(OA10) Patterns of Care and Factors Predictive of Overall Survival In Metastatic Rectal Cancer

Abstract

Results: 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]; pZ.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 pvalue <.0001). Conclusions: In an unselected group of patients treated at NCDBparticipating 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.