Imaging evaluation of blood supply changes after chemotherapy of osteosarcoma and its correlation with tumor necrosis rate.

BACKGROUND: Analysis of the tumour necrosis rate is an important method to evaluate the effect of neoadjuvant chemotherapy for osteosarcoma. However, at present, there is no specific imaging method to evaluate this effect. The purpose of this study was to evaluate the changes in blood supply after chemotherapy by measuring the CT enhancement rate and to analyse the correlation between the CT enhancement rate and the tumour necrosis rate.

METHODS: Patients with primary osteosarcoma of the extremities treated in our institute from 2016 to 2017 were analysed retrospectively. In total, 103 eligible patients were enrolled in the study, including 67 males and 36 females, with an average age of 17.7 (6-54) years. Sixty cases had tumour sites in the femur, 25 in the tibia, 10 in the humerus, and eight in other sites. All patients received neoadjuvant chemotherapy including methotrexate, cisplatin + doxorubicin and ifosfamide before surgical treatment. All patients underwent enhanced CT examination of the same tumour site before and after the neoadjuvant chemotherapy protocol. The CT value before and after chemotherapy was measured and the enhancement rate was calculated. The change in the CT enhancement rate after chemotherapy was analysed. Changes in the CT enhancement rate were compared between patients with a tumour necrosis rate greater than 90% and those with one <90%.

RESULTS: The average CT enhancement rates before and after chemotherapy were 1.68 (median 1.63, range 1.00-2.51) and 1.39 (median 1.28, range 1.00-2.83), respectively (P < 0.01). The average CT enhancement rate after chemotherapy decreased by 15.0% (median 16.7%, range -27.5-53%): 75 cases exhibited a decrease, three cases remained unchanged, and 25 cases exhibited an increase. The average enhancement rate before chemotherapy was 1.75 (median 1.68, range 1.18-2.51) in the group with a necrosis rate >90% and 1.62 (median 1.52, range 1.00-2.41) in the group with a necrosis rate < 90% (P = 0.068). The average CT enhancement rate after chemotherapy was 1.20 (median 1.21, range 1.00-1.53) in the group with a necrosis rate > 90% and 1.53 (median 1.43, range 1.00-2.83) in the group with a necrosis rate < 90% (P < 0.01). The enhancement rate of the group with a necrosis rate > 90% decreased by 29.0% (median 28%, range -2.3-53%) (P < 0.01); the enhancement rate of the group with a necrosis rate < 90% decreased by 3.8% on average (median 0.7%, range -27.5-44.5%) (P = 0.225).

CONCLUSION: After receiving neoadjuvant chemotherapy, most patients with osteosarcoma of the extremities exhibited reductions in the CT enhancement rate. In cases where the tumour necrosis rate was greater than 90%, the tumour blood supply was significantly reduced. This suggests that imaging evaluations based on the CT enhancement rate can be used as a reference for evaluating the preoperative effect of chemotherapy for osteosarcoma.