Effective drug dosage rounding reduces healthcare expenses in the Japanese healthcare system

Anticancer drugs are administered near the maximum tolerated dose, and their therapeutic range is significantly narrower compared to conventional drugs. Even for expensive anticancer drugs, some of the drug in the vial is used, whereas the remainder is discarded. Because body size impacts dosage and varies significantly among racial groups, in this study, we aimed to assess the impact of dose adjustment on healthcare expenses and bevacizumab dose fluctuations in Japan. We investigated the effects of bevacizumab dosage variation and the degree of dose adjustment on medical costs based on annual bevacizumab use data from the National Database of Health (NDB) Open Data. Additionally, a multicentre, retrospective study was conducted at four national university hospitals to record bevacizumab consumption. We analysed the impact of dose adjustments in the ranges of 10%, 5%, and 2% on drug costs. Simulations based on this data estimated potential cost savings. The use of bevacizumab has been steadily increasing: 1.59 million vials were used in Japan in 2021, costing JPY 101.6 billion. Dose adjustments of 10%, 5%, and 2% could reduce costs by approximately JPY 4,619,699,806, 1,777,439,323, and 420,016,889 per year, respectively. Dose adjustments for bevacizumab could significantly reduce healthcare costs in Japan. Numerous anticancer drugs exist beyond bevacizumab, and similar cost-reduction measures applied to these drugs could lead to further savings. Although prospective clinical trials are needed to assess the impact of dose adjustments on treatment effectiveness, significant healthcare cost reductions are anticipated if this approach proves effective.