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.
A fundamental assumption of lung cancer screening isthat 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 thecancer.
The authors of the study, based on the stage distribution of cancer in 620men and women with primary non-small-cell lung carcinomas, caution physicianswho have begun to use computed tomography (CT) scans for screening and earlylung cancer detection not to assume that small tumors represent early-stagecancer. They advise physicians against the widespread use of CT scans forscreening and early detection of lung cancer until further data becomeavailable.
"Our study found no statistically significant relationship between thesize 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 ofthe 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 than1 cm to 3 cm in size. Researchers concluded that even the smaller tumorscould represent an advanced stage of disease. They said that their studysuggested that the size of tumors less than or equal to 3 cm played only alimited role in the biology of lung cancer. Patients with a primary lesion thatis 3 cm or smaller in diameter will have an approximately 80% to 85% chance ofhaving stage I lung cancer and an approximately 10% chance of having stage IVlung cancer, regardless of tumor size at detection.
In recent years, low-dose spiral CT scans have been proposed as a potentialmethod to screen for lung cancer. Proponents of CT scans have argued that thesescans could detect smaller lesions not visible with chest x-rays, that thesesmaller tumors represented an early stage of cancer, and that detecting themwould lead to reduced lung cancer mortality, said the Duke researchers.
"Our study emphasizes the fact that size alone does not appear todetermine a cancer’s metastatic potential and ultimate stagedistribution," said the researchers. "While it is reassuring tobelieve there is a size threshold below which there is minimal or reduced riskof a tumor having metastasized, and thus that lung cancer screening can reducemortality, there are no conclusive data to support this notion. Early detectionwith imaging alone may not be enough to impact the natural course of lungcancer."
Size Alone Not Predictive
The researchers also found that while larger tumors presumably have more timeto grow and metastasize, it has become increasingly clear that size alone maynot predict the biological behavior of lung cancer. Other studies have reportedimproved survival in patients with tumors less than 3 cm as compared to patientswith tumors greater than 3 cm, said the researchers. However, in contrast, onerecent study found no correlation between the size of stage I lung cancer tumorsand survival.
The Duke researchers concluded that, "At this time, there is no clinicalor experimental evidence to confirm that the critical time for metastases iswhen lesions measure 5 to 10 mm, which is generally the targeted size of CTscreening, as opposed to 1 to 3 cm, when a lesion is visible on a chest x-ray.How size truly relates to metastatic potential and the natural history of thedisease remains to be seen."