Delivery of Adjuvant Oxaliplatin for Colon Cancer: Insights From Routine Clinical Practice

Background: Adjuvant oxaliplatin is now a standard treatment option for patients with early-stage colon cancer. However, treatment delivery and outcomes achieved in routine practice are not well described. Methods: All cases of colon cancer diagnosed in Ontario from 2002 to 2008 were identified using the Ontario Cancer Registry. Pathology reports were obtained for a 25% random sample to identify stage II and III cases; patients treated with adjuvant oxaliplatin were included in this analysis. Treatment records were reviewed to identify oxaliplatin dose reductions or omissions. Modified Poisson regression was used to evaluate factors associated with dose reduction/omission. Cox proportional hazards model was used to explore factors associated with cancer-specific survival (CSS) and overall survival (OS). Results: The study population included 532 patients; 88% (469/532) had stage Ill disease. The mean/median number of oxaliplatin cycles delivered was 10/12. A dose reduction/omission of oxaliplatin occurred in 54% of cases (288/532), and the dose was subsequently escalated in 34% of these (97/288). Women were more likely than men to have dose reduction/omission (relative risk, 1.29; 95% CI, 1.10-1.51). Dose reduction/ omission was not associated with inferior CSS (hazard ratio [HR], 0.76; 95% CI, 0.51-1.14) or OS (HR, 0.81; 95% CI, 0.59-1.13). Five-year CSS and OS of all cases were 77% (95% CI, 72-81) and 72% (95% CI, 68-76), respectively. On-treatment mortality rates were 1% and 3% within 30 and 90 days of oxaliplatin, respectively. Conclusions: Dose reductions of adjuvant oxaliplatin are common in routine practice but are not associated with inferior survival. Long-term survival achieved in the general population is comparable to the results of clinical trials.