Reassessment of Right Middle Lobe Lung Cancer: Comparison of Segments 4 and 5 Tumors.

BACKGROUND: The purpose of this study was to elucidate the clinical behavior of right middle lobe lung cancer, with focus on the tumor location.

METHODS: We reviewed retrospectively 711 patients who underwent lobectomy or bilobectomy for clinical stage I non-small cell lung cancer (upper lobe, 346; middle lobe, 82; lower lobe, 283). Factors affecting survival were assessed by log rank tests and Cox regression analyses.

RESULTS: The prognosis of patients with segment 5 tumors (n = 39) was significantly worse than that of patients with segment 4 tumors (n = 43; 5-year overall survival rates, 69.8% versus 87.6%, p = 0.040; and 5-year recurrence-free survival rates, 58.4% versus 73.0%, p = 0.029). Segment 5 tumors were an independent factor for poor prognosis in multivariable Cox regression analysis, and tended to cause more pathologic mediastinal lymph node metastases than segment 4 tumors (12.8% versus 2.3%, p = 0.097). Compared with tumors in the other lobes, patients with segment 4 tumors demonstrated no significant difference in prognosis; however, patients with segment 5 tumors demonstrated a significantly and outstandingly worse prognosis than patients with other lobe tumors (5-year overall survival rates, 69.8% versus 82.2%, p = 0.020; and 5-year recurrence-free survival rates, 58.4% versus 71.4%, p = 0.0071).

CONCLUSIONS: Patients with segment 5 tumors had a worse prognosis than patients with segment 4 and other lobe tumors. We speculate that is because segment 5 tumors cause more metastases to the mediastinal lymph nodes. Tumor location was an important prognostic factor for patients with right middle lobe lung cancer.