S1256
Clinical - Urology
ESTRO 2026
Material/Methods: HEAT randomized men aged 35-85 with biopsy- confirmed NCCN low- to intermediate-risk PCa, with International Prostate Symptom Score (IPSS) ≤ 12 and prostate-specific antigen ≤ 20, to either EHRT to 70.2 Gy in 26 fractions using intensity-modulated radiation therapy (IMRT), or AHRT to 36.25-40 Gy in five fractions. Short-term ( ≤ 6 months) androgen deprivation therapy (ST-ADT) was permitted. The primary endpoint of biochemical failure (BF) was assessed at 1.25, 2.25, 3.25, 4.25 and 5.25 years post- randomization and compared using a one-sided, two- sample Farrington-Manning test under non-inferiority margin of 12%. Kaplan-Meier failure-free (FFS) and overall survival (OS) were compared using a log-rank test. Cumulative incidences of GU and GI toxicity (CTCAE v. 4.0) were assessed via competing-risk analysis accounting for death from any cause and compared via Fine and Gray’s test. Results: 142 evaluable patients were randomized (70 EHRT, 72 AHRT). Median age was 69 years; 17.6% and 82.4% had low- and intermediate-risk disease, respectively.Patient characteristics were evenly distributed between the two arms. 28.6% and 26.4% of the EHRT and AHRT arms, respectively, received ST- ADT (p=0.728). At a median follow-up of 59.7 months (IQR=49.6-64.7), AHRT yielded non-inferior four-year BF (7.0% versus 7.4%, non-inferiority p ≤ 0.007), and non-significantly different FFS (median 73.8% versus 80.2%, p=0.089) (Figure 1A) and OS (median 94.1% versus 93.6%, p=0.740) (Figure 1B), compared to EHRT.
Conclusion: MRI-enhanced online adaptive SBRT for localized prostate cancer achieves robust plan adaptation with improved target coverage and reduced intermediate- dose exposure of the rectum compared to non- adaptive treatment. By parallelization of MRI simulation, adaptive replanning and dose delivery, the newly developed ARTEMIS Program has the potential to increase the treatment efficiency, thus paving the way towards a wide adoption of the described workflow for this patient population. Keywords: MRI-guided adaptive radiotherapy, SBRT Proffered Paper 3280 Results of a Randomized Non-inferiority Trial of Hypofractionation via Extended versus Accelerated Therapy (HEAT) for Prostate Cancer David J Lee 1 , Sunwoo Han 2 , Umberto Ricardi 3 , Giuseppe Carlo Iorio 4 , Thomas Eade 5 , Andrew Kneebone 5 , Debra E Freeman 6 , Radka Stoyanova 1 , Nesrin Dogan 1 , Benjamin Oren Spieler 1 , Sanoj Punnen 7 , Alan Dal Pra 1 , Brandon A Mahal 1 , Alan Pollack 1 , Matthew C Abramowitz 1 1 Department of Radiation Oncology, Sylvester Comprehensive Cancer Center, University of Miami Miller School of Medicine, Miami, USA. 2 Biostatistics and Bioinformatics Shared Resource, Sylvester Comprehensive Cancer Center, University of Miami Miller School of Medicine, Miami, USA. 3 Department of Oncology and Radiation Oncology, University of Turin, Turin, Italy. 4 Department of Radiation Oncology, University of Turin, Turin, Italy. 5 Department of Radiation Oncology, Northern Sydney Cancer Centre, Royal North Shore Hospital, Sydney, Australia. 6 Department of Radiation Oncology, Naples Radiation Oncology, Naples, USA. 7 Department of Urology, Desai Sethi Urology Institute, University of Miami Miller School of Medicine, Miami, USA Purpose/Objective: Prostate cancer (PCa) remains a leading cause of cancer-related morbidity and mortality in men. Definitive radiotherapy (RT) is a well-established management for localized PCa, but conventionally fractionated RT (CRT) is delivered over eight to nine weeks, incurring high costs and limiting access. Extended (EHRT) and accelerated hypofractionated RT (AHRT) are shorter alternatives shown to provide comparable PCa control and toxicity outcomes compared to CRT. However, one-to-one prospective comparisons between EHRT and AHRT are lacking. HEAT, an international phase III study, aims to determine whether AHRT achieves comparable PCa control and genitourinary (GU)/gastrointestinal (GI) toxicity outcomes relative to EHRT.
AHRT yielded non-significantly different acute (CIT4=5.6% versus 2.9%, p=0.425) and late (CIT4=1.4% versus 4.3%, p=0.297) grade ≥ 2 GU toxicity (Figures 2A- B), as well as improved acute (four-year cumulative incidence of toxicity [CIT4]=19.4% versus 40.0%, p=0.017) but non-significantly different late (CIT4=23.2% versus 16.4%, p=0.248) grade ≥ 2 GI toxicity (Figures 2C-D), compared to EHRT.
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