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

Prediction and evaluation of the response to chemotherapy (CTx) are importa nt for the correct and cost-effective treatment of patients with primary lu ng cancer. Although fluorine-18 fluorodeoxyglucose. positron emission tomog raphy (FDG-PET) is accepted as the most useful and accurate nuclear medicin e technique for this purpose, its expense and limited availability restrict its use. Compared with PET agents, technetium-99m methoxyisobutylisonitril e (MIBI), which is used in nuclear oncology, is cheaper and available in an y nuclear medicine clinic. With this in mind, in this study we aimed to eva luate the role of Te-99m-MIBI in monitoring the chemotherapeutic response i n primary lung cancer. Twenty patients with primary lung cancer underwent T c-99m-MIBI single-photon emission tomography (SPET) at 15 min (early) and 3 -4 h (delayed) after injection of the tracer. All patients underwent 99mTc- MIBI SPET study twice: before and after the 3rd cycle of CTx. Patients were divided into two groups, responders [R(+), n=10] and nonresponders [R(-), n=10], according to the change in tumour size on CT scan taken 2 weeks afte r 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(+) gro up, 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), respectiv ely. 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 i ncreased significantly, from 2.74 +/-1.37 to 3.27 +/-2.31 (P <0.03). The pe rcentage decreases in ER and DR in the R(+) group after CTx was significant ly 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), respect ively. Using a decrease of greater than or equal to 10% as a threshold for monitoring the chemotherapeutic response, Te-99m-MIBI had a sensitivity of 90% and a specificity of 100%. We found a positive correlation in 14 patien ts 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 Te-99m-MIBI might be used in routine practice to monitor the chemotherapeutic response in patients with primary lung cancer, especially when PET is not available.