One of the greatest challenges in treating lung cancer is diagnosing the disease early enough to treat effectively. That’s why any new research on early indicators of the disease —such as a recent study on the relationship of smoking cessation to lung cancer diagnosis—gets so much notice.
“Most of the time when we make a diagnosis, the stage is quite advanced beyond the point that you can consider curative surgery, and that is why it is a difficult disease to treat and manage,” said Kenneth K. Ng, MD, chief of medical oncology services at New York City’s Memorial Sloan-Kettering Cancer Center’s Rockville Centre on western Long Island.
Furthermore, there is a significant amount of variation in disease presentation and usually, “. . . because of the central location of the lungs, an invasive procedure is often needed for diagnosis, especially for early-stage disease,” noted Michael J. Kelley, MD, FACP, National Program Director for Oncology at VHA.
As can be true in other types of cancer, “The difficulty of making a diagnosis of lung cancer varies greatly among patients based on the type of lung cancer, the stage of disease, the location of metastases and the presence of co-morbid conditions,” Kelley added.
In the U.S., lung cancer kills more than 160,000 people a year, more than cancers of the breast, prostate, colon and pancreas combined.
A recent study, widely covered by the news media, suggested that smoking cessation could be a lung-cancer indicator. In an article published in March in the Journal of Thoracic Oncology, researchers said they interviewed patients from Philadelphia VAMC and found that 55 percent of the lung-cancer patients had quit before diagnosis, while only 11 percent were symptomatic at the time of smoking cessation.
“These results challenge the notion that patients with lung cancer usually quit smoking because of disease symptoms. The hypothesis that spontaneous smoking cessation may be a presenting symptom of lung cancer warrants further investigation,” the researchers noted in their conclusion.
New Trial May Provide Screening Tools
Overall, the goal is to find and develop new and effective ways to screen for the disease, Ng added, noting, “We don’t have any standard screening methods at this time. But things will change, and I foresee that things will change quite quickly very soon.”
Significant changes in diagnosis protocols likely will result from the National Lung Screening Trial (NLST), which compared the effects of two ways of detecting lung cancer—low-dose helical computed tomography (CT) and standard chest X-ray—on lung cancer mortality rates, Ng and other experts told U.S. Medicine.
In initial results released in November, the NLST found that there were 20 percent fewer lung cancer deaths among trial participants screened with CT. In a side note, researchers also pointed out that all-cause mortality (deaths due to any cause, including lung cancer) was 7 percent lower in those screened with CT compared with those screened with chest X-ray.
In its efforts, the NLST sought to do something no other research has accomplished: determine if screening with either CT or chest X-ray before the appearance of symptoms can reduce lung cancer deaths.
The trial was stopped and announcement of initial findings were made after the trial’s independent Data and Safety Monitoring Board (DSMB) determined that accumulated data provided a statistically convincing answer to the study’s primary question. More detailed results will soon be published in a peer-reviewed journal
“VHA will review the full results of NLST as they are published in peer-reviewed journals and will consider any changes to the screening recommendations for lung cancer by major guideline publishers, such as the U.S. Preventive Services Task Force,” according to Kelley.
The NLST, launched in September 2002, is a joint effort of the National Cancer Institute, part of the NIH, and the American Cancer Society and involved 53,000 current and former heavy smokers ages 55 to 74. In the randomized, controlled study, participants were assigned to receive either a chest X-ray or a CT once a year for three years.
Helical CT, also called spiral CT, is a relatively new technology introduced in the 1990s that uses X-rays to scan the entire chest in about 15 to 25 seconds, during a single breath-hold. A computer creates images from the scan, assembling them into a three-dimensional model of the lungs.
In a question-and-answer resource about the NLST results, the National Cancer Institute emphasizes that improved screening does not change the risk of getting lung cancer from smoking.
According to the CDC, men who smoke increase their risk of death from lung cancer by more than 22 times; women who smoke increase their risk of death from lung cancer by nearly 12 times. There are an estimated 90 million current and former smokers in the United States.
The issue is especially significant for military medicine. A recent study from the Institute of Medicine showed that 32 percent of active-duty military personnel smoke and that the prevalence of smoking may be more than 50 percent higher in military personnel returning from Iraq and Afghanistan than for those who were not deployed there.
Blood Test Could Be Available
Better diagnosis is key to improving outcomes, and researchers are exploring several avenues. Helen Ross, MD, of the Mayo Clinic in Phoenix/Scottsdale, Ariz., predicted that a blood test for diagnosing lung cancer could be available anywhere from five to 10 years down the road.
“Things move at different paces in the application of new diagnostic procedure,” Ross explained. “There are already techniques that can detect a cancer cell in the blood; [and] there are already techniques that can evaluate proteins and free DNA in the blood that have a higher suggestion that there may be some cancer in the person who’s affected.”
When current diagnostic tools such as routine chest X-rays raise suspicion of lung cancer, a conclusive diagnosis of lung cancer requires a fluid or tissue sample, Kelley said. Those would include cytopathological specimens—sputum, pleural fluid, bronchial washings, bronchial brushings, needle aspiration—and anatomical pathological samples—needle core biopsy, excisional biopsy, resection specimen.
The problem is that a chest X-ray is not an “effective screening tool to reduce lung-cancer mortality,” Kelley noted. “However, an abnormality on [an X-ray] performed for another purpose is often one of the findings that lead to an evaluation leading to a diagnosis of lung cancer.”
Also noted in the question-and-answer resource about NLST, NCI is not currently recommending using widespread low-dose helical CT screening for lung cancer, pointing out, “The NLST participants were a very specific population of men and women ages 55 to 74 who were heavy smokers. They had a smoking history of at least 30 pack-years but no signs or symptoms of lung cancer at the beginning of the trial. Pack-years are calculated by multiplying the average number of packs of cigarettes smoked per day by the number of years a person has smoked. It should also be noted that the population enrolled in this study, while ethnically representative of the high-risk U.S. population of smokers, was a highly motivated and primarily urban group, and these results may not fully translate to other populations.”