Ask just about anyone which cancer is most lethal and you're likely to hear breast, pancreatic, perhaps colon or melanoma. Few people realize that lung cancer causes more deaths annually than several cancers combined, according to the Centers for Disease Control and Prevention.
Smoking is by far the leading cause of lung cancer in the United States, but for reasons not fully understood, 10 to 20 percent of lung cancers occur in people who have never smoked.
"It's difficult to fathom," says Dr. W. Michael Alberts, chief medical officer and lung cancer specialist at H. Lee Moffitt Cancer Center and Research Institute in Tampa. "Studies tell us it's a different disease in nonsmokers, a different branch of the lung cancer tree. It tells us everyone should be watchful."
One of the biggest problems with lung cancer: no screening test for early detection. By the time symptoms show up, it is usually advanced and has spread throughout the body; chances for a cure are slim. Early lung cancers are usually picked up by an X-ray or CT scan taken for an unrelated health issue.
An ideal screening test finds a disease in its earliest stages, before it produces symptoms — but it also saves lives. Breast cancer has mammography; cervical cancer has the Pap test; colon cancer has the colonoscopy.
But a screening test for early lung cancer remains elusive.
Researchers have considered chest X-rays and sputum tests that look for cancer cells in saliva; neither has been shown to prevent lung cancer deaths.
One test, however, holds some promise: the spiral CT scan or spiral computed tomography, which uses X-rays to scan the chest in a matter of seconds.
The patient lies on a table and a large doughnut-shaped scanner rotates around the body. A computer uses information from the scanner to produce a three-dimensional picture of the lungs; different colors can be assigned to specific features within the body, making for a detailed image. Some machines can detect tumors smaller than a grain of rice.
Earlier this month, the National Cancer Institute released new results from a large clinical trial that showed using spiral CT scans in smokers and former smokers decreased lung cancer deaths by 20 percent.
That's good news and serves as the first glimmer of hope for a reliable screening test for the leading cancer killer in the country.
"The images are superb," says Dr. Reed Murtagh, a diagnostic radiologist and professor of radiology and oncology at Moffitt.
But it is not without risk. "The radiation dose is high, really high," Murtagh said. "That has to be weighed against the benefits."
Plus, CT scans are expensive, from several hundred dollars up to $1,000 each, and they are not always covered by insurance. Even more problematic, the scans are so sensitive they pick up benign abnormalities like scars from past infections such as pneumonia. The NCI estimates that 25 to 60 percent of spiral CT scans of smokers and former smokers show noncancerous lesions. That can lead to unnecessary, potentially risky procedures like biopsies or even major surgery.
"How do we differentiate between scars and tumors?" Alberts asks. "False positives are a big problem."
That's why doctors are still cautious about ordering spiral CT scans and only recommend them for the highest-risk patients, such as long-term, heavy smokers. Scientists are trying to find a low-dose scan that gives similar detail and the same excellent pictures, Murtagh said.
Meanwhile, doctors say the best defense against lung cancer is to never smoke or stop smoking now. And familiarize yourself with the symptoms of lung cancer: a persistent cough; coughing up blood; persistent dull, aching chest pain; shortness of breath; wheezing; and hoarseness.
Irene Maher can be reached at email@example.com.