Smokers and former smokers should be screened for lung cancer even if they don't have symptoms, according to a new study led by physician-scientists at NewYork-Presbyterian Hospital/Weill Cornell Medical Center.

The findings, based on data from the largest clinical trial of lung-cancer computed tomography (CT) screening ever conducted, represent the first time tumor size and lung cancer stage have been linked in an asymptomatic population. Results of the study were published today in the Archives of Internal Medicine.

"The smaller the lung cancer is at diagnosis, the more likely it is to be stage 1 and curable," says lead author Dr. Claudia Henschke, principal investigator of the International Early Lung Cancer Action Project (I-ELCAP); chief of the chest imaging division at NewYork-Presbyterian/Weill Cornell; and professor of radiology at Weill Cornell Medical College. "If small lung cancers are found, they may have a significantly improved chance of a cure."

Dr. Henschke advises smokers to consider CT screening because they are at high risk of lung cancer. Former smokers remain at high risk for lung cancer for 20 or 30 years after they quit smoking and should consider annual CT screening. "CT screening has the potential to save lives in both of these groups," she continues. "This new information should be most helpful in providing for an informed decision-making discussion between patients seeking CT screening for lung cancer and their physicians."

Lung cancer remains the leading cause of cancer death in both men and women, killing more people than breast, prostate, and colon cancers combined, according to the American Cancer Society.

Stage 1 lung cancer has been shown to have better a cure rate than any other stage. When lung cancer is detected outside of screening, typically because of symptoms, it has often spread to the lymph nodes and beyond. At this point, the opportunity for curative resection or any effective treatment is greatly diminished.

The largest study ever undertaken to determine if annual screening by CT is effective, I-ELCAP screened 30,235 men and women at 38 institutions across the globe. The study released today evaluated 438 lung cancers identified in I-ELCAP and studied the relationship of cancer stage to tumor diameter in asymptomatic, latent lung cancers to determine if size is an indicator of prognosis. The researchers considered tumor diameter, consistency, and presence or absence of metastases at the time of diagnosis.

"This report confirms that small-sized lesions are a good indicator of early, curable cancer," Dr. Henschke says. "Previously, concern regarding this relationship had led some to question the benefit of screening. This issue should no longer be of concern."

The current lung cancer staging criteria considers tumors smaller than 30 millimeters (mm) without evidence of spread to be in stage 1A (National Cancer Institute-sponsored Surveillance, Epidemiology, and End Results -- SEER -- definitions, based on data from symptomatic cases). The study found more than 90% of the lesions that are smaller than 15 mm (about the size of a dime) are in stage 1A, and almost all of those are curable. The researchers found that 85% of 16 mm to 25 mm malignancies had no lymph node metastases and that 63% of the 26 mm to 35 mm had not metastasized. Because screening is useful for finding small, asymptomatic cancers, the researchers did not have many lesions larger than 35 mm to study.

"Screening allows us to find smaller lung cancers than what we typically find when patients are symptomatic," says Dr. Henschke. "Clearly, the smaller the cancer the more curable it is, and stage 1 is the most hopeful. When found in later stages, the cure rate drops dramatically."

"Therefore, our findings suggest that tumor diameter serves as a prognostic indicator for curability, perhaps even for micro-metastases not detectable by our current techniques," she adds.

Since the early 1990s there have been remarkable advances in CT scanners, so that sub-millimeter "slicing" can now be applied to the entire chest in a single breath-hold; and as a result, lung cancer is being detected when it still is smaller than in cases diagnosable prior to 1986. While CT scans once yielded 30 images, current technology yields 900 images.

Dr. Henschke's co-authors include Dr. Steven Markowitz (CBNS, City University of New York at Queens College, Queens, N.Y.), Dr. Shusuke Sone (Azumi Hospital, Nagano, Japan), Dr. Karl Klingler (LungenZentrum Hirslanden, Zurich, Switzerland), Dr. Melvyn Tockman (Lee Moffitt Cancer Center & Research Institute, Tampa, Fla.), Dr. Dorith Shaham (Hadassah Medical Center, Jerusalem, Israel), and the other I-ELCAP investigators. Also contributing to the study were NewYork-Presbyterian/Weill Cornell's Dr. David F. Yankelevitz and Dr. Dorothy I. McCauley.

The original ELCAP study, which was led by Dr. Henschke and published in the July 1999 Lancet, determined that low-dose CT scans found more than 80% of the screening-detected cancers to be of stage I, the most curable stage of the cancer. An ELCAP study published in the August 2003 journal Chest, also led by Dr. Claudia Henschke, found that CT screening for lung cancer may not only improve a lung cancer patient's chances for a cure, but is also likely to be cost-effective when compared with other widely accepted cancer screening methods.