The introduction of proton beam therapy has brought with it a multitude of implications, which Neil Burnet, MA, MBBChir, FRCR, MD, of the Precise Group, University of Manchester, Manchester, UK, explores in this interview, recorded at the UK Oncology Forum (OF) 2018, held in Liverpool, UK. Notably, there are uncertainties regarding who exactly to treat. Although proton beam therapy offers clear advantages in pediatric oncology, the advantages offered to adults are unclear. To resolve this, Prof. Burnet suggests a thorough follow-up of patients receiving proton beam therapy; be it in terms of randomized clinical trials or life-long outcome tracking. He hopes that this will assist in adopting a safe approach to proton beam therapy.