Patterns of Care and Comparison of Outcomes Between Primary Anal Squamous Cell Carcinoma and Anal Adenocarcinoma

BACKGROUND: The management of adenocarcinoma of the anus can be challenging because there are few data on outcomes and trends in its treatment to date. OBJECTIVE: This study aimed to compare and analyze the patterns of care and survival outcomes of patients with anal squamous cell carcinoma and anal adenocarcinoma. DESIGN: This was a retrospective study. SETTING: This study was performed by utilizing the National Cancer Database. PATIENTS: We selected a total of 19,539 patients between 2004 and 2014 with stage II to III squamous cell carcinoma or adenocarcinoma of the anus. INTERVENTION: The treatment groups analyzed were surgery alone, neoadjuvant chemoradiation followed by surgery, surgery followed by adjuvant chemoradiation, or definitive chemoradiation. MAIN OUTCOME MEASURES: Patient- and clinical-related factors were compared between the 2 groups. Kaplan-Meier and Cox proportional hazards regression models were used to assess overall survival. RESULTS: Of the patients studied, 18,346 (93.9%) had primary squamous cell carcinoma and 1193 (6.1%) had primary adenocarcinoma of the anus. The 5-year overall survival for stage II squamous cell carcinoma was 69.2%, and, for stage II adenocarcinoma, 5-year overall survival was 54.2% (p < 0.001). The 5-year overall survival for stage III squamous cell carcinoma was 55.2%, and, for stage III adenocarcinoma, 5-year overall survival was 32.9% (p < 0.001). On multivariable Cox regression, treatment with chemoradiation alone (HR, 0.67; p = 0.008) was associated with improved survival in squamous cell carcinoma. For the adenocarcinoma group, stage III disease (HR, 2.26; p < 0.001) and high tumor grade (HR, 1.59; p < 0.011) had a negative impact on survival, but there were no differences in survival based on the type of treatment received. LIMITATIONS: The National Cancer Database does not include information on specific chemotherapeutic or immunotherapy agents given to patients, nor does it provide the exact cause of death. CONCLUSIONS: Anal adenocarcinoma in comparison to anal squamous cell carcinoma had a lower 5-year overall survival stage for stage. Anal adenocarcinoma appears to be treated similarly to the rectal cancer paradigm, with frequent use of neoadjuvant chemoradiation. See Video Abstract at http://links.lww.com/DCR/B50.