Values of ¹⁸F-FDG uptake and thyroid transcription factor-1 expression to predict the mutations of epidermal growth factor receptor in lung adenocarcinoma

Objective: To validate the value of ¹⁸F-fluorodeoxyglucose (FDG) uptake on PET/CT and thyroid transcription factor-1 (TTF-1) expression to predict the epidermal growth factor receptor (EGFR) mutations in lung adenocarcinoma. Methods: From May 2012 to May 2016, a total of 137 lung adenocarcinoma patients (89 males, 48 females, age range 33-84 years) pathologically proved were reviewed retrospectively. EGFR mutation testing, TTF-1 expression and PET/CT scan were performed for all patients. χ² test was used to assess the differences of EGFR mutation in different groups. Two-sample t test was used to compare the differences of maximum standardized uptake value (SUV_max) between EGFR mutation type and EGFR wild type, TTF-1 positive and negative expression. Multivariate logistic regression analysis was used to test the univariate models that yielded the best predictors of EGFR mutation receiver operating characteristic (ROC) curve analysis was performed to quantify the predictive value of those factors. Results: EGFR mutation was identified in 53 patients, including 2 cases in exon 18, 19 cases in exon 19, 3 cases in exon 20 and 29 cases in exon 21. The high risk factors of EGFR mutation were female (χ² = 7.465, P = 0.006), non-smoking (χ² = 7.193, P = 0.007) and positive expression of TTF-1 (χ² = 9.104, P < 0.05). The SUV_max of EGFR mutation type was significantly lower than that of EGFR wild type (8.76 ± 4.59 and 11.20 ± 5.09; t = 2.832, P = 0.005). Multivariate analysis showed that the lower SUV_max (SUV_max < 8.65) and positive expression of TTF-1 were the independent risk factors for EGFR mutation (P = 0.032, P = 0.018). The combined use of SUV_max and TrF-1 yielded a higher area under the ROC curve (area under curve = 0.697), suggesting a good discrimination. Conclusion: The combined evaluation of ¹⁸F-FDG uptake and expression of TTF-1 may be helpful in predicting EGFR mutation status in patients with lung adenocarcinoma, especially when the genetic testing is not available, and can provide meaningful clues for clinical treatment. (authors)