Proton Therapy in Children: A Systematic Review of Clinical Effectiveness in 15 Pediatric Cancers

Because it spares many normal tissues and reduces the integral dose, proton therapy (PT) is the preferred tumor irradiation technique for treating childhood cancer. However, to the best of our knowledge, no systematic review of the clinical effectiveness of PT in children has been reported in the scientific literature. A systematic search for clinical outcome studies on PT published between 2007 and 2015 was performed in Medline (through OVID), EMBASE, and the Cochrane Library. Twenty-three primary studies were identified, including approximately 650 patients overall. The median/mean follow-up times were limited (range, 19-91 months). None of the studies were randomized, 2 were comparative, and 20 were retrospective. Most suffered from serious methodologic limitations, yielding a very low level of clinical evidence for the outcomes in all indications. For example, for retinoblastoma, very low-level evidence was found that PT might decrease the incidence of second malignancies. For chondrosarcoma, chordoma, craniopharyngioma, ependymoma, esthesioneuroblastoma, Ewing sarcoma, central nervous system germinoma, glioma, medulloblastoma, osteosarcoma, and rhabdomyosarcoma, there was insufficient evidence to either support or refute PT in children. For pelvic sarcoma (ie, nonrhabdomyosarcoma and non-Ewing sarcoma), pineal parenchymal tumor, primitive neuroectodermal tumor, and "adult-type" soft tissue sarcoma, no studies were identified that fulfilled the inclusion criteria. Although there is no doubt that PT reduces the radiation dose to normal tissues and organs, to date the critical clinical data on the long-term effectiveness and harm associated with the use of PT in the 15 pediatric cancers under investigation are lacking. High-quality clinical research in this area is needed.