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SU_31_2317 - 68Ga-PSMA PET/CT-Guided Hypofractionated Salvage Radiation Therapy and Simultaneous Integrated Boost for PSMA-Avid Sites after Radical Prostatectomy: Safety and High PSA Response

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

68Ga-PSMA PET/CT-Guided Hypofractionated Salvage Radiation Therapy and Simultaneous Integrated Boost for PSMA-Avid Sites after Radical Prostatectomy: Safety and High PSA Response
X. Qi1, X. S. Gao1, S. C. Zhang1, B. Zhao1, C. Liu2,3, H. Zhu2,3, N. Li2,3, and Z. Yang2,3; 1Department of Radiation Oncology, Peking University First Hospital, Beijing, China, 2Key laboratory of Carcinogenesis and Translational Research (Ministry of Education), Beijing, China, 3department of nuclear medicine, Peking University Cancer Hospital & Institute, Beijing, China

Purpose/Objective(s): 68Ga-labeled PSMA PET/CT (PSMA) has shown a novel promising diagnostic tool to locate early biochemical failure after radical prostatectomy (RP) in prostate cancer patients, and would influence the decision for salvage radiation therapy (SRT) . In this study, we evaluated the PSMA-guided hypofractionated salvage radiation therapy and simultaneous integrated boost for PSMA-avid sites.

Materials/Methods: From June 2016 to December 2017, 31 patients with biochemical failure after RP who underwent PSMA were evaluated undergoing SRT in our department. The median time between RP and PSMA was 10 months (range: 1-96 months). 14 patients (45.2%) received ADT prior to PSMA. Prostate bed was treated with IG-VMAT to 62.5Gy in 25 fractions with PSMA-guided SIB of 66-67.5Gy for prostate fossa unsuspected disease, 60-64Gy for lymph nodes and bone metastasis. 28 patients(90.3%) received whole pelvis irradiation. Acute adverse effects were assessed with RTOG criteria. Treatment response was defined as >50% reduction in PSA.

Results: Median follow-up time was 7 months (range: 1-16 months). PSMA was positive in 22 patients (71.0%). Median PSA in positive patients was 1.15 ng/ml (range 0.003-27.3ng/ml). Pelvis nodes, non-pelvis nodes, bone and within the prostate suspected recurrence disease were detected in 10 (45.5%), 3 (13.6%), 7 (31.8%), and 8 (36.4%) patients, respectively. Median (range) dosimetric parameters included small bowel Dmax 4976.5cGy (0-5885.4), V45 29.0cc (0-126.8). rectum: V60 6.2% (0.5-16.2%), V50 17.2% (7.4-29.3%). Bladder: V60 23.5% (7.9-41.8%), V50 30.7% (13.9-55.2%). Acute grade 1 and 2 GI toxicity was 63.6% and 9.1%. Acute grade 1 and 2 GU toxicity was 59.1% and 18.2%. In patients who had finished SRT more than 3 months, 71% of patients had treatment response following SRT.

Conclusion: Our study suggests that hypofractionated SRT with SIB PSMA-avid sites was well tolerated and results in good PSA response in patient with biochemical failure after radical prostatectomy. However, the long-term survival outcomes need to be further explored.

Author Disclosure: X. Qi: None. X. Gao: None. S. Zhang: None. B. Zhao: None.

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SU_31_2317 - 68Ga-PSMA PET/CT-Guided Hypofractionated Salvage Radiation Therapy and Simultaneous Integrated Boost for PSMA-Avid Sites after Radical Prostatectomy: Safety and High PSA Response



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