(OA07) Outcomes of Patients in the National Cancer Database Treated Non-Surgically For Localized Rectal Cancer

Abstract

Some patients undergo a non-operative approach to localized rectal adenocarcinoma due to medical comorbidities that render them poor surgical candidates, and some patients decline surgical intervention. Published studies reporting excellent outcomes (5-year overall survival (OS) of 70-100%) with a “wait-and-see” approach have largely been small, single-institutional, and/or highly selected. In this study, we aimed to analyze the survival outcomes and prognostic factors for patients with localized rectal adenocarcinoma in the National Cancer Database (NCDB) undergoing chemoradiation without surgical intervention. The NCDB was queried for patients with non-metastatic rectal adenocarcinoma diagnosed from 2004-2014 and treated with external beam radiotherapy to the pelvis a total dose of 45 Gray (Gy) or higher who did not undergo a surgical resection either because the patient refused surgery or because surgery was medically contraindicated or otherwise unplanned. Patient, tumor and treatment-related characteristics were compared between those treated with 45Gy-50.3Gy, 50.4Gy-54Gy and >54Gy. Survivals were compared using the Log-Rank test. Univariate and multivariate Cox regression analyses were used for univariate analysis of factors associated with OS. Survivals were then compared utilizing a robust inverse-probability-weighted regression adjustment (IPWRA) method with nearest-neighbor matching based on sex, age, tumor size, Charlson-Deyo comorbidity score, N-stage, insurance status, and chemotherapy type. 8,408 patients were included for analysis: 2122 patients (25.2%) treated with 45-50.3Gy, 4704 patients (56.0%) treated with 50.4-54Gy, and 1579 patients (18.8%) treated with >54Gy. Patients who received moderate dose escalation (50.4-54Gy) had significantly higher survival on multivariate analysis (HR 0.8 [95% CI 0.72-0.88]; p<.001) when compared with patients who received 45-50.3Gy. Patients who received >54Gy did not have a significantly different OS (HR 0.96 [95% CI 0.85-1.09]; p=.553). Factors significantly associated with worse OS on multivariate analysis included male gender, age >67 years, Charlson-Deyo score of 1 or 2+, node-positive disease, having non-private medical insurance, not receiving chemotherapy and having medical contraindications to surgery as the reason no surgical intervention was performed. The median survival was 43.2 months for all included patients, with 1-year and 5-year OS of 41.3% [95% CI 25.3-28.7%] and 83.9% [95% CI 83.1-84.7%]. After case-matching and adjusting for other significant prognostic factors on IPWRA analysis, patients receiving 50.4-54Gy had a significantly longer median, 1-year and 5-year OS (49.4 months, 85.8%, 44.7%) compared with patients receiving 45-50.3Gy or >54Gy (37.2 months, 79.2%, 38.4% and 34.2 months, 84.5%, 35.3%, respectively; Log rank p-value <.0001). In an unselected group of patients treated at NCDB-participating institutions, survival rates with a non-surgical approach to non-metastatic rectal adenocarcinoma are much lower than those reported in well-selected single-institutional studies. Moderate dose escalation from 50.4-54Gy seems to be associated with better overall survival compared with doses <50.4Gy or >54Gy after adjusting for other significant covariants. These data may be useful in counseling patients who either refuse surgery or who are not surgical candidates on their expected outcomes with a non-surgical approach.