ESTRO 2020 Abstract book

S659 ESTRO 2020

analyzed. 3-year bPFS in low, favorable intermediate, unfavorable intermediate, high, and very high group were 100%, 100%, 100%, 94.6% and 84.1% respectively. 5-year bPFS in low, favorable intermediate, unfavorable intermediate, high, and very high group were 100%, 100%, 100%, 90.4% and 80.6% respectively. The incidence of acute ≥ grade 2 GU and GI toxicity were 9.3% and 5.6% respectively and the incidence of late ≥ grade 2 GU and GI toxicity were 7.1% and 5.2% respectively. In multivariate analysis, no association was found between dose fractionation or antiplatelet/anticoagulant drugs and ≥ grade 2 toxicity.

Conclusion This study demonstrates that 3’RNAseq (95%) and NSnC (100%) are technically feasible in FFPE diagnostic PCa biopsies, generating analysable data. Over 600 genes are identified by 3'RNAseq as differentially expressed between patients with PCa progression post-RT and those with stable disease with differences between these patient groups also seen on NSnC analysis. Further work is on-going to identify a predictive RT response signature. Similarities in gene expression appear to exist between baseline metastatic PCa and patients with post-RT PCa progression. PO-1161 The first study in outcomes and toxicity of definite VMAT for prostate cancer in Southeast Asia P. Wongsuwan 1 , S. Vanitchpongphan 1 , K. Tantisiriwat 1 , K. Sooksatian 1 , W. Sittiwong 1 , P. Dankulchai 1 1 Faculty of Medicine- Siriraj Hospital- Mahidol University, Division of Radiation Oncology- Department of Radiology, Bangkok, Thailand Purpose or Objective Volumetric-modulated arc radiation therapy (VMAT) has been well-demonstrated for improved plan quality and treatment-related side effect in prostate cancer. This study aims to report the treatment outcome and complication in prostate cancer patients treated with definite VMAT. This is the first report of VMAT in prostate cancer in Southeast Asia. Material and Methods This is a retrospective data analysis of patients with prostate cancer who received definite VMAT in conventional fractionation (2 Gy/F) to moderate hypo- fractionation (3-3.1 Gy/F) during 2012 to 2018. Biochemical failure was determined by using Phoenix definition which defined by a rise of >2 ng/ml above the nadir PSA. Biochemical progression-free survival (bPFS), locoregional recurrence free survival (LRRFS), distant metastatic-free survival (DMFS), and overall survival (OS) were analyzed by Kaplan-Meier survival analysis. Acute and late genitourinary (GU) and gastrointestinal (GI) toxicity were assessed according to Common terminology criteria for Adverse Event (CTCAE) version 5.0. Results A total of 324 patients were analyzed. Median follow up time was 3.4 years. 305 patient (94.1%) were delivered 2- Gy/F VMAT with a total dose of 72-78 Gy. Androgen deprivation therapy was prescribed in 307 patients (94.7%). 3-year bPFS, LRRFS, DMFS, and OS were 93.7%, 96.9%, 95.2% and 99.2% respectively and 5-year bPFS, LRRFS, DMFS, and OS were 90.9%, 95.3%, 93.1% and 97.8% respectively. bPFS stratified by NCCN risk group was

Conclusion Definite VMAT in prostate cancer results in an impressive survival outcome which is comparable to previous studies with conventional fractionation or moderate hypofractionation; whereas, the overall rates of acute and late GU and GI toxicity were relatively low.