Proton radiotherapy for gynecologic neoplasms

Abstract

Background: Proton beam therapy (PBT) is increasingly being used globally to treat a variety of malignancies. This is the first review assessing PBT for gynecologic neoplasms. Dose distribution to organs-at-risk (OARs), particularly bone marrow (BM), is addressed. Clinical outcomes and toxicity data are detailed. Material and methods: Systematic searches of PubMed, EMBASE, abstracts from meetings of the American Society for Radiation Oncology, Particle Therapy Co-Operative Group, and American Society of Clinical Oncology were conducted for publications. There were no restrictions on publication dates. Sixteen original investigations were identified and analyzed for this review. Results: The available evidence for PBT in treating gynecologic cancers is of both low quantity and quality. The most studied scenarios for PBT include treatment of para-aortic lymph nodes, re-irradiation, and as an alternative to brachytherapy, and these also represent indications with the greatest opportunity for demonstrating as yet unproven toxicity reductions. Dosimetric studies have shown significantly decreased dose to OARs, such as the rectum, bladder, bowel, kidneys, BM, and femoral heads. This dose reduction to OARs with PBT is more pronounced within the low-dose volumes than the higher dose volumes, which radiobiologically could be expected to lower second malignancy rates. Clinical data, though no level 1 evidence, show appropriate stage-specific tumor control and outcomes with PBT treatment, along with low toxicity rates. Conclusion: The existing data, albeit limited, warrant and can help guide larger scale and higher quality studies addressing whether PBT could provide clinically meaningful differences in toxicities and outcomes in women with gynecologic neoplasms.