To evaluate the clinical value of ¹⁸F-FDG PET/CT findings in patients with T1-2 lung adenocarcinoma spread through air spaces (STAS).

From June 2018 to June 2020, a total of 80 patients (36 males, 44 females; age: 19-84 (59.9±11.8) years) with surgically and pathologically confirmed T1-2 lung adenocarcinomas in Jiangmen Central Hospital were enrolled retrospectively. All patients underwent ¹⁸F-FDG PET/CT examination preoperatively and were divided into STAS positive and negative groups according to the histopathological diagnosis. Independent-sample t test, Mann-Whitney U test, χ² test and Fisher exact test were used to analyze differences of gender, age, tumor biomarker, SUV_max, SUV_mean, features showed on high resolution CT (HRCT; including diameter, lesion location, morphology, density, lobulated sharp, spiculated sign, vacuole sign, air bronchgram sign, pleural traction and para-emphysema), and pathologic findings (micropapillary pattern, lymphvascular inversion, pleural inversion and lymph node metastasis) between the two groups, and then multivariate logistic regression was performed. The ROC curve was employed to evaluate the predictive value of parameters for STAS of T1-2 lung adenocarcinomas.

Among the 80 patients with T1-2 lung adenocarcinomas, 12 (15.0%) were STAS positive and 68 (85.0%) were STAS negative. Significant differences were shown in SUV_max, SUV_mean, micropapillary pattern, lymphvascular inversion and lymph node metastasis between the two groups (z values: -2.60, -2.17; χ² values: 29.56, 9.28, 17.40, P<0.001 or P<0.05). SUV_max (odds ratio (OR): 1.348 (95% CI: 1.071-1.695), P=0.011), micropapillary pattern (OR=47.444 (95% CI: 4.592-490.214), P=0.001) and lymph node metastasis (OR=8.201 (95% CI: 1.129-59.576), P=0.038) were independent risk factors for STAS positive in multivariation logistic regression analysis. The optimum cut-off value for SUV_max was 3.85 in the ROC analysis with the AUC of 0.737 (95% CI: 0.614-0.859), the sensitivity of 11/12, the specificity of 55.9%(38/68) and the accuracy of 61.2%(49/80). The AUC of the SUV_max combined with micropapillary pattern and lymph node metastasis was 0.945 (95% CI: 0.892-0.999) with the sensitivity of 11/12, the specificity of 88.2%(60/68) and the accuracy of 88.7%(71/80).

The PET/CT characteristics may be useful in differentiating STAS status among patients with T1-2 lung adenocarcinoma. SUV_max >3.85, pathological papillary pattern and lymph node metastasis are independent risk factors to predict STAS.

Lung neoplasms; Adenocarcinoma; Neoplasm invasiveness; Positron-emission tomography; Tomography, X-ray computed; Fluorodeoxyglucose F18