Genitourinary Cancer

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SU_31_2314 - Interim results of a randomized trial of observation versus SABR for castration-sensitive oligometastatic prostate cancer

Sunday, October 21
1:15 PM - 2:45 PM
Location: Innovation Hub, Exhibit Hall 3

Interim results of a randomized trial of observation versus SABR for castration-sensitive oligometastatic prostate cancer
R. Phillips1, N. Radwan1, A. E. Ross2, S. Rowe3, M. Gorin2, E. S. Antonarakis1, C. Deville Jr1, S. C. Greco1, S. Denmeade1, C. Paller1, D. Song1, H. Wang1, M. Carudcci1, K. Pienta1, M. G. Pomper3, T. L. DeWeese4, A. P. Dicker5, M. Eisenberger1, and P. T. Tran4; 1Johns Hopkins Medicine, Baltimore, MD, 2Department of Urology, Johns Hopkins University School of Medicine, Baltimore, MD, 3Department of Radiology, Johns Hopkins University School of Medicine, Baltimore, MD, 4Department of Radiation Oncology and Molecular Radiation Sciences, Johns Hopkins University School of Medicine, Baltimore, MD, 5Department of Radiation Oncology, Thomas Jefferson University, Philadelphia, PA

Purpose/Objective(s): Local ablative treatment to oligometastatic patients can result in long term disease-free survival in colorectal, sarcoma and lung cancer patients. The importance of consolidating all macroscopic tumor deposits in prostate cancer in the modern era is an area of active investigation. Stereotactic ablative radiation (SABR) is highly focused, high-dose radiation that is ideally suited for treatment of oligometastatic patients. Here we report on interim safety and translational outcomes of our Phase II randomized trial of SABR to men with recurrent low volume (1-3 metastases) hormone sensitive metastatic prostate cancer.

Materials/Methods: Patients are randomized 2:1 to SABR:observation with minimization to balance assignment by primary intervention, prior hormonal therapy, and PSA doubling time. Progression after 6 months will be compared using Fisher's exact test. Hazard ratios and Kaplan-Meier estimates of progression free survival (PFS), ADT free survival (ADT-FS), time to locoregional progression (TTLP) and time to distant progression (TTDP) will be calculated based on an intention-to-treat. Local control will be assessed using RECIST 1.1 criteria. Adverse events will be summarized by type and grade. Quality of life pre- and post- SABR will be measured by Brief Pain Inventory. Further fundamental analysis of the oligometastatic state will be achieved through correlation with germline DNA repair gene mutations using the Color Genomics panel, investigational 18F-DCFPyL PET/CT imaging and measurement of circulating tumor cells, circulating tumor DNA and deep sequencing of circulating T-cell receptor repertoires.

Results: Since activation in April 2016 we have had enrollment of 50 men and subsequent randomization of 49 out of the target 54. Thus far, as expected only minimal side-effects (no >Grade 2 toxicity) have been observed from the SABR alone. 4/37 (11%) men tested had germline DNA repair gene mutations. A circulating tumor cell test detected only 1 CTC/7.5-ml in two men and the remaining eight men had no CTCs (20% detectability). In contrast, 9/17 (53% detectability) men had detectable CTCs using the HD-CTC platform and 3/4 (75%) interpretable cases showed a response following SABR.

Conclusion: This trial is the first randomized Phase II study in the Western Hemisphere evaluating the safety and efficacy of SABR in oligometastatic hormone-sensitive prostate cancer. Our leading-edge laboratory and imaging correlates will allow an unprecedented opportunity to characterize, in isolation, the effects of SABR on the dynamics of and immunologic response of the oligometastatic state.

Author Disclosure: R. Phillips: None. N. Radwan: None. A.E. Ross: Consultant agreement ended 2014, currently conducting collaborative research; GenomeDx. Consultant; GenomeDx. S. Rowe: None. M. Gorin: None. E.S. Antonarakis: None. D. Song: Stock; Roche. T.L. DeWeese: None. A.P. Dicker: Research Grant; Radiation Therapy Oncology Group. Travel Expenses; Prostate Cancer Foundation. Chair; Department of Defense. P.T. Tran: Research Grant; PCORI, Movember-PCF, American Lung Association, Astellas-Medivation, Kimmel Foundation, ACS, NIH-NCI. Honoraria; Dendreon. Consultant; RefleXion Medical. Advisory Board; Dendreon, Astellas-Medivation. Travel Expenses; Dendreon, RefleXion Medical. Patent/License Fees/Copyright; Natsar Pharmaceuticals, Compounds and Methods of Use in Ablative RT. Chair of Radiation Oncology Study Section; RSNA R&E Foundation. Senior Editor; Cancer Research. Co-Chair; NRG Oncology.

Ryan Phillips, MD, PhD

Johns Hopkins Medical Institutions

Disclosure:
Compensation
RefleXion Medical: Research Grants

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