Lung cancer staging undergoes major overhaul

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 urge 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 due to publish its 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 M.D. Anderson Cancer Center in Houston. By 1997, this database had grown to 5319 cases, and it long remained the primary basis for the classification of malignant tumors. But then the IASLC got involved, eventually 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.

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, as well as reassignment of 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 from the department of thoracic and cardiovascular radiology 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 contains 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 favourably 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.