The International Association for the Study of Lung Cancer (IASLC) Staging and Prognostic Factors Committee has developed proposals for revision of the T, N, and M categories of the 8th edition of the TNM Classification for lung cancer due to be published in late 2016. The new classification will be enacted in January 2017.
The changes proposed were based on the results of an analysis of a new database of 94,708 cases donated from 35 sources in 16 countries around the world.
The methods used and the proposals made were published in the Journal of Thoracic Oncology (2016;11:39-51).
Candidate proposals for the TNM stage groups were developed in conjunction with proposed changes to the T and M categories, which were previously published (J Thorac Oncol 2015;10:990-1003, and 2015;10:1515-22). There were no proposed changes to the N.
Changes to some T and M descriptors will result in these cases being assigned to a different stage than that to which they would have been assigned in the 7th edition. In addition, some TNM subsets have been moved to a new stage grouping, according to Dr. Peter Goldstraw of Imperial College, London, and his colleagues on behalf of the IASLC Staging and Prognostic Factors Committee.
Major new proposals
T1 changes: Size cut points have further proliferated in the proposals for the 8th edition, and outgrowth of the emphasis on tumor size in the 7th edition, such that size will now be a descriptor in all T categories, according to the authors. New stage groupings proposed divide stage T1 into T1a, T1b, and T1c, based on the new size cut points of 1 cm and 2 cm. This results in these cases (when associated with the categories N0 and M0) being assigned to stages 1A1, 1A2, and 1A3, respectively, which reflects the statistically different prognosis of these cases.
T3, T4 changes: A new group has been created for the most advanced local disease categories, T3 and T4 associated with N3 disease, but category M0. Such cases will now be classified as stage IIIC, reflecting their worse outcomes than seen in cases involving tumors that remain in stage IIIB. The prognosis for stage IIIC cases is similar to that of stage IVA cases, however the researchers justified the separation, based upon the different treatment approaches used for such cases.
M changes: Although cases with intrathoracic metastatic disease to the contralateral lung or with pleural/pericardial dissemination remain classified as M1a disease, the category M1b will now be assigned to cases with a single metastatic deposit (in one organ) and M1a and M1b cases will be moored to a new stage grouping called IVA. The more common situation of multiple metastatic deposits, usually in more than one organ, will be classified as M1c and staged as IVB. Separation of the M1a and M1b categories was maintained both for further data analysis and because some patients with oligometastatic disease are now receiving more aggressive local therapy in addition to systemic treatment, according to the authors.
A variety of more minor changes to stage groupings has also been proposed, some of which will result in a T descriptor being allocated to a higher stage. In some cases, tumors may be allocated to a different T category entirely, leading to a reclassification of stage. Among the examples given were tumors associated with diaphragmatic invasion to TV, which, when associated with N0 disease, will move from stage IIB to IIA.
Impact on treatment
The relationship of the proposed classification changes to treatment decisions is not direct, the authors stated in their discussion. “Although such changes might raise the issue of whether consequent changes to treatment algorithms are needed, it is important to remind ourselves that stage does not dictate treatment. Stage is one, and perhaps the most important, of several prognostic factors that guide the appropriate treatment option[s] to offer the patient. Any change to established treatment algorithms should be based on clinical judgment informed by prospective trials,” they emphasized.
New stage groupings should be used in any trials of novel therapies, they added.
“We hope that the thoracic oncology community finds the proposals of value and that, when accepted, will have a positive impact on the effectiveness of treatment for lung cancer, which will benefit patients around the globe,” the researchers concluded.
The research to develop the new proposals was funded by the IASLC, including funds obtained through unrestricted grants obtained from the pharmaceutical industry. The authors reported no other disclosures.