Nucpaedia
Nucpaedia
Short read · Oncology

An Isolated PSMA-Avid Rib Focus: What Should You Check Before Calling Metastasis?

Oncology · 3 min read

Alone in a rib, it is usually benign. Five checks before you call it.

A single hot rib on a staging PSMA PET can turn curative treatment into palliative. Most such foci are benign — healed fractures, fibrous dysplasia, or non-specific tracer uptake. Five checks stop the overcall.

What the evidence says

  • Chen 2020 (68Ga-PSMA-11, staging): 61 of 62 solitary rib foci benign (98%).
  • Stoffels 2025 (68Ga-PSMA-11): 46 of 54 patients with rib-only foci benign (85%). Only benign CT features discriminated.
  • Woo 2025 (18F-DCFPyL): 47 of 175 men had rib metastases — only 1 of the 47 with no disease anywhere else.
  • Rauscher 2020: 18F-PSMA-1007 showed about 5× more benign-origin lesions than 68Ga-PSMA-11 (245 vs 52).

The five Ts

Each T is a question. They run in order of weight — the first matters most.

TAskLeans benignLeans metastasis
TogetherAny other PSMA-avid metastasis — nodes, other bones, viscera?None — the rib is truly aloneYes — the rib is probably one more
TextureWhat does CT show at the focus?Fracture (callus, cortical step) or a benign lesion such as fibrous dysplasiaSclerosis or cortical destruction
TallyHow many ribs, in what pattern?One rib, or several in a line (trauma)Several ribs, scattered
Tumour riskHow likely are metastases at all?Low PSA, low ISUP gradeHigh PSA, high ISUP grade
TracerWhich PSMA ligand?18F-PSMA-1007 — frequent non-specific bone uptakeNo tracer tips it here — even with 68Ga-PSMA-11 most isolated rib foci were benign
  • No CT correlate fits either side — typical of non-specific uptake, but early marrow metastases can show on PET before CT changes.
  • Uptake intensity is deliberately not a T — metastases run hotter on average, but benign and malignant values overlap too much to decide on.
Remember

“Rib metastases travel in company.” A focus found alone is almost always benign.

What to do

Decision tree for a single PSMA-avid rib focus. Other PSMA-avid disease: if yes, part of metastatic disease. If no, fracture or clear benign lesion on CT: if yes, benign. If no, sclerotic or destructive, or high-risk patient: if yes, equivocal, MRI or follow-up, biopsy only if it changes treatment. If no, probably benign: do not upstage, follow up.YesNoYesNoYesNoA single PSMA-avid rib focusOther PSMA-avid disease(nodes, bones, viscera)?Part of metastaticdiseaseFracture or clear benignlesion on CT?Benign — say soSclerotic or destructive,or high-risk patient?Equivocal: MRI orfollow-up; biopsy onlyif it changes treatmentProbably benign:don’t upstage; follow up
  • Report it as equivocal — e.g. PSMA-RADS 3B — not M1b.
  • PSA settles most: an undetectable PSA after prostatectomy means the rib was benign.
Pitfalls
  • Don’t trust SUVmax alone. In Chen 2020, 69% of the benign foci were hotter than the one true metastasis.
  • Benign CT signs are reliable; malignant-looking ones are not. In Stoffels 2025 only a clear benign feature predicted the diagnosis — age, SUVmax and “malignant” CT features all misled. Sclerosis tilts towards metastasis; it never proves it.
Take home
  • An isolated PSMA-avid rib focus is benign in most men — a rib metastasis almost never occurs without disease elsewhere.
  • Run the five Ts: together, texture, tally, tumour risk, tracer.
  • Report equivocal, don’t upstage, and let CT, follow-up or PSA decide. Biopsy only if the answer changes treatment.
Sources
  1. Chen MY, Franklin A, Yaxley J, et al. Solitary rib lesions showing prostate-specific membrane antigen (PSMA) uptake in pre-treatment staging 68Ga-PSMA-11 positron emission tomography scans for men with prostate cancer: benign or malignant? BJU Int. 2020;126(3):396-401.
  2. Stoffels M, Cousin F, Lamande M, et al. Characterization of exclusive rib lesions detected by [68Ga]Ga-PSMA-11 PET/CT. Nucl Med Commun. 2025;46(1):95-105.
  3. Woo S, Becker AS, Leithner D, et al. PSMA-avid rib lesions in prostate cancer patients: differentiating false positives from metastatic disease. Eur Radiol. 2025;35(9):5337-47.
  4. Rauscher I, Krönke M, König M, et al. Matched-pair comparison of 68Ga-PSMA-11 PET/CT and 18F-PSMA-1007 PET/CT: frequency of pitfalls and detection efficacy in biochemical recurrence after radical prostatectomy. J Nucl Med. 2020;61(1):51-7.
  5. Shamshirgaran A, Samadi MH, Saeed M, et al. Fifty shades of PSMA-avid rib lesions: a comprehensive review. Cancers (Basel). 2025;17(21):3404.
← BackShort reads

Spotted an error or something out of date? Report an error