Proton Therapy for Prostate Cancer: Challenges and Opportunities

Abstract

The dosimetric advantages of proton therapy (PT) treatment plans are demonstrably superior to photon-based external beam radiotherapy (EBRT) for localized prostate cancer, but the reported clinical outcomes are similar. This may be due to inadequate dose prescription, especially in high-risk disease, as indicated by the ASCENDE-RT trial. Alternatively, the lack of clinical benefits with PT may be attributable to improper dose delivery, mainly due to geometric and dosimetric uncertainties during treatment planning, as well as delivery procedures that compromise the dose conformity of treatments. Advanced high-precision PT technologies, and treatment planning and beam delivery techniques are being developed to address these uncertainties. For instance, external magnetic resonance imaging (MRI)-guided patient setup rooms are being developed to improve the accuracy of patient positioning for treatment. In-room MRI-guided patient positioning systems are also being investigated to improve the geometric accuracy of PT. Soon, high-dose rate beam delivery systems will shorten beam delivery time to within one breath hold, minimizing the effects of organ motion and patient movements. Dual-energy photon-counting computed tomography and high-resolution Monte Carlo-based treatment planning systems are available to minimize uncertainties in dose planning calculations. Advanced in-room treatment verification tools such as prompt gamma detector systems will be used to verify the depth of PT. Clinical implementation of these new technologies is expected to improve the accuracy and dose conformity of PT in the treatment of localized prostate cancers, and lead to better clinical outcomes. Improvement in dose conformity may also facilitate dose escalation, improving local control and implementation of hypofractionation treatment schemes to improve patient throughput and make PT more cost effective.

The Current Trend of Radiation Therapy for Patients with Localized Prostate Cancer

“…Proton beam therapy (PBT) is a form of radiotherapy that utilizes high-energy protons to target tumors as opposed to X-rays. Protons can be directed more precisely toward the tumor site and have a lower probability of damaging adjacent organs [ 70 , 71 ] ( Table 8 ). Heavy ion radiotherapy is a specialized radiation therapy that utilizes high-energy ions such as carbon or helium [ 72 ].…”

Modelling the HPRT-gene mutation induction of particle beams: systematic in vitro data collection, analysis and microdosimetric kinetic model implementation

“…Next to the historical brain and head and neck cancers, protons are currently also considered for e.g. breast cancer (Kowalchuk et al 2022), prostate (Poon et al 2022), and lymphoma treatments (Loap et al 2021), with clinical trials already on-going. Together with paediatric patients, this raises specific concerns regarding the risk of late radiation effects for patients having a good survival probability and long-life expectancy.…”