Colorectal cancer: a threat worth watching.

Are you over 50? Then you're in the age group most at risk for the nation's second most deadly cancer - a cancer that strikes one in every 20 at some time in their lives.

Each year thousands of people learn they have cancer of the colon or rectum, the two organs that form the large bowel and move solid waste out of the body. Colorectal cancer accounts for 15 percent of all cancer diagnoses, and only lung cancer and common skin cancer occur more frequently.

The bad news about colorectal cancer is that in the past 15 years cases have climbed four percent per capita. Doctors believe the increase seen in industrialized nations can be linked to urban lifestyles and high-fat, low-fiber diets.

The good news is that deaths per capita have declined 11 percent, due to earlier detection and more effective treatments. Even so, more than 60,000 persons succumb each year to colorectal cancer; only lung cancer kills more often. If you're a nonsmoker, then statistics suggest colorectal cancer is a threat worth watching. Here are the top risk factors:

* Age. The incidence of colorectal cancer begins to rise after age 40 and increases markedly after 50; fewer than six percent of all cases occur before that age. The average age at the time of diagnosis is 60.

* Race and gender. On a per capita basis, colon cancer is more common among Blacks than Whites, while the reverse is true about rectal cancer. However, both cancers happen at a higher rate among men than women.

* Lifestyle. Colorectal cancer is more common in densely populated, industrialized regions than in rural areas. The United States has the highest incidence of the disease, followed by Canada and Europe. By contrast, colorectal cancer is unusual in Africa, Latin America, and Asia except in urban areas, where the rate is higher.

* Diet. When you don't eat enough fiber or roughage, waste material has a harder time moving through the bowel. And when you eat too much fat, doctors believe your body creates more bile acids to help digestion. How these processes may relate to the onset of colorectal cancer is not fully understood, but many studies suggest a link between a person's diet and the disease.

Eating meat, including fish, that's fried, smoked, grilled, or cooked at high temperature is also a possible risk factor that researchers are studying. No link has been proved, but doctors worry that these cooking methods may create cancer-causing chemicals in meats. Diets high in protein, which the body must break down by producing excess digestive compounds, are also a potential concern.

* Heredity. Geneticists believe an inherited tendency toward colorectal cancer is a contributing factor in less than one in 14 cases. For family members of patients with colon cancer, the risk of developing the disease is three to four times greater than the general population. And in families where a parent has developed colon cancer at an unusually early age, children face a nearly 50 percent chance of the same malady.

* Polyps. These growths are small tumors that form inside the colon or rectum. If benign, they may interfere with normal bowel functions, but they do not spread to other parts of the body and are seldom life-threatening. Yet some may have the potential to become cancerous, especially if they grow beyond an inch in diameter. The National Cancer Institute (NCI) notes that "most, perhaps all, colorectal cancers develop in polyps."

What can I do now? Colorectal polyps occur in an estimated 20 to 35 percent of all adult, and in one third of adults over the age of 50. The danger can't be ignored, but you can do much to reduce the risks:

* Eat smart. Increase your fiber intake (20 to 30 grams per day is recommended), and cut fat consumption to less than 30 percent of your daily calories. Watch meats that are fried, smoked, grilled, or cooked at high temperature. In general, follow a balanced diet.

As a possible cancer preventative, NCI is testing two diet-related strategies. First, researchers are looking at the effects of calcium, beta-carotene, and vitamins A, C, and E in shrinking or reducing the recurrence of colorectal polyps. And second, the agency is testing whether a modified diet can keep surgically removed polyps from recurring.

* Get checked. Whatever your age, at regular checkups have your doctor do a digital rectal exam. Then, beginning at age 50, have an annual fecal occult blood test to check for hidden (occult) blood in your stool. And every three years schedule a sigmoidoscopy, by which your doctor uses a thin, lighted tube to examine the rectum for polyps. If you have a family history of colorectal cancer, however, talk with your doctor about starting these tests even earlier.

* Exercise. People who tend to sit the majority of their workday or remain inactive in their leisure time have a 30 to 100 percent greater risk of colon cancer.

* Watch the symptoms. Warning signs for colorectal cancer include a change in bowel-habits; diarrhea, constipation, frequent gas pains, or a feeling that the bowel does not empty completely; stools that have blood or are narrower than usual; general stomach discomfort; unexpected weight loss; and constant tiredness. Ulcerative colitis, a disease that inflames the bowel lining, also greatly increases the risk of colorectal cancer.

These conditions are also caused by other problems such as ulcers, an inflamed colon, or hemorrhoids. To determine the cause, your doctor may examine the bowel region using either X-rays or a flexible lighted colonoscope. The scope can be used also to remove any polyps found, which are then lab-tested to check for cancer cells.

What if I have cancer? In recent years, says NCI, the outlook for persons with colorectal cancer has improved steadily. Compared to 20 years ago, the number of patients who survive at least five years has risen from less than half to nearly 60 percent. The difference is early detection and today's more effective treatments.

If a biopsy detects cancer, your doctor will conduct staging examinations, using X-ray, ultrasound, or CAT scans. Lungs, liver, and lymph nodes are also checked, since colorectal cancer tends to spread to these organs. The current stage of the disease is judged by the TNM standard: Tumor size, lymph Node spread, and Metastasis, or overall spread of the cancer.

Surgery is the most common treatment for colorectal cancer. Most patients undergo a partial colectomy, in which the surgeon removes the cancerous portion of the colon or rectum, then later reconnects the healthy portions after they heal. Only about 15 percent of patients need a permanent colostomy, so that stools must go through the abdomen into a collection bag. When cancer is found early, surgery is often the only treatment needed.

Want to know more? NCI's Cancer Information Service offers two free booklets about cancer of the colon and rectum, What You Need to Know and Research Report. Call 1- 800-4-CANCER.