Monitoring the chemotherapeutic response in primary lung cancer using (99m)Tc-MIBI SPET.

Abstract

Prediction and evaluation of the response to chemotherapy (CTx) are important for the correct and cost-effective treatment of patients with primary lung cancer. Although fluorine-18 fluorodeoxyglucose positron emission tomography (FDG-PET) is accepted as the most useful and accurate nuclear medicine technique for this purpose, its expense and limited availability restrict its use. Compared with PET agents, technetium-99m methoxyisobutylisonitrile (MIBI), which is used in nuclear oncology, is cheaper and available in any nuclear medicine clinic. With this in mind, in this study we aimed to evaluate the role of (99m)Tc-MIBI in monitoring the chemotherapeutic response in primary lung cancer. Twenty patients with primary lung cancer underwent (99m)Tc-MIBI single-photon emission tomography (SPET) at 15min (early) and 3-4h (delayed) after injection of the tracer. All patients underwent (99m)Tc-MIBI SPET study twice: before and after the 3rd cycle of CTx. Patients were divided into two groups, responders [R(+), n=10] and non-responders [R(-), n=10], according to the change in tumour size on CT scan taken 2 weeks after the last cycle of the CTx. From the SPET images early and delayed tumour/lung ratios (ER and DR) were obtained before and after CTx. In the R(+) group, ER and DR decreased significantly after CTx, from 3.28±1.55 to 1.78±0.72 (P<0.04) and from 3.23±1.55 to 2.0±0.88 (P<0.05), respectively. However, in the R(-) group, while ER showed a slight and statistically insignificant increase after CTx (from 2.51±1.23 to 2.65±1.86), DR increased significantly, from 2.74±1.37 to 3.27±2.31 (P<0.03). The percentage decreases in ER and DR in the R(+) group after CTx was significantly higher than that in the R(-) group: 34.36%±26.7% vs -13.78%±27.58% (P<0.0002) and 29.45%±25.23% vs -18.58%±20.51% (P<0.0005), respectively. Using a decrease of ≥10% as a threshold for monitoring the chemotherapeutic response, (99m)Tc-MIBI had a sensitivity of 90% and a specificity of 100%. We found a positive correlation in 14 patients between ER and DR and survival: r=0.6754 and P=0.008, and r=0.5755 and P=0.031, respectively. Our results suggest that (99m)Tc-MIBI might be used in routine practice to monitor the chemotherapeutic response in patients with primary lung cancer, especially when PET is not available.