2006-04-15 / Columnists

Maintaining Your Health on Mackinac

Primary Lung Cancer Does Occur in Nonsmokers
By Yvan Silva, M.D.

Primary lung cancer, that is, cancer originating in the lung, is thought to be so closely tied to smoking so that there is surprise when cases are reported in nonsmokers. Often they do not fit the mold; in public opinion, lung cancer is unequivocally caused by smoking. In fact, most doctors also think so. The first question asked is the smoking history, and doubt is expressed if non-smoking is claimed. If not smoking, what could have caused the cancer?

In reality, there are 180,000 cases of lung cancer diagnosed every year. Statistics reveal that about 80 percent occur in smokers, leaving 36,000 cases diagnosed in nonsmokers. There are around 150,000 deaths from lung cancer overall and 30,000 of these occur in nonsmokers. The latter figure

relates to prostate, breast, and colorectal cancer; thus, cancer in nonsmokers is as significant as these three cancers and the causes are important to consider.

Exposure to asbestos released in the atmosphere breathed by people in demolition, renovation of buildings, or released in older buildings is carcinogenic. Workers exposed on a chronic basis have a sevenfold risk for developing and dying from the disease. When coupled with smoking, these individuals' risk rises to 50 to 80 times that faced by people in general.

Indoor radon emitted into homes built over soil with natural uranium deposits can accumulate high levels indoors, increasing the risk two to three times for residents with long term exposure.

There has been much written about second-hand smoke. Chronic exposure in the home or workplace, especially where concentrations are chronically high, can elevate the risk 20 percent to 30 percent. Bans on smoking in the workplace, in public buildings, and other sites are expected to lower this risk.

There are several carcinogens that may exist in the workplace and are known to affect us, on a chronic basis, such as inhaled chemicals like beryllium, vinyl chloride, nickel chromates, mustard gas, chromo ethyl, and arsenic ethers; radioactive substances like uranium, and fuels like gasoline and diesel fumes.

There is no direct evidence relating to dietary factors, but a diet deficient in fruits and vegetables may increase the risk. Dense environmental pollution in crowded areas and in industrial areas may slightly increase risks.

Research in genetics and their role in cancer causation are providing new clues. People with a strong family history of lung cancer may share a genetic susceptibility and develop the disease even if they do not smoke. There is an increasing incidence in women nonsmokers that can be attributed to gender, as estrogen receptors have been found in lung cancer cells. There are more women nonsmokers.

The practical aspects of early diagnosis and treatment are imperative. Usually, by the time a lung cancer causes symptoms it can be too far advanced to be cured. A chronic cough that persists in spite of usual treatments should be regarded with suspicion. Shortness of breath, similarly, should be further investigated beyond cardiac conditions such as congestive failure. The main hope for long term survival lies in detection when the tumor is small and confined to the lung where it arose. There are no reliable screening methods for early detection of lung cancer in the broad population.

The first criterion is to suspect lung cancer, especially in nonsmokers, when respiratory symptoms persist. Chronic cough or hoarseness of voice persisting beyond three to four weeks requires medical attention. Yet, although lung cancer causes chronic cough, it accounts for only two percent of these cases. Coughing up blood is a serious symptom and generally requires bronchoscopy, in which a fiber optic scope is used to visualize the bronchial tubes. Chest Xrays and sputum analysis for cancer cells when used for screening have failed to save lives by early detection. A relatively new test, the spiral CT scan of the chest, is currently being evaluated in a national study of 50,000 individuals, smokers and former smokers, to see if there is a potential for early detection. At the present, it is not thought to be reliable for screening purposes because of the incidence of false findings that can lead to further testing.

There two broad cell types of lung cancer, small cell, most often related to smoking, and non-small cell, which can occur in smokers and nonsmokers. The latter type is subdivided into two categories, adenocarcinoma in smokers and former smokers, and squamous cell carcinoma. Another cell type, bronchiolar carcinoma, is being seen more often in women who have never smoked; it is a diffuse process in the lung that can even occur in several sites without the occurrence of a discrete tumor. Overall, there is progress in treating even advanced lung cancer.

The future of research in this area may lie in testing of sputum for genetic changes, certain protein markers, or organic chemicals that identify with lung cancer. Clearly, careful medical testing with available technology when chronic symptoms persist is important. A high index of suspicion when there are risk factors is warranted, in smokers and nonsmokers alike. For now, it is clear that in order to reduce cancer deaths, in the order of 400,000 per year, the best way is for people to stop smoking.

Dr. Silva is a professor of surgery at Wayne State University and a resident of Woodbluff on Mackinac Island.

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