Time trends in chemotherapy (administration and costs) and relative survival in stage III colon cancer patients - a large population-based study from 1990 to 2008

Background. Use of adjuvant chemotherapy for stage III colon cancer has increased since several trials have shown the beneficial effect on survival. In this population-based study we show time trends in the administration and costs of chemotherapy and relative survival of patients with stage III colon cancer. Methods. All patients surgically treated for adenocarcinoma of the colon stage III between 1990 and 2008 in The Netherlands were included. Relative survival (using period analyses) and Relative Excess Risks of death (RER) were calculated. The costs of chemotherapy were estimated. Results. A total of 24 111 colon cancer patients with stage III were included in the cohort. The administration (from 9.5% in 1990 to 61.8% in 2008; p < 0.001) and costs of chemotherapy (from (sic)38 467 in 1990 to (sic)3 876 150 in 2008) increased during the study period. Multivariable relative survival improved for patients receiving adjuvant chemotherapy (RER 0.93; 95% CI 0.92-0.94; p < 0.001). In contrast, relative survival remained stable for patients, younger than 80 years, who did not receive chemotherapy (RER 1.00; 95% CI 1.00-1.01; p = 0.3). Patients aged 80 years and older without chemotherapy, relative survival increased during the study period (RER 0.98; 95% CI 0.97-0.99; p < 0.001). Conclusions. The administration, the costs of chemotherapy and the survival of patients with stage III colon cancer increased over time. Whereas the costs and administration of chemotherapy increased extensively, relative survival increased to a lesser extent. For patients treated with adjuvant chemotherapy relative survival increased equally in all age groups.