Cost-effectiveness of adjuvant chemotherapy for patients with high-risk stage II and stage III colon cancer in South Africa.

Abstract

6599 Background: Colon cancer (CC) incidence is rising globally, and case fatality rates are greatest in low-income settings, such as South Africa (SA). Adjuvant chemotherapy is standard of care for high-risk stage II and stage III CC in the US. We evaluated the cost-effectiveness of adjuvant chemotherapy for CC in SA public hospitals. Methods: We developed a decision-analytic Markov model comparing lifetime costs and outcomes for 60-year-old high-risk stage II and stage III CC patients treated in a SA public hospital with no adjuvant chemotherapy, versus: capecitabine and oxaliplatin (CAPOX) for 3 or 6 months or capecitabine for 6 months. High-risk stage II was defined as ≥1 of: T4 disease; poorly differentiated tumor; lymphovascular/perineural invasion; <12 lymph nodes dissected, bowel obstruction/perforation. Transition probabilities were derived from clinical trials estimating toxicity, disease recurrence, and survival. Costs from a SA societal perspective and utility estimates were obtained from literature and local expert opinion. The primary outcome was the incremental cost-effectiveness ratio (ICER) in international dollars (I$) per disability-adjusted life year (DALY) averted, with a willingness-to-pay (WTP) threshold equal to 2021 GDP/capita of SA (I$13,764). Results: CAPOX for 3 months was the cost-effective strategy for stage III CC at a lifetime cost of I$5,284 and 5.55 DALYs averted, compared to no adjuvant treatment. All other strategies were absolutely dominated. For high-risk stage II CC, CAPOX for 3 months was the cost-effective strategy (ICER = I$711/DALY averted). No adjuvant chemotherapy was on the efficiency frontier, with a lower lifetime cost, but no DALYs averted. The results of one-way deterministic sensitivity analyses showed that the model is most sensitive to CC recurrence rate. In a probabilistic sensitivity analysis, CAPOX for 3 months was optimal in 88% of iterations for high-risk stage II CC and 79% of iterations for stage III CC. Conclusions: CAPOX for 3 months is the cost-effective adjuvant treatment for high-risk stage II and stage III CC in SA public hospitals. This strategy offers the highest quality of life benefit for the lowest cost and is well within the WTP threshold for SA. The optimal strategy in other settings will vary according to local WTP thresholds. Base case estimates of cost-effectiveness, in order of cost. [Table: see text]