Type of Lymph Node Involvement Influences Survival Rates in T1N1M0 Non-small Cell Lung Carcinoma (Materials and Methods)

In: Lung Carcinoma

20 Dec 2013

Type of Lymph Node Involvement Influences Survival Rates in T1N1M0 Non-small Cell Lung Carcinoma (Materials and Methods)From 1977 to 1993, 2,009 patients underwent pulmonary resection for bronchogenic carcinoma. From this group, 58 had a nonsmall cell carcinoma that was classified as pTINlMO. Staging was postsurgical, according to the New International Staging System for lung cancer. Before operation, all patients underwent cervical mediastinoscopy with lymph node sampling. Also at surgery mediastinal lymph node sampling was performed
Ages ranged from 41 to 85 years with a mean of 60.8 years (Table 1). There were 52 men (89.6%). Thirty primary tumors were located in the left lung, and 28 were in the right lung. The tumors were histologically classified as squamous cell carcinoma in 45 cases, adenocarcinoma in 12, and undifferentiated large-cell carcinoma in 1. Complete resection’’ consisted of lobectomy in 38 cases, sleeve lobectomy in 6, bilobectomy in 8, and pneumonectomy in 6. Lymph node metastases were marked using the map of Naruke et al. In addition, lymph node involvement was described with respect to classic anatomic boundaries (lobe and lung hilum).

Thus, two types of lymph node involvement were coded: node invasion by direct extension of the tumor and lymph node invasion by metastases, either at lobar level or confined to the lung hilum within the visceral pleural envelope (hilar). Direct extension is defined as infiltration of a primary lung carcinoma into an adjacent lymph node or fixation of the tumor with the infiltrated node per lymphatic vessel. Metastases are not fixed to the primary tumor.

The N1 lymph node sites of Naruke et al relate as follows: lobar includes stations 12 and 13, while hilar comprises numbers 10 and 11. Direct extension (either lobar or hilar) is marked as such, irrespective of Naruke et al numbers. If patients had more than one type of lymph node involvement, the one farthest away from the primary tumor was scored for. If both direct extension and metastases were found in the same lymph node groups, scoring was metastatic disease. There were five such patients, one labeled as having lobar metastases and four as having hilar metastases. In five patients, both lobar and hilar nodes were involved by metastases; with respect to the distance, the pattern in all patients was classified as hilar. Lymph node involvement in the 58 patients was by metastases in 34 (lobar in 9, hilar in 25) and by direct extension in 24 (lobar in 16 and hilar in 8).

The number of involved lymph nodes was not counted as some of them were conglomerated and therefore hardly identifiable. Postoperative follow-up status was complete as of September 1995. One patient was unavailable for follow-up, but his date of death could be retrieved. One patient with lymph node involvement by direct extension was excluded from the survival analysis because of in-hospital death. Survival was estimated from the date of operation, using the Kaplan-Meier survival analysis method. Differences in observed survival between groups were tested for statistical significance using the log-rank test. Differences were considered statistically significant when the p value was less than 0.05.

Incremental risk factors influencing survival were evaluated using Cox’s proportional hazards model.

Table 1—Characteristics of Patients With T1N1M0 Disease

Characteristics No.
Age, yr
Range 41-85
Mean 60.8
Male/female 52/6
Right/left 28/30
Squamous 45
Adenocarcinoma 12
Large cell 1
Nodal involvement
Lobar 9
Hilar 25
Direct extension 24
Type of resection
Lobectomy 38
Sleeve lobectomy 6
Bilobectomy 8
Pneumonectomy 6


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