Proposal for novel definition of radiologically less-invasive clinical stage IA solid predominant lung adenocarcinoma using the maximum standardized uptake value

Objective: This study aimed to evaluate the possibility of defining new imaging criteria to predict less-invasive clinical (c)-stage IA2-IA3 solid predominant lung adenocarcinoma using the maximum standardized uptake value (SUVmax) as the cutoff value.

Methods: Consecutive 364 patients who underwent anatomical resection with mediastinal lymphadenectomy and positron emission tomography for c-stage IA2-IA3 solid predominant lung adenocarcinoma with a tumor diameter < 3 cm were retrospectively evaluated. Less-invasive cancer was defined as the absence of nodal involvement, lymphovascular or pleural invasion, or spread through air spaces. The SUVmax cutoff value was determined based on the specificity of the receiver operating characteristic curve.

Results: 228 were pure-solid tumors, and 136 were part-solid tumors. 212 were c-stage IA2 and 152 were c-stage IA3. When the SUVmax was set at a cutoff value of 2.2, sensitivity and specificity were 33.0% and 97.6%, respectively, and it was possible to secure the sensitivity by more than 30% with high specificity among the solid predominant tumors. When the SUVmax was set at a cutoff value of 2.2, sensitivity and specificity were 40.7% and 95.7%, respectively, in whole tumor diameter ≤ 2 cm, and 27.0% and 99.0%, respectively in whole tumor diameter between 2 and 3 cm. When the SUVmax was set at a cutoff value of 2.2, sensitivity and specificity were 45.8% and 96.6%, respectively, in part-solid tumors, and 17.8% and 97.8%, respectively in pure-solid tumors.

Conclusion: Setting the SUVmax as cutoff value could predict pathologically less-invasive cancers in c-stage IA2-IA3 solid predominant lung adenocarcinoma.