Medicina Nuclear e Radioterapia

Evaluation of Early Response to Neoadjuvant Chemotherapy in Breast Cancer Patients by 18F-FDG and 99mTc-HL91 Imaging

Abstract

Zhan Song, Zhe Wang, Li-Wen Li, Jiang-Hao Chen and Jing Wang

By monitor breast cancer mass with ¹⁸F-fluorodeoxyglucose (FDG) and ⁹⁹mTc-HL91 positron emission tomography (PET) imaging, this study compares the efficacy of the two imaging methods in evaluation of the early response to neoadjuvant chemotherapy in stage II and III breast cancer patients. Images of region of interest were acquired with a hybrid PET/computed tomography scanner in forty patients after administration of ¹⁸F-FDG (4.44 MBq/kg) or ⁹⁹mTc-HL91 (12.3 MBq/kg) at baseline and after the third course of chemotherapy. And the values of tumor to non-tumor activity ratio (T/N) were compared between the two imaging methods and with the pathologic response. Surgery was performed after three courses of chemotherapy and pathological analysis revealed gross residual disease in 11 patients and minimal residual disease in 29 patients. When 20% reduction in T/N was set as the threshold for differentiation between responders and nonresponders by ¹⁸F-FDG imaging, 27 of 29 responders and 10 of 11 nonresponders were identified after three courses of chemotherapy. A linear correlation was observed between the T/N of ⁹⁹mTc-HL91 and the T/N of ¹⁸F-FDG (rs = 0.778, p<0.001), but almost lost after chemotherapy (rs = 0.518, p<0.001). In conclusion, we suggest that ¹⁸F-FDG imaging, but not ⁹⁹mTc–HL91 imaging with hybrid PET/CT provides a costeffective method, which could be well accepted for the low-income population in developing countries, to monitor early tumor response after three cycles of neoadjuvant chemotherapy in stage II and III breast cancer by using the reduction of N/T ratio as predictor.