DENVER – The term “precision medicine” can be applied to both clinical care and to pathology, as newly updated staging and classification systems for lung cancer show.
The proposed revised (8th) edition of the TNM staging system for lung cancer gives more weight to tumor size as a prognostic factor, reclassifies some primary tumor (T) descriptors, validates current nodal status (N) descriptors, modifies the definition of some types of metastases (M), and includes additional stages for better prognostic stratification, reported Dr. Ramón Rami-Porta from the Universitari Mútua Terrassa in Barcelona, at a world conference on lung cancer sponsored by the International Association for the Study of Lung Cancer.
Similarly, the updated World Health Organization (WHO) Classification of Lung Tumors, described by Dr. William D. Travis from the Memorial Sloan Kettering Cancer Center in New York, incorporates knowledge gained from immunohistochemistry and molecular testing for common genetic mutations into recommendations for treating the specific clinical circumstances of patients with lung cancer.
“The 2015 WHO Classification captures a remarkable decade of advances in every lung cancer specialty, from pathology – including histology, cytology, immunohistochemistry, genetics – to oncology, surgery, radiology, and epidemiology. The rapid expansion of immunohistochemical and molecular tools has had a profound impact on how we were able to reclassify a number of tumors, in addition to how we were able to contribute to improvement of subtyping of lung cancers, particularly non–small cell lung cancer,” Dr. Travis said at a media briefing following his discussion of the new classification at a plenary session.
The changes are expected to improve clinical management of patients with advanced lung cancer by clarifying criteria and terminology for small biopsies and cytology, establishing more accurate histologic subtyping, suggesting strategic management of small tissues, and streamlining the work flow for molecular testing. The classification also emphasizes the need for multidisciplinary cooperation among myriad clinicians, he said.
For surgically resected patients, the classification officially recognizes for the first time subsets of non–small cell lung cancer of adenocarcinoma histology with survival rates of 100% (adenocarcinoma in situ), or nearly 100% (minimally invasive adenocarcinoma).
Among the major changes that will affect the diagnosis of surgically resected patients are the adoption of the 2011 IASLC/ATS/ERS Lung Adenocarcinoma Classification, restriction of a diagnosis of large cell carcinoma to tumors lacking clear differentiation by both immunohistochemistry and morphology, reclassifying of squamous cancers into keratinizing, nonkeratinizing, and basaloid subtypes with elimination of clear cell, small cell, and papillary subtypes. Neuroendocrine subtypes are grouped together, but their classification otherwise remains largely unchanged.
The revised classification is expected to improve prediction of survival and recurrence, predict whether a patient is likely to have a survival benefit with platinum-based chemotherapy, allow radiologic pathologic correlations, and affects TNM staging by emphasizing solid tumor size (vs. whole tumor size), Dr. Travis said.
The proposed changes to the TNM tumor staging have been submitted for approval to the American Joint Committee on Cancer and the Union for International Cancer Control.
If adopted, they would represent the first significant changes since the 7th edition’s publication in 2009. The changes are based on data on more than 77,000 patients diagnosed with lung cancer from 1999 through 2010.
The proposed changes are not intended, however, to alter clinical practice, and instead “imply a taxonomic refinement rather than new indications of already established treatment protocols,” Dr. Rami-Porta said.
In some cases, the proposed changes would result in an upgrading of the T stage, while others would result in downgrading. For example, tumors that range in size between 1 and 2 cm, designated T1a in the 7th edition, would be T1b in the 8th edition. Similarly, tumors larger than 2 cm and up to 3 cm would be upgraded from T1b to T1c, those larger than 4 up to 5 would go from T2a to T2b, those larger 5 and up to 7 cm would rise from T2b to T3, and those larger than 7 cm would be reclassified from T3 to T4. Tumors invading the diaphragm would also be upgraded from T3 to T4 under the proposed revisions.
In contrast, tumors with limited invasion of the trachea (bronchus less than 2 cm from the carina) would be downgraded from T3 to T2, as would tumors associated with total atelectasis and/or pneumonitis.
The current N descriptors are adequate for predicting prognosis, the investigators determined, prompting the recommendation to retain them in the new edition.
The investigators propose slight changes to the M descriptors of metastases. Although they found no significant differences in survival found among patients with M1a (metastases within the chest cavity) descriptors, when distant metastases outside the chest cavity (M1b) were assessed by to the number of metastases, they found that patients with tumors with one metastasis in one organ had significantly better outcomes than those who had multiple metastases in one or more organs.