A Phase 1 Trial of Salvage Stereotactic Body Radiation Therapy for Radiorecurrent Prostate Cancer After Brachytherapy.

PURPOSE: NCT03253744 is a phase 1 trial with the primary objective to identify the maximum tolerated dose (MTD) of salvage stereotactic body radiation therapy (SBRT) in patients with local prostate cancer recurrence after brachytherapy. Additional objectives included biochemical control and imaging response. METHODS AND MATERIALS: This trial was initially designed to test 3 therapeutic dose levels (DLs): 40 Gy (DL1), 42.5 Gy (DL2), and 45 Gy (DL3) in 5 fractions. Intensity modulation was used to deliver the prescription dose to the magnetic resonance imaging and prostate-specific membrane antigen-based positron emission tomography imaging-defined gross tumor volume while simultaneously delivering 30 Gy to an elective volume defined by the prostate gland. This phase 1 trial followed a 3+3 design with a 3-patient expansion at the MTD. Toxicities were scored until trial completion at 2 years post-SBRT using Common Terminology Criteria for Adverse Events version 5.0. Escalation was halted if 2 dose limiting toxicities occurred, defined as any persistent (>4 days) grade 3 toxicity occurring within the first 3 weeks after SBRT or any grade ≥3 genitourinary (GU) or grade 4 gastrointestinal toxicity thereafter. RESULTS: Between August 2018 and January 2023, 9 patients underwent salvage SBRT and were observed for a median of 22 months (Q1-Q3, 20-43 months). No grade 3 to 5 adverse events related to study treatment were observed; thus, no dose limiting toxicities occurred during the observation period. Escalation was halted by amendment given excellent biochemical control in DL1 and DL2 in the setting of a high incidence of clinically significant late grade 2 GU toxicity. Therefore, the MTD was considered 42.5 Gy in 5 fractions (DL2). One- and 2-year biochemical progression-free survival were 100% and 86%, representing a single patient in the trial cohort with biochemical failure (prostate-specific antigen [PSA] nadir + 2.0) at 20 months posttreatment. CONCLUSIONS: The MTD of salvage SBRT for the treatment of intraprostatic radiorecurrence after brachytherapy was 42.5 Gy in 5 fractions producing an 86% 2-year biochemical progression-free survival rate, with 1 poststudy failure at 20 months. The most frequent clinically significant toxicity was late grade 2 GU toxicity.

A Phase 1 Trial of Focal Salvage Stereotactic Body Radiation Therapy for Radiorecurrent Prostate Cancer.

PURPOSE: NCT03253744 was a phase 1 trial to identify the maximum tolerated dose (MTD) of image-guided, focal, salvage stereotactic body radiation therapy (SBRT) for patients with locally radiorecurrent prostate cancer. Additional objectives included biochemical control and imaging response. METHODS AND MATERIALS: The trial design included 3 dose levels (DLs): 40 Gy (DL1), 42.5 Gy (DL2), and 45 Gy (DL3) in 5 fractions delivered ≥48 hours apart. The prescription dose was delivered to the magnetic resonance- and prostate-specific membrane antigen imaging-defined tumor volume. Dose escalation followed a 3+3 design with a 3-patient expansion at the MTD. Toxicities were scored until 2 years after completion of SBRT using Common Terminology Criteria for Adverse Events, version 5.0, criteria. Escalation was halted if 2 dose-limiting toxicities occurred, defined as any persistent (>4 days) grade 3 toxicity occurring within the first 3 weeks after SBRT and any grade 3 genitourinary (GU) or grade 4 gastrointestinal (GI) toxicity thereafter. RESULTS: Between August 2018 and May 2022, 8 patients underwent salvage focal SBRT, with a median follow-up of 35 months. No dose-limiting toxic effects were observed on DL1. Two patients were enrolled in DL2 and experienced grade 3 GU toxicities, prompting de-escalation and expansion (n = 6) at the MTD (DL1). The most common toxicities observed were grade ≥2 GU toxicities, with only a single grade 2 GI toxicity and no grade ≥3 GI toxicities. One patient experienced biochemical failure (prostate-specific antigen nadir + 2.0) at 33 months. CONCLUSIONS: The MTD for focal salvage SBRT for isolated intraprostatic radiorecurrence was 40 Gy in 5 fractions, producing a 100% 24-month biochemical progression free survival, with 1 poststudy failure at 33 months. The most frequent clinically significant toxicity was late grade ≥2 GU toxicity.

A Phase 1 Trial of Highly Conformal, Hypofractionated Postprostatectomy Radiation Therapy.

Purpose: This phase 1 trial aimed to identify the maximally tolerated hypofractionated dose schedule for postoperative radiation therapy (PORT) after radical prostatectomy. Secondary objectives included biochemical control and quality of life (QoL) measures. Methods and Materials: Patients were treated on 1 of 3 dose levels (DLs): 56.4 Gy in 20 fractions (DL1), 51.2 Gy in 15 fractions (DL2), and 44.2 Gy in 10 fractions (DL3). Treatment was delivered to the prostate bed without pelvic nodal irradiation. Dose escalation followed a standard 3 + 3 design with an expansion for 6 additional patients at the maximally tolerated hypofractionated dose schedule. Acute dose-limiting toxicity (DLT) was defined as grade 3 toxicity lasting >4 days within 21 days of PORT completion; late DLT was defined as grade 4 gastrointestinal (GI) or genitourinary (GU) toxicity. Results: Between January 2018 and August 2019, 15 patients underwent radiation treatment: 3 on DL1, 3 on DL2, and 9 on DL3. The median follow-up was 24 months. There were no DLTs, and the maximally tolerated hypofractionated dose schedule was identified as DL3. Two of the 15 patients (13.3%) experienced biochemical failure (prostate-specific antigen >0.1). Ten of 15 patients (67%) had grade 2+ acute toxicities, consisting of transient GI toxicities. Three patients experienced late grade 2+ GI toxicity, and 5 patients experienced late grade 2+ GU toxicity. Late grade 3 GU toxicity occurred in 2 patients. There were no grade 4+ acute or late toxicities. There were no significant differences in GI measures of QoL, however, there was an increase in GU symptoms and corresponding decrease in GU QoL between 12 and 24 months. Conclusions: The maximum tolerated hypofractionated dose schedule for hypofractionated PORT to the prostate bed was determined to be 44.2 Gy in 10 daily fractions. The most frequent clinically significant toxicities were late grade 2+ GU toxicities, which corresponded to a worsening of late GU QoL.

Detection of failure patterns using advanced imaging in patients with biochemical recurrence following low-dose-rate brachytherapy for prostate cancer.

PURPOSE/OBJECTIVE(S): This study describes the pattern of failure in patients with biochemical (BCR) recurrence after low-dose-rate (LDR) brachytherapy as a component of definitive treatment for prostate cancer. METHODS: Patients with BCR after LDR brachytherapy ± external beam radiation therapy (EBRT) were enrolled on prospective IRB approved advanced imaging protocols. Patients underwent 3T multiparametric MRI (mpMRI); a subset underwent prostate specific membrane antigen (PSMA)-based PET/CT. Pathologic confirmation was obtained unless contraindicated. RESULTS: Between January 2011 and April 2021, 51 patients with BCR after brachytherapy (n = 36) or brachytherapy + EBRT (n = 15) underwent mpMRI and were included in this analysis. Of 38 patients with available dosimetry, only two had D90<90%. The prostate and seminal vesicles were a site of failure in 66.7% (n = 34) and 39.2% (n = 20), respectively. PET/CT (n = 32 patients) more often identified lesions pelvic lymph nodes (50%; n = 16) and distant metastases (18.8%; n = 6), than mpMRI. Isolated nodal disease (9.8%; n = 5) and distant metastases (n = 1) without local recurrence were uncommon. Recurrence within the prostate was located in the transition zone in 48.5%, central or midline in 45.5%, and anterior in 36.4% of patients. CONCLUSION: In this cohort of patients with BCR after LDR brachytherapy ± EBRT, the predominant recurrence pattern was local (prostate ± seminal vesicles) with frequent occurrence in the anterior prostate and transition zone. mpMRI and PSMA PET/CT provided complementary information to localize sites of recurrence, with PSMA PET/CT often confirming mpMRI findings and identifying occult nodal or distant metastases.

Local failure after definitive radiation treatment of lymph-node positive prostate cancer: supporting the use of novel imaging techniques to personalize treatment options.

Patients with lymph-node positive prostate cancer are often treated with external beam radiotherapy with androgen deprivation therapy1, but are expected to have a high rate of biochemical failure. Recently, MRI and molecular imaging have afforded the opportunity to elucidate otherwise occult sites of recurrence after conventional imaging. We present an unusual case of local failure within the prostate after definitive radiation treatment of lymph-node positive prostate cancer, in which advanced imaging allowed for a potentially curative salvage treatment option.

Effect of Prostate Magnetic Resonance Imaging/Ultrasound Fusion-guided Biopsy on Radiation Treatment Recommendations.

PURPOSE: Targeted magnetic resonance imaging (MRI)/ultrasound fusion prostate biopsy (MRI-Bx) has recently been compared with the standard of care extended sextant ultrasound-guided prostate biopsy (SOC-Bx), with the former associated with an increased rate of detection of clinically significant prostate cancer. The present study sought to determine the influence of MRI-Bx on radiation therapy and androgen deprivation therapy (ADT) recommendations. METHODS AND MATERIALS: All patients who had received radiation treatment and had undergone SOC-Bx and MRI-Bx at our institution were included. Using the clinical T stage, pretreatment prostate-specific antigen, and Gleason score, patients were categorized into National Comprehensive Cancer Network risk groups and radiation treatment or ADT recommendations assigned. Intensification of the recommended treatment after multiparametric MRI, SOC-Bx, and MRI-Bx was evaluated. RESULTS: From January 2008 to January 2016, 73 patients received radiation therapy at our institution after undergoing a simultaneous SOC-Bx and MRI-Bx (n=47 with previous SOC-Bx). Repeat SOC-Bx and MRI-Bx resulted in frequent upgrading compared with previous SOC-Bx (Gleason score 7, 6.7% vs 44.6%; P<.001; Gleason score 8-10, 2.1% vs 38%; P<.001). MRI-Bx increased the proportion of patients classified as very high risk from 24.7% to 41.1% (P=.027). Compared with SOC-Bx alone, including the MRI-Bx findings resulted in a greater percentage of pathologically positive cores (mean 37% vs 44%). Incorporation of multiparametric MRI and MRI-Bx results increased the recommended use and duration of ADT (duration increased in 28 of 73 patients and ADT was added for 8 of 73 patients). CONCLUSIONS: In patients referred for radiation treatment, MRI-Bx resulted in an increase in the percentage of positive cores, Gleason score, and risk grouping. The benefit of treatment intensification in accordance with the MRI-Bx findings is unknown.