Modern Diagnostics Help Detect Cancer Early

by Food and Drug Administration (FDA)

Cancer is perhaps the disease Americans fear most. Our second leading cause of death (after heart disease) seems so formidable, so invincible a threat, that many dread it as "The Big C." But this notion of the disease is often not realistic in this "high-tech" age, and the exaggerated dread it instills may be counterproductive.

There are many kinds of cancer, not all inevitably fatal. Our increasing ability to detect and distinguish among them saves more lives every year.

It's more accurate to speak of various cancers rather than of cancer as a monolith, for there are some 200 such conditions, in which unrestrained growth of cells in an organ or tissue of the body causes a wide range of symptoms. Perhaps 90 percent of cancers are carcinomas, malignant tumors arising in the cells of the surface layer or lining of an organ. These cancers cause the palpable lumps so closely identified with the disease that some use "cancer" and "carcinoma" as if they were identical. Other kinds of cancer include:

Lymphoma, cancer of the immune system, usually appearing in the lymph node tissue.

Myeloma, a rare cancer of the immune system appearing in the bone marrow.

Leukemia, "cancer of the blood" that affects oxygen-bearing white blood cells and in which abnormally growing cells are scattered throughout the body rather than concentrated in a single tumor.

Sarcoma, a relatively rare cancer in supportive tissue, such as cartilage, muscle, bone, or fat.

The relation of cancer to environmental factors has been known since the 18th-century surgeon John Pott traced the high incidence of scrotal cancer among chimney sweeps to their exposure to soot. For generations, mushroom growers in France, who apparently nibble their fibrous crops on the job, have claimed that they have almost no incidence of cancers, owing to their diet.

Hereditary factors also come into play. The recent death from pancreatic cancer of Gloria Spann, sister of former President Carter, suggested a genetic susceptibility in a well-known American family. Her father, a brother, and a sister died of the same disease, while her mother died from a primary breast cancer that spread to other organs, including the pancreas.

Treatment Helps

The earlier a cancer is detected, the likelier it is to respond to treatment. Unfortunately, this is easier with some cancers than with others. Early ovarian cancer is one with no symptoms to warn of its growth, so it's rarely detected before an advanced stage.

Even cancers that exhibit warning signs aren't always recognized in time for the most effective therapies. So strong is the dread of cancer that many people shy from self-examination techniques for fear that they will reveal the disease. Some men shun examining themselves for testicular cancer (most prevalent from ages 15 to 34) just as some women avoid probing for breast cancers. Even when such simple self-examinations are performed conscientiously, they can detect only tumors large enough to feel, which are therefore already somewhat developed.

About 80 percent of breast lumps are not cancerous. Timely, accurate diagnosis through physician examination and mammography screening (see accompanying article, "Protecting Yourself from Cancer") thus can relieve anxiety as well as detecting more dangerous tumors.

Early detection increases survival rates for some cancers dramatically. The survival rate for early melanoma (a skin cancer) is 90 percent, but it decreases to under 40 percent in the later stages. If all melanomas were detected while still small and confined to one area, the cure rate could approach 100 percent. Three-fourths of colon or rectal cancer patients could be saved by early detection.

"If you can find things early enough, you can make a big difference in outcome," generalizes Peter Shields, M.D., of George Washington University Medical Center, who is devoting a fellowship at the National Cancer Institute to refining means of finding out which individuals might be most susceptible to which cancers.

"The truth is that some cancers can be resected [excised] at an early time and cured," says Shields as he dabs samples onto laboratory slides. Testicular cancer, he notes, is particularly receptive to chemotherapy; like some other cancers, it can be cured completely.

Shields works on devising tests to determine who is at increased risk of developing a cancer. He studies oncogenes, which in many cases started as normal genes regulating cell growth. Mutations can turn such a gene into one that permits uncontrolled growth: an oncogene. Suppressor genes, which inhibit cell growth, oppose oncogenes. By comparing these genetic variations in people not afflicted with cancer and in those who are, he tries to find which factors may predispose individuals to cancers.

"The field is called biochemical epidemiology, and we are specifically interested in things that happen to your genes that would increase your risk of cancer. Why is it," he wonders, "that some people who smoke get lung cancer and some don't? Why do some workers who are exposed to certain compounds get bladder cancer and others don't?"

Heredity, lifestyle and environment are all factors in the search. Microscope slide by slide, Shields and his colleagues around the world painstakingly sift the possibilities.

The reason early detection can be so critical isn't simply that the growth of a tumor may be arrested. Timely response can head off metastasis, the migration of tumor cells through the blood and lymph system to other parts of the body. Undetected, the cancer thus can spread not just into adjacent tissue but even to distant organs.

Metastasis is partly what distinguishes a damaging malignant tumor from a "benign" tumor, which may grow more slowly and doesn't travel through the system. But even a benign tumor can prove fatal if located in the wrong place — for instance, the brain.

About the Author

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