Comparative effectiveness of different chemotherapeutic regimens on survival of people aged 66 and older with stage III colon cancer: a "real world" analysis using Surveillance, Epidemiology, and End Results-Medicare data.

OBJECTIVES

To compare the effectiveness and utilization trends of irinotecan (IRI)-based and oxaliplatin (OX)-based regimens with those of 5-fluorouracil and leucovorin (5FU/LV) alone in people aged 66 and older with Stage III colon cancer.

DESIGN

Retrospective cohort study.

SETTING

Data from the Surveillance, Epidemiology, and End Results (SEER)-Medicare data.

PARTICIPANTS

People with Stage III surgically resected colon cancer who received adjuvant chemotherapy were categorized into 5FU/LV-alone (n = 3,581), OX-based regimen (n = 814), and IRI-based regimen (n = 219) subgroups.

MEASUREMENTS

Multivariable Cox proportional hazards models examined the effect of chemotherapies on overall survival, colon cancer-specific survival, and non-colon cancer-specific survival.

RESULTS

Use of the OX-based regimen increased, and use of the 5FU/LV-alone and IRI-based regimens decreased over time. OX was statistically significantly associated with longer overall survival (hazard ratio (HR) = 0.73, 95% confidence interval (CI) = 0.62-0.86, P < .001) and colorectal cancer-specific survival (HR = 0.39, 95% CI, 0.28-0.55, P < .001) than 5FU/LV alone. There was a greater risk of overall mortality (HR = 1.38, 95% CI = 1.14-1.67, P<.001) and cancer-specific mortality (HR = 1.92, 95% CI=1.49-2.47, P < .001) associated with IRI than with 5FU/LV. The superiority of OX on survival was found in participants aged 66 to 79 but not in those aged 80 and older.

CONCLUSION

This "real world" comparative effectiveness research extends randomized controlled trial results by documenting the relative survival benefit of OX in older adults with Stage III colon cancer. The associated shift in treatment away from 5FU/LV alone or IRI toward OX is consistent with evidence-based medicine from real-world outcomes research.