Role of texture parameters evaluated from F18-FDG PET/CT in treatment response assessment of Non-Small cell lung cancer

Objectives: To prospectively evaluate the role of texture parameters obtained from baseline and post-therapy F18-FDG PET/CT as well as their percentage changes in treatment response assessment of biopsy proven non-small cell lung cancer (NSCLC). Materials and Method: Thirty patients (25 male, 5 female) with biopsy proven NSCLC (16 adenocarcinoma, 8 Squamous cell carcinoma and 6 NOS) and mean age 55.83±11.72 years were enrolled in the study. Each patient underwent baseline and post-therapy whole body F-18 FDG PET/CT scan on Biograph mCT 64 slice, after 60 minutes of injecting 5.18-7.77 MBq/kg of F18-FDG intravenously. Patients were divided into two response groups on the basis of RECIST 1.1 criteria i.e. responders (complete and partial response) and non-responders (stable disease and progressive disease). For texture analysis, the displayed PET/CT images with maximum diameter of tumor were exported in JPEG format and texture parameters were evaluated using R version 3.4.3. Six intensity histogram based first order parameters(Entropy, Kurtosis, skewness, uniformity, average intensity, variance and RMS) and five Grey level co-occurrence matrix based parameters(contrast, correlation, energy, homogeneity1 and homogeneity2) were evaluated for both baseline and post-therapy scans along with their percentage changes(∆). Two metabolic F18-FDG PET/CT parameters i.e. TBR and SUVmax were also evaluated for both scans along with their ∆s. All parameters were compared among two response groups by using Mann Whitney-U test. Accuracy, sensitivity, specificity and threshold values of significant variables were determined using ROC analysis. P value < 0.05 was considered significant. Results: Among the baseline parameters, two texture parameters i.e. uniformity and energy were found to have significant role in prediction of response with cut-offs ≥ 0.116, ≥ 0.063 and AUROC 0.74(sensitivity 66.7% and specificity 75%), 0.72(sensitivity 77.8% and specificity 75%) respectively. Among the post-therapy parameters, skewness, average intensity and RMS were significantly associated with response with cut-offs ≥-0.178,