Survival benefit associated with the number of chemotherapy/biologic treatment lines in 5,129 metastatic colon cancer patients.

Abstract

559 Background: The purpose of this study was to investigate the association between multiple chemotherapy/biologic treatment lines and survival among patients diagnosed with metastatic colon cancer (mCC). Methods: Patients aged 66 to 105 years old diagnosed with mCC between 2003 and 2007 were selected for analysis from the Surveillance, Epidemiology and End Results SEER-Medicare data to determine the association between chemotherapy/biologic treatment lines and survival. We examined the survival benefits using Cox proportional-hazards regressions with inverse probability weighting method to adjust for the probability of receiving treatment lines. Results: Patients with no chemotherapy/biologic treatment had an adjusted median survival time of 6.8 months. Each chemotherapy/biologic treatment line received was associated with longer adjusted median survival times: 11.9 months, 23.2 months and 26.4 months for receipt of first-line treatment only, second-line treatment and subsequent treatment, respectively. Colon cancer-specific mortality hazard ratios (HRs) were 0.637, 0.391 and 0.350 (p<0.001 for each) for first-line, second-line and subsequent treatments, respectively. Overall mortality hazard ratios were 0.604, 0.398 and 0.364 (p<0.001 for each) for first-line, second-line and subsequent treatments, respectively. Compared to receiving only first-line treatment, proceeding to second-line treatment was associated with longer colon cancer-specific survival (HR=0.614, p<0.001) and longer overall survival (HR=0.659, p<0.001). Patients with a low-graded tumor had longer colon cancer-specific and overall survival (HR=0.746, p<0.001; HR=0.762, p<0.001, respectively) and lived 5.6 months longer. Factors associated with shorter survival were a higher age category and being female. Conclusions: Among mCC patients who survived at least 3 months from diagnosis, each chemotherapy/biologic treatment line was independently associated with significantly longer survival. Proceeding from first-line to second-line therapy or having a low-graded tumor was also associated with longer survival. Proceeding from second-line third-line therapy showed neither benefit nor harm.