Washington, Jan 1 (IANS): Driven by declines in smoking rates, cancer mortality in the US has dropped 22 percent over two decades, a new report says.

The American Cancer Society's annual cancer statistics report estimated that this drop in cancer mortality led to the avoidance of more than 1.5 million cancer deaths that would have occurred if peak rates had persisted.

"The continuing drops we are seeing in cancer mortality are reason to celebrate, but not to stop," said John Seffrin, PhD, chief executive officer of the American Cancer Society.

Largely driven by rapid increases in lung cancer deaths among men as a consequence of the tobacco epidemic, the overall cancer death rate rose during most of the 20th century, peaking in 1991.

The subsequent, steady decline in the cancer death rate is the result of decline in smoking, as well as advances in cancer prevention, early detection, and treatment.

During the most recent five years for which data are available (2007-2011), the average annual decline in cancer death rates was slightly larger among men (1.8 percent) than women (1.4 percent).

These declines are driven by continued decreases in death rates for the four major cancer sites: lung, breast, prostate, and colon.

However, the report also estimated that there will be 1,658,370 new cancer cases and 589,430 cancer deaths in the United States in 2015, corresponding to about 1,600 deaths per day.

Prostate, lung, and colorectal cancers will account for about one-half of all cases in men, with prostate cancer alone accounting for about one-quarter of new diagnoses.

The three most commonly diagnosed types of cancer among women in 2015 will be breast, lung, and colorectal cancer, accounting for one-half of all cases in women, the report added.

The findings appeared in CA: A Cancer Journal for Clinicians and its companion Cancer Facts & Figures 2015.