[Residential areas, travel burdens, and children with cancer: Analysis of mobility and mortality ratios using data from Japan's national population-based cancer registry].

Objectives　Although childhood cancer treatment has recently become centralized at specialized hospitals worldwide, the relationship between mortality ratios and living in rural areas or traveling long distances for treatment remains controversial. In the present study, we examined whether regional differences in patient mobility and mortality ratios exist in Japan.Methods　We investigated 10,713 patients with cancer aged ≤18 years, diagnosed between 2016 and 2019, registered in the national cancer registry data. The patients were divided into two categories based on their residence at diagnosis: urban and rural. Urban areas were defined as metropolitan or urban areas according to the 2015 census or as prefectural cities; all other areas were defined as rural. Additionally, we divided the patients into two groups based on the one-way travel time to the treatment hospital (≤1 h or >1 h), as estimated from location information at the community level using route-planner web services. Next, we calculated the percentage of patients who received treatment within their residences in both areas and for each treatment type. We compared the percentage of distant metastasis in all cancers and each diagnosis group between the two areas using the chi-square test. We finally applied Cox proportional hazard models to obtain adjusted mortality hazard ratios for urban versus rural areas and travel times of ≤1 h versus >1 h.Results　Overall, 77% of the patients were classified as urban residents. The percentages of patients receiving treatment within their residency, secondary medical care area, prefecture, and regional block levels were 22-46%, 80-87%, and 95-99%, respectively. Only central nervous system tumors (III) showed a significant difference in the percentage of distant metastases, which were more common in urban areas (6% vs. 3%). The adjusted mortality hazard ratios were not significantly different between urban and rural areas for all cancers or each diagnosis group. The travel time comparison yielded significant differences of 1.17 for all cancers and 2.57 for lymphomas (II).Conclusion　Approximately 80% of the patients received treatment within their prefecture, although a few traveled long distances across regional blocks. We observed no differences in the mortality ratio between urban and rural areas, although significant differences were found in all cancers and one cancer in the travel burden comparison. These results highlight the need for continued evaluation of the increasing trend in patient travel burden and its impact on survival, as childhood cancer treatment has become centralized in Japan.