Salvage stereotactic MR-Guided adaptive radiotherapy (SMART) re-irradiation for locally recurrent prostate Cancer: Clinical and dosimetric outcomes
Year: 2025
Type: article
Study design: Observational Study
Abstract: Introduction: Stereotactic ablative radiotherapy (SABR) is a salvage option for locally recurrent prostate cancer (LRPC); however, challenges remain. Stereotactic MRguided Adaptive Radiotherapy (SMART) permits daily adaptation, real-time tracking and automated beam gating, allowing critical organ sparing while potentially improving target coverage. Equivalent Dose in 2 Gy fraction (EQD2) calculation allows accurate organs-at-risk (OAR) dose accumulation in re-irradiation.We report safety and efficacy of daily SMART re-irradiation for LRPC, alongside an EQD2-based OAR tolerance calculation method. Methods: Salvage SMART to histologically proven non-metastatic hormone-sensitive LRPC was retrospectively analysed. Inclusion criteria included: ≥18 months post-RT, prostate-specific antigen (PSA) ≤ 30 ng/mL, PSA doubling-time > 6 months, International Prostate Symptom Score (IPSS) ≤ 19, prostate ≤ 80 cc and cT1-T3a/b.Reirradiation regimens were 30-35 Gy/5 fractions. Dose-boost and hormone therapy were allowed. Rectal spacer was recommended.Outcomes included toxicity, local control (LC), biochemical relapse-free survival (bRFS), progression free survival (PFS) and overall survival (OS). EQD2-based workflow to estimate OAR cumulative constraints was reported. Results: Between 2019 and 2023, nineteen patients underwent salvage-SMART to whole-gland (n = 12), hemi-gland (n = 5) or seminal vesicle (n = 2) at a median 87 months (range 35-587) from first radiotherapy. All 95 delivered fractions underwent online adaptation, meeting all estimated OAR.With 21 months follow-up, acute grade 2 genitourinary (GU) toxicity was 21 % with no acute ≥ grade 3 GU or ≥ grade 2 gastrointestinal (GI) toxicity observed. Late GU grade 3 toxicity occurred in 3 patients (15.7 %).OS was 100%; bRFS 73.7%; LC 84.2%; and median-PFS was not reached. One and two-year PFS were 94.7% and 89.4%. One and two-year LC was 100%. Two contralateral intraprostatic failures followed hemi-gland treatment were observed. Conclusion: Daily adaptive SMART re-irradiation is a feasible, non-invasive salvage option for LRPC, combining high LC with low toxicity. Our experience supports integrating MR- guidance with an individualized EQD2-informed planning.
Authors: Elena Moreno-Olmedo, Dan Murray, Ben George, Daniel Ford, Nicola Dallas, Prantik Das, Ami Sabharwal, Yoodhvir Nagar, Jamie Mills, Carla Perna, Yae-eun Suh, Alex Martin, Philip Camilleri
Language: English
Subfield: Radiation
Field: Physics and Astronomy
Domain: Physical Sciences
Open Access status: gold
Estimated APC paid: $2,430
OpenAlex ID: W4413682591