Frequency and Accuracy of Morphologic Alterations in Bone Metastases on [⁶⁸Ga]Ga-PSMA-11 PET/CT in Prostate Cancer

A new study provides insight into the diagnostic significance of [⁶⁸Ga]Ga-PSMA-11 PET/CT imaging in identifying prostate cancer bone metastases, even in cases where no clear structural abnormalities are visible on CT scans.

Researchers from a single-center retrospective analysis found that focal bone lesions exhibiting PSMA uptake without morphological correlates (MC) on CT are common and often malignant, particularly in patients undergoing scans for biochemical recurrence (BCR) of prostate cancer.

“This work reinforces the importance of functional imaging with PSMA PET, especially when CT fails to show visible lesions,” the study authors said.

In prostate cancer imaging, [¹⁸F]F-PSMA-1007 PET findings without CT correlates are often dismissed as benign. However, intense PSMA uptake in bone without an associated CT finding, especially on [⁶⁸Ga]Ga-PSMA-11 PET/CT, is increasingly recognized as potentially malignant, though its true prevalence and clinical significance have remained unclear.

The team reviewed [⁶⁸Ga]Ga-PSMA-11 PET/CT scans from April 2016 to November 2021 involving patients undergoing imaging for initial staging or BCR of prostate cancer. Among 824 total patients, 323 met study criteria, and 101 showed PSMA-positive bone lesions, leading to the analysis of 176 focal lesions.

Key results include:

• In the initial staging group, 25% of lesions had no CT correlate, yet 73% of were malignant.
• In the BCR group, 52% of lesions lacked a CT correlate, with 48% confirmed as malignant.
• Sensitivity and specificity using the PSMA-RADS 2.0 classification were notably high:
• 100%/100% for staging, and 83%/100% for BCR.
• In contrast, CT-based assessment showed lower accuracy, particularly in staging (78% sensitivity, 36% specificity).

The study concludes that PSMA-avid bone lesions without CT findings are not only frequent but often clinically significant, particularly in the context of BCR.

Importantly, using PSMA-RADS 4 criteria during initial staging improves diagnostic accuracy. In cases of BCR, integrating clinical context and applying PSMA-RADS 3B can further enhance lesion detection and interpretation.

“These findings support a more nuanced interpretation of PSMA PET/CT scans and argue against dismissing lesions without CT correlates—especially in high-risk patients,” the authors noted.

This research underscores the need for greater reliance on functional imaging markers and structured reporting systems like PSMA-RADS in the evolving field of prostate cancer management. Future prospective studies may help refine how best to integrate PET/CT findings with other diagnostic tools to guide clinical decision-making.