ESTRO 2020 Abstract book

S677 ESTRO 2020

baseline to week 8 (G1= 80%, G2=8%) and decreased again three months later (G1=8%). CTC proctitis was absent at baseline and reached 40% (G1) and 16% (G2) at week 8 and decreased to 18% of G1 3 months post RT. Acute RTOG rectum toxicity (Fig. 2) increased from baseline (0%) to 60% of G1 at week 8 and decreased to 8% of G1 three months after IGRT. No grade 3+ acute toxicity occurred in any scored item. Conclusion In this single-arm prospective study we were able to demonstrate feasibility of an ambitious imaging protocol with MR-based adaptive IGRT. In addition, the extent of acute toxicity of this weekly adaptive IGRT in PC was very encouraging. PO-1195 Impact of Adjuvant Radiotherapy in node positive prostate cancer patients G. Corrao 1 , M. Montesano 1 , G. Marvaso 1 , G.C. Mazzola 1 , J. Franzetti 1 , C. Fodor 1 , D. Zerini 1 , S. Gandini 2 , S.P. De Angelis 2 , F. Cattani 3 , O. De Cobelli 4 , R. Orecchia 5 , B.A. Jereczek-Fossa 1 1 European Istitute of Oncology, Radiotherapy, Milan, Italy ; 2 European Istitute of Oncology, Epidemiology and Biostatistics, Milan, Italy ; 3 European Istitute of Oncology, Medical Physics, Milan, Italy ; 4 European Istitute of Oncology, Urology, Milan, Italy ; 5 European Istitute of Oncology, Scientific Directorate, Milan, Italy Purpose or Objective Large, prospective randomized studies have demonstrated that low volume-nodal prostate cancer (PCa) patients (one or two positive lymph nodes) have significantly higher survival rates compared to ones with higher volume-nodal disease, regardless of adjuvant treatment administrated. Anyway, the management of this setting of patients is still under debate. The aim of this retrospective study was to assess the impact of adjuvant radiotherapy (aRT) in patients with pathological positive lymph nodes (pN1) in terms of Overall Survival (OS), biochemical, clinical and distant metastasis Progression Free Survival (b-PFS, c-PFS and m-PFS) and to correlates oncological outcomes with tumor characteristics. Urinary and rectal toxicities were evaluated. Material and Methods Patients with pN1 PCa, treated between 2008 and 2018 with radical prostatectomy, extended pelvic lymph node dissection, aRT within 6 months from surgery and +/- hormonal therapy, were included in this mono- institutional cohort. Log-rank tests and Cox proportional hazards were used to compare and identify independent prognostic factors of biochemical and clinical recurrence, with adjustment for relevant covariates. Results Hundred eighty-seven patients were included in this study with a median follow-up of 49 months (range 3-172). At 5- years, we observed b-PFS, c-PFS, m-PFS and OS of 56 %, 68 %, 71 % and 94 % respectively. To perform the analysis, patients were divided in two groups according to the most informative cut-off of positive nodes. A significant statistical impact was observed for patients who harbored 5 or more lymph-nodes (Figure. 1). At univariate analysis, vascular invasion and the number of positive nodes were significant predictors of b-PFS (all p < 0.002). Multivariate analysis confirmed an increased risk of biochemical relapse for initial PSA value (iPSA) (HR= 1.01 and 95% CI: 1.00 to 1.02 and p-value= 0.021), a reduced risk in patients without vascular invasion (HR= 0.5 and 95% CI: 0.31 to 0.79 and p-value= 0.003) and number of lymph-nodes from 1 to 4 vs 5 or more (HR= 0.47 and 95% CI: 0.27 to 0.83 and p- value= 0.010) (Table. 1). Multivariate proportional Cox hazard models confirmed also significantly reduced risk of c-PFS and m-PFS for ISUP < 3 and lymph-nodes <5. OS was correlated only with the increase in iPSA value (HR= 1.02 and 95% CI: 1.01 to 1.03 and p-value= 0.002).

Conclusion According to recent published studies, our data confirmed the excellent outcomes of pN1 PCa patients treated with adjuvant treatments. The significant beneficial effect of aRT on cancer-specific outcomes is supported by a low- grade of acute and chronic of toxicities. Moreover, we confirmed the key role represented by the number of positive nodes in predicting b-PFS, c-PFS and m-PFS. These results support the need of perspective, randomized, larger cohort studies to individuate the number of positive nodes which benefit aRT in order to choose the best adjuvant personalized treatment. PO-1196 long term results with moderately hypofractionated RT in high-risk localized prostate cancer. S. Maulik 1 , I. Mallick 1 , M. Arunsingh 1 , S. Chatterjee 1 , R. Achari 1 , S. Chakraborty 1 , B. Arun 2 , S. Prasath 2 1 Tata Medical Centre- Kolkata, Radiation Oncology, Kolkata, India ; 2 Tata Medical Centre- Kolkata, Medical Physics, Kolkata, India Purpose or Objective We report 5 year disease control and late toxicity outcomes of high risk localized prostate carcinoma treated with long-term androgen deprivation therapy and HypoRT. Material and Methods Patients with high risk localized prostate cancer were treated with a HypoRT regimen of 60 Gy/20#/4 weeks to the prostate and seminal vesicles with simultaneous elective irradiation of pelvic nodal volumes to a dose of 44 Gy/20#. Androgen deprivation therapy comprised of either orchidectomy or medical ADT (total duration of two to three years) starting at least three months before radiation therapy. The outcomes of the first 100 patients treated with this regimen were audited. The predictors of biochemical failure and distant metastases were analyzed. Late toxicity was graded using a modified version of the LENT SOMA scale Results The cohort of 100 consecutive patients completed RT between March 2012 and September 2015. Median follow up was 61 months. The crude number of biochemical relapses documented was 18. Re-staging at biochemical failure revealed distant metastases in 12 patients. Eight of 12 distant relapses involved non regional lymph nodes, and 5 of these were non regional adenopathy alone.