Cancer will become the leading cause of death in the nation early this century, and a new School of Public Health Web site hopes to help visitors assess their likelihood of facing the disease themselves.

A team from Harvard's Center for Cancer Prevention (CCP) designed the site, located at www.yourcancerrisk.harvard.edu, to show users how to adjust their lifestyle to decrease the risk of developing cancer.

"We hope this will become the leading cancer prevention Web site for people who want to know what they or members of their family can do to protect themselves against cancer," said Dr. David J. Hunter, CCP director.

After choosing which form of cancer (currently breast, lung, colon, or prostate) to evaluate, users submit a brief survey on diet, medical and family history. The Web site then returns an estimate of risk relative to others of the same age and gender.

Based on the results of the questionnaire, the Web site recommends behavioral changes, such as a healthier diet or increased exercise, that may help reduce cancer risk.

But some professionals have warned that a Web site, rather than a in-person professional consultation, may lead to misinformation and lack of follow-up.

Even people evaluated with "very much above average" risk, the highest possible risk designation, will be told that this "doesn't mean you'll definitely get cancer...If you have any concerns, talk to a doctor."

One genetics counselor, who asked that her name not be used, worried that users may misinterpret these risk assessments.

"Some people may freak out and be too scared to approach their doctor about it or some people may be falsely reassured [by a low risk assessment]," she cautioned in an e-mail message.

"On the other hand," she continued, "it may motivate people to speak with their doctors or do appropriate surveillance for cancer, and it may provide some reassurance for people who may be overestimating their true risk."

But Hunter emphasized that the purpose of the Web site is to alert people to the risk factors of cancer, catching them before treatment is necessary.

"We're not in the business of diagnosing symptoms...We're in the business of years before [possible cancer development] telling people what to do," he said.

But he did say that the Web site is targeted at people 40 and over. If a user enters an age of less than 40, the site cautions that a risk can only be estimated for later in the user's life, based on one's current lifestyle.

"It's not perfect for college students because a lot of the risks are in the future," said Michael Thune, who heads epidemiological research for the American Cancer Society.

However, "what is useful is that the appropriate time to think about cancer prevention is during one's life, not when you get cancer, so it identifies something you can do," he added.