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

Abstract

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(α/β) DIL aimed at 111.6 Gy, PTV(initial) D(pres) was 80.9 Gy (EBRT) with CTV D90%=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(α/β) D50% to DIL 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 D(mean) were 21.0±5.5, 15.6±4.3 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.

Keywords: DIL; HDR-BT; IMPT; Prostate cancer; SIB; VMAT.