Tumor, node and metastasis classification of lung cancer – M1a versus M1b – Analysis of M descriptors and other prognostic factors
Introduction
The current 7th edition of the tumor, node and metastasis (TNM) classification of lung cancer (LC), was based upon an unprecedented large data base with cases from all over the world, treated by all modalities of care. This edition provides significant insight into a more universal and precise description of the disease [1], [2], [3], [4]. One of the relevant changes that have been made relates to the M1 category which has now been divided into two subgroups, depending on the location of the metastases: M1a or M1b [3], [4].
However, this retrospective database and most of the contributing datasets were based on previous works not designed to study the TNM classification. To overcome these limitations, the International Association for the Study of Lung Cancer (IASLC) proposed a Prospective Project to refine future editions of the TNM classification. Thus, an international database was launched in 2009 to collect data from different medical centers from all over the world [5], [6].
The Bronchogenic Carcinoma Cooperative Group of the Spanish Society of Pneumology and Thoracic Surgery-II (Grupo Cooperativo de Carcinoma Broncogénico de la Sociedad Española de Neumología y Cirugía Torácica-II, GCCB-S-II), a consortium of Spanish specialists in Thoracic Surgery and Pulmonology, decided to participate in this IASLC project (see appendix). To this end, a national committee was created to promote and organize the participation of the different hospitals. Finally, 30 centers were registered and 28 of them recruited patients.
The objectives of this study are: (1) to analyze the survival differences between M1a and M1b LC patients and to examine the prognostic influence of every M descriptor in our prospective cohort of patients; (2) to examine their independent prognostic value taking into account other prognostic factors (epidemiological, clinical, and other known prognostic factors).
Section snippets
Patients and methods
This is a prospective, observational and multiregional study aimed at analyzing survival and prognostic factors, especially the M descriptors included in the latest TNM classification of LC. The structure and organizing characteristics of the GCCB-S-II were described in a previous paper [7].
Results
865 LC patients with M1 disease not surgically treated were registered in the database. After of exclusion of patients with SCLC and carcinoids tumors, the final number of NSCLC patients included was 640. Patient characteristics are presented in Table 1. There were 532 men and 108 women. 195 tumors were classified as M1a and 445 as M1b. Concerning the histological type, 271 were adenocarcinoma, 230 squamous cell, and 139 corresponded to other tumor types (see details in Table 1). Most patients
Discussion
To our knowledge, this is the first prospective study specifically designed to assess the prognostic differences between the M1a and M1b categories of the latest edition (seventh) of the TNM classification of lung cancer [1], [2], [3], [4]. Our results support the current division of the M1 category into two subsets, but also taking into account the most well-known relevant prognostic factors, such as PS, sex, age, weight loss and certain laboratory parameters. In this series, all patients were
Conflicts of interest
There are no conflicts of interest.
Author contributions
Dr. Sánchez de Cos Escuín contributed to the study design, data collection, data analysis, and to the writing of the manuscript.
Drs. Hernández Hernández, Serra Mitjans and Hernández Rodríguez contributed to the study design, data collection, and to the writing of the manuscript.
Drs. Abal Arca, Melchor Íñiguez, Miravet Sorribes, Núñez Ares, García Arangüena, Núñez Delgado, Pavón Fernández, Francisco Corral, Esteban Júlvez and González Budiño contributed to data collection, the revision of the
Acknowledgment
Elena Dopino Sperry, MSc (Editing and Translation in Science and Medicine) assisted in the revision of the English version of the manuscript.
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