Lung cancer staging: an overview of the new staging system and implications for radiographic clinical staging

The Cancer Commission of the League of Nations Health Organization established the Radiological Sub-Commission in 1929 with the primary mandate of creating a common cancer staging system in order to facilitate effective communication across institutions around the world. Shortly thereafter by Dr. Pierre Denoix developed the TNM system used in almost all solid cancer staging today, and he continued to broaden and refine his TNM based staging approach through a series of articles published in the 1940’s and 50’s.1 Denoix’s approach gained its first institutional endorsement when the 7th International Congress of Radiology adopted TNM staging for laryngeal and breast cancer in 1953. Subsequently, as chairman of the Union Contre Le Cancer (UICC) staging committee, Denoix oversaw the publication of a series of “fascicles” (brochures) released during the 1960’s establishing standardized TNM staging for 23 solid organ cancers. A tradition of international consensus in cancer staging was established in 1969, when the American Joint Committee for Cancer Staging and End Results Reporting (renamed American Joint Committee on Cancer in 1980) and the UICC agreed that all subsequent staging recommendations by either body would be published in consultation with the other.2 Lung cancer staging was incorporated into the UICC TNM staging system in 1966. The first substantial revision of the lung cancer TNM staging was proposed by Dr. Mountain et al. in 1973 with the publication of “A Clinical Staging System for Lung Cancer”. This work was based on the outcomes of 2,155 cases of lung cancer, 1,712 of which were non-small cell lung cancer. It further specified the T, N and M descriptors and introduced stage groupings for the first time.3 Over the next 25 years, the lung cancer TNM staging system underwent three major revisions, all based on Dr. Mountain’s growing database, which had increased to 5,319 cases by 1996.4 It was at this point that the International Association for the Study of Lung Cancer (IASLC) initiated the IASLC Lung Cancer Staging Project. The IASLC Lung Staging Project sought to revise lung cancer staging to by using a data set more powerful, current, and universal than any single institutional database. From 1997 until 2009, this group developed a database incorporating patient data gathered from participating institutions around the world, collecting over 81,000 cases of lung cancer. The majority of cases were from Europe and the United States (58% and 21%, respectively), but a significant number of patients from Asia and Australia were included. Patients treated with all modalities were accepted into the database (including surgery, chemotherapy and radiation therapy) in order to better sample the true lung cancer population.2 The 7th edition of the lung cancer staging system thus represents the culmination of a remarkably comprehensive review process. Improvements in surgical, medical and radiation treatments, surveillance, radiographic staging, post-operative care and minimally invasive surgery have all changed lung cancer treatment and survival in the last decade. These new factors have not been accounted for in the previous staging schema and impact treatment decisions. Based on outcomes data from patients treated with these improved modalities, the TNM staging is more representative of current treatment patterns and helps better guide the clinician. The IASLC Lung Cancer Staging Project set out to accomplish a series of goals: Aid the clinician in planning treatment Give some indication of prognosis for each stage Assist in the evaluation of the results of treatment Facilitate the exchange of information between centers across the globe To contribute to the continuing investigation of human cancer.2 This article will review the AJCC 7th edition Cancer Staging for lung cancer and will compare it to the 6th edition, with emphasis on operable disease. Clinical staging, its strengths and weakness, along with minimally invasive staging supplements will be discussed to aid the clinician in the preoperative staging of lung cancer.