Gastrointestinal Cancer

PV QA 1 - Poster Viewing Q&A 1

SU_3_2024 - Nationwide Management and Survival Outcomes of Adenocarcinoma of the Anal Canal

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

Nationwide Management and Survival Outcomes of Adenocarcinoma of the Anal Canal
R. Li1, A. Shinde1, M. Fakih2, S. Sentovich3, K. Melstrom3, S. M. Glaser1, Y. J. Chen1, K. A. Goodman4, and A. Amini1; 1Department of Radiation Oncology, City of Hope National Medical Center, Duarte, CA, 2Department of Medical Oncology, City of Hope National Medical Center, Duarte, CA, 3Department of Surgical Oncology, City of Hope National Medical Center, Duarte, CA, 4Department of Radiation Oncology, University of Colorado Denver School of Medicine, Aurora, CO

Purpose/Objective(s): Anal adenocarcinoma is a rare malignancy with poor prognosis, and no randomized data is available to guide management. Our purpose was to compare survival outcomes for 3 treatment strategies: 1) definitive chemoradiation (CRT), 2) neoadjuvant chemoradiation followed by surgery (CRT+S), and 3) upfront surgery, with or without adjuvant therapy (US).

Materials/Methods: Patients with adenocarcinoma of the anus diagnosed from 2004 to 2015 were identified using the National Cancer Database. Patients with metastatic disease and survival <90 days (to adjust for immortal time bias) were excluded. Patients receiving chemotherapy alone, RT alone or no treatment were excluded. Logistic regression was used to evaluate predictors of utilization of CRT+S. Overall survival (OS) was compared among treatment strategies using Cox proportional hazards. Two propensity score-matched (PSM) cohorts (comparing CRT+S versus CRT and CRT+S versus US) were generated using logistic regression.

Results: We identified 3,729 patients with anal adenocarcinoma at a median follow-up of 39.6 months (interquartile range: 21.2 to 69.1 months); 817 patients received local excision alone (21.9%) and were excluded from analysis. Of the remaining patients, 742 (25.5%) received CRT, 1027 (35.3%) received CRT+S, and 1143 (39.3%) received US. Patients receiving CRT+S had a 5-year OS of 60.7%, compared to 39.9% for CRT and 56.8% for US (log-rank p<0.001). On multivariate analysis, CRT alone (hazard ratio [HR] 1.68; 95% confidence interval [CI] 1.44-1.95; p<0.001) was associated with inferior OS when compared to the reference group of CRT+S; there was no significant difference in OS between CRT+S and US (HR 1.12, 95% CI 0.97-1.29; p=0.134). When stratified by clinicals AJCC stage, there was a statistically significant difference in survival among treatment strategies in stage II patients (log-rank p=<0.001) and stage III patients (p<0.001) but not in stage I patients (p=0.086). In the PSM cohorts: when comparing CRT+S to CRT in 1,294 matched patients, CRT demonstrated worse OS (HR 1.83; 95% CI 1.56-2.15; p<0.001). When comparing CRT+S to US in 1,698 matched patients, US demonstrated trend toward worse OS (HR 1.15; 95% CI 0.99-1.35; p=0.074). Predictors of treatment with CRT+S were: later year of diagnosis (p<0.001), T3-T4 disease (p<0.001), age ≥65 (p<0.001). There were no differences in utilization of CRT+S by region, facility volume, or community versus academic facility type.

Conclusion: In the largest series of anal adenocarcinoma cases to date, treatment with CRT+S was associated with a significant survival benefit compared to CRT on PSM analysis. Our findings support current national guidelines of neoadjuvant CRT followed by resection for patients with anal adenocarcinoma. However, there was significant heterogeneity in treatment approaches and only 35.3% of patients in our cohort received CRT+S.

Author Disclosure: R. Li: None. A. Shinde: None. M. Fakih: None. S. Sentovich: None. K. Melstrom: None. Y. Chen: None. K.A. Goodman: Consultant; RenovoRx.

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