NEW YORK — A new look at cancer in the U.S. finds that nearly half of cancer deaths are caused by smoking, poor diet and other unhealthy behaviors.That's less than commonly-cited estimates from more than 35 years ago, a result of new research methods and changes in American society. Smoking rates have plummeted, for example, while obesity rates have risen dramatically.The study found that 45 percent of cancer deaths and 42 percent of diagnosed cancer cases could be attributed to what the authors call "modifiable" risk factors. These are risks that are not inherited, and mostly the result of behavior that can be changed, like exposure to sun, not eating enough fruits and vegetables, drinking alcohol and, most importantly, smoking.A British study conducted in 1981 attributed more than two-thirds of cancer deaths to these factors.The study used 2014 data and was conducted by the American Cancer Society.