Early Diffusion and Regional Variation in Robot-Assisted Laparoscopic Resection for Malignant Colon Tumors in Japan:...

Robot-assisted laparoscopic resection for malignant colon tumors was newly reimbursed in Japan in April 2022, but early national billing-based uptake and geographic variation after reimbursement have not been described using public aggregate claims data.

We analyzed the ninth and tenth National Database Open Data releases for fiscal years 2022 and 2023. Using inpatient K-surgery tables by treating-institution prefecture, we calculated the robot-assisted proportion as robot-assisted malignant colon tumor resection billing counts divided by the sum of conventional and robot-assisted laparoscopic malignant colon tumor resection billing counts. National proportions were calculated from suppression-free total columns. Prefecture-level summaries were reported among displayed prefectures, with a bounded small-cell sensitivity assessment for masked robot-assisted cells.

National robot-assisted billing counts increased from 1652 to 6141, and the total-based national proportion rose from 3.38% to 11.42%. The number of prefectures with displayed robot-assisted numerator cells increased from 36 to 43. The displayed-prefecture median increased from 1.72% to 8.63%. In a bounded small-cell sensitivity analysis constrained to the hidden national-total difference, the possible fiscal year 2022 median was 0.90%-1.83%, and the fiscal year 2023 median was 8.45%. Among 33 prefectures with displayed data in both years, the median proportion rose from 1.89% to 9.65%, with a median within-prefecture change of +6.76 percentage points; 30 prefectures increased, one decreased, and two were unchanged. Under a direction-of-change sensitivity classification incorporating masked transitions, 43 prefectures were classifiable as increased, one decreased, two were unchanged, and one remained indeterminate. Fiscal year 2023 variation remained substantial among displayed prefectures, with values ranging from 0.00% to 27.79%, and paired ranks were moderately stable (Spearman ρ = 0.77).

Robot-assisted billing among laparoscopic malignant colon tumor resection codes increased rapidly from the first to the second reimbursement year, but inter-prefectural variation remained.