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Proton versus photon therapy for high-risk prostate cancer with dose escalation of dominant intraprostatic lesions: a preliminary planning study

Ong, Ashley Li Kuan; Knight, Kellie; Panettieri, Vanessa; Dimmock, Mathew; Tuan, Jeffrey Kit Loong; Tan, Hong Qi; Wright, Caroline

Authors

Ashley Li Kuan Ong

Kellie Knight

Vanessa Panettieri

Jeffrey Kit Loong Tuan

Hong Qi Tan

Caroline Wright



Abstract

Background and purpose: This study aimed to investigate the feasibility of safe-dose escalation to dominant intraprostatic lesions (DILs) and assess the clinical impact using dose-volume (DV) and biological metrics in photon and proton therapy. Biological parameters defined as late grade ≥ 2 gastrointestinal (GI) and genitourinary (GU) derived from planned (D P) and accumulated dose (D A) were utilized. Materials and methods: In total, 10 patients with high-risk prostate cancer with multiparametric MRI-defined DILs were investigated. Each patient had two plans with a focal boost to the DILs using intensity-modulated proton therapy (IMPT) and volumetric-modulated arc therapy (VMAT). Plans were optimized to obtain DIL coverage while respecting the mandatory organ-at-risk constraints. For the planning evaluation, DV metrics, tumor control probability (TCP) for the DILs and whole prostate excluding the DILs (prostate-DILs), and normal tissue complication probability (NTCP) for the rectum and bladder were calculated. Wilcoxon signed-rank test was used for analyzing TCP and NTCP data. Results: IMPT achieved a higher Dmean for the DILs compared to VMAT (IMPT: 68.1 GyRBE vs. VMAT: 66.6 Gy, p < 0.05). Intermediate–high rectal and bladder doses were lower for IMPT (p < 0.05), while the high-dose region (V60 Gy) remained comparable. IMPT-TCP for prostate-DIL were higher compared to VMAT (IMPT: 86%; α/β = 3, 94.3%; α/β = 1.5 vs. VMAT: 84.7%; α/β = 3, 93.9%; α/β = 1.5, p < 0.05). Likewise, IMPT obtained a moderately higher DIL TCP (IMPT: 97%; α/β = 3, 99.3%; α/β = 1.5 vs. VMAT: 95.9%; α/β = 3, 98.9%; α/β = 1.5, p < 0.05). Rectal D A-NTCP displayed the highest GI toxicity risk at 5.6%, and IMPT has a lower GI toxicity risk compared to VMAT-predicted Quantec-NTCP (p < 0.05). Bladder D P-NTCP projected a higher GU toxicity than D A-NTCP, with VMAT having the highest risk (p < 0.05). Conclusion: Dose escalation using IMPT is able to achieve a high TCP for the DILs, with the lowest rectal and bladder DV doses at the intermediate–high-dose range. The reduction in physical dose was translated into a lower NTCP (p < 0.05) for the bladder, although rectal toxicity remained equivalent.

Citation

Ong, A. L. K., Knight, K., Panettieri, V., Dimmock, M., Tuan, J. K. L., Tan, H. Q., & Wright, C. (in press). Proton versus photon therapy for high-risk prostate cancer with dose escalation of dominant intraprostatic lesions: a preliminary planning study. Frontiers in oncology, 13, 1241711. https://doi.org/10.3389/fonc.2023.1241711

Journal Article Type Article
Acceptance Date Oct 23, 2023
Online Publication Date Nov 8, 2023
Deposit Date Nov 27, 2023
Journal Frontiers in Oncology
Print ISSN 2234-943X
Publisher Frontiers Media
Peer Reviewed Peer Reviewed
Volume 13
Pages 1241711
DOI https://doi.org/10.3389/fonc.2023.1241711
Keywords biological modeling, magnetic resonance imaging, intraprostatic lesions, proton therapy, high-risk prostate cancer