Gastrointestinal Cancer

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SU_5_2049 - Definitive Pelvic Radiation Therapy and Survival of Patients With Newly Diagnosed Metastatic Anal Cancer

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

Definitive Pelvic Radiation Therapy and Survival of Patients With Newly Diagnosed Metastatic Anal Cancer
Y. Wang Jr1, X. Yu2, N. Zhao3, J. Wang4, C. Lin3, D. L. Schwartz1, N. V. Dubal1, B. Somer5, M. T. Ballo6, and N. A. VanderWalde1; 1Department of Radiation Oncology, West Cancer Center, University of Tennessee Health Science Center, Memphis, TN, 2Department of Preventive Medicine, University of Tennessee Health Science Center and School of Public Health, University of Memphis, Memphis, TN, 3Department of Radiation Oncology, University of Nebraska Medical Center, Omaha, NE, 4Department of Preventive Medicine, University of Tennessee Health Science Center, Memphis, TN, 5Department of Hematology/Oncology, West Cancer Center, University of Tennessee Health Science Center, Memphis, TN, 6West Cancer Center, University of Tennessee Health Science Center, Memphis, TN

Purpose/Objective(s): There is growing evidence that local therapies, including radiotherapy (RT) may increase patient’s survival for some types of metastatic cancers. We hypothesized that definitive pelvic RT with chemotherapy would associate with increased overall survival (OS) than chemotherapy alone for patients with metastatic anal cancer (MAC).

Materials/Methods: The National Cancer Database (NCDB) was analyzed to evaluate OS for newly diagnosed MAC patients treated with chemotherapy with or without pelvic RT. Those without treatment, treated with surgery, or without baseline variables were excluded. OS was analyzed using the Kaplan-Meier method, log-rank test, Cox proportional hazards models, landmark analysis and propensity score-matched analysis.

Results: From 2004 to 2014, 1,457 patients with MAC treated with chemotherapy were identified. Among them, 1020 (70%) received pelvic chemo-radiation (CRT). At a median follow-up of 17.3 months, CRT was associated with improved median survival (21.3 vs 15.6 months) and 2-year OS (47% vs 34%) on univariate (P < 0.001) and multivariate analysis (HR, 0.70; 95% CI, 0.61-0.81; P < 0.001) than chemotherapy alone. Propensity score analysis with matched baseline characteristics (including age, year of diagnosis, race, grade, comorbidity score, T stage, N stage, facility type, insurance status and metastatic site) re-demonstrated superior median (21.3 vs 15.9 months) and 2-year OS (46% vs 34%) with CRT (P < 0.001). Landmark analyses limited to long-term survivors of ≥1, ≥2, and ≥4 years demonstrated improved OS with CRT in all subsets (all P < 0.05). RT with therapeutic doses (≥ 45 Gy) had longer median survival than palliative doses (< 45 Gy) and chemotherapy alone for analysis of all patients (24.9 vs 10.9 vs 15.6 months, P < 0.001), as well as in the propensity score-matched patients (24.6 vs 10.3 vs 15.9 months, P < 0.001). Subgroup analysis demonstrated the benefit of pelvic RT was present not only among those with distant lymph node metastasis (HR 0.63; 95% CI, 0.41-0.98; p = 0.04), but also those with distant organ disease (HR 0.74; 95% CI, 0.61-0.89; P < 0.001). Finally, among patients receiving RT, 803 (78%) had concurrent CRT and they had slightly better median survival (22.8 vs 18.9 months) than non-concurrent CRT, which ruled out the bias in which RT was selectively delivered to patients who received chemotherapy first and had good response.

Conclusion: In this large contemporary analysis, newly diagnosed metastatic anal cancer patients who received definitive pelvic radiation with chemotherapy lived significantly longer than patients who received chemotherapy alone. Prospective trials evaluating definitive local radiotherapy for metastatic anal cancer are warranted.

Author Disclosure: Y. Wang: None. X. Yu: None. C. Lin: Research Grant; Eppley Cancer center at UNMC, DHHS/NIH/NCI. To purchase a research drug; Eppley Cancer center at UNMC. Focus is on translational studies that address basic and clinical issues of importance to improving outcome of patients with pancreatic cancer. Role: Project Leader Title of the project: Novel Target(s) in the Radiosensitization of Pancreatic Cancer; DHHS/NIH/NCI. Vice chair of Research; University of Nebraska Medical Center. Colorectal track leader; ASCO 2018 annual meeting. D. Schwartz: None. N.V. Dubal: None. B. Somer: None. N.A. VanderWalde: None.

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