Survival of patients with anal adenocarcinoma in comparison to rectal adenocarcinoma: A perspective from the United States National Cancer Database.

Abstract

e15504 Background: Primary adenocarcinoma of the anal canal is a rare malignancy, accounting for only 5%-10% of all anal canal cancers. Due to its aggressive nature, the treatment approach for anal adenocarcinomas is often more intensive, typically involving surgery. This study aimed to compare the survival of anal vs. rectal adenocarcinoma using a large-scale national database. Methods: Patients with anal and rectal adenocarcinoma were identified from the NCDB database from 2005 to 2022. A 1:3 propensity-score matching (PSM) was applied to persons with anal carcinoma and patients with rectal adenocarcinoma to match sex, age, race, primary payor, income, education, Charlson comorbidities, facility type/location, diagnosis years, American Joint Committee on Cancer (AJCC) TNM and overall staging, and treatment. Overall survival (OS) was analyzed by Kaplan-Meier (KM) model and log-rank tests. Results: There were 3853 persons diagnosed with anal adenocarcinoma and 196347 persons diagnosed with rectal adenocarcinoma. After PSM , anal adenocarcinoma (n=3477) and rectal adenocarcinoma (n=6779) patients had statistically significant differing overall mortality rates (48.43% vs 45.46%, p<0.01), medium OS (90.71 ± 1.74 vs 98.55 ± 1.24 months, p<0.01). The KM curves of the two groups showed a log-rank p=0.0003. Landmark survival rates of anal adenocarcinoma patients and rectal adenocarcinoma patients at 6 months [0.915 (95 CI 0.909-0.922) vs 0.919 (95 CI 0.909-0.28), p=0.63], 1 year [0.853 (95 CI 0.843-0.861) vs 0.856 (95 CI 0.844-0.868), p=0.78], 2 years [0.741 (95 CI 0.730-0.752) vs. 0.739 (95 CI 0.723-0.754), p=0.78], and 3 years [0.661 (95 CI 0.649-0.673) vs 0.645 (95 CI 0.627-0.662), p=0.27] were all comparable. In contrast, survival at 5 years [0.552 (95 CI 0.539-0.566) vs 0.509 (95 CI 0.490-0.528), p=0.01], and 10 years [0.390 (95 CI 0.374-0.406) vs 0.334 (95 CI 0.312-0.357), p<0.01] showed significant differences of better survival rates in those with anal adenocarcinoma. Conclusions: There was a significant difference in survival rate between persons with anal adenocarcinoma being higher than persons with rectal adenocarcinoma at 5 and 10 years. Overall mortality, mean survival time, and landmark survival rates between anal adenocarcinoma and rectal adenocarcinoma after 1:2 propensity-score matching. Anal adenocarcinoma(n =3477) rectal adenocarcinoma(n =6779) p-value Overall mortality (n, %) 1684 (48.43%) 3082 (45.46%) <0.01 Survival month (mean ± SE) 90.707 ± 1.74 98.549 ± 1.243 <0.01 Landmark survival rates (%, 95 CI) 6-month 0.919 (0.909-0.928) 0.915 (0.909-0.922) 0.63 1-year 0.856 (0.844-0.868) 0.853 (0.843-0.861) 0.78 2-year 0.739 (0.723-0.754) 0.741 (0.730-0.752) 0.88 3-year 0.645 (0.627-0.662) 0.661 (0.649-0.673) 0.27 5-year 0.509 (0.490-0.528) 0.552 (0.539-0.566) 0.01 10-year 0.334 (0.312-0.357) 0.390 (0.374-0.406) <0.01