Intensity-modulated proton therapy decreases dose to organs at risk in low-grade glioma patients: results of a multicentric in silico ROCOCO trial

Abstract

Background and purpose: Patients with low-grade glioma (LGG) have a prolonged survival expectancy due to better discriminative tumor classification and multimodal treatment. Consequently, long-term treatment toxicity gains importance. Contemporary radiotherapy techniques such as intensity-modulated radiotherapy (IMRT), volumetric modulated arc therapy (VMAT), tomotherapy (TOMO) and intensity-modulated proton therapy (IMPT) enable high-dose irradiation of the target but they differ regarding delivered dose to organs at risk (OARs). The aim of this comparative in silico study was to determine these dosimetric differences in delivered doses.

Material and methods: Imaging datasets of 25 LGG patients having undergone postoperative radiotherapy were included. For each of these patients, in silico treatment plans to a total dose of 50.4 Gy to the target volume were generated for the four treatment modalities investigated (i.e., IMRT, VMAT, TOMO, IMPT). Resulting treatment plans were analyzed regarding dose to target and surrounding OARs comparing IMRT, TOMO and IMPT to VMAT.

Results: In total, 100 treatment plans (four per patient) were analyzed. Compared to VMAT, the IMPT mean dose (D_mean) for nine out of 10 (90%) OARs was statistically significantly (p < .02) reduced, for TOMO this was true in 3/10 (30%) patients and for 1/10 (10%) patients for IMRT. IMPT was the prime modality reducing dose to the OARs followed by TOMO.

Discussion: The low dose volume to the majority of OARs was significantly reduced when using IMPT compared to VMAT. Whether this will lead to a significant reduction in neurocognitive decline and improved quality of life is to be determined in carefully designed future clinical trials.

Disclosure statement

The authors D.B.P. Eekers MD, E. Roelofs PhD, M. Cubillos-Mesías MSc, C. Niёl MD, R.J. Smeenk PhD MD, A. Hoeben PhD MD, A. Minken PhD, M. Granzier, G.O.R.J. Janssens PhD MD, Professor J.H.A.M. Kaanders PhD MD, Professor E.G.C. Troost PhD MD declared no conflict of interest. Professor P. Lambin PhD MD is a recipient of research grant from www.pttheragnostic.com. Dr. Philippe Lambin reports, within and outside he submitted work, grants/sponsored research agreements from Varian medical, Oncoradiomics, ptTheragnostic, Health Innovation Ventures and DualTpharma. He received an advisor/presenter fee and/or reimbursement of travel costs/external grantwriting fee and/or in kind manpower contribution from Oncoradiomics, BHV, Merckand Convert pharmaceuticals. Dr. Lambin has shares in the company Oncoradiomics SA and Convert pharmaceuticals SA and is co-inventor of two patents onradiomics (PCT/NL2014/050248, PCT/NL2014/050728) licensed to Oncoradiomics and one patent on mtDNA (PCT/EP2014/059089) licensed to ptTheragnostic/DNAmito, three non-pate table invention (softwares) licensed to ptTheragnostic/DNAmito, Oncoradiomics and Health Innovation Ventures.