[Clinical Characteristics and Prognosis of Sub-centimeter Lung Adenocarcinoma]

Background: With the increase of lung cancer screening, more and more patients have been diagnosed as sub-centimeter (≤1 cm) lung adenocarcinoma. Sub-centimeter lung adenocarcinoma is mostly early stage lung cancer, but the research on sub-centimeter lung adenocarcinoma is still insufficient. This study analyzed the clinical characteristics and prognosis of patients with sub-centimeter lung adenocarcinoma in order to provide the basis for the diagnosis and treatment of such patients.

Methods: A retrospective study was performed to analyze patients with sub-centimeter lung adenocarcinoma who underwent VATS in Peking University People's Hospital from January 2012 to December 2016. Patients were divided into pure ground-glass nodules (pGGN) group, mixed ground-glass nodules (mGGN) group and solid nodules (SN) group according to the features of nodular imaging. The clinical characteristics of the three groups were compared and the subgroup analysis of nodules in different diameter was performed. We also performed multivariate logistic regression analyses to identify the risk factors for sub-centimeter lung invasive adenocarcinoma.

Results: The study included 182 patients (57 men and 125 women) with a median age of 54 (27-75) years. Female sub-centimeter lung adenocarcinoma patients had a significantly lower proportion of non-smoking history than males (P<0.001). All patients with 1 mm-10 mm pGGN, 1 mm-5 mm mGGN and 1 mm-5 mm SN had no other pathologically positive findings except for the primary lesion. Of the 46 patients with 6 mm-10 mm mGGN, 3 had pleural invasion and 1 had vascular tumor thrombus. Of the 39 patients with 6 mm-10 mm SN, 5 had pleural invasion, 2 had vascular tumor thrombus and 2 had lymph node metastasis. The pathological type in each patient with pleural invasion, vascular tumor thrombus or lymph node metastasis was invasive adenocarcinoma. Logistic regression analysis indicated that smoking history (OR=4.727, P=0.009), previous tumor history (OR=3.408, P=0.015), mGGN (OR=3.735, P=0.004), SN (OR=8.921, P<0.001) and tumor diameter >5 mm (OR=4.241, P=0.001) were independent risk factors for sub-centimeter lung invasive adenocarcinoma. The median follow-up time was 44 (22-82) months. The 5-year recurrence-free survival rate was 100.0% and the overall survival rate was 98.9%.

Conclusions: Patients with sub-centimeter lung adenocarcinoma have a relatively earlier onset age. Sub-centimeter lung invasive adenocarcinoma patients with 6 mm-10 mm mGGN and 6 mm-10 mm SN may be involved in pleural invasion or lymph node metastasis. Smoking history, previous tumor history, mGGN, SN and tumor diameter >5 mm are independent risk factors for sub-centimeter lung invasive adenocarcinoma. For patients with sub-centimeter lung adenocarcinoma, early detection and appropriate surgical intervention can lead to a good prognosis.