Fluorodeoxyglucose positron emission tomography of soft tissue tumours: isa non-invasive determination of biological activity possible?

Since musculoskeletal tumours comprise a large heterogeneous group of entit ies with different biological behaviour, clinical diagnosis of such lesions can be very difficult. The aim of this prospective study was to assess the usefulness of 2-[F-18]-fluoro-2-deoxy-D-glucose (FDG) positron emission to mography (PET) in the non-invasive evaluation of soft tissue tumours. One h undred and two patients with suspected soft tissue neoplasms were investiga ted by FDG-PET. The uptake of FDG was evaluated semiquantitatively by deter mining the tumour to background ratio (TBR). All patients underwent biopsy, resulting in the histological detection of 39 high-grade sarcomas, 16 inte rmediate-grade sarcomas, 11 low-grade sarcomas, 25 benign tumours, 10 tumou r-like lesions such as spontaneous myositis ossificans (n = 6) and one non- Hodgkin lymphoma. All lesions except for two lipomas disclosed an increased FDG uptake. Sarcomas showed significantly higher TBR values than latent or active benign lesions (P<0.001) and aggressive benign lesions (P<0.05). Us ing a TBR cut -off level of 3.0 for malignancy, sensitivity of FDC-PET was 97.0%, specificity 65.7% and accuracy 86.3%. From our data there are three main conclusions: (1) Except for patients with pseudotumoral myositis ossif icans, lesions with a TBR >3 were sarcomas (91.7%) or aggressive benign tum ours (8.3%). (2) Tumours with a TBR <1.5 were latent or active benign lesio ns, exclusively. (3) The group with intermediate TBR values (<3 and >1.5) c omprised primarily latent or active benign lesions, but also four aggressiv e benign tumours and two low-grade sarcomas. Our data suggest that FDG-PET represents a useful tool for the evaluation of the biological activity of s oft tissue neoplasms.