ESTRO 2021 Abstract Book

S1096

ESTRO 2021

Purpose or Objective Salvage radiotherapy (sRT) can have similar outcomes to adjuvant radiotherapy (aRT) if it is administered at the earliest evidence of biochemical recurrence. Thus, sRT has been positioned as the strategy of choice in the majority of institution globally. Recent report from RADICALS-RT supports this hypothesis confirming no benefit for adjuvant aRT for patients with adverse pathological features after radical prostatectomy. Therefore, a policy of observation after radical prostatectomy, with early sRT (up to 0.2 ng/mL) reserved for use only in patients with prostate-specific antigen (PSA) biochemical progression has become the new standard of care. The aim of the present study is to assess the impact of RADICALS-RT in the clinical practice regarding the timing of sRT for prostate cancer initially treated with radical prostatectomy. Materials and Methods Data from patients who underwent sRT after radical prostatectomy at our institution was retrospectively collected for study purposes. Patient demographics and disease-related clinical information, tumors characteristics, and PSA level before sRT were recorded. Patients with non-metastatic adenocarcinoma of the prostate were eligible if they had undergone radical prostatectomy, received sRT given later to those who develop a rising PSA, and had at least one specified risk factor (pathological T-stage 3 or 4, Gleason score 7– 10, positive margins, or preoperative PSA of 10 ng/mL or more). The entire cohort of patients was divided based on the date of RADICALS-RT presentation at ESMO (November 2019). Two groups were created and analyzed separately: from February 2016 to October 2019 (group 1) and from November 2019 to February 2021 (group 2). Results Two hundred and nineteen patients were recruited over 5 years between February 2016, and February 2021. One hundred and sixty-one patients were assigned to group 1 and 66 to group 2. Median age at diagnosis was 67 years (IQR 62 - 71). Pathological T-stage 2, 3a, 3b and 4 were 41.5%, 27.7%, 29,9% and 0.9% respectively. Median PSA at diagnosis was 8 ng/mL (IQR 5.6 – 12). Thirty five percent of patients had a PSA 10 ng/mL or greater. Distribution of Gleason score 6, 7 and 8 or greater were 7.5%, 67.7% and 24.8%. Forty six percent of patients had positive margins. Median PSA of the entire cohort at the time of sRT was 0.31(IQR 0.2 – 0.48). Median PSA for group 1 and 2 were 0.33 and 0.26. Less than one third of patients of group 1 and 2 (26% and 32% respectively) had PSA of 0.2 ng/mL or less at the time of sRT (p=0.42). Conclusion RADICALS-RT shows an impact in clinical practice revealing a slight trend of lower PSA at the time of sRT over time, although is not statistically significant. Despite of this, less than 30% of patients early sRT as per RADICALS-RT protocol. Clinician should be caution regarding adopting a sRT strategy if conditions are not appropriate. In this setting an aRT strategy should be revisited. PO-1335 PSMA-PET impact on post-prostatectomy recurrencies multidisciplinary management: focus on RT V. Chiofalo 1 , G.C. Iorio 1 , I. Bonavero 1 , R. Parise 1 , R. Carlevato 1 , S. Bartoncini 1 , V. Richetto 2 , F. Ceci 3 , S. Grimaldi 3 , S. Dall'Armellina 3 , D. Deandreis 3 , B. Lillaz 4 , M. Oderda 4 , P. Gontero 4 , A. Guarneri 1 , U. Ricardi 1 1 University of Turin, Department of Oncology, Turin, Italy; 2 University of Turin, Department of Medical Physics, Turin, Italy; 3 University of Turin, Department of Medical Sciences, Nuclear Medicine, Turin, Italy; 4 University of Turin, Department of Surgical Sciences, Urology, Turin, Italy Purpose or Objective to evaluate the impact of PSMA-PET in the management of recurrent prostate cancer patients following radical prostatectomy (RP), with a main focus on RT. Materials and Methods we retrospectively analyzed data of patients experiencing biochemical recurrence (BCR) post-RP and staged at our Center with PSMA-PET prior to any treatment. Primary endpoints were: biochemical progression-free survival (bPFS) rate after any radiotherapy treatment guided by PSMA-PET (regardless of its result); and bPFS rate following any treatment. BCR was defined as PSA ³0.2 ng/ml. Secondary endpoints included: change in the treatment plan, defined as SRT abort or the addition of metastasis-directed therapy (MDT) to SRT, and rate of SRT abort. In patients treated exclusively with SBRT, as MDT, ADT-free survival was evaluated. Patterns of failure in patients receiving prostate-bed SRT following a negative PSMA-PET were also evaluated. Results 95 patients with BCR following RP (pN0-pNx) staged between November 2016 and March 2019 with PSMA-PET were included in the present analysis. The median follow-up time (PSMA to the last follow-up) was 36 months (range 11-50). The median PSA at PSMA was 0.5 ng/ml (range 0.13-8.9). PSMA was positive in 26 patients (27.3%), with 31 lesions detected as shown in Table 1. The SRT abort rate was 57.6% (15 patients), as only 9 patients underwent prostate-bed SRT guided by local PSMA uptake. A change in management was observed for 17 patients (65.3%). ADT only was administred in 4 patients (15.3%). One patient underwent SBRT+ADT and 2 patients received SRT+SBRT+ADT. Exclusive MDT approaches included salvage pelvic lymph node dissection (s- PLND) for 3 patients (11.5%) and SBRT for 7 patients (26.9%). Fifteen out of the 26 positive patients (57.6%) treated with PSMA-guidance experienced a recurrence, with a 9 months median interval from the end of any treatment (range 1-32). Among the 7 patients treated with SBRT- only 6 recurred with a median bPFS of 15 months (range 3-30). The median interval to ADT initiation in the SBRT-only group was 8 months (ADT-free survival). PSMA following RP was negative in 69 patients, of whom 87% (60) received SRT (with ADT in 3/60). Among the remaining PSMA-negative patients, 7 were observed and 2 received ADT-only. After SRT 13 patients (21.6%) experienced a recurrence, with a median time of 6 months (range 1-28). Sites of recurrence following SRT in PSMA negative patients are shown in Table 1. Overall, a statistically significant difference (p<0.001) in terms of bPFS (Fig. 1) was recorded between PSMA negative patients treated with SRT (± ADT; n=57 as 3 patients were lost in follow-up) and PSMA positive patients that received targeted treatments (n=24, as 2 patients were lost in follow-up).