Increased distance from a treating proton center is associated with diminished ability to follow patients enrolled on a multicenter radiation oncology registry

•Residential distance from MGH significantly affects follow-up duration.•Employing numerous follow-up methods may improve long-term contact with patients.•Health outcomes of patients are fundamental to understanding the role of proton radiotherapy. Purpose: Consistent follow-up and data collection are necessary to identify long-term benefits/detriments of proton radiotherapy. Obtaining comprehensive clinical follow-up can be difficult and time-intensive for proton centers. Here we evaluate what factors affect maximum follow-up time among MGH Pediatric Proton Consortium Registry (PPCR) participants. Patients and methods: Enrollment in the PPCR was offered to any patient