Abstract
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Objectives: To prospectively evaluate the role of MTV based and SUV based parameters evaluated from baseline and post-therapy whole body 18F-FDG PET/CT as well as their percentage changes in prediction of OS of NSCLC patients.
Methods: One hundred and thirty two patients (109 Male, 23 Female) with biopsy proven NSCLC (53 squamous cell carcinoma, 69 adenocarcinoma, 10 NOS) and mean age 57.05 ± 10.815(range: 31 - 80) were enrolled in the study. All 132 patients underwent a baseline WB 18F-FDG PET/CT scan. Sixty four patients out of 132 also underwent post-therapy WB 18F-FDG PET/CT scan either after four cycles of platinum based chemotherapy/three months of the start of gefitinib or crizotinib. Scans were performed on Biograph mCT PET/CT with 64 slice CT after 60 minutes of injecting 5.18-7.77 MBq/kg of 18F-FDG intravenously. Four MTV based parameters [primary tumor MTV(MTVt), primary tumor total lesion glycolysis (TLGt), whole body MTV(MTVwb) and whole body TLG (TLGwb)]and three SUV based parameters [maximum SUV (SUVmax), average SUV(SUVavg) and tumor to background ratio(TBR)] were evaluated for baseline scan (pre-) in 132 patients and post-therapy scan (post-) in 64 patients using anellipsoid isocontour ROI with threshold 2.5 SUVmax. Percentage changes (∆) in these parameters were also evaluated. The association of parameters with OS and suitable cut-offs were determined using ROC curve analysis. Univariate survival analysis was performed on the parameters which were found to be associated with OS in ROC curve analysis.The survival patterns were compared by log rank method and presented using Kaplan-Meier curves. Univariate and Multivariate Cox-regression analysis was performed and hazard ratios were evaluated.
Results: Mean OS for 132 patients was 8.49 ± 7.62 months (range: 1 day to 31 months) whereas, for 64 patients who also underwent post-therapy scan was 13.53 ± 7.91 months (range: 3.40 ± 31.10 months). Among the parameters evaluated from baseline whole body 18F-FDG PET/CT scans, the four MTV based parameters i.e. pre-MTVt, pre-TLGt, pre-MTVwb and pre-TLGwb were found to be significantly associated with OS with cut-off values 100 ml, 700 ml, 139 ml and 1100 ml and hazard ratios of 2.10 (p=0.001), 1.85 (p=0.004), 1.99 (p=0.003) and 1.91 (p=0.003), respectively. In multivariate cox-regression analysis of baseline parameters, pre-MTV was found to be the independent predictor of OS. Among the post-therapy parameters, post-TLGwb showed a marginally significant association with OS with cut-off 180 ml and HR 1.99(p=0.049). Among the percentage changes∆SUVmax, ∆SUVavg, ∆TBR, ∆MTV, ∆MTVwb, ∆TLGwbwere found to associated with OS in ROC analysis with cut-offs 33%, 23%, 27%, 62%, 62% and 80%, respectively but in cox-regression anlaysis,only ∆TLGwb was found to be significant in prediction of OS with HR 0.48 (p=0.043).
Conclusions: Baseline MTV based parameters evaluated from primary tumor as well as the whole body tumor lesions are reliable prognostic markers of OS in NSCLC patients. Also, among the post-therapy parameters and percentage changes, whole body MTV based parameters i.e. post-TLGwb and ∆TLGwb can predict OS of NSCLC patients.However, SUV based whole body PET/CT parameters (SUVmax, SUVavg, and TBR) evaluated from baseline as well as post-therapy scans have no prognostic value in these patients.