Genitourinary Cancer

SS 30 - GU 4 - SBRT for Prostate and Renal Cancers

217 - Long-Term Outcomes of Stereotactic Body Radiation Therapy for Low and Intermediate-Risk Prostate Adenocarcinoma: A Multi-Institutional Consortium Study

Tuesday, October 23
5:05 PM - 5:15 PM
Location: Room 214 C/D

Long-Term Outcomes of Stereotactic Body Radiation Therapy for Low and Intermediate-Risk Prostate Adenocarcinoma: A Multi-Institutional Consortium Study
A. U. Kishan1, A. Katz2, C. A. Mantz3, F. I. Chu1, L. Appelbaum4, D. A. Loblaw5, I. D. Kaplan4, H. T. Pham6, M. K. Buyyounouski7, D. B. Fuller8, R. Meier9, S. P. Collins10, N. Shaverdian1, A. T. Dang11, Y. Yuan12, H. P. Bagshaw7, N. D. Prionas13, N. Nickols1, M. L. Steinberg14, and C. R. King1; 1Department of Radiation Oncology, University of California, Los Angeles, Los Angeles, CA, 2FROS Radiation Oncology and CyberKnife Center, Flushing, NY, 321st Century Oncology, Fort Myers, FL, 4Beth Israel Deaconess Medical Center, Boston, MA, 5Institute of Health Policy, Management and Evaluation, University of Toronto, Toronto, ON, Canada, 6Virginia Mason Medical Center, Seattle, WA, 7Stanford University School of Medicine, Palo Alto, CA, 8Genesis Healthcare Partners, San Diego, CA, 9Swedish Cancer Institute, Seattle, WA, 10Department of Radiation Medicine, Georgetown University Hospital, Washington, DC, 11Ochsner, New Orleans, LA, 12UCLA Department of Radiation Oncology, Los Angeles, CA, 13Stanford Cancer Institute, Stanford, CA, 14University of California, Los Angeles, Los Angeles, CA

Purpose/Objective(s): While a growing body of evidence supports the use of stereotactic body radiation therapy (SBRT) for the treatment of low- and intermediate-risk prostate adenocarcinoma (PCa), some trepidation exists regarding its long-term efficacy and safety.

Materials/Methods: Men with low- and intermediate-risk PCa, as defined per the National Comprehensive Cancer Network guidelines, who were enrolled on various institutional phase II trials of SBRT between 2000- 2012 were included in a multi-institutional consortium. Men with multiple intermediate-risk factors, primary Gleason pattern 4 disease, or ≥50% positive cores (if known) were further subclassified as having unfavorable intermediate-risk disease. Biochemical relapse (BCR) was defined as PSA > “nadir +2” or initiation of androgen deprivation therapy (ADT). Toxicity data were scored according to the CTCAE v 3.0 or Radiation Therapy Oncology Group scoring systems.

Results: A total of 1641 men were eligible for analysis, with a median follow-up of 7.1 years. 297 patients (18.1%) had at least 9 years of follow-up. Fractionation schemes ranged from 33.50-40 Gy in 4-5 fractions. 1034 patients (63.0%) had low-risk disease, 444 (27.0%) had favorable intermediate-risk disease, and 163 (9.9%) had unfavorable intermediate-risk disease. 58 patients (3.6%) received short-term ADT. 100 patients (6.0%) experienced BCR, 10 (0.6%) experienced distant metastases, and no patients died of PCa. By Kaplan-Meier analysis, 5- and 10-year freedom from BCR (FFBCR) rates were 97% and 91% in the low-risk group and 94% and 89% in the favorable intermediate-risk group; 5- and 8-year rates (as no 10-year follow-up was available) in the unfavorable intermediate-risk group were and 93% and 85% (p < 0.05 by log-rank test). Corresponding 5- and 10-year overall survival rates were 94% and 87% and 96.6% and 90.0% for the low and favorable-intermediate risk groups, and 5- and 8-year rates were and 90.5% and 88.4% in the unfavorable-intermediate risk group (p < 0.05 by log-rank test). Toxicity rates are displayed in table 1. Five patients (0.3%) experienced grade 3 acute genitourinary (GU) toxicities and 32 (2%) experienced grade 3 late GU toxicity. One late grade 4 GU toxicity (hemorrhagic urethritis) and one late grade 4 gastrointestinal toxicity (fistula-in-ano) were seen.

Conclusion: To the best of our knowledge, this is the largest analysis of long-term outcomes following SBRT for PCa, and suggest an efficacy and toxicity profile that compares favorably with other radiation modalities, such as conventionally-fractionated radiation therapy and brachytherapy. Offering SBRT in the context of a balanced discussion and shared decision making is appropriate for men with low and intermediate risk prostate cancer. Table 1. Physician-Scored Toxicity (CTCAE or RTOG)
Grade 1 Grade 2 Grade 3 Grade 4
Acute GU 344 (20.1%) 145 (8.8%) 5 (0.3%) 0
Acute GI 256 (15.6%) 52 (3.2%) 0 (0%) 0
Late GU 148 (9.0%) 129 (7.9%) 32 (2.0%) 1 (0.1%)
Late GI 86 (5.2%) 52 (3.2%) 2 (0.1%) 1 (0.1%)

Author Disclosure: A.U. Kishan: None. A. Katz: None. C.A. Mantz: None. F. Chu: None. L. Appelbaum: None. D. Loblaw: Honoraria; AbbVie, Astellas, Bayer, Janssen. Consultant; AbbVie. Advisory Board; Amgen, Astellas, Ferring, Janssen. Patent/License Fees/Copyright; Sunnybrook Research Institute. H.T. Pham: Honoraria; American College of Radiology. M.K. Buyyounouski: None. R. Meier: None. N. Shaverdian: None. A.T. Dang: None. N. Nickols: Research Grant; Janssen LLC, Nanobiotix, Varian Medical Systems. Stock; GeneSciences Inc. Stock Options; GeneSciences Inc. M.L. Steinberg: Honoraria; Accuray.

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