ESTRO 2024 - Abstract Book

S5077

Physics - Radiomics, functional and biological imaging and outcome prediction

ESTRO 2024

with chemoradiation and MRI-guided adaptive brachytherapy for locally advanced cervical cancer: results from the prospective multicenter EMBRACE study. Radiotherapy and oncology, 120(3), 412-419.

4. Steyerberg, E. W., Eijkemans, M. J. C., & Habbema, J. D. F. (2001). Application of shrinkage techniques in logistic regression analysis: a case study. Statistica Neerlandica, 55(1), 76-88.

5. Austin, P. C., & Steyerberg, E. W. (2019). The Integrated Calibration Index (ICI) and related metrics for quantifying the calibration of logistic regression models. Statistics in medicine, 38(21), 4051-4065.

1737

Proffered Paper

Multiparametric MRI and PET relates to immunoreactivity for prostate specific antigen and Ki67

Erik Nilsson 1 , Kristina Sandgren 1 , Josefine Grefve 1 , Joakim Jonsson 1 , Jan Axelsson 1 , Angsana K Lindberg 1 , Karin Söderkvist 2 , Camilla T Karlsson 2 , Anders Widmark 2 , Lennart Blomqvist 3 , Sara Strandberg 4 , Katrine Riklund 4 , Anders Bergh 5 , Tufve Nyholm 1 1 Umeå University, Department of Radiation Sciences, Radiation Physics, Umeå, Sweden. 2 Umeå University, Department of Radiation Sciences, Oncology, Umeå, Sweden. 3 Karolinska Institutet, Department of Molecular Medicine and Surgery, Solna, Sweden. 4 Umeå University, Department of Radiation Sciences, Diagnostic Radiology, Umeå, Sweden. 5 Umeå University, Department of Medical Biosciences, Pathology, Umeå, Sweden

Purpose/Objective:

We differentiated between immunoreactivity scores for prostate specific antigen (PSA) and Ki67 using cut-off values derived from [ 68 Ga]PSMA-11 positron-emission tomography (PSMA-PET), [ 11 C]Acetate-PET (Acetate-PET) and multiparametric MRI (mpMRI) in a co-registered dataset, using whole-slide histopathology as reference standard.

Material/Methods:

Preoperative PSMA-PET/mpMRI and Acetate-PET/CT were obtained for 55 men with elevated prostate-specific antigen (PSA) and biopsy-proven prostate cancer (PCa), planned for radical prostatectomy. Resected prostates were placed in 3D printed molds, tailored to each patient based on delineations of prostate glands on T2-weighted (T2w) images. Molds containing prostates were imaged to yield ex-vivo T2w images, and subsequently prepared for histopathological evaluation. Gleason grading on whole-slide images resulted in digital annotations of lesions and their International Society of Urological Pathology (ISUP) grade groups (IGG). Sections were stained for Ki67 and prostate specific antigen (PSA), providing additional information on tumor aggresiveness [1]. Immunoreactivity for Ki67 was quantified by the fraction of Ki-67 positive cells, estimated as the weighted average from ten sample regions per lesion each containing at least 50 cells. Immunoreactivity for PSA was quantified as the product of two scores; one based on the percentage of epithelial cells stained (0: no staining, 1: 1%–25%, 2: 26%–50%, 3: 51%–75%, and 4: 76%–100%) and the other by the intensity of the staining (0: negative, 1: weak, 2: moderate and 3: intense). The image data, including histopathology, was co-registered with the in-vivo T2w as a common frame of reference.