Survival of patients with anal small cell carcinoma: A perspective from the United States National Cancer Database.

e15505 Background: Anal canal malignancies, though relatively rare, are associated with significant clinical challenges. While the majority of anal cancers are squamous cell carcinomas, which typically have well-established treatment protocols and a relatively favorable prognosis, small cell carcinoma of the anal canal is a much rarer and more aggressive form of cancer. Small cell carcinoma of the anus is known for its rapid progression and a high potential for early distant metastases. This study aimed to assess the survival of patients with anal small cell carcinoma 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 score, facility type/location, comorbidities, regional lymph node involvement, metastasis at diagnosis, treatment, American Joint Committee on Cancer (AJCC) pathologic stage, and presence of ulceration. Overall survival (OS) was analyzed by Kaplan-Meier (KM) and log-rank models. Results: There were 276 persons diagnosed with small cell carcinoma and 828 persons diagnosed with squamous cell carcinoma after PSM. Small cell carcinoma had a significantly higher overall mortality rate than squamous cell carcinoma (70.65% vs 38.04%, p<.001), OS (45.121 ± 4.16 vs 120.174 ± 4.022 months, p<.001). Landmark survival rates of anal adenocarcinoma patients and rectal adenocarcinoma patients at 1 year [0.701 (95 CI 0.640-0.754) vs 0.877 (95 CI 0.852-0.899), p<.001], 2 years [0.382 (95 CI 0.321-0.443) vs. 0.773 (95 CI 0.741-0.802), p<.0001], 3 years [0.289 (95 CI 0.232-0.348) vs 0.711 (95 CI 0.676-0.743), p<.001], 5 years [0.224 (95 CI 0.171-0.282) vs 0.642 (95 CI 0.604-0.677), p<.001], and 10 years [0.121 (95 CI 0.069-0.189) vs 0.501 (95 CI 0.455-0.545), p<.001] showed significant differences. Conclusions: Small cell carcinoma had significantly higher overall mortality and survival rates at 1,2,3,5, and 10 years compared to squamous cell carcinoma. Overall mortality, mean survival time, and landmark survival rates between small cell carcinoma and squamous cell carcinoma after 1:3 propensity-score matching. Small cell carcinoma (n =276) Squamous cell carcinoma(n =828) p-value Overall mortality (n, %) 195 (70.65%) 315 (38.04%) <.001 Survival month (mean ± SE) 45.121 ± 4.16 120.174 ± 4.022 <.001 Landmark survival rates (%, 95 CI) 6-month 0.898 (0.854-0.929) 0.934 (0.914-0.950) 0.16 1-year 0.701 (0.640-0.754) 0.877 (0.852-0.899) <.001 2-year 0.382 (0.321-0.443) 0.773 (0.741-0.802) <.001 3-year 0.289 (0.232-0.348) 0.711 (0.676-0.743) <.001 5-year 0.224 (0.171-0.282) 0.642 (0.604-0.677) <.0001 10-year 0.121 (0.069-0.189) 0.501 (0.455-0.545) <.0001