Stage IV lung cancer: the relevance of tumour profile for the construction of prognostic groups

Believe it or not, the first edition of the tumour, node and metastasis (TNM) classification, published by the Union for International Cancer Control (UICC) in 1968, did not have stages. Stages, that is the grouping of tumours classified by the TNM system that have similar prognosis, were introduced in the second edition, published in 1975. There were only three, with metastatic disease included in stage III. It was not until the third edition of 1978 that stage IV was created to accommodate metastatic spread. The three categories then established (MX, metastasis cannot be assessed; M0, no distant metastasis; and M1, distant metastasis) remained unchanged until the seventh edition of the TNM classification [1]. The UICC and the American Joint Committee on Cancer, the two institutions responsible for the promulgation and periodic revisions of the classification, decided then to eliminate the MX category based on the fact that the presence or absence of distant metastases could be assessed by a well-taken medical history and a thoroughly performed physical examination. The other innovations derived from the analyses of international databases undertaken by the International Association for the Study of Lung Cancer (IASLC), who had taken the responsibility to revise the forthcoming editions of the TNM classification of thoracic malignancies based on data collected internationally. To inform the seventh edition, the IASLC database included 81 495 evaluable patients diagnosed of small and non-small cell lung cancer (NSCLC) [2]. The combination of anatomic and non-anatomic prognostic factors will increase our capacity to prognosticate for an individual patient with stage IV lung cancer