“The mortality trends reflected in our current report, including the largest drop in overall cancer mortality ever recorded from 2016 to 2017, reflect prevention, early detection and treatment advances that occurred in prior years,” Gary M. Reedy, the American Cancer Society’s chief executive, said in a statement.

Experts attributed the decline in mortality to reduced smoking rates and to advances in lung cancer treatment. New therapies for melanoma of the skin have also helped extend life for many people with metastatic disease, or cancer that has spread to other parts of the body.

Mr. Reedy said that, since taking office, the president had signed multiple spending bills that increased funding for cancer research at the National Institutes of Health and National Cancer Institute. But, he said, “the impact of those increases are not reflected in the data contained in this report.”

The White House did not immediately respond to a request for comment on Saturday.

Mr. Trump’s critics pointed out that he had also proposed deep cuts in cancer research funding.

In his first budget in 2017, he called for a reduction of $5.8 billion, or 18 percent, from the National Institutes of Health, which fund thousands of researchers working on cancer and other diseases. Congress rejected the cuts and members of both parties joined forces to increase spending on biomedical research.