Abstract
ObjectiveThis study aimed to (1) compare the agreement of two evaluation methods of metabolic response in patients with non-small cell lung cancer (NSCLC) and determine their prognostic value and (2) explore an optimal cutoff of metabolic reduction to distinguish a more favorable subset of responders.MethodsThis is a secondary analysis of prospective studies. Enrolled patients underwent 18F-PET/CT within 2 weeks before, during, and months after radiotherapy (post-RT). Metabolic response was assessed using both Peter MacCallum (PM) method of qualitative visual assessment and University of Michigan (UM) method of semiquantitative measurement. The agreement between two methods determined response, and their prediction of outcome was analyzed.ResultsForty-four patients with median follow-up of 25.2 months were analyzed. A moderate agreement was observed between PM- and UM-based response assessment (Kappa coefficient = 0.434), unveiling a significant difference in CMR rate (p = 0.001). Categorical responses derived from either method were significantly predictive of overall survival (OS) and progression-free survival (PFS) (p < 0.0001). Numerical percentage decrease of FDG uptake also showed significant correlations with survival, presenting a hazard ratio of 0.97 for both OS and PFS. A 75 % of SUV decrease was found to be the optimal cutoff to predict OS and 2-year progression.ConclusionsThere was a modest discrepancy in metabolic response rates between PM and UM criteria, though both could offer predictive classification for survival. The percentage decrease provides an ordinal value that correlates with prolonged survival, recommending 75 % as the optimal threshold at identifying better responders.
Highlights
Introduction18F-fluorodeoxyglucose positron emission tomography/ computed tomography (FDG PET/CT)-based metabolic response has been reported to be a prognostic indicator for patients with non-small cell lung cancer (NSCLC) by a large number of studies [1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20,21,22]
These studies were approved by the institutional review board (IRB) of the University of Michigan, and written informed consent was obtained from each patient
SCC squamous cell cancer, NSCLC-NOS non-small cell lung cancer-not otherwise specified a Presented as median b Four patients underwent the stereotactic body radiation therapy (SBRT) including two with 11 Gy×5, one treated with 10 Gy×5, and another with 20 Gy×3 squamous cell carcinoma, 1 with large cell carcinoma, and 23 with NSCLC but unknown subtype, primarily due to the limited specimen obtained from fine needle aspiration-based biopsy
Summary
18F-fluorodeoxyglucose positron emission tomography/ computed tomography (FDG PET/CT)-based metabolic response has been reported to be a prognostic indicator for patients with non-small cell lung cancer (NSCLC) by a large number of studies [1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20,21,22]. J Radiat Oncol (2015) 4:249–256 for evaluating metabolic response on FDG-PET include qualitative visual assessment such as Peter MacCallum (PM) criteria [5], semiquantitative assessment using reduction of metabolic activity (e.g., SUV) such as EORTC [23], University of Michigan (UM) [10], and PERCIST [24] methods, and quantitative evaluation using kinetic modeling [25]. Quantitative method of kinetic modeling or Patlak plot is used infrequently in clinical practice due to the complexity, including the needs for arterial blood sampling or dynamic imaging of a blood-pool structure to acquire a precise input function [25]. The best method of metabolic response evaluation is currently unknown, both for predicting outcome and being applicable into routine clinic practice. All of the aforementioned response criteria are currently being used in clinical practice, and there was no direct cross-comparison between the various methods yet
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