ESTRO 2021 Abstract Book

S1108

ESTRO 2021

In a matched cohort treated without a spacer, mean rectal D2cc without a spacer was higher at 7.7 Gy +/- 0.9 compared with 6.0 Gy +/- 0.9 with a spacer p<0.05. Isodose levels ≥ V30 were lower with a spacer (4.5Gy) (Table 2).

Conclusion An adapted, novel technique of spacer injection at the time of HDR brachytherapy is feasible. The described method allowed clear visualisation of the prostate during HDR catheter placement unaffected by presence of a spacer. Insertion of a spacer resulted in greater separation between the prostate and anterior rectum, with reduced rectal volume receiving isodoses >V30 and a reduced D2cc compared with a matched cohort. Further work will report the clinical impact of this dosimetric improvement using prospective patient reported outcome measures. PO-1350 SBRT for localized prostate cancer: there is still a role for androgen deprivation therapy? M.L. Bonù 1 , A. Magli 2 , F. Tonetto 3 , E. Moretti 4 , G. De Giorgi 5 , L. Spiazzi 6 , M. Trovò 3 , D. Tomasini 7 , S.M. Magrini 7 , L. Triggiani 7 1 University of Brescia and Spedali Civili Hospital, Radiation Oncology, Istituto del Radio Olindo Alberti, Brescia, Italy; 2 University Hospital of Udine, Italy, Radiation Oncology, Udine, Italy; 3 University Hospital of Udine, Italy, Department of Radiation Oncology, Udine, Italy; 4 University Hospital of Udine, Italy, Department of Medical Physics, Udine, Italy; 5 University Hospital of Udine, Italy, Department of Urology,, Udine, Italy; 6 University of Brescia and Spedali Civili Hospital, Brescia, Italy, Department of Medical Physics, Brescia, Italy; 7 University of Brescia and Spedali Civili Hospital, Brescia, Italy, Istituto del Radio O. Alberti, Department Of Radiation Oncology, Brescia, Italy Purpose or Objective Stereotactic prostate radiotherapy (SRT) is an opportunity to treat safety and effectively localized prostate cancer. Intermediate unfavorable risk patients (pts) presents similar outcomes to high risk ones. The aim of this study is to analyse a series of pts treated with SRT for localized prostate cancer with a focus on intermediate unfavourable and Androgen Deprivation Therapy. Materials and Methods pts were treated with SRT with 42 Gy in seven fractions. Study endpoints were biochemical relapse free survival (bRFS), overall survival (OS), acute and late toxicity, pts reported outcomes as International prostate cancer symptoms scale (IPSS) and international index of erectile function (IIEF). Results 170 consecutive pts were identified. 76 pts (44.7%) of unfavorable intermediate and 30 pts (17.6%) of high-risk class. ADT was administered to 106 pts (62%). 5 years bRFLS resulted 88%, pts with intermediate unfavorable and high risk presented a bRFS of 81.7% and 76.9% at 5 years.5 years OS resulted 83,2%. At univariate analysis, factors associated with worse bRFS included intermediate unfavorable and high-risk class, PSA more than 20ng/ml, ISUP 3-4-5 and T stage. 5 years OS resulted 83,2%, at univariate analysis, the only variable significantly associated with worse OS resulted Primary Tumor stage T3a-b or T4 ( p = 0.001). IPSS reached a peak after SRT and showed a return to basal value after 6 months. Conclusion SRT consisting in 42 Gy in 7 fraction with short term ADT is a safe and effective treatment for localized prostate cancer. Our series shows fair outcomes also for intermediate unfavourable and high-risk pts. The next step in this clinical scenario is to clarify the role of ADT in a prospective and randomized fashion.