ESTRO 38 Abstract book

S835 ESTRO 38

.1% of patients were free from recurrence and 49.3 % had complete biochemical response. Median BRFS was 26 months (95% CI 23-46), Gleason score was the only prognostic independent factor associated with BRFS. Only 1 acute and 2 late G2 rectal and vesical toxicities were reported. Conclusion Stereotactic radiotherapy for prostate bed recurrence is safe and effective, regardless concomitant use of ADT and adverse prognostic factors. Prospective studies are needed to compare outcomes of conventional SRT to this technique EP-1547 Developing an empirical nomogram for clinical visualization of DFS/OS for prostate cancer patients R.M. Abdul 1 , E.P.P. Pang 1 , Y.S. Koh 1 , S.A. Gan 1 , J.K.L. Tuan 1,2 1 National Cancer Centre Singapore, Division of Radiation Oncology, Singapore, Singapore ; 2 Duke-NUS, Graduate Medical School, Singapore, Singapore Purpose or Objective To develop a predictive nomogram to provide clinical visualization on the probability of treatment outcomes [i.e. disease-free survival (DFS) and overall survival (OS)] for prostate cancer. Material and Methods This is a pilot longitudinal cohort study that analyzed 549 patients (enrolled in the DRO Cancer Registry) diagnosed with prostate cancer between 1998 and 2010. All the patients were stratified based on NCCN guidelines and have received radiotherapy up to 74Gy in 37# (+/- pelvic nodes irradiation). A multivariate analysis was conducted to predict DFS and OS as primary endpoints. Baseline prostate-specific antigen (PSA) level, T and N staging, Gleason scores (primary, secondary and total) were collected as independent prognostic factors in the building of this nomogram. Incidence of biochemical failure and death, along with its respective time from date of diagnosis to date of incidence, were tabulated to provide a binary predictor (SSMS, Microsoft). This is then input into a script utilizing R (survival), by using the Kaplan-Meier (K- M) survival estimate model. The resulting data output are then published on SQL Server Reporting Services (SSRS, Microsoft) to provide a visual representation of the model. Results Output from R provides a 95% Confidence Interval on DFS and OS based on input of the independent variables. A K- M survival curve (Figure 1), as well as a visual presentation based on a sample size of 100 patients of 5-year or 2-year survival estimates are displayed for facilitation of patients’ meaningful understanding of the results (Figure 2). However, there were wide confidence variances for certain stratified groups with small sample size.

Conclusion We have developed a cohort-based nomogram that served as a tool to facilitate the shared-decision making discussion between clinicians and patients on the management options. EP-1548 Patterns of progression in metastatic prostate cancer: who might benefit from targeted radiotherapy? P. Patel 1 , N. Tunariu 2 , A. Tree 1 1 Royal Marsden NHS Foundation Trust- London and the Institute of Cancer Research, Clinical Oncology, London, United Kingdom ; 2 Royal Marsden NHS Foundation Trust- London and the Institute of Cancer Research, Radiology, London, United Kingdom Purpose or Objective Treatment for metastatic castrate-resistant prostate cancer (mCRPC) patients has rapidly changed since the introduction of androgen receptor targeted therapies (ART) such as Abiraterone and Enzalutamide. These treatments are better tolerated and have less toxicities compared to chemotherapies used. Therefore, methods of maintaining patients on these oral medications are of great interest. The aim of this study was to document patterns of progression of patients on ART and to identify the number of patients potentially amenable to Stereotactive body radiotherapy (SBRT) for oligo- progressive disease (OPD). OPD is a relatively newly described disease state whereby 1-3 metastatic lesions are progressing/new whilst all other sites of disease are well- controlled by a systemic agent. Theoretically SBRT to OPD lesions could allow continued therapeutic benefit of these oral treatments. Material and Methods This is a single centre retrospective cohort study. Data was collected from electronic patient records from the first 50 patients treated with ART for mCRPC between April 2015 – 2017. Data including patient demographics, tumour staging, radiological and symptomatic response to ART, PSA trend, and progression pattern on serial imaging were collected. Results This study analysed 50 patient records. The median age of patients was 81 years. Median PSA at presentation was 26. At the time of analysis 37 patients had progressed on ART, and 5 remained in remission. Four patients stopped treatment due to toxicity, 1 patient transferred care and 3 patients died due to other causes. Of those patients who had progressed 6 patients (12%) demonstrated OPD. Further details of the patients demonstrating OPD is represented in Table 1. Patient no.1 was treated with SBRT twice for OPD occurring 3 years apart. Patient no. 4 demonstrated further OPD 6 months later. The majority of patients remained asymptomatic at the time of OPD, 2 patients presented with related pain not requiring intervention. OPD lesions were detected by multiple different imaging modalities including CT, Whole body diffusion weighted MRI (WBDWMRI) and PET/CT.