The role of the ground-glass opacity ratio in resected lung adenocarcinoma

OBJECTIVES: The goal of this study was to investigate the role of the ground-glass opacity (GGO) ratio in lung adenocarcinoma in predicting surgical outcomes. METHODS: Patients who underwent surgical resection for pulmonary adenocarcinoma between January 2004 and December 2013 were reviewed. The clinical data, imaging characteristics of nodules, surgical approaches and outcomes were analysed with a mean follow-up of 87 months. RESULTS: Of 789 enrolled patients, 267 cases were categorized as having a GGO ratio >= 0.75; 522 cases were categorized as having a GGO ratio <0.75. The gender, tumour differentiation, epidermal growth factor receptor mutation, smoking habits, lymphovascular space invasion, tumour size, maximum standard uptake value and carcinoembryonic antigen levels were significantly different in the 2 groups. In the group with a GGO ratio >= 0.75, 63.3% of the patients underwent sublobar resection (18.8% with a GGO ratio <0.75, P < 0.001). These patients had fewer relapses (2.2% for GGO ratio >= 0.75, 26.8% for GGO ratio <0.75, P < 0.001) and a better 5-year survival rate (95.5% for GGO ratio >= 0.75, 77.4% for GGO ratio <0.75, P < 0.001). None of the patients with a GGO ratio >= 0.75 had lymph node involvement. The multivariable Cox regression analysis revealed that a GGO ratio <0.75 was an independent factor for postoperative relapse with a hazard ratio of 3.96. CONCLUSIONS: A GGO ratio >= 0.75 provided a favourable prognostic prediction in patients with resected lung adenocarcinoma. Sublobar resection and lymph node sampling revealed a fair outcome regardless of tumour size. However, anatomical resection is still the standard approach for patients with tumours with a GGO ratio <0.75, size >2 cm.