3282 - Preliminary Outcomes of a Phase II Trial of Focal Salvage LDR Brachytherapy for Local Recurrence of Prostate Cancer following External Beam Radiation Therapy

12:45pm - 02:00pm PT

Hall F

Screen: 17

POSTER

Presenter(s)

Ting Martin Ma, MD, PhD - University of Washington, Seattle, WA

T. M. M. Ma¹, A. Pham², H. Parsai³, J. R. Bradlo⁴, J. Bell³, R. Mangibin³, M. Montague⁵, S. Rieth⁵, and R. A. Hsi⁶; ¹University of Washington, Seattle, WA, ²University of Washington, Department of Radiation Oncology, Seattle, WA, ³EvergreenHealth Department of Radiation Oncology, Kirkland, WA, ⁴Prostate Cancer Center of Seattle, Seattle, WA, ⁵Fred Hutchinson Cancer Center Peninsula, Poulsbo, WA, ⁶University of Washington School of Medicine, Seattle, WA

Purpose/Objective(s):

To assess the clinical outcomes of low dose rate focal salvage brachytherapy (FSB) for biopsy-proven local recurrence of prostate cancer after definitive external beam radiation therapy (EBRT).

Materials/Methods:

Patients experiencing a Phoenix definition of PSA recurrence (nadir + 2.0 ng/dL) or three consecutive PSA increases following definitive EBRT for localized prostate cancer, and who had a negative metastatic workup, were enrolled in a Phase II clinical trial. Patients underwent an MR-guided transperineal templated biopsy of the prostate. Those with pathologically confirmed recurrence were treated with FSB using iodine-125 seeds at a prescribed dose of 145 Gy. The brachytherapy planning target volume (PTV) was delineated based on the positions of pathologically negative core biopsies adjacent to the positive ones, as recorded on the template grid during the biopsy. An intraoperative treatment plan was then created to cover the PTV with the 145 Gy isodose line. Follow-up included evaluating genitourinary (GU) and gastrointestinal (GI) toxicities using the Common Terminology Criteria for Adverse Events version 4.03 (CTCAE v4.03), patient-reported outcomes through the International Prostate Symptom Score (IPSS) and Expanded Prostate Cancer Index (EPIC) forms, as well as serial PSA monitoring.

Results:

Nineteen patients underwent FSB. The median prior EBRT dose was 7805 cGy (interquartile range IQR 7560-7920) and the median time from completion of EBRT to FSB was 75 months (IQR 56-111). The median PSA prior to FSB was 2.5 ng/dL (IQR 2.0 – 3.8). The median follow-up after FSB was 23 months (IQR 11-44). Sixteen patients were free of Phoenix definition of PSA failure at last follow up. One and two-year biochemical recurrence-free survival rates were 94.4% and 85.0%, respectively. Of the three patients who experienced a PSA failure, one developed distant metastases 5 months after FSB, one had a biopsy proven seminal vesicle recurrence 3 years after FSB, and another had biochemical failure 22 months after FSB pending imaging workup. The median change in post-FSB IPSS score compared to the pre-FSB IPSS score was an increase of 1.5 (IQR -1 to 6.8) at 3 month follow-up and an increase of 2.0 (IQR -2.5 to 6.8) at last follow-up (=1 year). The median change in post-FSB EPIC urinary domain score compared to the pre-FSB score was -2.0 (IQR -20.5 to +5.0) at 3 month follow-up and -5.5 (IQR -12.3 to +1.0) at last follow-up (=1 year). The median change in post-FSB EPIC bowel domain score compared to the pre-FSB score was -3.0 (IQR -13.0 to 0.0) at 3-month follow-up and -1.0 (IQR -3.3 to +1.3) at last follow-up (=1 year). One patient experienced post-FSB Grade 3 GU toxicity and there was no grade 3 GI toxicities.

Conclusion:

High dose FSB offers excellent biochemical control with a favorable toxicity profile for patients with local recurrence of prostate cancer after EBRT. Further clinical trials and longer follow-up are needed to better assess long term outcomes.