimodal treatment, combining surgery with CCRT, offered the best OS rates for stage I, II, and IV cancers (I: 84.87%; II: 75.12%; IV: 33.08%), comparable with survival of stage III patients treated with CCRT (III: 61.14%). Radiation alone had the worse OS rates, and on adjusted analysis, radiation treatment alone had the greatest risk of mortality (I: hazard ratio, 2.01; 95% confidence interval, 1.14-3.54; P = 0.016; II: 2.05, 1.44-2.93, P < 0.001; IV: 1.99, 0.99-4.02, P = 0.054).

ASCC has increased in prevalence, notably in stage III and IV disease. Although CCRT is the most commonly used treatment type for all stages of ASCC, multimodal treatment offers better OS in stages I, II, and IV. Treatment with radiation alone offers the worst OS no matter the stage and should no longer be used as a solitary treatment modality.