Feasibility of dominant intraprostatic lesion boosting using advanced photon-, proton- or brachytherapy

Background and purpose: Advancements in imaging and dose delivery enable boosting of the dominant intraprostatic lesions (DIL), while maintaining organs-at-risk (OAR) tolerances. This study aimed to assess the feasibility of DIL boosting for volumetric modulated arc therapy (VMAT), intensity modulated proton therapy (IMPT) and high dose rate brachytherapy (HDR-BT). Material and methods: DILs were defined on multiparametric magnetic resonance imaging and fused with planning CT for twelve patients. VMAT, IMPT and HDR-BT plans were created for each patient with an EQD2(alpha/beta) DIL aimed at 111.6 Gy, PTVinitial D-pres was 80.9 Gy (EBRT) with CTV D-90% = 81.9 Gy (HDR-BT). Hard dose constraints were applied for OARs. Results: Higher boost doses were achieved with IMPT compared to VMAT, keeping major OAR doses at similar levels. Patient averaged EQD2 alpha/beta D505 to D-50% were 110.7, 114.2 and 150.1 Gy(IsoE) for VMAT, IMPT and HDR-BT, respectively. Respective rectal wall D-mean were 30.5 +/- 5.0, 16.7 +/- 3.6, 9.5 +/- 2.5 Gy(IsoE) and bladder wall Dmean were 21.0 +/- 5.5, 15.6 +/- 43 and 6.3 +/- 2.2 Gy(IsoE). Conclusions: DIL boosting was found to be feasible with all investigated techniques. Although OAR doses were higher than for standard treatment approach, the risk levels were reasonably low. HDR-BT was superior to VMAT and IMPT, both in terms of OAR sparing and DIL boosting. (C) 2015 Elsevier Ireland Ltd. All rights reserved.