In patients tracked for as long as 20 years, the mortality rate from colorectal cancer was cut by 53 percent among those who had had precancerous growths, called adenomatous polyps, removed during those exams, researchers reported on Wednesday in The New England Journal of Medicine. The exams involved inspecting the large intestine with a camera-tipped tube. Earlier studies have shown that removing precancerous polyps can drastically reduce the incidence of colorectal cancer. But a major question remained: Does removing polyps really save lives? Theoretically, it is possible that if doctors remove growths, patients will not die from them, or at least not as many will die. A research team led by Dr. Sidney Winawer of Memorial Sloan-Kettering Cancer Center in New York followed 2,602 patients whose precancerous polyps were removed during colonoscopies from 1980 to 1990. They compared their death rate from colorectal cancer with that expected in the general population, in which 25.4 deaths from the disease would have been anticipated in a group of the same size. But in the polyp group, only 12 people died from colorectal cancer, reducing the death rate by 53 percent. "For any cancer screening test, reducing cancer-related mortality is the holy grail," said Dr. Gina Vaccaro of the Knight Cancer Institute at Oregon Health and Science University, who studies gastrointestinal tumors and was not involved in the study. "This study shows that there is mortality reduction if polyps are removed, and 53 percent is a very strong reduction." Colorectal cancer is one of the leading causes of cancer death in the United States and one of the few cancers that is largely preventable and detectable through screening. This year, more than 143,000 new cases and 51,000 deaths are expected. The incidence and death rates have dropped for about 20 years, possibly because of increased use of screening tests and better treatments. But only about six out of 10 adults have been screened for colorectal cancer, according to federal estimates. While doctors differ on which method is best, they agree it is important to get screened, starting generally at age 50. Screening is worthwhile because colorectal cancer is one of the few kinds (along with cervical and skin cancers) that has a defined precancerous condition that can be detected and cut out. Studies show that not every polyp becomes cancer, but almost every large tumor begins as an adenomatous polyp. "This study puts that argument to rest," said Dr. David Rothenberger, a professor and chairman of surgery at the University of Minnesota Masonic Cancer Center, who was not involved in the study. Even when colon cancer has developed, it still can be cured if caught and treated early. The new study did not compare colonoscopy with other methods of screening for colorectal cancer, so it does not fully resolve the longstanding medical debate over which method is best. Tests besides colonoscopy look for blood in stool or use different techniques to examine the large intestine. All the tests are unpleasant, and people often resist having them. "Not all adenomas turn into cancer, and not all cancers lead to death," said Ann Zauber, the study's lead author and a biostatistician at Sloan-Kettering. But in many cases, she said, "We've gotten those that have the potential to go on and lead to cancer death." Cancer screening has come under more rigorous scrutiny recently. In October, a government expert panel recommended that people stop getting a blood test for prostate-specific antigen to screen for prostate cancer after concluding that it was not saving lives. The new study on colonoscopies has limitations -- it was not a randomized clinical trial, though some experts say it was as well done as such trials and helps answer questions about the procedure's effectiveness. "This is a big deal," said Robert Smith, senior director of cancer control at the American Cancer Society. The new study provides what some experts call the best evidence yet that colonoscopy -- perhaps the most highly regarded screening test -- prevents deaths. Although many have assumed that colonoscopies must save lives because they are so often recommended, solid proof has been lacking until now. Related theme articles: All job seekers 5 million pixel camera If detected early