Gastrointestinal Cancer

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SU_2_2017 - Patterns of Care and Comparison of Outcomes Between Primary Anal Squamous Cell Carcinoma and Anal Adenocarcinoma

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

Patterns of Care and Comparison of Outcomes Between Primary Anal Squamous Cell Carcinoma and Anal Adenocarcinoma
A. Kavi1, A. Lee1, N. Sheth2, P. Adedoyin1, A. J. Lederman1, and D. Schreiber1; 1Department of Radiation Oncology, SUNY Downstate Medical Center, Brooklyn, NY, 2SUNY Downstate Medical Center, Brooklyn, NY

Purpose/Objective(s): To compare and analyze the patterns of care and survival outcomes of patients with anal squamous cell carcinoma (SCC) and anal adenocarcinoma (AC).

Materials/Methods: The National Cancer Database was explored to identify patients diagnosed with primary stage II-III SCC or AC of the anus from 2004-2014. Patients were included if they were treated with surgery alone (S), neoadjuvant chemoradiation followed by surgery (CRT+S), surgery followed by adjuvant chemoradiation (S+CRT), or definitive chemoradiation (CRT). Surgery was defined as abdominal perineal resection while chemoradiation was defined as starting either modality within 14 days of each other. Median radiation dose was 5400cGy. Patient- and clinical-related factors were compared between the two groups. Overall survival (OS) was obtained and treatment groups compared via the log-rank test after stratifying by histology. Univariate and multivariate Cox proportional hazards regression models were performed to assess the impact of covariates on survival for each group.

Results: There were 19,539 patients included in this study, of which 18,346 (93.9%) had primary SCC and 1,193 (6.1%) had primary AC of the anus. Median follow-up of living patients was 47.6 months. Of the SCC group, 96.2% received CRT alone (p<0.001). The 5-year OS by treatment for SCC was 48.2% for S alone, 46.3% for CRT+S, 60.8% for S+CRT, and 67.8% for CRT alone (p<0.001). For the AC group, 38.8% received CRT alone, 44.5% received CRT+S, and 12.5% received S alone (p<0.001). The 5-year OS by treatment for AC was 57.6% for S alone, 64.6% for CRT+S, 51.7% for S+CRT, and 39.2% for CRT alone (p<0.001). There were differences in survival between SCC and AC comparing stage for stage. The 5-year OS for stage II SCC was 69.2% and for stage II AC was 54.2% (p<0.001). Five-year OS for stage III SCC was 55.2% and for stage III AC was 32.9% (p<0.001). On multivariable Cox regression, for SCC, age > 65 (HR 1.52, 95% CI 1.35-1.72), tumor size > 5 cm (HR 1.46, 95% CI 1.17-1.81), and stage III disease (HR 1.62, CI 95% 1.48-1.77) were found to have a negative impact on survival (p≤0.001), whereas, treatment with CRT alone (HR 0.67, 95% CI 0.50-0.90, p=0.008) had a positive impact on survival. For the AC group, age > 65, (HR 2.11, 95% CI 1.26-3.55, p<0.005) tumor size 2.5 – 5 cm (HR 2.44, 95% CI 1.16-5.13, p<0.019), tumor size > 5 cm (HR 2.78, 95% CI 1.33-5.84, p<0.007), stage III disease (HR 2.26, 95% CI 1.58-3.24, p<0.001), and high tumor grade (HR 1.59, 95% CI 1.11-2.26, p<0.011) had a negative impact on survival.

Conclusion: Anal AC when compared to anal SCC had a lower 5-year OS stage for stage. Anal AC appears to be treated similarly to the rectal cancer paradigm, with frequent use of neoadjuvant CRT. When definitive CRT was used, outcomes were very poor, with a 5-year OS of 39%, though this may be due to patient intolerance of surgery or other co-morbidities and warrants further investigation.

Author Disclosure: A. Kavi: None. A. Lee: None. N. Sheth: None. P. Adedoyin: None. A.J. Lederman: None. D. Schreiber: None.

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