Yale doctor says lung cancer cannot be detected before symptoms appear
Despite advances in surgery, chemotherapy and radiology, the best way to beat cancer is early detection, before the malignancy has had a chance to spread.
Mammograms, Pap smears, protein specific antigen in menâ€™s blood and colonoscopy are among the dozens of tests to identify cancer well before symptoms appear.
But there is no effective way to screen for the deadliest kind of cancer in the United States.
Lung cancer kills more men and women every year than any other cancer.
Almost all could be prevented if people stopped smoking cigarettes, said Dr. Lynn T. Tanoue, assistant professor and lung cancer expert at the Yale School of Medicine.
About 25 percent of smokers will acquire a related disease, including about 6 percent who will develop lung cancer.
Cessation is difficult, however, so the toll continues.
In Connecticut, 7,010 people died of cancer in 2004, based on the most recent numbers from the American Cancer Society.
Out of that figure, 1,850 succumbed to cancer of the lung and bronchial tubes -- more than one quarter of all cancer deaths in the state.
Tanoue said cigarette smoke contains at least 4,000 chemicals, many of which are carcinogenic.
"Lung cancer is a multi-hit problem. DNA is damaged and repaired. Sometimes that doesnâ€™t work," she said.
Damaged DNA, a genetic predisposition and a compromised DNA repair system can lead to the formation of cancer, she said.
"Colon, prostate and breast cancer have screening. Thereâ€™s no way to screen for lung cancer," Tanoue said.
Existing methods are either insufficiently sensitive or reveal too much.
X-rays do not seem to detect lung cancer effectively. Another X-ray imaging system, computerized tomography, is too sensitive, she said.
CT scans pick up many abnormalities in the lungs, a great majority of which are not cancerous or dangerous, she said.
One study at Cornell University found that 23 percent of people screened showed an abnormality.
Of that fraction, 2.7 percent were cancer.
A similar study of screening at the Mayo Clinic disclosed abnormal lung lesions in 51 percent of participants. Of that group, 1.4 percent had lung cancer. The Early Lung Cancer Action Program screened 26,000 people with CT scans.
Three hundred cases of cancer were revealed with 82 percent at the most curable stage 1.
That means slightly more than 1 percent had cancer.
"To find people with early stage lung cancer, you need to distinguish between benign and cancerous tissue," Tanoue said.
In practice, CT scanning did find early stage lung cancer but many more benign lesions, she said.
Almost everyone has them. Some are small scars left by viral infections, others are areas of inflammation and still more are non-cancerous tumors of various kinds.
"Now with CT scan, screening would lead to unnecessary surgery for benign lesions. It would cost $15 billion a year for the 50 million current and past smokers in the U.S.," Tanoue said.
Physicians could note suspicious lesions and follow them until their nature becomes clear, but this would create enormous and needless anxiety in patients, she said.
Most lung cancers arise from the mucus-producing cells that line the lungs.
There are two basic types: small-cell and non-small-cell.
Small-cell spreads more rapidly, but since its cells divide more frequently, it is more vulnerable to chemotherapy.
Apparently, more cancers are forming in the smaller air sacs of the lungs rather than in the airway, Tanoue said.
Treatments include surgery, chemotherapy and radiation. About 15 percent of lung cancer patients survive for five years.
That includes about 49 percent of those patients whose lung cancer is found early. After the tumor spreads beyond the lungs, the five-year survival rate sinks to 16 percent.
Once lung cancer reaches other parts of the body, the five-year rate is a dismal 2.1 percent.
Only pancreatic cancer has a worse prognosis. Stomach and esophagus cancers are also among the least survivable.
Men and women did not realize the dangers of lung cancer when smoking became popular during World War II.
Twenty years passed before the U.S. Surgeon General issued the 1964 report linking smoking with lung cancer. Smoking is also increases the risk of chronic bronchitis, emphysema and heart disease.
At one point, 60 percent to 70 percent of men smoked. Since 1991, the number of male smokers has decreased.
Female smoking rose during the 1970s, and in 1985 lung cancer surpassed breast cancer as the leading cause of cancer death in women.
Although the many health risks of smoking are well known, people continue because they are addicted to the stimulant nicotine, Tanoue said.
Cigarettes are also an appetite suppressant, and many smokers say the habit relieves stress.
"You donâ€™t quit unless you really want to quit," Tanoue said.
Positron emission tomography, magnetic resonance imaging and advanced CT all hold promise as future diagnostic tools, she said.
"Maybe weâ€™ll be able to see metabolic abnormalities in the future," she said.
Meanwhile, smokers and others who think they may be at higher risk for lung cancer should consult their physicians, Tanoue said.
"There are no guidelines for screening, and none will be ready for years," she said.