Stereotactic Body Radiotherapy for Prostate Cancer

Stereotactic Body Therapy for Urologic Cancers-What the Urologist Needs to Know

BACKGROUND

stereotactic ablative body radiotherapy (SABR) is a disruptive radiation therapy technique which is increasingly used for the treatment of urologic cancers. The aim of this narrative review is to provide an overview on the current landscape of SABR in urologic cancers and highlight advancements on the horizon.

METHODS

a narrative review of the contemporary role of SABR in urologic cancers is conducted.

RESULTS

in localised prostate cancer, SABR boasts excellent tumour control and biochemical control, with acceptable GU and GI toxicity. Its comparison to laparoscopic radical prostatectomy is currently ongoing. SABR appears to be practical for metastasis-directed therapy in metastatic prostate cancer, with good local control and a low toxicity profile, either alone or in combination with ADT. In localised RCC, SABR offers adequate local control with a modest impact on renal function in patients unfit for surgical management. Its role in metastatic RCC is much more established, where it has been shown to be superior to conventional radiotherapy. Emerging evidence suggests that SABR has a role in delaying systemic therapy whilst maintaining QOL and overall survival. Intriguingly, in metastatic prostate cancer and metastatic RCC, SABR results in a cytoreductive and immunomodulatory 'abscopal effect', a focus of current investigations.

CONCLUSIONS

SABR has emerged as a safe, effective, and feasible treatment for urologic cancers. Urologists should be aware of its increasing use in localised prostate cancer and metastatic RCC, with good oncological outcomes combined with acceptable toxicity. In addition, SABR holds promise for both metastatic prostate cancer and localised RCC treatment in terms of toxicity and oncological outcomes.

Innovations and Emerging Trends in Prostate Cancer Management: A Literature Review

Prostate cancer (PC) is considered the second most diagnosed cancer in men worldwide. It remains a leading cause of cancer-related death. Recently, many modalities have been discovered and used in the diagnosis and management of PC, with the incorporation of many treatment options such as hormonal therapy, chemotherapy, targeted therapies, immunotherapy, and precision medicine. Robotics and artificial intelligence (AI) have further modified the diagnosis and management of PCs, improving the diagnosis accuracy and disease progression. This comprehensive review offers an in-depth exploration of the historical modalities of treatments, an evaluation of current therapeutic techniques, a discussion of the use of robotic surgery and AI, and an examination of ongoing clinical trials and emerging procedures. Additionally, this review also covers the challenges. By inspecting these aspects, the review may provide valuable information regarding future research and clinical practice directions in PC treatment, contributing to a thorough understanding of the complex and emerging context of PC management.

Intrafractional motion and dosimetric analysis in prostate stereotactic body radiation therapy with auto beam hold technique

Objective: To summarize our institutional prostate stereotactic body radiation therapy (SBRT) experience using auto beam hold (ABH) technique for intrafractional prostate motion and assess ABH tolerance of 10-millimeter (mm) diameter.Approach: Thirty-two patients (160 fractions) treated using ABH technique between 01/2018 and 03/2021 were analyzed. During treatment, kV images were acquired every 20-degree gantry rotation to visualize 3-4 gold fiducials within prostate to track target motion. If the fiducial center fell outside the tolerance circle (diameter = 10 mm), beam was automatically turned off for reimaging and repositioning. Number of beam holds and couch translational movement magnitudes were recorded. Dosimetric differences from intrafractional motion were calculated by shifting planned isocenter.Main Results: Couch movement magnitude (mean ± SD) in vertical, longitudinal and lateral directions were -0.7 ± 2.5, 1.4 ± 2.9 and -0.1 ± 0.9 mm, respectively. For most fractions (77.5%), no correction was necessary. Number of fractions requiring one, two, or three corrections were 15.6%, 5.6% and 1.3%, respectively. Of the 49 corrections, couch shifts greater than 3 mm were seen primarily in the vertical (31%) and longitudinal (39%) directions; corresponding couch shifts greater than 5 mm occurred in 2% and 6% of cases. Dosimetrically, 100% coverage decreased less than 2% for clinical target volume (CTV) (-1 ± 2%) and less than 10% for PTV (-10 ± 6%). Dose to bladder, bowel and urethra tended to increase (Bladder: ΔD10%:184 ± 466 cGy, ΔD40%:139 ± 241 cGy, Bowel: ΔD1 cm3:54 ± 129 cGy; ΔD5 cm3:44 ± 116 cGy, Urethra: ΔD0.03 cm3:1 ± 1%). Doses to the rectum tended to decrease (Rectum: ΔD1 cm3:-206 ± 564 cGy, ΔD10%:-97 ± 426 cGy; ΔD20%:-50 ± 251 cGy).Significance: With the transition from conventionally fractionated intensity modulated radiation therapy to SBRT for localized prostate cancer treatment, it is imperative to ensure that dose delivery is spatially accurate for appropriate coverage to target volumes and limiting dose to surrounding organs. Intrafractional motion monitoring can be achieved using triggered imaging to image fiducial markers and ABH to allow for reimaging and repositioning for excessive motion.

Addressing challenges in low-income and middle-income countries through novel radiotherapy research opportunities

Although radiotherapy continues to evolve as a mainstay of the oncological armamentarium, research and innovation in radiotherapy in low-income and middle-income countries (LMICs) faces challenges. This third Series paper examines the current state of LMIC radiotherapy research and provides new data from a 2022 survey undertaken by the International Atomic Energy Agency and new data on funding. In the context of LMIC-related challenges and impediments, we explore several developments and advances-such as deep phenotyping, real-time targeting, and artificial intelligence-to flag specific opportunities with applicability and relevance for resource-constrained settings. Given the pressing nature of cancer in LMICs, we also highlight some best practices and address the broader need to develop the research workforce of the future. This Series paper thereby serves as a resource for radiation professionals.

Predictive value of magnetic resonance imaging diffusion parameters using artificial intelligence in low-and intermediate-risk prostate cancer patients treated with stereotactic ablative radiotherapy: A pilot study

INTRODUCTION

To investigate the predictive value of the pre-treatment diffusion parameters of diffusion-weighted magnetic resonance imaging (DW-MRI) using artificial intelligence (AI) for prostate-specific antigen (PSA) response in patients with low- and intermediate-risk prostate cancer (PCa) treated with stereotactic ablative radiotherapy (SABR).

METHODS

Retrospective evaluation was performed for 30 patients using pre-treatment multi-parametric MR image datasets between 2017 and 2021. MR-based mean- and minimum apparent diffusion coefficients (ADCmean, ADCmin) were calculated for the intraprostatic dominant lesion. Therapeutic response was assessed using PSA levels. Predictive performance was assessed by the receiver operating characteristic (ROC) analysis. Statistics performed with a significance level of p ≤ 0.05.

RESULTS

No biochemical relapse was detected after a median follow-up of twenty-three months (range: 3-50), with a median PSA of 0.01 ng/ml (range: 0.006-2.8) at the last examination. Significant differences were observed between the pre-treatment ADCmean, ADCmin parameters, and the group averages of patients with low and high 1-year-PSA measurements (p < 0.0001, p < 0.0001). In prediction, the random forest (RF) model outperformed the decision tree (DT) and support vector machine (SVM) models by yielding area under the curves (AUC), with 0.722, 0.685, and 0.5, respectively.

CONCLUSION

Our findings suggest that pre-treatment MR diffusion data may predict therapeutic response using the novel approach of machine learning in PCa patients treated with SABR.

IMPLICATIONS FOR PRACTICE

Clinicians shall measure and implement the evaluation of the suggested parameters (ADCmin, ADCmean) to provide the most accurate therapy for the patient.

Long term update on toxicity and survival of a phase II trial of linac-based stereotactic body radiation therapy for low-intermediate risk prostate cancer

BACKGROUND

In 2016 we published a phase II study exploring safety and efficacy of Stereotactic Body Radiation Therapy (SBRT) delivered with Volumetric Modulated Arc Therapy (VMAT) and Flattening Filter Free (FFF) beams techniques in prostate cancer (PC) patients. We present herein the updated results on late toxicity and long-term survival.

METHODS

Patients enrolled in the study had a biopsy-confirmed localized PC and the features of a low- or intermediate-risk disease (National Comprehensive Network Criteria). The radiotherapy (RT) schedule consisted of 35 Gy delivered in five fractions every other day. Toxicities were registered according to the common toxicity adverse events v4.0. Biochemical recurrence was defined as an increase of prostate specific antigen after nadir, confirmed at least once. Local recurrence (LR) and distant metastases were detected either with Choline- or PSMA-PET/CT scans. Kaplan-Meier curves for Biochemical Recurrence-Free Survival (BFS), Local Control (LC), Distant Metastasis Free Survival (DMFS) and Cancer Specific Survival, were calculated by using MedCalc.

RESULTS

Ninety patients were submitted to SBRT between February 2012 and March 2015. Fifty-eight patients (64.5%) had a Gleason Score of 6, while 32 (35.5%) had a Gleason Score of 7. A late grade 1 Genito-Urinary toxicity was observed in 54.5% of patients while a grade 2 in 3.3%. A late Gastro-intestinal grade 1 toxicity was reported in 18.9% of patients, while a grade 2 in 2.2%. Erectile dysfunction was reported by 13% of patients No heavier toxicities were observed. At a median follow-up of 102 months, 5- and 8-year BFS were 93.0% and 84.4% respectively, 5- and 8-year LC were 95.2% and 87.0% respectively, 5- and 8-year DMFS were 95.3% and 88.4%, respectively.

CONCLUSIONS

This long-term update confirms that SBRT is a valid therapeutic strategy for low-intermediate risk PC. RT with VMAT and FFF warrants optimal results in terms of toxicity and disease control.

Dosimetric comparison between stereotactic body radiotherapy and carbon-ion radiation therapy for prostate cancer

Background

Prostate cancer rates have been steadily increasing in recent years. As high-precision radiation therapy methods, stereotactic body radiation therapy (SBRT) and carbon-ion radiation therapy (CIRT) have unique advantages. Analyzing the dosimetric differences between SBRT and CIRT in the treatment of localized prostate cancer can help provide patients with more accurate, individualized treatment plans.

Methods

We selected computed tomography positioning images and the contours of target volumes of 16 patients with localized prostate cancer who received radiotherapy. We delineated the organs at risk (OARs) on the CyberKnife (CK) treatment planning system (TPS) MultiPlan4.0, which were imported into the CIRT uniform scanning TPS HIMM-1 ci-Plan. Two treatment plans, SBRT and CIRT, were designed for the same patient, and we used SPSS 22.0 for the statistical analysis of data.

Results

Both SBRT and CIRT plans met the prescribed dose requirements. In terms of target volume exposure dose, D2 (P<0.001), D5 (P<0.001), D50 (P<0.001), D90 (P=0.029), D95 (P<0.001), D98 (P<0.001), and Dmean (P<0.001) under SBRT were significantly higher than those under CIRT; the conformity index (CI) under SBRT was significantly better than that under CIRT (P<0.001); the target volume coverage rate (V95%) and dose homogeneity index (HI) under CIRT were significantly better than those under SBRT (P<0.001). In terms of OAR exposure dosage, the Dmax of the bladder and rectum under SBRT was significantly lower than that under CIRT (P<0.001), but Dmean was in the other direction; the exposure dose of the intestinal tract under CIRT was significantly lower than that under SBRT (P<0.05); Dmax of the femoral head under CIRT was significantly lower than that under SBRT (P<0.05), and there was no statistical difference between them at other doses.

Conclusions

In this study, we found that when CIRT was used for treating localized prostate cancer, the dose distribution in target volume was more homogeneous and the coverage rate was higher; the average dose of OARs was lower. SBRT had a better CI and higher dose in target volume; the dose hotspot was lower in OARs. It is important to comprehensively consider the dose relationship between local tumor and surrounding tissues when selecting treatment plans.

A dosimetric comparison for SBRT plans of localized prostate cancer between Cyberknife and Varian Truebeam STX device

As the Stereotactic Body Radiotherapy (SBRT) approach began to increase in treating patients with localized prostate cancer, it became necessary to investigate which methods used in practice were better. The aim of this study is to perform a dosimetric comparison of the advantages and disadvantages of SBRT treatments for localized prostate cancer delivered by CyberKnife (CK) and Varian Truebeam STX (FF and FFF). Seventeen intermediate and high-risk patients with localized prostate cancer were included in the study. SBRT plans for the CK system and Varian Truebeam STX systems with and without Flattening Filters (Tru-FF and Tru-FFF) were prepared for each patient. Plans prepared for each patient were planned at a fraction dose of 6.7 Gy at 6 MV energy and a target dose of 33.5 Gy in 5 fractions. For all plans, cumulative dose-volume histograms (DVHs) were generated for target volumes and organs at risk (OAR). The maximum doses of PTV (41 Gy) in CK plans are higher than the maximum doses (35 Gy) in VMAT plans prepared with Tru-FF or Tru-FFF beams. The mean dose of the rectal wall (10.06 ± 2.40Gy for CK) is still relatively low compared to other plans (13.46 ± 2.16 Gy for Tru-FF and 13.61 ± 2.32 Gy for Tru-FFF). The bladder wall (14 Gy for CK, 26 Gy for Tru-FF and Tru-FFF) and femoral head (6.8 Gy for CK, 9 Gy for Tru-FF and 9.4 Gy Tru-FFF) doses were also lower for CK plans. The CK plans provide better tumour control due to low doses in critical organs and high target doses than the Tru-FF or Tru-FFF plans. It was observed that CK and VMAT plans for SBRT with 6 MV photon beams provided acceptable results in term of treatment planning criteria such as Conformity Index and Homogeneity Index. It is recommended to use a target tracking system to provide an accurate and reliable SBRT treatment with VMAT and CK techniques.

The Utility of 68Ga-PSMA PET/CT in Decisions Regarding Administering Salvage Radiotherapy to Men with Prostate Cancer

BACKGROUND

Numerous papers have described 68Ga-prostate-specific membrane antigen (PSMA) positron emission tomography/computed tomography (PET/CT)'s sensitivity in identifying prostate cancer (PCa) recurrence. This study aimed to characterize the role of 68Ga-PSMA PET/CT in deciding to re-irradiate pelvic structures.

METHODS

68Ga-PSMA PET/CT scans performed at Sheba Medical Center over seven years in 113 men were reviewed. All had undergone radiation to the prostate (70, 61.9%) or post-radical prostatectomy radiation to the prostate fossa (PF) (43, 48.1%), and had local or oligometastatic PCa recurrence and received salvage radiotherapy (SRT) based on PET/CT findings.

RESULTS

Mean age was 70.7 years. The mean grade group was 2.9; the mean prostate-specific antigen was 9.0. The 68Ga-PSMA PET/CT positive findings included: 37 (32.7%) in the prostate, 23 (20.4%) in seminal vesicles, 7 (6.2%) in the PF, and 3 (2.7%) in the seminal vesicle fossa. The mean standardized uptake value was 10.6 ± 10.2 (range: 1.4-61.6); the mean lesion size was 1.8 ± 3.5 mm (range: 0.5-5.1). SRT was directed toward the prostate and seminal vesicles in 48 (42.5%), PF in 18 (15.9%), and intrapelvic lymph node and bone in 47 (41.6%). Toxicities were mostly mild to moderate.

CONCLUSION

68Ga-PSMA PET/CT-identified relapse with targeted SRT was well-tolerated and may result in less onerous treatments.

A radiation resistance related index for biochemical recurrence and tumor immune environment in prostate cancer patients

PURPOSE

To establish and verify a novel radiation resistance related index for predicting biochemical recurrence and tumor immune environment in prostate cancer (PCa) patients.

MATERIALS AND METHODS

The transcriptome information of PCa were obtained from GEO and TCGA portal. We identified radiation resistance related genes (RRGs) between radioresistant and radiosensitive PCa cells. We conducted multivariate Cox analysis to construct a novel radiation resistance related index for predicting biochemical recurrence (BCR)-free survival (BCRFS). Internal and external validations were conducted. Preliminary experimental verifications were performed.

RESULTS

We identified 194 differentially expressed RRGs and three radiation resistance related molecular clusters for PCa. Moreover, we established a novel radiation resistance related index and succeeded in conducting internal and external validations. High-risk populations meant significantly worse BCRFS in training, testing and validating cohort. The area under receiver operating characteristic curve were 0.809, 0.698, and 0.712 in training, testing, and validating cohort. The immune microenvironment was significantly different between high and low-risk score patients. Preliminary experiment identified and validated three potential biomarkers related to radiation resistance (ZNF695, TM4SF19, CCDC3) of PCa.

CONCLUSIONS

This study successfully established and verified a novel radiation resistance related index, which had an excellent performance in predicting BCR and tumor immune microenvironment in patients with PCa.