A single (99m)Tc-MIBI study to predict response to neoadjuvant treatment in sarcoma patiens

Technetium-99m methoxy isobutyl isonitrile ((99m)Tc-MIBI) was used as a tumour imaging agent to predict the response of neoadjuvant treatment in patients with bone and soft tissue sarcoma. Our study included 31 patients (M:F = 23:8), 17 having osteosarcomas and 14 with soft-tissues sarcomas. Scintigraphy with (99m)Tc-MIBI was performed before the initiation of the neoadjuvant treatment. Static images were acquired at 10 and 60min post-injection and lesion to normal (L/N) ratios and washout rates (WR%) were calculated. Tumour response was assessed by detecting percent necrosis in a surgically resected specimen. Responses were correlated and compared with WR%. Percentage of tumour necrosis was 71.35±20.20% (mean±SD) with eight good and 23 poor responses. On visual analysis, 16 showed homogeneous, 11 heterogeneous and 4 doughnut shaped pattern of uptake. Seventy five percent of good responders had homogeneous uptake. Early and delayed L/N ratios were significantly different in both good and poor responders (P=0.006 and P<0.001, respectively) but correlated poorly with the tumour necrosis values in the specimen (R=0.23 and 0.06 respectively). Mean washout rate was 26.13±11.25% (median = 29%) and there was weak correlation between tumour necrosis and WR% (r=-0.32, P=0.029). The mean WR% of good responders was 15.0±10.0% and that of poor responders was significantly higher (30.1±8.8%, P=0.003). Good responders by 88% were below the median cut-of value. In conclusion WR% of (99m)Tc-MIBI may be used before surgery to identify poor responders to neoadjuvant treatment in patients with bone and soft tissue sarcomas.