Case-Matched Outcomes of Proton Beam and Intensity-Modulated Radiation Therapy for Localized Prostate Cancer

Efficacy and Safety of Newly Installed Spot Scanning Proton Beam Therapy for Prostate Cancer

BACKGROUND/AIM

This study aimed to analyse retrospectively the initial treatment outcomes and associated toxicities of a spot scanning proton beam therapy for prostate cancer at the Shonan-Kamakura General Hospital.

PATIENTS AND METHODS

A laterally opposing single-field uniform dose of spot-scanning proton beam was used. The doses were determined to be 60 Gy in 20 fractions for low-risk prostate cancer and 63 Gy in 21 fractions for intermediate- and high-risk prostate cancers. Genitourinary (GU) and gastrointestinal (GI) toxicities were also evaluated. Toxicity was assessed using the Common Terminology Criteria for Adverse Events (CTCAE) version 5.0.

RESULTS

A total of 135 patients were treated over two years, 51 of whom underwent hydrogel spacer insertion. During the limited observation period, no patient experienced a recurrence. Grade 2 GU toxicities were observed in 17 patients, whereas grade 1 or greater GI toxicities were observed in seven patients. None of the patients in whom a hydrogel spacer was inserted experienced grade 1 or higher GI toxicity.

CONCLUSION

Proton beam therapy is safe for the treatment of prostate cancer. The insertion of a gold marker and hydrogel spacer led to a reduction in the rectal radiation dose and GI toxicity.

Health Disparities and Inequities in the Utilization of Proton Therapy for Prostate Cancer

Our study sought to review and summarize the reported health disparities and inequities in the utilization of proton beam therapy (PBT) for prostate cancer. We queried the PubMed search engine through 12/2023 for original publications examining disparate utilization of PBT for prostate cancer. The query terms included the following: prostate cancer AND proton AND (disparities OR IMRT OR race OR insurance OR socioeconomic OR inequities)". Studies were included if they involved United States patients, examined PBT in prostate cancer, and addressed health inequities. From this query, 22 studies met the inclusion criteria, comprising 13 population-based analyses, 5 single-institutional analyses, 3 cost/modeling investigations, and 1 survey-based study. The analyses revealed that in addition to age-related and insurance-related disparities, race and socioeconomic status played significant roles in the receipt of PBT. The likelihood of receiving PBT was lower for non-White patients in population-based and single-institution analyses. Socioeconomic metrics, such as higher median income and higher education level, portended an increased likelihood of receiving PBT. Conclusively, substantial age-based, racial, socioeconomic/insurance-related, and facility-associated disparities and inequities existed for PBT utilization in prostate cancer. The identification of these disparities provides a framework to better address these as the utility of PBT continues to expand across the US and globally.

Proton Therapy in The Treatment of Head And Neck Cancers- Review

PURPOSE OF REVIEW

Head and neck cancers rank as the seventh most common cancer worldwide, nearly half of which result in death. The most common treatment methods for head and neck cancers include radiotherapy and surgery. Proton therapy has emerged in radiotherapy for cases where tumors are located near anatomically sensitive areas where the radiation dose must be strictly limited. The purpose of the work is to discuss the role of the proton therapy in the treatment in various types of cancer, and particularly head and neck tumors.

RECENT FINDINGS

Proton therapy allows for the delivery of radiation doses to critical organs to be reduced, resulting in a decrease in the occurrence of late adverse effects on these organs. The occurrence of side effects caused by proton therapy depends on the relative and absolute volume of organs at risk receiving specific radiation doses. Proton therapy represents a promising alternative to conventional radiotherapy due to the reduced number of complications in healthy tissues by delivering a lower radiation dose outside the tumor area.

Understanding Relative Biological Effectiveness and Clinical Outcome of Prostate Cancer Therapy Using Particle Irradiation: Analysis of Tumor Control Probability With the Modified Microdosimetric Kinetic Model

PURPOSE

Recent experimental studies and clinical trial results might indicate that-at least for some indications-continued use of the mechanistic model for relative biological effectiveness (RBE) applied at carbon ion therapy facilities in Europe for several decades (LEM-I) may be unwarranted. We present a novel clinical framework for prostate cancer treatment planning and tumor control probability (TCP) prediction based on the modified microdosimetric kinetic model (mMKM) for particle therapy.

METHODS AND MATERIALS

Treatment plans of 91 patients with prostate tumors (proton: 46, carbon ions: 45) applying 66 GyRBE [RBE = 1.1 for protons and LEM-I, (α/β)x = 2.0 Gy, for carbon ions] in 20 fractions were recalculated using mMKM [(α/β)x = 3.1 Gy]). Based solely on the response data of photon-irradiated patient groups stratified according to risk and usage of androgen deprivation therapy, we derived parameters for an mMKM-based Poisson-TCP model. Subsequently, new carbon and helium ion plans, adhering to prescribed biological dose criteria, were generated. These were systematically compared with the clinical experience of Japanese centers employing an analogous fractionation scheme and existing proton plans.

RESULTS

mMKM predictions suggested significant biological dose deviation between the proton and carbon ion arms. Patients irradiated with protons received (3.25 ± 0.08)  GyRBEmMKM/Fx, whereas patients treated with carbon ions received(2.51 ± 0.05)  GyRBEmMKM/Fx. TCP predictions were (86 ± 3)% for protons and (52 ± 4)% for carbon ions, matching the clinical outcome of 85% and 50%. Newly optimized carbon ion plans, guided by the mMKM/TCP model, effectively replicated clinical data from Japanese centers. Using mMKM, helium ions exhibited similar target coverage as proton and carbon ions and improved rectum and bladder sparing compared with proton.

CONCLUSIONS

Our mMKM-based model for prostate cancer treatment planning and TCP prediction was validated against clinical data for proton and carbon ion therapy, and its application was extended to helium ion therapy. Based on the data presented in this work, mMKM seems to be a good candidate for clinical biological calculations in carbon ion therapy for prostate cancer.