Establishing a threshold for maximum standardized uptake value on 18 F-fluorodeoxyglucose PET/CT to predict high-grade lung adenocarcinoma and its prognostic significance.

Objective: The objective of this study is to determine an optimal threshold for the maximum standardized uptake value (SUVmax) of 18 F-fluorodeoxyglucose PET/CT to predict the newly proposed high-grade tumor classification and assess its prognostic significance in invasive lung adenocarcinoma (LUAD).

Methods: Surgical specimens from 185 patients with pathological stage I invasive LUAD in the training group, along with 90 patients in the validation group, were analyzed using the novel IASLC grading system. The receiver operating characteristic curve was used to determine the optimal SUVmax threshold and assess its predictive accuracy. Disease-free survival (DFS) and overall survival (OS) were analyzed using Kaplan-Meier survival curves and Cox regression analysis.

Results: Linear correlation analysis demonstrated a significant positive association between SUVmax and the proportion of high-grade histological patterns ( R ² = 0.346, P  < 0.001). The optimal SUVmax cutoff for predicting grade 3 tumors was 3.8, with an area under the curve of 0.866 in the training dataset and 0.899 in the validation dataset. Multivariate logistic regression analysis identified an SUVmax >3.8 as an independent predictor of grade 3 tumors ( P  < 0.001). In Cox regression analysis, SUVmax >3.8 was independently associated with reduced DFS (HR = 4.009, 95% CI: 1.568-10.250, P  = 0.004) and OS (HR = 5.536, 95% CI: 1.175-26.075, P  = 0.030).

Conclusions: As a noninvasive preoperative parameter, SUVmax >3.8 is a significant indicator of high-grade tumors as classified by the IASLC grading system and is strongly associated with worse DFS and OS.