ESTRO 2023 - Abstract Book

S1183

Digital Posters

ESTRO 2023

Conclusion Analysed radiomic features – excepting kurtosis - showed convergence of values for WP and DIL over time, implying these regions become less distinct with treatment. The early rise and fall in mean intensity during RT implies an imaging biomarker for treatment response should be acquired at multiple time points during treatment to fully understand dynamic changes during RT. The treatment time of the 5# regimen is half the 20# regimen, however when images are sampled at points with equivalent percentage of total dose received, the 5 and 20# curves show no difference in mean intensity suggesting biological processes underly MR imaging changes occur at an earlier time points with higher doses per fraction.

PO-1461 Omission of pelvic RT in elderly patients with prostate cancer. Institutional experience

G. Ferraris 1 , A.M. Gomez Palacios 1 , M.F. Diaz Vazquez 1 , O. Perez Conci 1 , L. Caussa 1 , D. Fernandez 1 , L. Brun 1 , B. Raiden 1

1 Centro de Radioterapia Dean Funes, Radiotherapy, Cordoba, Argentina

Purpose or Objective To analyze the clinical outcomes and toxicities of patients older than 75 years treated at our institution with hypofractionated treatments (IMRT and SBRT) to prostate and seminal vesicles volumes alone, as well as the risk factors associated with greater biochemical relapse. Materials and Methods Retrospective, descriptive and observational study of 90 patients older than 75 years with organ-confined prostate cancer treated with hypofractionated treatments for prostate volume +/- seminal vesicles (IMRT 20Fx/60Gy and SBRT 5Fx/36.25Gy) at the Centro de Radioterapia Dean Funes. None of the patients received pelvic lymph node irradiation. The data extracted from the institutional medical records of the patients treated with their respective follow-ups were analyzed. To assess risk factors (PSAi ≥ 20, ISUP ≥ 4, T ≥ 2c, high-grade PIN, IPN, compromised cylinders ≥ 50%, high-grade NCCN), univariate and multivariate analysis with Cox regression were performed. To assess overall survival, biochemical relapse-free survival (BRFS), and metastasis-free survival (MFS), Kaplan Meier curves were performed. Results 90 patients older than 75 years were treated, with a mean age of 78.3 years. The mean follow-up was 3 years. 60% presented high risk according to NCCN classification, 40% unfavorable intermediate risk. Androgen blockade was performed in 60% of the patients. 86% performed IMRT and 14% SBRT. No patient had to discontinue treatment. At follow-up, 90% of the patients were alive, 5% had biochemical relapse and 2% had distant metastases. The BRFS at 2 years was 100% and at 3 years 95%. The MFS was 100% at two years and 97% at 3 years. Among the risk factors analyzed, high-grade PIN (p=0.01), involvement >50% of cylinders in the biopsy (p=0.001) and T ≥ 2c (p=0.04) were predictors of biochemical relapse in univariate analysis; however, only T ≥ 2c(p=0.02) and high-grade PIN(p=0.03) were confirmed as independent variables in the multivariate analysis. Regarding toxicity, 60% had acute toxicity GU G 1-2 (dysuria-polyaquiuria) and 1% G3. At the GI level, 25% had G1 2 toxicity (diarrhea) and 4% G3. G1-2 late GU toxicity was 17% and G3 1%, G1-2 late GI toxicity was 9% and G3 1%. There was no statistically significant difference in BRFS (p=0.31) or acute or late toxicity depending on the applied technique. Conclusion The results obtained in this work agree with the international literature in the general population, therefore the omission of pelvic radiotherapy and hypofractionated radiotherapy to the prostate volume in elderly patients with organ-confined prostate cancer is a safe and effective treatment, with excellent local control and good tolerance. Longer follow up is need to evaluate the pattern of recurrences. C. Vestergaard Madsen 1 , M. Berg 2 , A. Zedan 1 , B. Mortensen 2 , T. Andersen 2 , H. Nissen 2 , L. Volmer 1 , M. Svenson 1 , T. Siersbæk 1 , L. Fokdal 1 1 Vejle Hospital, University Hospital of Southern Denmark, Department of Oncology, Vejle, Denmark; 2 Vejle Hospital, University Hospital of Southern Denmark, Radiotherapy Research Team, Department of Oncology, Vejle, Denmark Purpose or Objective Salvage radiotherapy (SRT) with bicalutamide is a recommended treatment option for patients with biochemical relapse after radical prostatectomy for prostate cancer (PCa). However, early and late toxicity for both gastro-intestinal (GI) and for genito-urinary (GU) tract can be expected, making the timing for SRT still debatable. Data on quality of life from a patient perspective are important because they enable the healthcare personnel to focus on what really matters to the patient. So far, this clinical information seems to be less investigated in patients receiving SRT and bicalutamide. Materials and Methods Between December 2017 and June 2022, eighty-one consecutively selected patients treated with SRT (70 Gy in 35 fxt, VMAT technique) and two years of concomitant bicalutamide were included in an open prospective observational study. Systematic collection of common terminology criteria for adverse events (CTCAE v 4.0) and patient-reported outcome measures (PROMs) were done at baseline (BL), at end of SRT treatment (EOT), and at regular intervals during a five-year PO-1462 Patient-reported outcome measures after salvage radiotherapy for prostate cancer