Focal dose intensification strategies targeting the dominant intra-prostatic lesion (DIL) improve outcomes of patients with prostate cancer. The purpose was to determine whether the 6-month multiparametric (mp)MRI response of the DIL is associated with post-treatment prostate-specific antigen (PSA) kinetics after MRI linear accelerator (LINAC) guided stereotactic body radiotherapy (SBRT) with focal dose intensification.
Retrospective, single-center study including 72 patients with localized prostate cancer treated with MRI-LINAC SBRT with focal dose intensification and without androgen deprivation therapy. Patients were followed up at 6 months after SBRT with mpMRI and PSA. mpMRI complete response (CR) was defined as no residual lesion on diffusion-weighted imaging and dynamic contrast-enhanced MRI. This was correlated with PSA responses including PSA reduction (%), PSA reduction ≥ 50.0% (PSA50), and PSA ≤ 1.0 ng/mL.
mpMRI CR was achieved in 37 patients (51.4%) at 6 months. Patients with mpMRI CR had greater PSA reduction (81.8% vs 66.1%, p < 0.001), and more commonly had PSA50 (100.0% vs 82.9%, p = 0.010) and PSA ≤ 1.0 ng/mL (45.9% vs 11.4%, p = 0.001) compared to those without mpMRI CR. In 10 patients without 6-month mpMRI CR but had further MRI follow-up (median 13 months), DILs either further decreased in size (30.0%) or resolved (70.0%).
Initial 6-month mpMRI response correlates with PSA kinetics, which is associated with important clinical outcomes. mpMRI can be used for post-SBRT evaluation to gauge local tumor response of the DIL, where most recurrences occur.
Radiotherapy and oncology : journal of the European Society for Therapeutic Radiology and Oncology. 2026 Mar 07 [Epub ahead of print]
Sungmin Woo, Anton S Becker, Hebert Alberto Vargas, Angela Tong, Charlotte Charbel, Doris Leithner, Marius E Mayerhoefer, Peter B Schiff, Ting Chen, Hesheng Wang, Nicholas Colangelo, Jeffrey D Cooney, Ryan Walters, Matthew Long, Michael J Zelefsky
Department of Radiology, NYU Grossman School of Medicine & NYU Langone Health, New York, NY, the United States of America. Electronic address: ., Department of Radiology, NYU Grossman School of Medicine & NYU Langone Health, New York, NY, the United States of America., Department of Radiation Oncology, NYU Grossman School of Medicine & NYU Langone Health, New York, NY, the United States of America.