Revision overhauls classification of lung cancer T and M staging

The imminent publication of eagerly anticipated new international guidelines promises to transform the complex area of lung cancer staging.

In two separate education exhibits at RSNA 2008, presenters from the U.S. and France urged all radiologists to become familiar with the seventh edition of the tumor, node, metastasis classification for lung cancer. The International Association for the Study of Lung Cancer is expected to publish its updated recommendations in early 2009.

The original TNM staging of lung cancer proposed in 1973 was based on 2155 cases from the database of Dr. Clifton Mountain from the M.D. Anderson Cancer Center in Houston. By 1997, this database had grown to 5319 cases, and remained the primary basis for the classification of malignant tumors. But then the IASLC got involved, resulting in a huge new database of more than 81,000 cases obtained between 1990 and 2000.

"Given the important role radiologists play in the staging of lung cancer, an understanding of the new classification system will be necessary for relevant imaging analysis of lung cancer patients," said Dr. Constantin A. Raptis, a radiologist from Washington University in St. Louis.

The authors of the seventh edition have made substantial changes for T and M staging, but they have left N staging unchanged. For T staging, they have introduced new size stratifications and reassigned several invasion criteria. For M staging, they have formulated a subclassification for M1a and M1b metastases.

The new recommendations look set to be accepted as a guide for estimating patient prognosis. They will form the basis for treatment decisions in practice, according to Dr. Antoine Micheau, a radiologist at the Arnaud de Villeneuve University Hospital in Montpellier.

Extensive corrections have been made to remove many deficiencies of the old staging system, he said. The sixth edition, from 2002, contained many controversial aspects. For instance, a satellite tumor nodule in the primary lobe was defined as T4, but some experts suggested that it might behave more favorably than in patients with another subgroup of T4. As a result, distinguishing the prognosis of patients with stage 3a and 3b was sometimes unclear.

"The proposed changes will improve the alignment of TNM stage with prognosis and treatment," Micheau said.