New techniques for detecting lung cancer earlier, as well as with more accuracy and precision, have experts cautiously optimistic that significant progress in battling the nation's leading cause of cancer-related death may finally be at hand.
In a July study in the British journal The Lancet, researchers in New York and Montreal reported that helical low-dose computed tomography scanning appears to be useful in detecting malignant lung tumors relatively early.
At the same time, the U.S. Food and Drug Administration has approved a new diagnostic imaging agent test kit for patients with suspicious lung abnormalities. And the preliminary results of a pilot biomarkers study make the possibility of eventually developing a blood test for lung cancer more likely (see sidebar).
CT Scans vs. X-rays
In the New York/Montreal study, Cornell Medical Center chest imaging division chief Claudia Henschke, Ph.D., M.D., and colleagues, used low-dose helical CT to screen 1,000 asymptomatic smokers or former smokers, who smoked at least one pack of cigarettes a day for 10 years, or two packs per day for 5 years. All were age 60 or older.
|
All tumors were subsequently surgically removed. None of the stage I patients underwent radiation or chemotherapy and have thus far shown no signs of disease, while the four patients diagnosed with later-stage disease have since died. Very small tumors were studied to look for growth and these were removed from patients if growth was detected.
The study has stirred interest in the research community because, at present, routine screening for lung cancer using chest x-rays and other modalities is discouraged. Existing diagnostic technologies are considered too limited to detect tumors early enough to benefit patients and also prone to identifying lung nodules that require biopsy but are not cancer.
Although experts find the study's results both intriguing and potentially promising, all agree they are far from definitive. Larger, more varied additional trials will be needed before CT scanning can be deemed effective and viable, they caution.
In 1999, there will be an estimated 159,000 lung cancer-related deaths and 172,000 new cases.
Detection and Survival
According to a study by coauthor Olli Miettinen, M.D., Ph.D., who is both a professor of epidemiology and biostatistics and a professor in the Department of Medicine at Montreal's McGill University, at issue is "the feasibility [through screening] of enhancing survival in lung cancer on the basis of advancing the time or the stage of intervention "
Investigators attempted to determine one of two key factors: the extent to which lung cancer can be detected earlier and to what extent subsequent intervention improves survival, Miettinen said.
"This study addressed the former of these two questions showing that the use of modern CT scanning leads to the detection of lung malignancies at a distinctly earlier stage meaning that the size of tumors is smaller," he added.
Because the issue of repeat screening is essential, the team is already screening patients beyond baseline to determine the size distribution of malignancies. The investigators are also following diagnosed cases with a view toward determining the impact on mortality.
Efficacy and Cost
Small non-malignant abnormalities can arise from tuberculosis and other pulmonary conditions, making accurate and precise diagnosis essential to avoid additional, sometimes more invasive, biopsies. In repeat screens, new nodules are rare but usually malignant, according to the study investigators. Because the clinical picture changes dramatically after baseline screening, false positives are not likely, Miettinen said.
At present, the low-dose helical scanning technique is performed at a few U.S. medical centers: Cornell and New York University, New York; Mayo Clinic in Rochester, Minnesota; and the H. Lee Moffitt Cancer Center and Research Institute, Tampa, Fla. Scans for lung cancer screening. Of those, some limit the technique only to clinical trial participants.
"Spiral CT imaging for lung cancer has exciting potential and it needs to be studied further to determine the precise benefits that may be achieved," said Christine Berg, M.D., acting chief of the lung and upper aerodigestive cancer research group in the National Cancer Institute's Division of Cancer Prevention.
According to Berg, traditional randomized control trials will be necessary to determine the benefits as well as the potential risks.
In addition, Berg said, the cost-effectiveness of this approach should be assessed by evaluating the rate of overdiagnosing non-malignant, relatively common abnormalities and comparing CT imaging to other diagnostic technologies such as PET imaging and biopsies.
Finally, additional studies should investigate the effectiveness of CT scans in detecting fast-growing as well as slower-growing tumors and in detecting different types of tumors such as small cell and squamous cell cancers which are more representative of the distribution of lung cancer in the general population. The impact of this technique on mortality has yet to be determined.
"For a preliminary study to assess a procedure by screening a group of individuals at risk, it was a very useful study," Berg said. "It is informative and interesting and exciting, but in terms of a mortality benefit, one needs to study the issue carefully and the traditional mechanism [for doing this] has been a randomized trial."
Policy Implications
American Cancer Society Cancer screening chief Robert Smith, Ph.D., likewise credited the study's authors for stimulating discussion and interest, but cautioned that "we're still in a period of infancy in terms of determining how efficacious these screening tests can be."
According to Smith, there is not enough existing evidence for his organization to advocate or discourage lung cancer screening as a matter of formal policy, but said the group is planning to convene a meeting before the end of this year to discuss "what to tell the public at this point about making an informed decision."
Even though large lung cancer trials that include a mortality endpoint are expensive and time-consuming, Smith said, they offer the best way to convince clinicians, policymakers, and third-party payers. Nevertheless, he acknowledged that the public often demands new technologies regardless of cost or proof of benefit.
"The public is not interested in all this modeling how you would weigh one test against another. People with a history of smoking whether they've quit or not certainly don't want to die of lung cancer. Even if you said this imaging technology costs $3,000, people are going to look for it, whether there is an acceptable level of proof or not," he explained.
Refining Studies
Harvey Pass, M.D., professor of surgery and oncology at Detroit's Karmanos Cancer Institute of Wayne State University, said the study is an intriguing feasibility analysis of CT scans in lung cancer early detection, but additional studies should more specifically characterize participants by both their tobacco consumption and the size of nodules detected.
|
"Obviously the name of the game is screening, mortality, and stage migration. To prove there is a definitive benefit in this regard will take a long-term study and thousands of patients," Pass predicted.
![]() |
||||
|
Oxford University Press Privacy Policy and Legal Statement |