The spread of metastatic lymph nodes to the mediastinum from left upper lobe cancer: results of superior mediastinal nodal dissection through a median sternotomy.

BACKGROUND

This study endeavored to clarify the location, frequency, and prognostic value of metastatic lymph nodes in the mediastinum among patients with left upper lung cancer who underwent complete dissection of the superior mediastinal lymph node through a median sternotomy.

METHODS

Forty-four patients with left upper lobe cancer underwent extended radical mediastinal nodal dissection (ERD), all of whom were analyzed in this retrospective study. The group comprised 12 females and 32 males, with ages ranging from 28 to 70 years (median age, 60 years). Mediastinal nodal status was assessed according to the systems of Mountain/Dresler 7 and Naruke 8. The clinicopathological records of each patient were examined for prognostic factors, including age, sex, histology, tumor size, c-N number, preoperative serum CEA level, metastatic stations and distribution of metastatic nodes according to Naruke's system 8. The superior mediastinal lymph nodes which cannot be dissected through a left thoracotomy (bilateral #1 and #2, #3, right #3a, and right #4 according to Naruke's map 8 were defined as extra-superior mediastinal nodes for left lung cancer (ESMD).

RESULTS

Fourteen patients had one or more metastases to mediastinal lymph nodes, among whom the most common metastatic station was the aortic nodes: 71.4% had metastasis to #5 or #6 (57.1% to #5 and 50% to #6). The next most common metastatic station was the left tracheobronchial nodes (42.8%). Metastasis to the ESMD occurred in 7 of the 44 study subjects (16%), representing a 50% rate of occurrence (7/14) among those with mediastinal nodal involvement. Univariate analysis found that CN factor and aortic nodal involvement (#5, #6) were significant predictive factors for ESMD metastasis. Multivariate analysis determined that only aortic nodal involvement was significant (p = 0.008). Furthermore, ESMD metastasis was rare (5.8%) in the absence of aortic node metastasis. The overall survival rate at 5 years was 50% among the patients without ESMD metastasis. However, the survival rate was 32% at 3 years and 0% at 5 years among the seven patients with ESMD metastasis.

CONCLUSIONS

The aortic lymph node is the most common site of metastasis from left upper lobe cancer. Multivariate analysis demonstrated that aortic nodal involvement was a significant predictive factor for ESMD metastasis. Based upon the rates of metastasis and the post-operative prognosis in our study patients, dissection of aortic nodes and left tracheobronchial nodes may be important for patients with left upper lobe cancer. Whether ESMD dissection has a beneficial effect on prognosis remains controversial.