Association between variations in the number of hospital beds and inpatient chemo/radiotherapy for breast cancer: a study using a large claim database.

OBJECTIVE: Chemo/radiotherapy for breast cancer patients does not require hospitalisation in most cases. We investigated the relationship between the proportion of hospitalisation for chemo/radiotherapy over total hospitalisation and the number of hospital beds per capita among breast cancer cases. DESIGN: A retrospective observational study. SETTING: Hospitals in Japan. PARTICIPANTS: In total, 561,165 records of hospitalisation of breast cancer cases were extracted from the Japanese Diagnosis Procedure Combination database from April 2012 to March 2016.Intervention(s) and main outcome measure(s): A multivariable beta regression model accounting for the clustering effect within each prefecture was used to examine the relationship between the number of hospital beds per capita in each prefecture and the proportion of hospitalisation for inpatient chemo/radiotherapy treatment or the number of surgical operations for breast cancer patients in each prefecture. RESULTS: The proportion of hospitalisation for inpatient chemo/radiotherapy treatment varied from 2.6% to 61.8% in 2016. The logit proportion of hospitalisation for inpatient chemo/radiotherapy treatment was significantly higher for every additional hospital bed per capita (0.0027, 95% confidence interval (95% CI) 0.0014-0.0040). In contrast, no significant relationship was observed between the number of surgical operations for breast cancer per capita and the number of hospital beds per capita. CONCLUSIONS: We found that a higher number of regional hospital beds were associated with a higher proportion of hospitalisation for chemo/radiotherapy treatment, suggesting that inpatient chemo/radiotherapy may be a provider-induced practice.