Early chemotherapy response evaluation in tumors by 99mTc-DTPA-DG

The aim of this study was to evaluate the utility of 99mTc-diethylenetriaminepentaacetic acid-deoxyglucose (DTPA-DG) for monitoring the early response of tumors to chemotherapy.

To evaluate the role of 99mTc-DTPA-DG in vitro chemotherapy, the uptake ratios assays were conducted using A549 lung cancer and MCF-7 breast cancer cells after the 2 tumor cell types had been treated with cisplatin and paclitaxel chemotherapeutic agents, respectively. Apoptosis in the 2 cell types, an indicator of chemotherapeutic action, was assessed by inverted fluorescence microscope and flow cytometry. The assessment of 99mTc-DTPA-DG in vivo was performed by scintigraphic imaging studies of 99mTc-DTPA-DG in MCF-7 mammary tumor cell xenografts at timed intervals after treatment. The animals were randomly assigned to 5 groups: group A, saline injection; group B, low-dose cisplatin; group C, high-dose cisplatin; group D, low-dose combination chemotherapy; and group E, high-dose combination chemotherapy. Imaging findings were correlated with the effectiveness of chemotherapy.

The uptake rates of 99mTc-DTPA-DG by A549 lung cancer cells and MCF-7 breast cancer cells in the chemotherapeutic groups were all significantly lower than those in the controls (p < 0.01). The apoptotic ratios in the control groups were significantly lower than the apoptotic ratios in the chemotherapeutic treatment groups in the 2 tumor cell types. The uptake ratios and the apoptosis ratios are inverse correlation, which suggested that we could evaluate the chemotherapy response by the uptake of 99mTc-DTPA-DG in vitro. Scintigraphy in MCF-7 mammary tumor xenografts mice demonstrated that tumor could be clearly visualized by 99mTc-DTPA-DG. The efficacy of combined chemotherapy treatment in this xenograft model was assessed by scintigraphy of tumor/muscle ratios.

99mTc-DTPA-DG is a targeted molecular imaging agent, promising in the evaluation of early response of tumors to chemotherapy.