A fundamental assumption of lung cancer screening is that small tumors are less likely to have metastasized than large tumors. However, in a new study conducted at Duke Comprehensive Cancer Center, researchers showed that size does not necessarily indicate the severity of the cancer.
The authors of the study, based on the stage distribution of cancer in 620 men and women with primary non-small-cell lung carcinomas, caution physicians who have begun to use computed tomography (CT) scans for screening and early lung cancer detection not to assume that small tumors represent early-stage cancer. They advise physicians against the widespread use of CT scans for screening and early detection of lung cancer until further data become available.
"Our study found no statistically significant relationship between the size of small tumors and the stage of cancer," said Dr. Edward F. Patz, Jr, professor of radiology at Duke University Medical Center and senior author of the article appearing in a recent issue of the journal Cancer (92:3051-3055, 2001).
Smaller Tumors and Advanced Disease
The study focused on patients with tumors that measured from less than 1 cm to 3 cm in size. Researchers concluded that even the smaller tumors could represent an advanced stage of disease. They said that their study suggested that the size of tumors less than or equal to 3 cm played only a limited role in the biology of lung cancer. Patients with a primary lesion that is 3 cm or smaller in diameter will have an approximately 80% to 85% chance of having stage I lung cancer and an approximately 10% chance of having stage IV lung cancer, regardless of tumor size at detection.
In recent years, low-dose spiral CT scans have been proposed as a potential method to screen for lung cancer. Proponents of CT scans have argued that these scans could detect smaller lesions not visible with chest x-rays, that these smaller tumors represented an early stage of cancer, and that detecting them would lead to reduced lung cancer mortality, said the Duke researchers.
"Our study emphasizes the fact that size alone does not appear to determine a cancer’s metastatic potential and ultimate stage distribution," said the researchers. "While it is reassuring to believe there is a size threshold below which there is minimal or reduced risk of a tumor having metastasized, and thus that lung cancer screening can reduce mortality, there are no conclusive data to support this notion. Early detection with imaging alone may not be enough to impact the natural course of lung cancer."