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.