Lymph node metastasis outside of a tumor-bearing lobe in primary lung cancer and the status of interlobar fissures

Abstract

The new Tumor Node Metastasis staging system does not recognize fissure status with respect to adjacent lobe invasion (ALI) in lung cancer. Furthermore, no specific surgical strategies have been recommended for lymph node dissections around adjacent nontumor-bearing lobes (NTBLs) according to fissure status. Therefore, this study was undertaken to investigate the necessity of removing additional adjacent lobe lymph nodes in patients with nonsmall cell lung cancer (NSCLC) for lesions limited to in the vicinity of the interlobar fissure. From August 2013 to March 2015, the records of 332 patients, who underwent systematic mediastinal lymph node dissection, were reviewed in this retrospective study. The bronchial lymph nodes had been subjected to pathological examination, and the status of the fissures was also recorded. A statistical analysis was performed to identify the significant predictors of lymph node metastasis. The patients were divided into a nonadjacent lobe invasion (NALI) group (n = 295) and an ALI group (n = 37). There was a significant difference in tumors with pN2 disease between the ALI and NALI groups (37.8% vs 8.8%, P = .001). ALI tumors had significantly more frequent pleural involvement than NALI tumors (62.2% vs 43.1%, P = .035). The frequency of N2 involvement among tumors invading across the complete fissure was higher than that of the tumors invading across the incomplete fissure (44.4% vs 14.3%, P = .015). However, the frequency of N1 involvement among tumors invading across the incomplete fissure was not statistically different than that of tumors not invading across incomplete fissure (32.1% vs 24.2%, P = .357). Regarding lymph node metastasis in NTBL, 15 (12.7%) patients had lymph node metastases in NTBLs. Pleural involvement was an independent predictor of lymph node metastasis in an NTBL. A greater frequency of N2 lymph nodes existed in NSCLC with invading adjacent lobe across complete fissure, extensive lymphatic resection within the hilum, and NTBL in tumors with pleural involvement are justifiable and necessary.

Risk factors of lobar lymph node metastases in non-primary tumor-bearing lobes among the patients of non-small-cell lung cancer

“…This study retrospectively investigated the prevalence and risk factors of lobar lymph node metastasis from NTBL in patients with NSCLC. In our study, NTBL lobar lymph nodes were involved in 12.6% of patients, which is consistent with the published results, ranging from 6.5 to 13.2% [ 11 , 14 , 15 , 21 ]. A higher proportion of adenocarcinomas were observed in the positive NTBL group compared to the negative NTBL group.…”

“…Given the retrospective design, some selection bias could not be avoided: the percentage of metastatic N1 and N2 patients was more than that of other studies [ 11 , 14 ]; this retrospective study was carried out in a single center with a limited number of enrolled patients. But the rate of aberrant lymph node metastases to NTBL was 12.6% (38 out of 301 patients), which is consistent with the published results, ranging from 6.5% to 13.2% [ 11 , 14 , 15 , 21 ]. Besides, there is no significant difference between 301 enrolled patients with the excluded 40 patients who performed extended NTBL lymph node dissection but missed pathology diagnosis, in terms of demographic information such as sex and age ( S5 Table ).…”

“…This rate is higher than two previously reported studies: 6.5% by Yamanaka and colleagues [ 14 ] and 9.2% by Sato and colleagues [ 11 ]. But it is similar as the rate reported by Li and colleagues at 13.2% [ 15 ], and 12.7% [ 21 ]. These rates of anomalous lymph node metastases, which have received little investigation previously, suggest that extended lymphadenectomy including the lobar lymph nodes of NTBL should be considered to improve the accuracy of staging, and decrease locoregional recurrence.…”

“…NTBL is not a new concept, but there are quite a few studies involving lymph node dissection in this field. Yamanaka et al suggests that NTBL metastasis is more common in primary right tumors and metastatic lymph node metastases, regardless of tumor sizes and histological types [ 14 ]; Li et al suggests that NTBL metastases are common among pleural invaders, especially those whose tumors break through the pleura and invade adjacent lung tissue [ 21 ]. In addition, tumors located in the dorsal segment of the lower lobe of the lung and invading the posterior segment of the upper lobe are also prone to metastatic bronchial lymph node metastasis, and tumor size, N1/N2 lymph node status and NTBL lymph node metastasis seem to have little relationship; Sato et al only described the necessity of dissecting the bronchial lymph nodes of the upper lobe during primary tumor located in the lower or middle lobe from a small sample (14 cases), and no risk factors for NTBL lymph node metastasis were involved [ 11 ].…”

“…Our study considers lymph channel blockage which leads to abnormal drainage. Li et al indicates that the tumor invades the adjacent lung tissue and metastasizes to the adjacent intra-pulmonary lymph node through the subpleural lymphatic duct [ 21 ]. Our study has many cases of NTBL dissection, and systematically studied multiple risk factors including tumor size and location, pathological type, N1/N2 lymph node status, viceral pleural invasion and lymphatic vessel invasion and other clinical indicators which is different from the previous reports.…”