Surgery followed by adjuvant chemotherapy has been standard treatment for stage III colon cancer since 1990. However, to date, clinical trials have not been conducted to determine the definitive outer time limit by which adjuvant chemotherapy should be received for optimal survival benefit. The objective of the current study was to assess the association between the receipt/timing of adjuvant chemotherapy and patient survival in clinical practice.
Residents of Alberta who were diagnosed with stage III colon adenocarcinoma in years 2000 to 2005 who underwent surgery were included in the study. Patients were identified from the Alberta Cancer Registry and were linked to hospital data and neighborhood-level socioeconomic data from the 2001 Canadian Census. Cox proportional hazards models were used to estimate hazard ratios of death according to the timing of chemotherapy.
There were 1053 patients in the study; 648 (61%) initiated adjuvant chemotherapy within 16 weeks of surgery. There was no difference in overall survival or colon cancer-specific survival between those who received adjuvant chemotherapy from 8 to 12 weeks postsurgery compared with those who received it within 8 weeks. However, those who received chemotherapy 12 to 16 weeks after surgery and those who either received it >16 weeks after surgery or received no treatment had a 43% and 107% greater risk of dying, respectively, than those who received chemotherapy within 8 weeks of surgery (hazard ratio, 1.43 [95% confidence interval, 0.96-2.13] and hazard ratio, 2.07 [95% confidence interval, 1.56-2.76], respectively). Analyses were controlled for age, year, and region of residence at diagnosis; sex; neighborhood-level socioeconomic factors; and number of comorbidities.
The results from this study were consistent with current guideline recommendations in Alberta that patients with stage III adenocarcinoma should receive chemotherapy within 12 weeks of surgery.