Background
Robotic-assisted radical prostatectomy (RARP) has become the dominant approach for prostate cancer surgery, replacing open and laparoscopic procedures. However, whether the introduction of robotic surgical systems has increased the overall number of radical prostatectomies (RPs) remains unclear, particularly within social health insurance systems.

Methods
We conducted a nationwide longitudinal observational study using hospital-level data from Japan between 2016 and 2023. Hospitals performing at least one RP annually and reporting complete data on robotic surgical system status and RP volume across the study period were included in the primary analysis. The primary outcome was the annual number of RPs per hospital. Using a staggered difference-in-differences (DID) design, we compared hospitals that adopted robotic surgical systems with hospitals that had not yet adopted them and estimated the association between adoption and annual hospital-level RP volume.

Results
A total of 288 hospitals were categorized as 189 previous adopters, 77 new adopters, and 22 non-adopters. New adopters demonstrated a sustained increase in RP volume, rising from 2608 procedures in 2016 to 4371 in 2023, whereas RP volumes among previous adopters and non-adopters remained stable. Compared with hospitals that had not yet adopted robotic surgical systems, adoption was associated with an increase of 17.4 RPs per hospital per year (95% CI, 10.7 to 24.1). No significant differences were observed between groups during the pre-adoption period, consistent with the parallel trends assumption.

Conclusion
In Japan’s social health insurance context, adoption of robotic surgical systems was associated with a significant and sustained rise in RP volume. These findings highlight the need for further research to determine whether the observed increase reflects changes in patient selection, referral patterns, clinical appropriateness, or other mechanisms, as well as the associated clinical and economic implications.