Gastrointestinal Cancer

PV QA 1 - Poster Viewing Q&A 1

SU_3_2022 - Survival Outcomes and Patterns of Management for Anal Adenocarcinoma: An Analysis of the National Cancer Data Base

Sunday, October 21
1:15 PM - 2:45 PM
Location: Innovation Hub, Exhibit Hall 3

Survival Outcomes and Patterns of Management for Anal Adenocarcinoma: An Analysis of the National Cancer Data Base
G. Lewis1, W. Haque2, E. B. Butler2, and B. S. Teh2; 1Department of Radiation Oncology, UTMB-Galveston, Galveston, TX, 2Department of Radiation Oncology, Houston Methodist Hospital, Houston, TX

Purpose/Objective(s): Anal adenocarcinoma (AA) is an uncommon malignancy and is thought to carry a worse prognosis than anal squamous cell carcinoma (AS). There are currently no evidence-based recommendations on the proper management of AA, though it is typically treated similarly to a low-lying rectal adenocarcinoma. The purpose of this study was to evaluate the survival outcomes and patterns of management of AA using the National Cancer Data Base (NCDB) to determine if specific treatment paradigms result in improved outcomes. We hypothesize AA has worse survival outcomes and a different pattern of management compared to AS. Materials/Methods: The NCDB was queried (2004-2015) for patients with newly-diagnosed non-metastatic anal cancer treated with upfront chemoradiation. Patients were divided into two groups (either AA or AS) based on their histology. Statistics included Fisher’s exact or χ2 test to analyze categorical proportions in demographic information between adenocarcinoma and squamous cell carcinoma, Kaplan-Meier analysis to evaluate overall survival (OS), and Cox proportional hazards modeling to determine variables associated with OS. Results: A total of 24,461 patients met selection criteria, of which 1,183 (4.8%) had adenocarcinoma, while 23,278 (95.2%) had squamous cell carcinoma. As compared to squamous cell carcinoma, patients with AA were more likely to present at an older age (>65), present at a more advanced stage, be of male sex, and undergo abdominoperineal resection (APR). Out of AA patients undergoing APR, 96.2% underwent APR within 6 months of completion of upfront chemoradiation (CRT). The median OS of AA patients was 72.5 months versus 143.8 months (P<0.001) for patients with AS. Amongst all AA patients, survival was greater for those undergoing APR within 6 months of CRT (88.3 months vs 58.1 months, P<0.001). On multivariate analysis, adenocarcinoma histology, age ≥55, male sex, T stage ≥3, Charlson-Deyo Score ≥1, lower socioeconomic status, and receipt of treatment at a non-academic facility were associated with worse OS. Conclusion: Adenocarcinoma of the anus is a rare and highly aggressive cancer. This is the largest study of AA to date and our findings suggest that this disease be managed similar to low- lying rectal cancers, as chemoradiation followed by prompt abdominoperineal resection is associated with improved survival outcomes.
Author Disclosure: G. Lewis: None. E. Butler: Chair; Houston Methodist Hospital, Department of Radiation Oncology.

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