Purpose: The most important prognostic factor of osteosarcoma is the percentage of tumor necrosis. Only well trained and experienced musculoskeletal pathologists can count and assess the percentage of tumor necrosis from the resected specimens. The purpose of the present study was to characterize the correlation of Tc-99m MIBI scintigraphy for assessing the percentage of tumor necrosis using postoperative histology as a gold standard.
Material and Method: During September 2002 to August 2004, nine consecutive patients with the diagnosis of conventional osteosarcoma were included in the present study. The osteosarcoma protocol comprises 3 courses of doxorubicin and cisplatin preoperatively followed by wide resection of tumors and another 3 courses of postoperative chemotherapy. The Tc 99m MIBI scintigraphy examination was carried out before commencing chemotherapy and after completing preoperative chemotherapy. The tumor uptake was measured using the tumor to the background ratio (TBR). Comparison of TBR before and after preoperative chemotherapy was used to calculate the alteration ratio which was reported in terms of percentage. All of the resected specimens were sent to the pathological department. The histological assessment of the response to chemotherapy was performed using the standard technique according to the current practice of osteosarcoma from the Mayo Clinic. The percentages of tumor necrosis from histology were also reported.
Results: The analysis of the correlation between the reduction of tracer uptake and the postoperative histological response was performed. The correlation and linear regression analysis showed that the two methods had a significant correlation (R = 0.75) regression coefficient (1.172) with p = 0.020 and 0.043, respectively.
Conclusion: The present study showed that Tc-99m MIBI scintigraphy had a significant correlation with percentage of tumor necrosis from histology. This technique can be used to predict the response of osteosarcoma after preoperative chemotherapy.

Keywords: Osteosarcoma, Tumor necrosis, Tc-99m MIBI scintigraphy