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 either because they decline surgery or because their medical comorbidities preclude surgical intervention. Published studies reporting excellent outcomes with a "wait-and-see" approach have been small and highly-selected. We aimed to analyze survival outcomes and prognostic factors for patients with localized rectal adenocarcinoma in the National Cancer Database (NCDB) undergoing definitive radiation without surgical intervention. The NCDB was queried for patients with non-metastatic rectal adenocarcinoma treated with definitive radiotherapy who did not undergo a surgical resection either because the patient refused surgery, surgery was medically contraindicated, or surgery was otherwise unplanned. Patient, tumor and treatment-related characteristics were compared between those treated with 45-50.3 Gray (Gy), 50.4-54 Gy and >54 Gy. Survivals were compared using the Log-Rank test. Univariate and multivariate Cox regression analyses were performed. Survivals were then compared utilizing a robust inverse-probability-weighted regression adjustment method with nearest-neighbor matching. Eight thousand four hundred and eight patients were included for analysis. After case-matching and adjusting for significant prognostic factors, patients receiving 50.4-54 Gy had a significantly longer median, 1- and 5-year overall survival (OS) (49.4 months, 85.8%, 44.7%) compared with patients receiving 45-50.3 or >54 Gy (37.2 months, 79.2%, 38.4% and 34.2 months, 84.5%, 35.3%, respectively; Log rank P value <0.0001). 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 50.4-54 Gy was associated with better OS compared with doses <50.4 Gy or >54 Gy after adjusting for significant covariant.