# Fifty Shades of PSMA-Avid Rib Lesions: A Comprehensive Review

## TL;DR

This paper reviews how to distinguish cancerous from non-cancerous rib lesions seen in prostate cancer scans, aiming to improve accurate diagnosis and treatment decisions.

## Contribution

The paper introduces a clinical decision tree to differentiate benign from metastatic rib lesions in prostate cancer using PSMA imaging characteristics.

## Key findings

- Solitary rib lesions in low-risk patients are often benign, especially in anterior/lateral rib regions.
- Metastatic lesions are more likely to be multiple, show cortical destruction on CT, and occur in high-risk patients.
- 18F-PSMA-1007 is more prone to unspecific uptake in ribs compared to 68Ga-PSMA-11.

## Abstract

Prostate cancer often spreads to the bones, and the ribs are a frequent site of suspicious findings on advanced scans. New imaging methods are very sensitive, but they sometimes show spots in the ribs that look like cancer even when they are not. This creates uncertainty for doctors and patients, since a mistaken diagnosis of rib metastasis can change treatment decisions and lead to unnecessary therapies. Our review gathers the current knowledge about these rib findings and explains how to tell apart true cancer from harmless changes, such as old fractures or other benign conditions. By highlighting patterns related to scan intensity, lesion number, location, patient risk, and follow-up results, we suggest a practical approach to interpretation. This guidance may help clinicians avoid false alarms, ensure accurate staging, and make treatment more personalized for men with prostate cancer.

Background: While prostate-specific membrane antigen (PSMA)-targeted imaging has revolutionized metastatic detection, unspecific bone uptake (UBU)—particularly in the ribs—is a common but diagnostically challenging finding in prostate cancer (PCa) patients. This review aims to synthesize current evidence on PSMA-avid rib lesions in PCa and to propose a structured approach for differentiating true metastases from benign mimics. Methods: A comprehensive literature search across PubMed, EMBASE, Scopus, and Web of Science identified relevant studies on PSMA imaging interpretation, tracer-specific patterns, rib lesion morphology, and clinical correlates. Data on uptake intensity, CT features, lesion number, location, tracer type, patient-specific risk factors, and follow-up behavior were extracted and analyzed. Results: Most solitary rib lesions are benign, particularly in low-risk patients or when located in the anterior/lateral arcs. Metastatic lesions are more likely to present as multiple foci, show cortical destruction on CT, exhibit high uptake intensity, and occur in patients with elevated PSA, high Gleason score, or ongoing androgen deprivation. 18F-PSMA-1007 is especially prone to UBU in the ribs compared to 68Ga-PSMA-11. Based on these variables, we propose a clinical decision tree to guide interpretation of PSMA-avid rib lesions. Conclusions: Accurate interpretation of rib lesions on PSMA PET/CT requires a multimodal, context-sensitive approach. Our diagnostic decision tree guides precise differentiation of benign versus metastatic rib lesions, enhancing staging accuracy and clinical decision-making. Biomarker-guided therapies offer potential for personalized treatment, though rib-specific validation remains a critical need.