S2965
Late-Breaking
ESTRO 2026
Villejuif, France. 3 Radiotherapy, Clinique St Grégoire, Rennes, France. 4 Radiation Oncology, Institut Català d'Oncologia, Badalona, Spain. 5 Service d’oncologie médicale, Grand hôpital de Charleroi, Charleroi, Belgium. 6 Radiation Oncology, Centre Azuréen de Cancérologie, Mougins, France. 7 Radiation Oncology, Institut Bergonié, Bordeaux, France. 8 Radiothérapie, Centre de radiothérapie Saint Louis, Toulon, France. 9 Oncologie Médicale, CHU St Etienne, St Etienne, France. 10 Radiothérapie, Clinique Pasteur, Toulouse, France. 11 Medical Oncology, Parc Taulí Hospital Universitari, Sabadell, France. 12 Oncologie Médicale, ICO Angers, Angers, France. 13 Medical Oncology, Hospital Virgen de la Victoria de Málaga, Málaga, Spain. 14 Medical Oncology, Institut Mutualiste Montsouris, Paris, France. 15 Radiothérapie, Clinique Pasteur, Brest, France. 16 Medical Oncology, Centre François Baclesse, Caen, France. 17 Medical Oncology, Hospital del Mar, Barcelona, Spain. 18 R&D, Unicancer, Paris, France. 19 Radiation Oncology, Hospital Universitari de la Vall d’Hebron, Barcelona, Spain. 20 Medical Oncology, Centre Oscar Lambret, Lille, France Purpose/Objective: Men with very high-risk localized prostate cancer patients face a risk of metastatic spread, which can lead to patient death. Prophylactic pelvic radiotherapy (RT) targeting pelvic nodal micrometastases and/or cabazitaxel may both reduce the risk of relapse and
Next generation imaging (mostly choline PET/CT) was used in 18%. Using the STAMPEDE definition, 622 patients (82%) had very high-risk disease; 299 patients (39%) had a risk of nodal disease >35% according to the Roach formula. There was no interaction between cabazitaxel and pelvic RT effects, hence the groups were combined two by two on the basis of RT fields.After a median follow-up of 87 months, there was no improvement of cPFS with pelvic RT (HR: 0.81 [0.63;1.03], p=0.09; 7-year cPFS: 67.1% vs 62.9%). Similarly, there were no improvements with pelvic RT in biochemical PFS (HR: 0.84 [0.66;1.07]), metastasis- free survival (MFS, HR: 0.90 [0.69;1.19]), cancer specific survival (CSS, HR: 0.95 [0.56;1.64]) or overall survival (OS, HR: 1.21 [0.84;1.73], 5y OS of 91% and 92% respectively). There was no significant toxicity signal associated with pelvic RT. Conclusion: Pelvic RT is associated with a borderline improvement in cPFS in node negative (conventional imaging) very- high risk localized prostate cancer, but no improvement was found in bPFC, MFS, CSS or OS. Keywords: prostate cancer; pelvic radiotherapy DART: Darolutamide Added to Radiotherapy — A Randomised Phase II Trial of SBRT With or Without Darolutamide for Oligorecurrent Prostate Cancer Piet Ost 1,2 , Valérie Fonteyne 3 , Ruben De Groote 4 , François-Xavier Otte 5 , Meersschout Sabine 6 , Wim Dutoy 7 , Siska Van Bruwaene 8 , Leen Noé 9 , Tom Van den Mooter 10 , Renée Bultijnck 11 , Piet Dirix 2 1 Ghent University, Department of Human Structure and Repair, Ghent, Belgium. 2 Department of radiation oncology, Iridium Network, Wilrijk, Belgium. 3 Radiation Oncology, Ghent University Hospital, Ghent, Belgium. 4 Department of Urology, OLV Aalst, Aalst, Belgium. 5 Department of Radiation Oncology, Bordet, Brussels, Belgium. 6 Department of radiation oncology, AZ St-Jan Brugge, Brugge, Belgium. 7 Department of radiation oncology, AZ St-Lucas, Ghent, Belgium. 8 Department of Urology, AZ Groenige, Kortrijk, Belgium. 9 Department of radiation oncology, AZ Jessa, Hasselt, Belgium. 10 Department of Medical Oncology, Medical Oncology, Wilrijk, Belgium. 11 Department of Human Structure and Repair, Ghent University Hospital, Ghent, Belgium Purpose/Objective: PSMA PET still understages a proportion of patients at the time of biochemical recurrence, leaving subclinical micrometastatic disease untreated. Combining SBRT with short-course systemic therapy might address this limitation by providing coverage of occult disease while consolidating local control. We aimed to assess whether 24 weeks of darolutamide (DARO), an Proffered Paper 5541
improve outcomes. Material/Methods:
PEACE 2 (NCT01952223) is a 2x2 factorial design randomized trial for patients with very high-risk localized prostate cancer defined by at least 2 criteria among Gleason 8-10, T3/T4 disease (MRI T-stage permitted) and PSA ≥ 20 ng/mL, and no detectable metastases on conventional imaging. Eligible patients all received standard of care (SOC), which consisted of prostate only fractionated RT (74-78Gy in 37-39 fractions) and 3 years of ADT. Patients were randomized 1:1:1:1 to receive SOC only, SOC + pelvic RT (46-50 Gy in 23-25 fractions), SOC + 4 cycles of cabazitaxel (20-25 mg/m2/3 weeks, before RT), or SOC + both cabazitaxel and pelvic RT. The primary endpoint is clinical progression-free survival (cPFS) with death, metastases and proven local relapses as events. Initially 1048 patients were planned to detect a treatment effect corresponding to a hazard ratio of 0.70 for both comparisons. The accrual was closed early but the target event number was maintained, maintaining statistical power. Results: Overall, 761 patients were included from 2013 to 2021 (median age: 67y) in four EU countries, with two (79%) or three (21%) risk factors. They were randomized to receive pelvic RT (n=381) or prostate only RT (n=380).
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