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Ultra-hypofractionated radiotherapy with focal boost for high-risk localized prostate cancer (HYPO-RT-PC-boost) : in silico evaluation with histological reference

Nilsson, Erik ; Nilsson, Anneli ; Jonsson, Joakim ; Sandgren, Kristina ; Grefve, Josefine ; Axelsson, Jan ; Lindberg, Angsana K. ; Söderkvist, Karin ; Karlsson, Camilla T. and Zackrisson, Björn , et al. (2025) In Acta Oncologica 64. p.1482-1488
Abstract

Background and purpose: The study aims to evaluate dosimetric properties of hypofractionated treatment plans integrating focal boost, using registered whole-mount histopathology (WMHP) as reference standard. Methods: Fifteen men from the PAMP trial (EudraCT: 2015-005046-55) were included. Participants had ≥ 1 ISUP Grade group ≥ 4 lesion and underwent [68Ga]prostate-specific membrane antigen (PSMA) positron emission tomography/multiparametric magnetic resonance imaging (PET/mpMRI) and [11C]Acetate-PET/ computed tomography before radical prostatectomy. Four radiation oncologists delineated gross tumor volumes (GTVs) on PSMA-PET/mpMRI. Sixty treatment plans were optimized, one per GTV and patient. Prostate planning... (More)

Background and purpose: The study aims to evaluate dosimetric properties of hypofractionated treatment plans integrating focal boost, using registered whole-mount histopathology (WMHP) as reference standard. Methods: Fifteen men from the PAMP trial (EudraCT: 2015-005046-55) were included. Participants had ≥ 1 ISUP Grade group ≥ 4 lesion and underwent [68Ga]prostate-specific membrane antigen (PSMA) positron emission tomography/multiparametric magnetic resonance imaging (PET/mpMRI) and [11C]Acetate-PET/ computed tomography before radical prostatectomy. Four radiation oncologists delineated gross tumor volumes (GTVs) on PSMA-PET/mpMRI. Sixty treatment plans were optimized, one per GTV and patient. Prostate planning target volumes were prescribed 42.7 Gy in seven fractions, with a simultaneous GTV boost up to 49.0 Gy, prioritizing organs at risk (OARs). Digital WMHP provided Gleason grading and was co-registered with in-vivo imaging. Target coverage for GTVs and voxels sharing Gleason patterns (GPs) was assessed via dose-volume histogram (DVH) analysis. Interobserver agreement in GTV-delineations was quantified with Fleiss’ kappa. Results: The median GTV dose per plan (D50) ranged from 48.3 to 49.1 Gy. For voxels with the highest GP, D50 was 42.9–49.2 Gy, exceeding 47.2 Gy in all except one plan. In lowest pattern voxels, D50 was 42.5–49.3 Gy, and below 43.4 Gy in over half the plans. Significant positive correlations between Fleiss’ kappa and DVH parameters appeared only for GP 5 regions, specifically for Fleiss’ kappa and D50 for two observers and the average D50 across observers. Interpretation: The histologically confirmed tumor was only partially boosted. Regions with more aggressive disease received better coverage. These findings provide a rational for prioritizing OARs in treatment planning.

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type
Contribution to journal
publication status
published
subject
keywords
focal boost, hypofractionation, In silico, prostate cancer, radiotherapy
in
Acta Oncologica
volume
64
pages
7 pages
publisher
Taylor & Francis
external identifiers
  • pmid:41146436
  • scopus:105020246766
ISSN
0284-186X
DOI
10.2340/1651-226X.2025.44211
language
English
LU publication?
yes
id
5028c1dc-7f41-43b1-b074-17e9e98f8ef0
date added to LUP
2025-12-16 13:31:28
date last changed
2025-12-19 15:14:00
@article{5028c1dc-7f41-43b1-b074-17e9e98f8ef0,
  abstract     = {{<p>Background and purpose: The study aims to evaluate dosimetric properties of hypofractionated treatment plans integrating focal boost, using registered whole-mount histopathology (WMHP) as reference standard. Methods: Fifteen men from the PAMP trial (EudraCT: 2015-005046-55) were included. Participants had ≥ 1 ISUP Grade group ≥ 4 lesion and underwent [<sup>68</sup>Ga]prostate-specific membrane antigen (PSMA) positron emission tomography/multiparametric magnetic resonance imaging (PET/mpMRI) and [<sup>11</sup>C]Acetate-PET/ computed tomography before radical prostatectomy. Four radiation oncologists delineated gross tumor volumes (GTVs) on PSMA-PET/mpMRI. Sixty treatment plans were optimized, one per GTV and patient. Prostate planning target volumes were prescribed 42.7 Gy in seven fractions, with a simultaneous GTV boost up to 49.0 Gy, prioritizing organs at risk (OARs). Digital WMHP provided Gleason grading and was co-registered with in-vivo imaging. Target coverage for GTVs and voxels sharing Gleason patterns (GPs) was assessed via dose-volume histogram (DVH) analysis. Interobserver agreement in GTV-delineations was quantified with Fleiss’ kappa. Results: The median GTV dose per plan (D<sub>50</sub>) ranged from 48.3 to 49.1 Gy. For voxels with the highest GP, D<sub>50</sub> was 42.9–49.2 Gy, exceeding 47.2 Gy in all except one plan. In lowest pattern voxels, D<sub>50</sub> was 42.5–49.3 Gy, and below 43.4 Gy in over half the plans. Significant positive correlations between Fleiss’ kappa and DVH parameters appeared only for GP 5 regions, specifically for Fleiss’ kappa and D<sub>50</sub> for two observers and the average D<sub>50</sub> across observers. Interpretation: The histologically confirmed tumor was only partially boosted. Regions with more aggressive disease received better coverage. These findings provide a rational for prioritizing OARs in treatment planning.</p>}},
  author       = {{Nilsson, Erik and Nilsson, Anneli and Jonsson, Joakim and Sandgren, Kristina and Grefve, Josefine and Axelsson, Jan and Lindberg, Angsana K. and Söderkvist, Karin and Karlsson, Camilla T. and Zackrisson, Björn and Strandberg, Sara and Riklund, Katrine and Bergh, Anders and Moreau, Mathieu and Gunnlaugsson, Adalsteinn and Olsson, Lars E. and Nyholm, Tufve}},
  issn         = {{0284-186X}},
  keywords     = {{focal boost; hypofractionation; In silico; prostate cancer; radiotherapy}},
  language     = {{eng}},
  pages        = {{1482--1488}},
  publisher    = {{Taylor & Francis}},
  series       = {{Acta Oncologica}},
  title        = {{Ultra-hypofractionated radiotherapy with focal boost for high-risk localized prostate cancer (HYPO-RT-PC-boost) : in silico evaluation with histological reference}},
  url          = {{http://dx.doi.org/10.2340/1651-226X.2025.44211}},
  doi          = {{10.2340/1651-226X.2025.44211}},
  volume       = {{64}},
  year         = {{2025}},
}