At the time the NCA was passed 35 years ago, the term chemoprevention - using drugs to prevent cancer in those at high risk - had yet to be coined. The first results from a chemoprevention clinical trial wouldn't be published until 1990 (an analog of vitamin A to prevent mouth and throat tumors), but by the end of that decade, the Breast Cancer Prevention Trial would demonstrate that, compared with placebo, tamoxifen cuts the risk of breast cancer nearly in half in women at increased risk, a result that led it to be the first drug approved by the FDA for cancer risk reduction.

Since then, exciting results have also been seen in chemoprevention trials for prostate and colon cancer, while the STAR trial, published earlier this year, showed that the osteoporosis drug raloxifene was as effective as tamoxifen at reducing breast cancer risk, but with fewer serious side effects.

"Medical approaches to cancer prevention have taken hold and are an exciting research frontier," says Dr. Peter Greenwald, director of NCI's Division of Cancer Prevention.

As the chemoprevention results demonstrate, the science of prevention has matured tremendously since the NCA was enacted. Improvements in statistical methods, for instance, have allowed researchers to determine with a good degree of certainty whether factors such as alcohol consumption, smoking, dietary and physical activity patterns, workplace exposures, and others increase - or decrease - the risk of certain cancers.

Improvements in technology that have allowed researchers to more closely scrutinize the molecular machinery of cancer have helped identify mutated genes that put a person at increased risk of specific cancers - the most well known and well studied of which may be BRCA1 and BRCA2 in breast and ovarian cancer.

Meanwhile, for several cancer types, improvements in screening have allowed clinicians to detect cancers, or precancerous conditions, at very early stages, resulting in vastly improved outcomes for many thousands of patients.

Of the advances made over the last 35 years in cancer prevention, the substantial reduction in smoking prevalence has been among the most important.

Dr. Robert Croyle, director of NCI's Division of Cancer Control and Population Sciences, cites numerous factors that helped to bring about this reduction, including higher taxes on tobacco products, restrictions on smoking in workplaces and public places, comprehensive state-based tobacco control programs, local and national antismoking campaigns, and effective treatments for nicotine dependence.

"Research funded by NCI has helped us understand that, to be effective, we need to impact the individual and change the environment to support a nonsmoking norm," Dr. Croyle said.

This year marked a truly remarkable prevention milestone: the FDA's approval of an HPV vaccine, which protects against the two HPV types that are responsible for 70 percent of all cases of cervical cancer and is the first-ever vaccine designed specifically to prevent cancer.

As Dr. Greenwald stresses, though, the last three decades of cancer prevention research have made one conclusion abundantly clear: "More and more evidence has established that the way you live your life affects your chances of getting cancer.

"The key things most people should do are eat smaller portions of food, establish a balanced diet, limit high-calorie drinks, exercise throughout life, and, of course, don't start smoking and, if you do smoke, stop."