Among patients with asymptomatic primary lung cancer, smaller tumors appear to be less likely to metastasize than larger tumors, suggesting early screening may improve the rate of detection of potentially curable disease, according to an article in the February 13 issue of the Archives of Internal Medicine.

Cancers that are still confined to the lungs are divided by size into stage IA (tumors less than 30 millimeters in diameter) and stage IB (tumors larger than 30 millimeters in diameter). The development of computed tomography scanning has allowed physicians to detect lung tumors at a smaller size, prompting some to call for more subdivisions of stage I cancers.

Although tumor size has been linked to cancer prognosis in patients with symptoms, the relationship between tumor size, metastasis, and prognosis in asymptomatic individuals had been unclear.

Claudia I. Henschke, M.D., Ph.D., New York Presbyterian Hospital-Weill Cornell Medical Center, New York, and colleagues from the International Early Lung Cancer Action Program screened 28,689 men and women for lung cancer at 38 institutions worldwide between 1993 and 2004.

A total of 464 patients were diagnosed with lung cancer as the result of the screening. The researchers classified the participants' lung cancers based on type and size at diagnosis and presence or absence of metastasis. They also recorded the consistency of tumors as solid, nonsolid, or partly solid.

For the 436 patients with non-small cell lung cancers, the likelihood of metastasis increased with tumor size. When the researchers analyzed tumors by consistency, they found the association strongest for solid tumors, weaker for partly solid tumors, and not apparent for nonsolid tumors. For the few (28) cases of small cell cancer, the relationship appeared strong. The percentages of non-metastasized cancer of all types were much higher than those reported in previous studies.

"The pattern confirmed herein suggests the usefulness of finding latent cancers at small sizes," the authors concluded. "Most lung cancers without evidence of lymph node metastases are curable, with the curability rate being higher at smaller sizes. This suggests that tumor diameter also serves as a prognostic indicator for curability, perhaps even for micrometastases not detectable by our current techniques."