ESTRO 2025 - Abstract Book

S1886

Clinical - Urology

ESTRO 2025

Conclusion: Tumor ADC values are a reliable biomarker for differentiating between GS 3+4 and 4+3 tumors in the GS 7 category. Tumors exhibiting lower ADC values have been associated to higher risk factors and an increased likelihood of disease progression, particularly in GS 3+4 tumors where GS upgrading could happen.

Keywords: Prostate cancer, MRI, radiotherapy.

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Poster Discussion Feasibility of combined focal boost and whole pelvis radiotherapy in high-risk prostate cancer: A prospective phase II trial (NCT01962324) Camilla Thellenberg Karlsson 1 , Kristina Notstam 1 , Per Fransson 2 , Kristina Lundquist 3,4 , Björn Tavelin 5 , Karin Söderkvist 1 1 Diagnostics and Intervention, oncology, Umeå University, Umeå, Sweden. 2 Department of Nursing, Umeå University, Umeå, Sweden. 3 Department of Chemistry, Umeå University, Umeå, Sweden. 4 Diagnostics and Intervention, Umeå University, Umeå, Sweden. 5 Cancercentrum, Umeå University Hospital, Umeå, Sweden Purpose/Objective: The optimal treatment of high-risk localised prostate cancer is still debated. This trial aimed to evaluate the feasibility of a radiotherapy (RT) regimen including whole pelvis RT (WPRT) with focal boosting to an intraprostatic lesion, as well as a boost to PET-positive lymph nodes, within a high-risk prostate cancer population. Material/Methods: This single-centre, prospective phase II trial included 85 consecutive patients diagnosed with high-risk prostate cancer who were eligible for definitive RT between 2013-2017. High-risk was defined as any T, N0-1, M0 with an estimated risk of lymph node involvement > 15% (MSKCC) and a maximum of three pelvic lymph node metastases on ACE-PET. The prescribed doses were 77 Gy in 35 daily fractions to the prostate, 56 Gy in 35 fractions to the whole pelvis, and 70 Gy to positive pelvic lymph nodes, if applicable. A total dose of 84 Gy was prescribed for the intraprostatic focal boost GTV. If no intraprostatic lesion or pathological lymph nodes could be visualized in mpMRI or planning CT, the boost could be opted out by the attending physician. All patients received 3 months of neo-adjuvant ADT, followed by 3 months of concurrent ADT and 6 months of adjuvant antiandrogen treatment. Study endpoints included PFS, OS, physician-scored GU and GI toxicity (RTOG), and PROMs (Prostate Cancer Symptom Scale). Results: Of the 85 patients enrolled in the study, seven patients were excluded from per-protocol analyses as they did not receive the intended treatment. All participants had a high-risk prostate cancer, with a median estimated nodal involvement risk of 43% (MSKCC). 20 patients (26%) had N1 disease (ACE-PET and/or RECIST) and 5 patients (6%) had