Global treatment costs of breast cancer by stage: A systematic review.

BACKGROUND: Published evidence on treatment costs of breast cancer varies widely in methodology and a global systematic review is lacking. OBJECTIVES: This study aimed to conduct a systematic review to compare treatment costs of breast cancer by stage at diagnosis across countries at different levels of socio-economic development, and to identify key methodological differences in costing approaches. DATA SOURCES: MEDLINE, EMBASE, and NHS Economic Evaluation Database (NHS EED) before April 2018. ELIGIBILITY CRITERIA: Studies were eligible if they reported treatment costs of breast cancer by stage at diagnosis using patient level data, in any language. STUDY APPRAISAL AND SYNTHESIS METHODS: Study characteristics and treatment costs by stage were summarised. Study quality was assessed using the Drummond Checklist, and detailed methodological differences were further compared. RESULTS: Twenty studies were included, 15 from high-income countries and five from low- and middle-income countries. Eleven studies used the FIGO staging system, and the mean treatment costs of breast cancer at Stage II, III and IV were 32%, 95%, and 109% higher than Stage I. Five studies categorised stage as in situ, local, regional and distant. The mean treatment costs of regional and distant breast cancer were 41% and 165% higher than local breast cancer. Overall, the quality of studies ranged from 50% (lowest quality) to 84% (highest). Most studies used regression frameworks but the choice of regression model was rarely justified. Few studies described key methodological issues including skewness, zero values, censored data, missing data, and the inclusion of control groups to estimate disease-attributable costs. CONCLUSIONS: Treatment costs of breast cancer generally increased with the advancement of the disease stage at diagnosis. Methodological issues should be better handled and properly described in future costing studies.