From anatomy to lung cancer: questioning lobe-specific mediastinal lymphadenectomy reliability

Characterisation of microbiota in saliva, bronchoalveolar lavage fluid, non-malignant, peritumoural and tumour tissue in non-small cell lung cancer patients: a cross-sectional clinical trial

BACKGROUND

While well-characterised on its molecular base, non-small cell lung cancer (NSCLC) and its interaction with local microbiota remains scarcely explored. Moreover, current studies vary in source of lung microbiota, from bronchoalveolar lavage fluid (BAL) to tissue, introducing potentially differing results. Therefore, the objective of this study was to provide detailed characterisation of the oral and multi-source lung microbiota of direct interest in lung cancer research. Since lung tumours in lower lobes (LL) have been associated with decreased survival, characteristics of the microbiota in upper (UL) and lower tumour lobes have also been examined.

METHODS

Using 16S rRNA gene sequencing technology, we analysed microbiota in saliva, BAL (obtained directly on excised lobe), non-malignant, peritumoural and tumour tissue from 18 NSCLC patients eligible for surgical treatment. Detailed taxonomy, diversity and core members were provided for each microbiota, with analysis of differential abundance on all taxonomical levels (zero-inflated binomial general linear model with Benjamini-Hochberg correction), between samples and lobe locations.

RESULTS

Diversity and differential abundance analysis showed clear separation of oral and lung microbiota, but more importantly, of BAL and lung tissue microbiota. Phylum Proteobacteria dominated tissue samples, while Firmicutes was more abundant in BAL and saliva (with class Clostridia and Bacilli, respectively). However, all samples showed increased abundance of phylum Firmicutes in LL, with decrease in Proteobacteria. Also, clades Actinobacteria and Flavobacteriia showed inverse abundance between BAL and extratumoural tissues depending on the lobe location. While tumour microbiota seemed the least affected by location, peritumoural tissue showed the highest susceptibility with markedly increased similarity to BAL microbiota in UL. Differences between the three lung tissues were however very limited.

CONCLUSIONS

Our results confirm that BAL harbours unique lung microbiota and emphasise the importance of the sample choice for lung microbiota analysis. Further, limited differences between the tissues indicate that different local tumour-related factors, such as tumour type, stage or associated immunity, might be the ones responsible for microbiota-shaping effect. Finally, the "shift" towards Firmicutes in LL might be a sign of increased pathogenicity, as suggested in similar malignancies, and connected to worse prognosis of the LL tumours.

TRIAL REGISTRATION

ClinicalTrials.gov ID: NCT03068663. Registered February 27, 2017.

Lung cancer staging: a concise update

Diagnosis and clinical staging of lung cancer are fundamental to planning therapy. The techniques for clinical staging, i.e anatomic and metabolic imaging, endoscopies and minimally invasive surgical procedures, should be performed sequentially and with an increasing degree of invasiveness. Intraoperative staging, assessing the magnitude of the primary tumour, the involved structures, and the loco-regional lymphatic spread by means of systematic nodal dissection, is essential in order to achieve a complete resection. In resected tumours, pathological staging, with the systematic study of the resected specimens, is the strongest prognostic indicator and is essential to make further decisions on therapy. In the present decade, the guidelines on lung cancer staging of the American College of Chest Physicians and the European Society of Thoracic Surgeons are based on the best available evidence and are widely followed. Recent advances in the classification of the adenocarcinoma of the lung, with the definition of adenocarcinoma in situ, minimally invasive adenocarcinoma and lepidic predominant adenocarcinoma, and the publication of the eighth edition of the tumour, node and metastasis classification of lung cancer, have to be integrated into the staging process. The present review complements the latest guidelines on lung cancer staging by providing an update of all these issues.

Metachronous Lung Cancer: Clinical Characteristics and Effects of Surgical Treatment

The occurrence of a second lung tumor after surgical removal of lung cancer usually indicates a lung cancer metastasis, but sometimes a new lesion proves to be a new primary lung cancer, i.e., metachronous lung cancer. The goal of the present study was to conduct a clinical evaluation of patients with metachronous lung cancer and lung cancer metastasis, and to compare the early and distant outcomes of surgical treatment in both cancer types. There were 26 age-matched patients with lung cancer metastases and 23 patients with metachronous lung cancers, who underwent a second lung cancer resection. We evaluated the histological type of a resected cancer, the extent of thoracosurgery, the frequency of early postoperative complications, and the probability of 5-year survival after the second operation. The findings were that metachronous lung cancer was adenocarcinoma in 52% of patients, with a different histopathological pattern from that of the primary lung cancer in 74% of patients. In both cancer groups, mechanical resections were the most common surgery type (76% of all cases), with anatomical resections such as segmentectomy, lobectomy, or pneumectomy being much rarer conducted. The incidence of early postoperative complications in metachronous lung cancer and lung cancer metastasis (30% vs. 31%, respectively) and the probability of 5-year survival after resection of either cancer tumor (60.7% vs. 50.9%, respectively) were comparable. In conclusion, patients undergoing primary lung cancer surgery require a long-term follow-up due to the risk of metastatic or metachronous lung cancer. The likelihood of metachronous lung cancer and pulmonary lung cancer metastases, the incidence of postoperative complications, and the probability of 5-year survival after resection of metachronous lung cancer or lung cancer metastasis are similar.