Early Discontinuation but Not the Timing of Adjuvant Therapy Affects Survival of Patients With High-Risk Colorectal Cancer: A Population-Based Study

Abstract

Adjuvant therapy results in significant improvement in survival of patients with high-risk colorectal cancer. Little is known about the significance of timing and early discontinuation of adjuvant treatment in such patients. Our study aims to determine the prognostic impact of timing and completion of adjuvant therapy in patients with high-risk colorectal cancer. Medical records of patients with stage III colon and stage II/III rectal cancer diagnosed between 1993 and 2000 in the province of Saskatchewan were reviewed. Cox proportional hazards models were used to analyze the impact of timing and completion of adjuvant therapy on survival. Six hundred sixty-three eligible patients with a median age of 66 years were identified. Sixty-five percent patients received adjuvant <56 days after surgery and 79% patients completed planned treatment. Median follow-up was 54.6 months. Five-year disease-free survival and overall survival of patients who received adjuvant therapy <56 days after surgery was 54.6% and 59.5%, respectively, compared with 51.9% and 57.1%, respectively, of patients who received therapy ≥56 days after surgery (P = NS). The five-year disease disease-free survival and overall survival of patients who completed planned treatment was 56.7% and 62.3%, respectively, compared with 42.1% and 45%, respectively, of patients who required early treatment discontinuation (P < .0001). On multivariate analysis, age ≥65 years, T4 tumor, grade 3 cancer, node-positive disease, rectal tumor, and early treatment discontinuation were identified as poor prognostic factors. Although time to adjuvant therapy following surgical resection did not impact the outcomes, failure to complete planned therapy was associated with adverse prognosis.