* Deaths rates fell an average 1.5 percent per year, 2000 to 2009 * In men, mortality rose for melanoma, cancers of liver and pancreas * Much of improvement in incidence, mortality reflects less smoking By Sharon Begley NEW YORK, Jan 7 (Reuters) - As the United States enters the fifth decade of its "war on cancer," deaths continue to decline, according to an exhaustive report based on official data released on Monday.