SS 30 - GU 4 - SBRT for Prostate and Renal Cancers
219 - Outcomes of Stereotactic Body Radiation Therapy Delivered by Gantry-Based Linear Accelerators for Low and Intermediate-Risk Prostate Adenocarcinoma: A Multi-institutional Study
Tuesday, October 23
5:25 PM - 5:35 PM
Location: Room 214 C/D
Outcomes of Stereotactic Body Radiation Therapy Delivered by Gantry-Based Linear Accelerators for Low and Intermediate-Risk Prostate Adenocarcinoma: A Multi-institutional Study
A. T. Dang1, C. R. King1, D. Shabsovich2, C. A. Mantz3, K. L. Stephans4, D. A. Loblaw5, P. Cheung6, M. Scorsetti7, L. Cozzi7, A. S. DeNittis8, Y. Wang9, N. Nickols1, P. A. Kupelian1, M. L. Steinberg10, and A. U. Kishan1; 1Department of Radiation Oncology, University of California, Los Angeles, Los Angeles, CA, 2David Geffen School of Medicine at UCLA, Los Angeles, CA, 321st Century Oncology, Fort Myers, FL, 4Department of Radiation Oncology, Taussig Cancer Institute, Cleveland Clinic, Cleveland, OH, 5Institute of Health Policy, Management and Evaluation, University of Toronto, Toronto, ON, Canada, 6Department of Radiation Oncology, Sunnybrook Odette Cancer Centre, University of Toronto, Toronto, ON, Canada, 7Humanitas Cancer Center, Rozzano, Italy, 8Lankenau Medical Center/Lankenau Institute for Medical Research, Wynnewood, PA, 9Lankenau Medical Center/Lankenau Insitute for Medical Research, Wynnewood, PA, 10University of California, Los Angeles, Los Angeles, CA
Purpose/Objective(s): Stereotactic body radiation therapy (SBRT) is increasingly being used to treat low- and intermediate-risk prostate cancer (PCa). Much of the available published data are derived from patients treated with robotic-arm mounted linear accelerators (LINACs). However, SBRT can also be delivered using gantry-mounted LINACs. We sought to review the efficacy and safety of gantry-based SBRT for localized PCa from a multi-institutional consortium pooled analyses.
Materials/Methods: Individual patient-level data from six institutional prospective phase II trials of gantry-based SBRT from 2006-2017 were obtained. Patients were stratified into low- and intermediate-risk cohorts, as defined by the National Comprehensive Cancer Network guidelines. Biochemical relapse (BCR) was defined as PSA rise >2 ng/ml above nadir. Toxicity data was scored according to the CTCAE v 4.0 or Radiation Therapy Oncology Group scoring system. Kaplan Meier analysis was used to analyze freedom from BCR (FFBCR) and overall survival (OS) rates.
Results: 928 men were eligible for analysis, (506 [54.5%] with low risk and 422 [45.5%] with intermediate risk PCa). The median follow-up was 3 years (range, 0.5-10.8 years). Fractionation schemes ranged from 7-8 Gy in 5 fractions. 21 patients (2.3%) received ADT with SBRT. 31 patients (3%) experienced BCR, 5 patients (0.5%) experienced distant metastases, and 0 patients (0%) died of PCa. The 5-year FFBCR rate was 97% in low-risk patients and 87% in intermediate-risk patients. Corresponding 5-year OS rate was 99% in the low-risk group and 98% in the intermediate-risk group. Toxicity rates are displayed in table 1. 10 patients (1.1%) experienced acute grade 3 genitourinary (GU) toxicities, including urinary frequency, retention, dysuria, and bladder outlet obstruction. Two (0.2%) acute grade 3 gastrointestinal (GI) toxicities (diarrhea) were observed. 7 patients (0.8%) experienced late grade 3 GU toxicities, including urinary retention, obstruction, mixed urinary incontinence, frequency, dysuria, and urethral necrosis. Three (0.3%) late grade 3 GI toxicities (radiation proctitis) were observed. One (0.1%) late grade 4 GU toxicity (necrosis) and two (0.2%) late grade 4 GI toxicities (fistula-in-ano and necrosis) were observed.
Conclusion: To the best of our knowledge, this is the largest analysis of gantry-based SBRT for localized PCa. The results indicate a favorable efficacy and toxicity profile that is equal to robotic-arm mounted LINACs, though longer term follow-up is warranted to draw firm conclusions regarding comparative efficacy. Table 1. Physician-Scored Toxicity (CTCAE or RTOG)
| || Grade 1 || Grade 2 || Grade 3 || Grade 4 |
| Acute GU || 306 (33%) || 117 (12.6%) || 10 (1.1%) || 1 (0.1%) |
| Acute GI || 127 (13.7%) || 39 (4.2%) || 2 (0.2%) || 1 (0.1%) |
| Late GU || 223 (24%) || 63 (6.8%) || 7 (0.8%) || 1 (0.1%) |
| Late GI || 99 (10.7%) || 28 (3%) || 3 (0.3%) || 2 (0.2%) |
Author Disclosure: A.T. Dang: None. D. Shabsovich: None. C.A. Mantz: None. D. Loblaw: Honoraria; AbbVie, Astellas, Bayer, Janssen. Consultant; AbbVie. Advisory Board; Amgen, Astellas, Ferring, Janssen. Patent/License Fees/Copyright; Sunnybrook Research Institute. P. Cheung: Independent Contractor; Ontario Ministry of Health and Long-Term Care. Research Grant; Sanofi Aventis, Pfizer, Abbvie. M. Scorsetti: None. L. Cozzi: None. N. Nickols: Research Grant; Janssen LLC, Nanobiotix, Varian Medical Systems. Stock; GeneSciences Inc. Stock Options; GeneSciences Inc. P.A. Kupelian: Research Grant; Varian Medical Systems, Inc. Honoraria; Accuray. Consultant; ViewRay. Advisory Board; Accuray, ViewRay. Travel Expenses; Accuray, ViewRay. M.L. Steinberg: Honoraria; Accuray. A.U. Kishan: None.