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. 2024 May 29;16(11):2056.
doi: 10.3390/cancers16112056.

Reasons for Discordance between 68Ga-PSMA-PET and Magnetic Resonance Imaging in Men with Metastatic Prostate Cancer

Jade Wang  1 , Elisabeth O'Dwyer  2 , Juana Martinez Zuloaga  2 , Kritika Subramanian  2 , Jim C Hu  3 , Yuliya S Jhanwar  2 , Himanshu Nagar  4 , Arindam RoyChoudhury  5 , John Babich  6 , Sandra Huicochea Castellanos  2 , Joseph R Osborne  2 , Daniel J A Margolis  2
Affiliations

Reasons for Discordance between 68Ga-PSMA-PET and Magnetic Resonance Imaging in Men with Metastatic Prostate Cancer

Jade Wang et al. Cancers (Basel). .

Abstract

Background: PSMA PET has emerged as a "gold standard" imaging modality for assessing prostate cancer metastases. However, it is not universally available, and this limits its impact. In contrast, whole-body MRI is much more widely available but misses more lesions. This study aims to improve the interpretation of whole-body MRI by comparing false negative scans retrospectively to PSMA PET.

Methods: This study was a retrospective sub-analysis of a prospectively collected database of patients who participated in a clinical trial of PSMA PET/MRI comparing PSMA PET and whole-body MRI from 2018-2021. Subjects whose separately read PSMA PET and MRI diagnostic reports showed discrepancies ("false negative" MRI cases) were selected for sub-analysis. The cases were reviewed by the same attending radiologist who originally read the scans. The radiologist noted specific features on MRI indicating metastatic disease that were initially missed.

Results: Of 263 cases, 38 (14%) met the inclusion criteria and were reviewed. Six classes of mpMRI false negatives were identified: anatomically normal (18, 47%), atypical MRI appearance (6, 16%), mischaracterization (1, 3%), undercall (6, 16%), obscured (4, 11%), and no abnormality on MRI (3, 8%). Considering that the atypical and undercalled cases could have been adjusted in retrospect, and that 4 additional cases had positive lesions to the same extent and 11 further cases had disease confined to the pelvis, only 11 (4%) of the original 263 would have had disease outside of a conventional radiation treatment plan.

Conclusion: Notably, almost 50% of the cases, including most lymph node metastases, were anatomically normal using standard criteria. This suggests that current anatomic criteria for evaluating prostate cancer lymph node metastases are not ideal, and there is a need for improved criteria. In addition, 32% of cases involved some element of human interpretive error, and, therefore, improving reader training may lead to more accurate results.

Keywords: MRI; PET; PSMA; cancer; prostate; whole-body.

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Conflict of interest statement

John Babich is Founder, President and Chief Scientific Officer, Ratio Therapeutics, Inc. Daniel J. A. Margolis has received an ad hoc consulting consideration from Guerbet and Promaxo. None of these companies was involved in the funding or analysis of the data herein. The Corresponding Author assumes ultimate responsibility for the content.

Figures

Figure 1
Figure 1
Flow diagram.
Figure 2
Figure 2
Six classes of MRI false negatives.
Figure 3
Figure 3
Post-contrast fat-saturated gradient T1-weighted image (A), diffusion-weighted imaging with b = 900 s/mm2 (DWI) (B), and fused PET/single-shot T2-weighted imaging (C) through the pelvis. In Figure 3A, the lesion is marked with measurement calipers. In Figure 3B,C, the lesion is denoted with a red arrow. Yellow arrows indicate the ureters, which show physiologic PSMA PET uptake.
Figure 3
Figure 3
Post-contrast fat-saturated gradient T1-weighted image (A), diffusion-weighted imaging with b = 900 s/mm2 (DWI) (B), and fused PET/single-shot T2-weighted imaging (C) through the pelvis. In Figure 3A, the lesion is marked with measurement calipers. In Figure 3B,C, the lesion is denoted with a red arrow. Yellow arrows indicate the ureters, which show physiologic PSMA PET uptake.
Figure 4
Figure 4
Post-contrast fat-saturated gradient T1 (A), DWI (B), and fused PET (C) images. In Figure 4A, the lesion is retrospectively measured (calipers). In Figure 4C, the lesion is denoted with a red arrow.
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