Predicting early chemotherapy response with technetium-99m methoxyisobutylisonitrile SPECT/CT in advanced non-small cell lung cancer

Purpose: The purpose of this study is to examine the prognostic value of prechemotherapy technetium-99m methoxyisobutylisonitrile (^99mTc-MIBI) uptake with single photon emission computed tomography/computed tomography (SPECT/CT) in relation to tumor size change measured by CT. Methods: Eleven patients with stage IIIB/IV non-small cell lung cancer (NSCLC) underwent ^99mTc-MIBI SPECT/CT within 24 h before starting platinum-containing chemotherapy. Following the Response Evaluation Criteria in Solid Tumors guidelines, 20 lesions from the 11 patients were available for evaluation. Maximum (C_max) and mean (C_mean) MIBI counts were calculated for each lesion. One-dimensional (1D; longest diameter) and two-dimensional (2D; area of the largest transverse surface) tumor measurements were assessed by two observers on the diagnostic CT and the response assessment CT after two cycles of chemotherapy. Results: Bland-Altman analysis demonstrated no clinically significant bias between the observers. A solid correlation was found between ^99mTc-MIBI C_mean and change in the longest diameter (1D change) of the target lesion (ρ=-0.62) using Spearman's rank correlation test. C_mean also correlated negatively with change in the area of the largest transverse surface (2D change) of the target lesion (ρ=-0.53). Furthermore, a correlation was established between ^99mTc-MIBI C_max and 1D change (ρ= -0.56) in tumor size as well, though less strongly when compared to its C_mean counterpart. Conclusions: Our series demonstrated solid, negative correlations between prechemotherapy ^99mTc-MIBI uptake and tumor size change measured by CT for advanced NSCLC, particularly with C_mean and 1D change.