Only lung cancer takes more American lives, but no one likes to think about cancer developing "down there," in the large intestine, or colon. Among cancers, this one stands out as a disease that can be largely prevented, but few people believe colon cancer will happen to them. Fear, denial, ignorance all work against it. Health officials estimate that the death toll from colon cancer could be cut in half with widespread screening and early detection, but that message hasn't gotten across to the public. Who likes to talk about enemas and bowel movements, or even say the words -- rectum, anus. Until now, colon cancer has been a silent cancer in the U.S. Much more attention has been focused on breast cancer and prostate cancer. Senators and generals go public to urge their colleagues to get screened for prostate cancer. The month of October is officially designated Breast Cancer Control Month and National Breast Cancer Awareness Month by federal legislation. Those are the high-profile cancers. No one wants to talk about colon cancer. They should. Not just because of the numbers, though the toll is high: 131,200 new cases each year; 54,900 deaths. But because colon cancer is highly preventable and treatable. If the cancer is detected early, more than 90 percent of patients survive five years or more after diagnosis. If the cancer has spread to other organs, survival plummets to less than 10 percent. And because colon cancer is the test case for cancer genetics. So far three genes have been discovered and genetic tests are available for people who are at risk of carrying the gene because of their family history. But the revolution in genetics is so new, researchers are still sorting out how to use this information for better in medicine, not worse. As with many aspects of good health, the main responsibility for confronting the risk of colon cancer lies with the individual. The steps are straightforward: Know your risk, which includes family history and genetic makeup. Get screened so that if you have a colon cancer, you can find out in time to do something about it. It's why health officials are taking aim at colon cancer. And why the Health section is devoting a whole issue to the cancer no one wants to talk about. Yet. CAPTION: ON THE COVER: Starting with the top row, from left to right: Ronald Reagan was diagnosed in 1985, during his second term as president. Rudy Perpich, former governor of Minnesota, died in 1995. Boog Powell, former Oriole slugger, was diagnosed 1997. Barbara Barrie, actress, was diagnosed in 1994. Cleavon Little, actor, died in 1992. Donald Hall, poet, was diagnosed in 1989. Letitia Baldrige, etiquette expert, was diagnosed in 1978. Morris Siegel, sportswriter, died in 1994. Arshile Gorky, abstract painter, was diagnosed with colon cancer and committed suicide in 1948. Tammy Faye Bakker, former evangelist, was diagnosed in 1996. Jay Monahan, NBC commentator, died in 1998. Quentin Burdick, senator, was diagnosed in 1988 and died of heart failure in 1992. Ida Lupino, actress, died in 1995. John Tower, former senator, was diagnosed in 1989 and died in a plane crash in 1991. John Hersey, author, died in 1993. Paul Nitze, presidential adviser, was diagnosed in 1993. Ben Hogan, professional golfer, died in 1997. Thomas P. (Tip) O'Neill, former Speaker of the House, was diagnosed in 1987 and died in 1994 of cardiac arrest. Eric Davis, Orioles outfielder, was diagnosed in 1997. Pat Paulsen, comedian, died in 1997 of colon and brain cancer. Audrey Hepburn, actress, died in 1993. Albert Lasker, philanthropist, died in 1952. Steve Allen, entertainer, was diagnosed in 1982. Edward Bennett Williams, Washington lawyer, died in 1988. Sala Burton, U.S. representative, died in 1987.