S1299
Clinical - Urology
ESTRO 2026
Poster Discussion 4557
NCT04943536 is a prospective, single-center, single- arm study to assess the safety, feasibility and pharmacokinetic profile for Biolen® for the localized delivery of bicalutamide into prostate tumors when delivered with radiotherapy. Eligible patients had at least one MRI-visible biopsy-confirmed prostate cancer lesion and were an appropriate candidate for RT+ADT (NCCN intermediate risk prostate cancer or NCCN high risk prostate cancer due to Grade or PSA and refusing systemic ADT). 9-16 implants were deployed transperineally into MRI-visible prostate lesions. Implant planning was conducted with the goal of inclusion of the MRI visible tumor(s) entirely within the anticipated bicalutamide high dose region. RT was delivered 9 weeks after implant and patients were monitored for adverse events through 24 months. Plasma and semen pharmacokinetic samples were collected for bicalutamide levels at serial timepoints. MRI was obtained 4 and 8 weeks after implant and 6 and 24 months after RT. Longitudinal QOL was evaluated via EPIC-26. Results: 10 patients with intermediate and high risk localized prostate cancer received a 9-16 (median 16) Biolen® implants and RT. All patients completed the implant procedure and radiotherapy as planned. Grade 2 or higher device or drug-reported adverse events were uncommon with only a single instance of erectile dysfunction deemed possibly related to study drug reported. No clinically significant impact on QOL was noted using the EPIC-26 during the 8 week period between implant and radiotherapy. Minimal systemic exposure to bicalutamide was noted in plasma (mean 37.3 ng/mL + 9.2 versus ~8900 ng/mL reported for oral bicalutamide) and semen (mean 199.89 ng/mL + 21.6) at 4 weeks. Implants continued to elute for 2 years. 16/20 (80%) tumor lesions demonstrated shrinkage on MRI within 8 weeks. Conclusion: Biolen® implants can be safely deployed into prostate cancer via an image-guided transperineal approach. Minimal bicalutamide levels in semen and plasma demonstrate proof of principle for localized image- guided anti-androgen delivery. This new prostate tumor directed therapy may potentially have meaningful applications for patients undergoing active surveillance, focal therapy, RT, or prostatectomy. Keywords: prostate cancer, radiotherapy, implantable drug
Dominant Intraprostatic Lesion Simultaneous Integrated Boost (SIB-DIL) in Prostate Single-Dose Radiotherapy (SDRT) for unfavorable intermediate risk Carlo Greco 1 , Bruno Vieira 1 , Miguel Simas 1 , Oriol Parés 1 , Nuno Pimentel 1 , Justyna Kociolek 1 , Vasco Louro 1 , Sandra Vieira 1 , Joep Stroom 1 , Dalila Mateus 2 , Elda Freitas 1 , Ana Soares 1 , Graça Coelho 1 , Zvi Fuks 1,3 1 Radiation Oncology, Champalimaud Foundation, Lisbon, Portugal. 2 Radiation Oncology, Mercurius Health, Lisbon, Portugal. 3 Radiation Oncology, Memorial Sloan Kettering Cancer Center Foundation, New York, USA Purpose/Objective: Local relapses primarily occur at the site of the dominant intraprostatic lesion (DIL). Improvements in local control deploying a simultaneous integrated boost (SIB) to the DIL needs to be weighed against the risk of increased toxicity. The present analysis provides preliminary results on acute and late toxicity, patient-reported quality of life (QoL) and PSA outcomes after whole gland 24 Gy single dose radiotherapy (SDRT) with a 68Ga-PSMA PET-derived concomitant boost up to 30 Gy. Material/Methods: Between April 2019 and November 2025, 139 patients were enrolled in an IRB-approved phase II study to receive 24 Gy SDRT with dose-escalated DIL-SIB in patients with unfavourable intermediate risk (UIR). Planning consisted of back-to-back 68Ga-PSMA PET/CT and MRI scans acquired in treatment position with placement of an endorectal air-filled balloon (150 cc) and a Foley catheter to achieve organ motion mitigation. The PTV was obtained with an isotropic 2 mm expansion of the CTV (whole prostate and lower half of the seminal vesicles). Dose prescription was 24 Gy to the PTV (10MV FFF VMAT) with escalating boost doses to the PSMA-derived DIL (26.4Gy, 28.8Gy and 30Gy). A 20% reduction of dose was applied to the urethral wall. SIB coverage was ≥ 80% of the prescribed dose while fulfilling all dose/volume constraints. Genito-urinary (GU) and gastro-intestinal (GI) toxicity were graded according to the NCI CTCAE v.4, and QoL by EPIC and IPSS questionnaires. PSA was assessed at 1, 3, 6, 12 months, and at 6 months intervals thereafter.
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