Adjudicating Indeterminate Bone Lesions in Prostate Cancer Imaging

"Adjudicating Indeterminate Bone Lesions in Prostate Cancer Imaging" takes up the question of how to manage an indeterminate bone lesion without subjecting patients to unnecessary biopsies.

Dr. Ghesani asks how the panelists approach an isolated, indeterminate bone lesion, or IBL, discovered in a patient with otherwise limited disease. Dr. Mendel describes these as frequent red herrings, often faintly PSMA-avid enchondromas or other benign rib findings that generated unnecessary negative biopsies early in his experience. He explains that he now weighs pretest probability heavily, often ignoring low-uptake lesions in patients with low-risk features and a low PSA, while ordering additional imaging such as MRI when he is more concerned. Dr. Yonover describes his own approach, starting with assessing pretest probability and whether the lesion is rib-only, multifocal, or solitary. He notes that fluorine-18 tracers carry a higher rate of IBLs than gallium, so tracer type factors into his initial assessment alongside SUV and imaging correlates. He explains he has largely abandoned bone biopsies for these lesions because they are painful, carry risk, and yield little actionable tissue, and describes instead serially scanning patients on systemic therapy to see whether a suspicious lesion resolves within six to twelve months. Dr. Ghesani notes that PSMA PET has upended older radiology teaching that absent sclerosis rules out bone metastasis, since early lesions are often isodense with no imaging correlate. Dr. Yonover adds that his practice now asks technologists to inquire about rib trauma at the time of scanning to help contextualize equivocal findings. Both panelists emphasize that ambiguous IBLs create real anxiety for patients and clinicians alike, and Dr. Yonover criticizes the phrase cannot rule out in radiology reports. Dr. Mendel describes maintaining close working relationships with dedicated PET readers, including quarterly case-review meetings, to resolve difficult reads collaboratively. Dr. Ghesani closes by noting that rib biopsies are particularly difficult technically, and that imprecise biopsy targeting relative to the site of peak PSMA uptake can produce a false-negative sample.

Up next, in "Avoiding False Positives on Prostate Cancer PSMA PET Scans," the experts walk through the normal biodistribution of PSMA tracers and the anatomic traps that can produce false positives.