What is the appropriate operative strategy for radiologically solid tumours in subcentimetre lung cancer patients?†

Solid lung cancers, even subcentimetre lesions, are considered to be invasive pathologically. However, the clinicopathological features and appropriate operative strategies in patients with these small lesions are still controversial, especially for those with a radiologically solid appearance.

Between 2004 and 2011, 135 patients underwent pulmonary resection for subcentimetre lung cancer with clinical-N0 (c-N0) status. The findings of preoperative thin-section computed tomography (CT) were reviewed, and subcentimetre lung cancer was divided into three groups: pure ground-glass nodule, part-solid and pure-solid lesions.

Among the 135 subcentimetre lung cancer patients with c-N0 status, 71 showed a solid appearance on thin-section CT scan. Furthermore, pathological nodal examinations were performed in 49 patients, and nodal involvement was found pathologically in 6 (12.2%) patients. All of them had pure-solid tumours (P = 0.0010). Among the patients with solid subcentimetre lung cancers, the maximum standardized uptake value (SUVmax) was the only significant predictor of nodal involvement by a multivariate analysis (P = 0.0205). With regard to the surgical outcomes, the overall 5-year survival and disease-free survival rates were 100 and 97.8% for part-solid lesions, and 87.3 and 74.8% for pure-solid lesions, respectively. Moreover, there was a significant difference in disease-free survival between a high SUVmax group (60.0%) and a low SUVmax group (94.9%) (P = 0.0013).

There might be a possibility of lymph node metastasis despite subcentimetre lung cancer, especially for radiological pure-solid nodules that show a high SUVmax. If limited surgery is indicated for solid subcentimetre lung cancer, a thorough intraoperative evaluation of lymph nodes is needed to prevent loco-regional failure.