Survival and time interval from surgery to start of chemotherapy among colon cancer patients.

Colon cancer is one of the most common cancers diagnosed within the United States. Survival with stage III colon cancer has improved with the addition of adjuvant chemotherapy as a component of treatment. Some patients with stage II colon cancer also receive chemotherapy. There has been a dearth of research about the effect of the timing of chemotherapy on survival. Recent studies have shown a possible link between the length of time between surgery and chemotherapy treatment and probability of survival. The present study investigated the association of chemotherapy with survival, and the association of initiating treatment within 45 days vs. more than 45 days after surgery with survival. We used Kaplan-Meier methods and multivariable Cox proportional hazards models to analyze the association of treatment and its timing with survival among patients who were listed as diagnosed with and having surgery for stage II or III colon cancer from 1997 to 1999 in the Massachusetts Cancer Registry. All tests were two-sided. Of the 3,006 patients who met the eligibility criteria, 61% were still alive on December 31, 2003. Patients who received chemotherapy after surgery were more likely to survive than those who received surgery alone. However, those who received chemotherapy within 45 days did not have better survival than those who began treatment later (hazard ratio 1.16, 95% CI 0.92-1.47). Among stage II colon cancer patients alone, those who received chemotherapy after surgery had significantly lower mortality than those who received surgery alone (hazard ratio 0.75, 95% CI 0.58-0.96). Adjuvant chemotherapy treatment after surgery for stage II and III colon cancer cases, but not the timing of its initiation, was associated with improved survival. Our study shows a benefit of chemotherapy for patients with stage II disease.