A paper by MGH published in the Green Journal evaluated the factors that affect maximum follow-up time among MGH Pediatric Proton Consortium Registry (PPCR) participants. Among the 333 PPCR patients, the median follow-up was 2.4 years and median distance away from the proton center was 256.4 km. Loss in average follow up was 0.53 years for patients living outside >121 km from the proton center compared to those living within 121 km.

Loss in average follow-up was also associated with Medicaid insurance. The authors concluded that increased distance from treating centers may adversely affect clinical outcomes research. Sharing of medical information among care providers and improved collection methods are needed to effectively evaluate the benefits of proton therapy.