To the best of my knowledge, five methods have been used to try to detect lung cancers at a small size, before they have spread (metastasized) to lymph nodes or other body organs.’
1. Chest roentgenogram (chest x-ray)
2. Computerized tomography (CT scan)
3. Cytology- looking at cells in secretions under the microscope
4. DNA testing to look for characteristic mutations.
5. Electronic “nose” a method to measure chemicals in expired air.
Methods 3-5 are works in progress, that are not currently approved in clinical practice guidelines. Medical history is full of exampleso how a technology improves over time. Perhaps one of more of these methods will have proven utility in the near future, but they will not be discussed further here.
Chest s-ray was the first method of screening that showed favorable results. Early studies in London, Philadelphia and Czechoslovakia showed no benefit, but 3 prospective studies at Memorial Hospital in New York City, Johns Hopkins in Baltimore and the Mayo Clinic in Rochester Minnesota all showed striking improvement in survival in male smokers screened with chest x-ray compared to unscreened lung cancers in national databases. But although survival was improved, there was no measurable reduction in mortality. As a result the National Cancer Institute (NCI) concluded that chest roentgenographic screening was ineffective and potentially harmful.
On a personal note, I personally cared for patients during and after operations for screen detected lung cancers as a surgeon in training at Mayo in the early 1970s I knew then that the lives of some patients were saved by chest x-ray screening. I believe that many lives could have been saved, if we implemented chest X-ray screening in the 1980s, but in any case CT scan is a far superior method.
CT Scan: I saw the first CT scan machine in the U.S. in a basement lab at Mayo, – during the early 1970s. No one thought of using it for screening. This was first done in Japan during the early 1990s. Japanese radiologists first showed that CT scans could detect lung cancers as small as 2 or 3 mm in diameter i.e. the size of a BB-gun pellet. They also showed that this could be done with very. low doses of radiation.
These concepts were introduced in the United States by two radiologists at Cornell University in New York City, Claudia Henschke MD and David Yankelevich MD. They studied CT scans for lung cancer screening, compared to chest x-rays in 1000 research participants in the Lung Cancer Action Program (ELCAP) trial.
How does a CT scan work? I can’t describe the physics behind the method, but from the patients perspective, you do not have to disrobe, there is no IV or injection and all that is required is to lie down on a table for a few seconds. The machine is open and so claustrophobia should not be a concern.
The ELCAP study, published in 1999 showed that CT was three times as sensitive as chest-x-rays in detecting small lung nodules.
The most important finding of the study was that more than 80% of lung cancers were detected in stage 1. To put that in perspective, in 1999 only about 15% of lung cancers in the U.S. were diagnosed in stage 1. Since it had already been shown convincingly that the large majority of patients in stage 1 are cured (i.e. survive more than 5-years after surgical resection) it could reasonably be assumed that CT screening could save many of the 160,000 who die each year of lung cancer in our country.
To try to prove this point, the ELCAP study was extended first to a number of hospitals in the New York City area (NY-ELCAP) and subsequently internationally to more than 70 centers around the world (I-ELCAP).
When the IELCAP study results were published in the New England Journal of Medicine in 2006, they showed that more than 80% of patients with lung cancers diagnosed by CT screening experienced 10-year actuarial survival.