Objectives: Lung adenocarcinoma frequently manifests as subsolid nodules, and the solid portion and ground-glass-opacity (GGO) portion on CT have different prognostic significance. Therefore, current T descriptor, defined as the whole tumour diameter without discrimination between solid and GGO, is insufficient. We aimed to determine the prognostic significance of solid tumour size and attempt to include prognostic factors such as tumour disappearance rate (TDR) on CT and SUVmax on PET/CT.
Methods: Five hundred and ninety-five patients with completely resected lung adenocarcinoma were analyzed. We developed a nomogram using whole tumour size, TDR, and SUVmax. External validation was performed in another 102 patients.
Results: In patients with tumours measuring ≤2 cm and >2 to 3 cm, disease free survival (DFS) was significantly associated with solid tumour size (P < 0.001), but not with whole tumour size (P = 0.052). Developed nomogram was significantly superior to the conventional T stage (area under the curve of survival ROC; P = 0.013 by net reclassification improvement) in stratification of patient survival. In the external validation group, significant difference was noted in DFS according to proposed T stage (P = 0.009).
Conclusions: Nomogram-based T descriptors provide better prediction of survival and assessment of individual risks than conventional T descriptors.
Key points: • Current measurement of whole tumour diameter including ground-glass opacity is insufficient • TDR enables differentiation between invasive solid portion and non-invasive GGO portion • SUVmax demonstrates the biological aggressiveness of the tumour • We developed a nomogram using whole tumour size, TDR, and SUVmax • Nomogram-based clinical T descriptors provide better prediction of survival.
Keywords: Adenocarcinoma; Lung neoplasm; Multidetector Computed Tomography; Positron-Emitted Tomography; Tumour staging.