ESTRO 2023 - Abstract Book

S1181

Digital Posters

ESTRO 2023

Active surveillance of prostate cancer helps to avoid the side effects of curative treatments (surgery, radiotherapy, and brachytherapy) in patients with indolent disease. However, monitoring is invasive, requiring repeated biopsies that can be stressful. Since none of the standard prostate cancer treatments alter overall survival, preserving quality of life (QOL) remains the key objective. Stereotactic body radiation therapy (SBRT) of the prostate may be a treatment alternative to active surveillance. Moreover, unlike other such focused treatments, it does not require general anesthesia. This prospective monocenter Phase-II trial was conducted to study the feasibility and safety of SBRT for low-favorable intermediate-risk prostate cancer. Materials and Methods Patients were prospectively recruited in 2016–2019 if they had localized CAPRA score <3 prostate adenocarcinoma, an isolated PIRADS >4 macroscopic tumor on MRI, WHO Performance Status 0–1, no major urinary symptoms (IPSS ≤ 15). SBRT involved 36.25Gy (80% isodose prescription) delivered in 5 fractions every other day with Cyberknife-M6. Gross-target volume was delineated on MRI and validated by the same prostate cancer imaging radiology specialist. Primary outcome was delay between SBRT and initiation of a salvage treatment. Secondary outcomes were acute and late genitourinary and gastrointestinal (rectal) toxicity (assessed by CTCAEv4), biological, clinical, and MRI control, and QOL. QOL was assessed with IPPS, Urinary QOL (U-QOL), and International Index of Erectile Function (IIEF)5 Scale before treatment and at last follow-up. Results In total, 24 patients were included. Median follow-up was 36 months. Salvage prostatectomy was never required. Three year biochemical progression-free survival was 96% (23/24). The single biochemical recurrence was due to a small Gleason 6 (3+3) score, 2 mm-lesion in the non-irradiated lobe. Complete radiological response was found in all 19 patients who underwent one or more post-treatment MRI evaluations. Acute/late grade >3 toxicities did not occur: all acute toxicities were grade-1 genitourinary (38% of patients), grade-2 genitourinary (8%), or grade-1 rectal (13%) toxicities, and there was one (4%) transient late grade-1 genitourinary toxicity. QOL was unchanged at last follow-up, as shown by IPSS (the mean changed from 2.86 at baseline to 3.29, p>0.05), U-QOL (from 0.71 to 0.67, p>0.05), and IIEF5 (none of the 14 patients who were initially potent lost potency). Conclusion SBRT is a focused therapy that is feasible, well-tolerated, and preserves quality of life. This innovative robotized approach challenges other focused treatment alternatives as well as active surveillance. G. Francolini 1 , L. Burchini 2 , V. Di Cataldo 3 , B. Detti 3 , M. Loi 4 , G. Frosini 5 , B. Guerrieri 6 , M. Ganovelli 2 , A. Allegra 6 , V. Salvestrini 7 , L. Visani 7 , E. Olmetto 4 , C. Becherini 4 , G. Simontacchi 8 , M. Roghi 6 , M.G. Carnevale 6 , I. Desideri 2 , I. Meattini 9 , L. Livi 10 1 University of Florence, Radiation Oncology, Azienda Ospedaliero-Universitaria Careggi, Florence, Italy; 2 University of Florence, Department of Experimental and Clinical Biomedical Sciences "M. Serio", Florence, Italy; 3 University of Florence, Radiation Oncology Unit, Azienda Ospedaliera Universitaria Careggi, Florence, Italy; 4 University of Florence, Radiation Oncology Unit, Azienda Ospedaliera Universitaria Careggi , Florence, Italy; 5 University of Florence , Department of Experimental and Clinical Biomedical Sciences "M. Serio" , Florence, Italy; 6 University of Florence, Department of Experimental and Clinical Biomedical Sciences "M. Serio" , Florence, Italy; 7 Istituto Fiorentino di Cura e Assistenza (IFCA), CyberKnife Center, Florence, Italy; 8 University of Florence, Radiation Oncology Unit, Azienda Ospedaliera Universitaria Careggi , Florence, Italy; 9 University of Florence, Department of Experimental and Clinical Biomedical Sciences "M. Serio", Florence, Italy; 10 University of Florence, , Department of Experimental and Clinical Biomedical Sciences "M. Serio" , Florence, Italy Purpose or Objective Rate of biochemical recurrences in men affected by localized prostate cancer (pT2-3, N0) after radical prostatectomy (RP) ranges between 20 and 50%. Biochemical recurrence can be managed with curative purpose through salvage radiation therapy (SRT). However, positive metabolic imaging detecting local recurrence negatively impacts outcomes after SRT in this setting. Increasing radiation dose in this setting may improver relapse-free survival according to literature data, and stereotactic salvage radiotherapy (SSRT) in this setting has been shown to be a promising approach, achieving acceptable toxicity rates. STARR trial (STereotactic sAlvageRadiotherapy for macroscopic prostate bed Recurrence after prostatectomy-NCT05455736), is a prospective trial including patients affected by macroscopic prostate bed recurrence undergoing stereotactic radiotherapy on prostate bed. This trial is currently running in Florence radiotherapy department, here we present an early analysis from first cohort of patients enrolled. Materials and Methods Patients affected by biochemical recurrence (PSA > 0.2 ng/ml) after radical prostatectomy, in whom macroscopic prostate bed recurrence was detected through PSMA or Choline PET and confirmed through Magnetic resonance Imaging (MRI) were enrolled within this trial. All patients underwent Cyberknife stereotactic SSRT on macroscopic prostate bed relapse with a total dose of 35 Gy in 5 fractions. Concomitant Androgen Deprivation Therapy (ADT) is not allowed (adjuvant ADT after radical prostatectomy should have ended > 12 months before enrollment). Complete biochemical response (CBR) and Biochemical response (BR) were defined as a PSA nadir < 0.2 ng/ml and < 50% of baseline, respectively. Acute Gastrointestinal (GI) and Genitourinary (GU) Toxicity was assessed every 3 months after treatment according to Common Terminology Criteria for Adverse Events (CTCAE) score v.4.03. Results Twenty five patients have been enrolled since March 2021. Of these, 16 patients had at least 3 months of follow up after their treatment and were evaluable for early response and acute toxicity. Overall, CBR and BR were detected after 3 months in 4 (25%) and 9 (56.2%) of cases, respectively. One patient had biochemical progression at first evaluation and PO-1459 Stereotactic salvage radiotherapy for prostate red relapse, early analysis from a prospective trial