The death rate for cancer in the United States has dropped 22 percent from a peak in 1991, new figures released by the American Cancer Society indicate.

That percentage translates to more than 1.5 million cancer deaths avoided, the society says in its "Cancer Statistics 2015," which both reports previous figures and estimates numbers of new cancer cases and deaths that are expected to occur in the United States in the coming year.

A total of 1,658,370 new diagnoses of cancer and 589,430 cancer are predicted to occur in the U.S. in 2015, according to statistics published in the society's journal CA: A Cancer Journal for Clinicians.

During the most recent 5 year period for which there are figures (2007-2011), new diagnosed cancer cases fell by 1.8 per year in men and remained the same in women, while cancer death rates were reduced by 1.8 percent per year in men and 1.4 percent in women.

Despite those encouraging figures, the society's report predicted cancer would overtake heart disease within just a few years as the leading cause of death in the United States.

That's because "the decrease in mortality rates from heart disease has been much larger than the decrease in mortality from cancer," says Dr. Ahmedin Jemal, the society's vice president of surveillance and health services research.

"Cancer is a collection of maybe 200 diseases," he explained. "It's not like heart disease, where you have maybe some variation but it is a single entity compared to cancer."

In 2011, more than 308,000 men and 288,000 women in the United States died from heart disease, while cancer claimed the lives of more than 302,000 men and 274,000 women.

A major factor in the reduction of cancer death rates has been a trend of American's being convinced to quit smoking, Jemal says, with the smoking rate having been halved.

Just one in five people in the U.S. are now smokers, and the rate of lung cancer deaths fell 36 percent from 1990 to 2011 for men, and 11 percent in a similar period for women, the society reports.

Cancer rates have also been reduced through the increased utilization of early detection tests including colonoscopy, mammography and cervical exams, Jemal noted.

"Really, it's due to screening, as well as improved treatment," he says. "It's really remarkable."

However, there were geographical differences in the rates of cancer death declines, the society found, with the smallest declines -- about 15 percent -- generally occurring in the South, while the biggest advances took place in Northeastern states.