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Pre-Radiotherapy (RT) 18F-FDG PET as a Means to Predict Outcomes After RT for Stage III Non-Small Cell Lung Cancer

M Thor1*, A Apte1 , A Fontanella1 , A Rimner1 , J Deasy1 , (1) Memorial Sloan Kettering Cancer Center, New York, New York


(Sunday, 7/29/2018) 4:30 PM - 5:00 PM

Room: Exhibit Hall | Forum 5

Purpose: To investigate if 18F-FDG PET has a role in predicting ≥grade 2 acute esophagitis (AE), radiation pneumonitis (RP), and loco-regional failure (LRF) after intensity-modulated radiotherapy (IMRT) for stage III Non-Small Cell Lung Cancer (NSCLC).

Methods: A total of 19 statistics, and 15 size zone features were extracted from 18F-FDG PET pre-treatment scans of 134 patients treated with chemo-IMRT to a median of 64.7Gy (EQD2�₀) using the CERR radiomics toolbox. The cohort was randomly split into training and holdout validation data (N=94, 40), but preserving the outcome rate across the two splits (54%/11%/46% AE/RP/LRF). Esophageal, heart and lung, and tumor features were input for AE, RP, and LRF, respectively. For each outcome, modeling in training was based on univariate analysis, and features with a 5% false discovery rate-adjusted median p≤0.05 across 1000 Bootstrap populations were considered final. If >1 candidate feature was identified, these were subject to Bootstrapped multivariate analysis. AE and RP were modeled using logistic regression, and LRF using Proportional Hazard’s. Final models were explored in the validation data. Discrimination was assessed using C-statistics.

Results: The same gray level non-uniformity (GLN) feature predicted AE and LRF (C-statistics: 0.63, 0.57 (p=0.01, 0.03)). Additionally, size zone non-uniformity (SZN) predicted LRF (C-statistics: 0.59 (p=0.02)). Both GLN and SZN describe the 18F-FDG PET heterogeneity and were positively associated with LRF (0.01*GLN; 3e-4*SZN), but GLN was negatively associated with AE (1.93-0.11*GLN). Discrimination on validation decreased somewhat for AE (C-statistics: 0.59 (p=0.06)), and considerably for LRF (C-statistics<0.50). Neither features of the heart, nor of the lung predicted RP.

Conclusion: Homogeneous esophageal uptake on pre-treatment 18F-FDG PET scans predicted AE after chemo-IMRT for stage III NSCLC. A similar trend but for the heterogeneous end of the tumor uptake was observed for loco-regional failure. Esophageal 18F-FDG PET distributions could assist to further optimize patient-tailored treatment protocols.


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