Scintigraphic evaluation of primary bone tumours with Technetium-99m-MIBI

Assessment of distribution pattern of 99mTc-MIBI in primary bone tumours to evaluate potential of 99mTc-MIBI in lesion characterization and prediction of response to chemotherapy.

40 patients with various primary bone neoplasms (20 GCT/8 Chondrosarcoma/7 Osteosarcoma/5 Ewing's sarcoma) underwent 2 phase (30 min/2hrs) planar and SPECT scintigraphy with CT co-registration with 15 mCi of 99mTc-MIBI.

Images were analyzed visually (parameters included intensity and distribution of tracer, tumour margins, distortion of bony outline). Quantitative analysis was done by drawing ROI on lesion and background. In 12 patients who underwent chemotherapy, washout rates were calculated from T/B ratios of early and delayed phase, and statistically correlated with WHO categories of clinical response MIBI scan findings were correlated with CT/MRI and histopathology).

Tracer uptake pattern was significantly different in various tumours. Non aggresive tumours like GCT showed moderate to increased uptake, well defined tumour margins and mild distortion of bony outline. Aggressive tumours (osteosarcoma/Ewing's sarcoma) showed patchy, intense tracer uptake, poorly defined tumour margin and considerable distortion of bony outline. Washhout rates showed significant difference between responders and non responders (p value −0.030).

Besides being a useful aid in differentiating aggressive from non aggressive neoplasms, 99mTc-MIBI enable selection of cases potentially responsive to chemotherapy, while those found to be non responders with high washout rates, can be planned for alternative treatment, thereby optimizing patient care.