Extreme hypofractionated proton radiotherapy for prostate cancer using pencil beam scanning: Dosimetry, acute toxicity and preliminary results

Abstract

Introduction Extreme hypofractionated radiotherapy for prostate cancer is a common modality in photon therapy. Pencil beam scanning (PBS) in similar fractionation allows better dose distribution and makes proton therapy more available for such patients. The purpose of this study is the feasibility of extreme proton hypofractionated radiotherapy and publication of early clinical results. Methods Two hundred patients with early‐stage prostate cancer were treated with IMPT (intensity‐modulated proton therapy), extreme hypofractionated schedule (36.25 GyE in five fractions) between February 2013 and December 2015. Mean age of the patients was 64.3 years, and the mean value of prostate‐specific antigen (PSA) before treatment was 6.83 μg/L (0.6–17.3 μg/L). Ninety‐three patients (46.5%) were in the low‐risk group. One hundred and seven patients (53.5%) were in the intermediate‐risk group. Twenty‐nine patients (14.5%) had neoadjuvant hormonal therapy, and no patients had adjuvant hormonal therapy. Acute toxicity, late toxicity and short‐term results were evaluated. Results All patients finished radiotherapy without interruptions. The median follow‐up time was 36 months. The mean treatment time was 9.5 days (median 9 days). Acute toxicity according to Common Terminology Criteria for Adverse Events (CTCAE) v 4.0 was (gastrointestinal toxicity) GI (grade) G1‐17%, G2‐3.5%; (genitourinary toxicity) GU G1‐40%, G2‐19%; and no G3 toxicity was observed. Late toxicity was GI G1‐19%, G2‐5.5%; GU G1‐17%, G2‐4%; and no G3 toxicity was observed. PSA relapse was observed in one patient (1.08%) in the low‐risk group (pelvic lymph node involvement was detected) and in seven patients (6.5%) in the intermediate‐risk group (three lymph node metastases, two lymph node and bone metastases, two PSA relapses). No patient died of prostate cancer, and three patients died from other reasons. No local recurrence of cancer in the prostate was observed. Conclusions Proton beam radiotherapy for prostate cancer is feasible with a low rate of acute toxicity and promising late toxicity and effectivity.

Ultra-Hypofractionated Proton Therapy in Localized Prostate Cancer: Passive Scattering versus Intensity-Modulated Proton Therapy

“…Using the same fractionation scheme techniques as Kole et al, Moteabbed et al [5] found that the PTV coverage (D 98 isodose) was 95%, which is similar to our results (96.79%). The mean PTV dose for IMPT in our study was 37.18 CGE, which is similar to the results observed by Kubes et al (36.71 CGE) [13]. Compared to standard fractionation, we found a lower mean PTV dose (% prescribed dose) for PS (98.27%) than Vargas et al [12] (102.4%) and for IMPT when compared to the data reported by Tran et al (102.6% vs. 104.8%) [28].…”

“…Unfortunately, our study design does not allow us to assess treatment-related toxicity. IMPT is generally considered to have better dose distribution than PS [13,15]. Mishra et al [17] compared PS to IMPT, finding no differences in mean quality of life scores or acute grade ≥ 2 GI toxicity at one-year, but they did observe higher rates of acute grade ≥ 2 GU toxicity in the IMPT group.…”

“…Vargas et al [14] were the first authors to describe an ultra-hypofractionated model for PCa (38 Gy in five fractions). A similar ultra-hyperfractionated technique with IMPT was developed by Kubes et al [13] and Vargas et al [14]. Other authors have compared proton beam with PS to photon beam techniques [10,26,27].…”

“…In recent years, there has been a growing interest in ultra-hypofractionated radiotherapy. This technique involves the administration of large daily fractions (4 to 8 Gy), which can be delivered through either photon or proton beam therapy [10][11][12][13][14][15]. Although both techniques can achieve satisfactory results, proton therapy has a theoretical advantage in terms of better sparing of normal tissues due to dose modulation along the beam path to create a spread-out Bragg peak (SoBP).…”

Applying Tissue Slice Culture in Cancer Research—Insights from Preclinical Proton Radiotherapy

“…Although the number of PBRT centers are increasing worldwide [5], additional experimental data, e.g., on combination with drugs (chemotherapy, small molecules, inhibitors), tumor microenvironment, and alternative fractionation schedules, are needed to explore the full potential of this therapy [6][7][8]. Like cancer research in general, PBRT faces the problem of defining reproducible, reliable, and practical models of tumors and normal tissues, which reflect the effects of complex treatment modalities and the heterogeneous response of patients [9].…”