ESTRO 2023

Session Item

Saturday

May 13

15:15 - 16:15

Stolz 1

Prostate

Chair: , Italy;

Co-Chair: William Kinnaird, United Kingdom

Session Code: 1420

Session Type: Mini-Oral

Track: Clinical

Histopathology-validated detection rates of intraprostatic lesions with mpMRI, PSMA-PET and ACE-PET

Kristina Sandgren, Sweden

Presentation Number: MO-0219

Abstract

Abstract Title:

Histopathology-validated detection rates of intraprostatic lesions with mpMRI, PSMA-PET and ACE-PET

Authors:

Kristina Sandgren¹, Sara Strandberg², Joakim Jonsson¹, Josefine Grefve¹, Angsana Keeratijarut Lindberg¹, Erik Nilsson¹, Anders Bergh³, Karin Söderkvist⁴, Camilla Thellenberg Karlsson⁴, Bengt Friedrich⁵, Anders Widmark⁴, Lennart Blomqvist⁶, Vibeke Berg Loegager⁷, Jan Axelsson¹, Mattias Ögren⁸, Margareta Ögren⁸, Tufve Nyholm¹, Katrine Riklund⁸

¹Umeå University, Radiation Sciences, Radiation Physics, Umeå, Sweden; ²Umeå University , Radiation Sciences, Diagnostic Radiology, Umeå, Sweden; ³Umeå University, Medical Biosciences, Pathology, Umeå, Sweden; ⁴Umeå University, Radiation Sciences, Oncology, Umeå, Sweden; ⁵Umeå University, Surgical and Perioperative Sciences, Urology and Andrology, Umeå, Sweden; ⁶Karolinska Institute, Molecular Medicine and Surgery, Umeå, Sweden; ⁷Copenhagen University Hospital in Herlev, Radiology, Copenhagen, Denmark; ⁸Umeå University, Radiation Sciences, Diagnostic Radiology, Umeå, Sweden

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Purpose or Objective

Radiotherapy is a commonly used treatment method for patients with high-risk prostate cancer. Emerging evidence shows a benefit of increasing the dose to the dominant intra-prostatic lesion. In this study we examined the performance of [68Ga]PSMA-11 PET (PSMA-PET), [11C]Acetate PET/CT (ACE-PET) and multiparametric MRI (mpMRI) for the detection of intra-prostatic lesions in patients with intermediate and high-risk prostate cancer, using whole-mount histopathology as the reference standard, stratified by Gleason score (GS) and lesion volume.

Material and Methods

Fifthy-five study participants with intermediate to high-risk prostate cancer planned for radical prostatectomy were included. PSMA-PET/mpMRI and ACE-PET/CT examinations were performed prior to surgery. After excision, the specimen was placed in a custom-made mold to prevent deformation and an ex-vivo T2w MRI was performed. The specimen was fixed in formalin at least 24 h prior to slicing into 5 mm thick slices from apex to base. Standard histopathology procedures including paraffin embedding and microtoming in 5 µm thick slices were performed. Each slice was stained with hematoxylin and eosin and examined by the pathologist, who segmented and graded tumor foci. The slices were registered to the in-vivo images using the software MICE toolkit, resulting in an uncertainty of below 2 mm. Two radiologists examined the mpMRI data and two nuclear medicine specialists examined the PET data in a blinded manner and reported the findings according to PI-RADS v2.1 and E-PSMA guidelines, respectively. The detection rate was determined and stratified by GS and lesion volume.

Results

The histopathological evaluation found 130 lesions >0.05 cc, 88 lesions >0.1 cc and 43 lesions >0.5 cc. The GS-distribution was 26% (3+3), 38% (3+4), 18% (4+3), 15% (4+4) and 3% (>4+4). The mean detection rate for lesions with a GS ≥3+4 and a volume >0.05 cc (96 in total) was 18% (ACE-PET), 40% (mpMRI) and 42% (PSMA-PET). 56 (58%) lesions in this group were identified by either mpMRI, PSMA or both.

The histopathological examination identified 42 lesions with a GS ≥3+4 and a volume >0.5 cc. The mean detection rate for this group were 37% (ACE-PET), 70% (PSMA-PET) and 74% (mpMRI). 40 (93%) lesions in this group were identified by either mpMRI, PSMA or both.

Conclusion

The degree of detection increases with increasing GS and lesion volume. PSMA-PET and mpMRI generate high detectability, but they do not always detect the same lesions, which may indicate the value of a combined PSMA-PET/MRI examination.