Prognosis and segment-specific nodal spread of primary lung cancer in the right lower lobe

Background: Although lobe-specific nodal spread of primary lung cancer has been recently described, segment-specific nodal spread remains unclear. We investigated the frequency of hailer and mediastinal lymph node involvement and survival in patients with tumors located in the superior segment (SS) and basal segment (BS) in the right lower lobe.

Methods: Two hundred and sixty-three patients with primary lung cancer originating in the right lower lobe underwent lobectomy with systematic mediastinal lymph node dissection. Patients were categorized into two groups: SS (n = 114) or BS (n = 149).

Results: Frequencies of metastasis to station 11s and 11i were significantly higher in the SS (P < 0.0001) and BS groups (P = 0.022), respectively. Both the SS and BS groups showed a high frequency of subcarinal mediastinal zone (station 7) metastasis (96.9% and 90.6%, respectively; P = 0.271). The frequencies of superior mediastinal zone (station 2R and 4R) metastasis were 37.5% in the SS and 35.8% in the BS group (P = 0.878). In patients with pN2 disease, three-year disease-free survival was significantly shorter in the SS (22.6%) than the BS group (42.1%; P = 0.020). In the BS group, the independent predictive factors of a poor or good prognosis were metastasis to station 11i or skip metastasis, respectively; however, we did not detect an independent prognostic factor in the SS group. In the right lower lung lobe, there was no segment-specific nodal spread.

Conclusion: When segmentectomy is undertaken, mediastinal lymph node dissection should be performed in proportion to lobectomy.