title: Tumor, node and metastasis classification of lung cancer--M1a versus M1b--analysis of M descriptors and other prognostic factors.
abstract: BACKGROUND
  The current edition of the tumor, node and metastasis (TNM) classification of lung cancer (LC) divides the presence of metastasis (M1) into two categories: M1a and M1b, depending on its anatomical location. To assess this new classification, the survival and the M descriptors of LC patients with metastatic disease registered by the Bronchogenic Carcinoma Cooperative Group of the Spanish Society of Pneumology and Thoracic Surgery II (GCCB-S-II), were analyzed.
  
  
  METHODS
  Non-small cell lung cancer (NSCLC) patients, with M1a or M1b disease, included in the GCCB-S-II, from April 2009 to December 2010, staged in accordance with the prospective staging project protocol of the International Association for the Study of Lung Cancer (IASLC), and with complete TNM staging and follow-up data, were studied. The overall survival associated with each M1 category and each M descriptor, besides other prognostic factors (sex, age, performance status [PS] and others) were analyzed by univariate and multivariate models.
  
  
  RESULTS
  640 NSCLC patients (195 M1a and 445 M1b) were included. M1b tumors had significantly worse survival than M1a tumors (p < 0.001). The prognostic value of M1 category was independent from other prognostic variables such as PS, weight loss, and others. The number of metastatic sites (isolated versus multiple) and the number of lesions (single versus multiple) in patients with isolated metastasis showed prognostic value, especially in those with brain metastasis.
  
  
  CONCLUSIONS
  The current division of the M1 category into two subsets (M1a and M1b) is warranted by their prognostic significance. The number of metastatic sites and the number of lesions in patients with isolated metastasis should be taken into account, because they also have prognostic relevance.
authors.affiliation: Pulmonology Section, Hospital San Pedro de Alcántara, Cáceres, Spain; Biomedical Research Center Network for Respiratory Diseases (CibeRes), Spain. Electronic address: juli1949@separ.es.
authors.forename: Julio
authors.initials: J
authors.lastname: Sánchez de Cos Escuín
authors.affiliation: Pulmonology Section, Complejo Hospitalario de Ourense, Spain.
authors.forename: José
authors.initials: J
authors.lastname: Abal Arca
authors.affiliation: Pulmonology Section, Fundación Jiménez Díaz, Madrid, Spain.
authors.forename: Rosario
authors.initials: R
authors.lastname: Melchor Íñiguez
authors.affiliation: Pulmonology Section, Hospital de La Plana, Castelló, Spain.
authors.forename: Luis
authors.initials: L
authors.lastname: Miravet Sorribes
authors.affiliation: Pulmonology Section, Complejo Hospitalario de Albacete, Spain.
authors.forename: Ana
authors.initials: A
authors.lastname: Núñez Ares
authors.affiliation: Pulmonology Section, Hospital Nª Sª de Sonsoles, Ávila, Spain.
authors.forename: Jesús R
authors.initials: JR
authors.lastname: Hernández Hernández
authors.affiliation: Pulmonology Section, Hospital de Sierrallana, Torrelavega, Cantabria, Spain.
authors.forename: Luis
authors.initials: L
authors.lastname: García Arangüena
authors.affiliation: Pulmonology Section, Hospital de Meixoeiro, Vigo, Spain.
authors.forename: Manuel
authors.initials: M
authors.lastname: Núñez Delgado
authors.affiliation: Pulmonology Section, Hospital de Leganés, Madrid, Spain.
authors.forename: Ma José
authors.initials: MJ
authors.lastname: Pavón Fernández
authors.affiliation: Pulmonology Section, Complejo Hospitalario La Mancha Centro, Ciudad Real, Spain.
authors.forename: Gloria
authors.initials: G
authors.lastname: Francisco Corral
authors.affiliation: Pulmonology Section, Hospital Joan XXIII, Tarragona, Spain.
authors.forename: Leonardo
authors.initials: L
authors.lastname: de Esteban Júlvez
authors.affiliation: Pulmonology Section, Hospital Central de Asturias, Oviedo, Spain.
authors.forename: Ma Teresa
authors.initials: MT
authors.lastname: González Budiño
authors.affiliation: Pulmonology Section, Hospital La Fe, Valencia, Spain.
authors.forename: Francisco
authors.initials: F
authors.lastname: Abad Cavaco
authors.affiliation: Pulmonology Section, Hospital La Fe, Valencia, Spain.
authors.forename: Emilio
authors.initials: E
authors.lastname: Ansótegui Barrera
authors.affiliation: Pulmonology Section, Hospital Germans Trias i Pujol, Barcelona, Spain.
authors.forename: Felipe
authors.initials: F
authors.lastname: Andreo García
authors.affiliation: Thoracic Surgery, Hospital Universitari Mutua Terrassa, Spain.
authors.forename: Mireia
authors.initials: M
authors.lastname: Serra Mitjans
authors.affiliation: Thoracic Surgery, Hospital Universitario de Tenerife, Spain.
authors.forename: Helena
authors.initials: H
authors.lastname: Hernández Rodríguez
mesh_terms: D000230:Adenocarcinoma / Q000145:classification* / Q000401:mortality / Q000556:secondary; D000368:Aged; D001932:Brain Neoplasms / Q000145:classification* / Q000401:mortality / Q000556:secondary; D002289:Carcinoma, Non-Small-Cell Lung / Q000145:classification* / Q000401:mortality / Q000556:secondary; D005260:Female; D006801:Humans; D053208:Kaplan-Meier Estimate; D008175:Lung Neoplasms / Q000145:classification* / Q000401:mortality / Q000473:pathology; D008297:Male; D009367:Neoplasm Staging; D018307:Neoplasms, Squamous Cell / Q000145:classification* / Q000401:mortality / Q000556:secondary; D011379:Prognosis; D016016:Proportional Hazards Models; D011446:Prospective Studies
keywords: Lung cancer; M1a; M1b; Metastasis; Non-small cell lung cancer; Prognostic factors; TNM classification