180 Background: Current guidelines recommend six months of chemotherapy (CT) for stage III colon cancer and consideration for high-risk stage II colon cancer. No previous studies have examined the impact of CT gaps on survival. This retrospective study examines determinants of CT gaps and the effect of gaps on survival. Methods: Using national Surveillance, Epidemiology, and End Results registry-Medicare linked data, high-risk stage II and stage III colon cancer patients diagnosed between 2000-2007 who received surgery and CT were identified. CT duration and gaps were calculated. CT gap was defined as 30 to 90 days between two CT claims. Data on demographics, clinical factors (comorbidity, tumor grade), and treatment factors (time to CT initiation, toxicity, hospitalization) were collected. Multivariable regression was used to examine factors associated with gaps. Cox proportional hazards analysis examined the effect of gaps on risk of mortality. Results: 7,371 patients were identified. Median age was 75 (IQR: 71-79); 47% were male. Among all patients, 1,803 (24%) had a gap. 2,674 patients (36%) received 5 to 7 months of CT, of which 469 (18%) had a gap. Multivariable regression analysis showed that patients who were black (OR 1.3, 95% CI: 1.1-1.7), stage III (1.2, 1.0-1.3), had toxicity (1.3, 1.1-1.4), or had 3 to 4 months of CT (vs. 5-7 months, 2.6, 2.3-3.0) were more likely to have a gap, while patients with a more recent diagnosis in 2007(vs. 2000, 0.6, 0.5-0.8) were less likely to have a gap. 3-year cancer-specific survival was the same in all patients with CT gaps compared with no gaps (80%, 95% CI: 78%-82% vs. 81%, 95% CI: 80%-82%). Cox proportional hazard models showed that patients with gaps did not have increased risk of mortality (HR 0.99, 0.89-1.1) adjusting for patient and clinical factors. Among those who received 5 to 7 months of CT, 3-year survival was 8% lower in patients with gaps compared to those with no gaps (80%, 95% CI: 75%-83% vs. 88%, 95% CI: 87%-90%). Conclusions: Nearly 25% of high-risk stage II and III patients who received CT had a gap. CT gaps were associated with worse survival in patients who received 5 to 7 months of CT. Interventions to improve CT toxicity management and reduce gaps are needed to maximize the benefit of CT.
Review: Combination therapy in high-risk stage II or stage III colon cancer: current practice and future prospects
