Impact of tumor disappearance ratio on the prognosis of lung adenocarcinoma ≤2 cm in size: A retrospective cohort study

Background/Purpose: Lung cancer patients can have advanced-stages at diagnosis, even the tumor size is ≤2 cm. We aimed to study the relationship between image characteristics, clinical, and patholoigcal results. Methods: We retrospectively enrolled patients with lung adenocarcinoma at Taichung Veterans General Hospital and Chang Gung Memorial Hospital from 2007 to 2015, who were diagnosed with treatment naïve primary tumor lesions at sizes less than 2 cm, as measured by computed tomography (CT) scans. The patient was analyzed for lymph node (LN) and distant metastasis evaluation, with clinicopathological characteristics, including tumor-disappearance ratio (TDR) (tumor diameter at the mediastinal/lung window) over chest CT scans, pathological diagnosis, disease-free survival (DFS), and overall survival (OS). Results: Totally 280 patients were surveyed initially and showed significantly increase of clinical LN involvement and distant metastasis when TDR ≤75% compared with >75% (21.6% vs 0% for LN involvement; 27.1% vs 0% for distant metastasis; both p < 0.001). We included 199 patients having surgical treatment and follow-up for the survival analysis. With a TDR ≤75%, significantly worse DFS (HR, 19.23; 95% CI, 2.60–142.01; p = 0.004) and a trend of worse OS (HR, 4.97; 95% CI, 0.61–40.61; p = 0.134) were noted by Kaplan–Meier method. TDR ≤75% revealed more advanced pathological stage, and more tumors containing micropapillary or solid subtypes when diagnosed adenocarcinoma. Conclusion: For lung cancer patients with primary tumor ≤2 cm, TDR ≤75% was related to more advanced stages, the presence of micropapillary or solid components of adenocarcinoma subtypes, worse DFS, and a trend of worse OS.