S1253
Clinical - Urology
ESTRO 2026
alone or in combination with SBRT in patients with oligometastatic recurrence. All patients received re- SBRT after primary prostate radiotherapy or postoperative radiotherapy. Primary end-point was acute tolerability. Secondary end-points were: late tolerability, biochemical relapse-free survival (BRFS), disease-free survival (DFS), overall survival (OS). Results: 102 patients with localized recurrence after primary prostate RT or postoperative RT received reirradiaiton on MRL (46) or conventional linac (56). The mediantime to reirradiaiton was 78 months (range 12- 190). The median follow-up was 38 months (11-64) and 49 months (12-68) in MRL and CL respectively. Acute GU toxicity between MRL and CL was represented by grade 1 in 15 (32.6%) versus 19 (34%), grade 2 in 4 (8.6%) versus 9 (16%), grade 3 in 2 (4.3%) versus 4 (7.1%) cases, respectively (p=0.048). GU toxicity for MRL and CL was: grade 1 in 6 (13%) versus 8 (14.2%) cases, grade 2 in 5 (10.8%) and 9 (16%) cases, grade 3 in 0 and 1 (1.7%) cases, respectively (p=0.058).Late GU toxicity for MRL and CL was: grade 1 in 41.3% and 50%, grade 2 in 17.3% and 23.2%, respectively.The 3-year BRFS was 76% versus 73.2% (p=0.27). The 3-year OS was 95.6% versus 98.2%. Conclusion: The results of the present study demonstrated the feasibility of prostate reirradiation both with MRL and CL and suggest a potential improved toxicity profile with MRL. These findings support its use in selected patients and encourage further prospective studies. Keywords: Prostate, reirradiation, adaptive radiotherapy SBRT with Simultaneous Focal Boost for Localized Prostate Cancer: Early Outcomes and Impact of Rectal Spacing from a Prospective Study Federico Colombo 1 , Marco Galaverni 1 , Claudia Grondelli 1 , Francesco Salaroli 1 , Michele Maddalo 2 , Francesco Ziglioli 3 , Cristina Dell'Anna 1 , Ilaria Renna 1 , Maria Luisa Bergamini 1 , Giovanni Ceccon 1 , Elisabetta Lattanzi 1 , Stella Gianni 1 , Carmelinda Manna 4 , Giulio Negrini 4 , Livia Ruffini 5 , Umberto Maestroni 3 , Caterina Ghetti 2 , Nunziata D'Abbiero 1 , Nicola Simoni 1 1 Department of Radiation Oncology and Radiosurgery, University Hospital of Parma, Parma, Italy. 2 Medical Physics Unit, University Hospital of Parma, Parma, Italy. 3 Urology Department, University Hospital of Digital Poster 3177 Parma, Parma, Italy. 4 Scienze Radiologiche, Department of Medicine and Surgery (DiMeC), University Hospital of Parma, Parma, Italy. 5 Nuclear Medicine Division, University Hospital of Parma, Parma, Italy
Purpose/Objective: Dose escalation to the dominant intraprostatic lesion (DIL) is a promising approach to increase the therapeutic ratio of Stereotactic Body Radiotherapy (SBRT) in prostate cancer. This study evaluated early oncological outcomes and the impact of rectal spacer insertion in prostate SBRT with a Simultaneous Integrated Boost (SIB) to the DIL (SBRT-SIBDIL). Material/Methods: Patients with histologically confirmed localized prostate adenocarcinoma and gland volume ≤ 90 cc were included in this prospective observational study. DIL was defined using mpMRI T2-weighted, diffusion and perfusion images. SBRT prescription dose was 36.25 Gy in 5 fractions to the Planning Target Volume (PTV) with a SIB to the DIL up to 45 Gy. Genitourinary (GU) and gastrointestinal (GI) side effects, planning dosimetry data, as well as biochemical parameters were analyzed. Results: From June 2022 to August 2024, a total of 41 men prospectively treated with prostate SBRT-SIBDIL at our Institution were analyzed. Median patient age was 76 years (IQR 73-78). D’Amico/NCCN class risk was defined as low-, intermediate- and high-risk in 7 (17.1%), 29 (70.7%), and 5 (12.2%) patients, respectively. Thirty-two (72.7%) DILs were located in the peripheral zone and 3 (7.3%) patients had 2 DILs. SBRT was delivered with volumetric modulated arc radiotherapy (VMAT), fiducial markers tracking was used for all (100%) patients, while rectal spacer insertion was optional and placed in 24 (58.5%) patients (Figure 1). Androgen deprivation therapy (ADT) was administered in 14 (34.1%) cases. At a median estimated follow up of 21.0 months (95% CI 18.5-28.3), no G ≥ 3 side effects were observed, with a cumulative G2 GU and GI adverse events rate of 24.4% and 14.6%, respectively (Table 1A). A summary of DIL dosimetric parameters and OAR constraints is outlined in Table 1B. Rectal dosimetric parameters were significantly improved by the use of rectal spacer (spacer vs no spacer rectal V38Gy 0.0 cc vs 0.2 cc, p <0.001; V36Gy 0.0 cc vs 1.7 cc, p <0.001; V24Gy 5.9% vs 15.3%, p <0.001); however, this did not translate into a significant difference in G2 rectal side effects (spacer vs no spacer 23.5% vs 8.3%, p 0.175). All patients experienced biochemical response. Patient-reported QoL metrics at last follow-up were not significantly different from pre-SBRT baseline.
Made with FlippingBook - Share PDF online