New York – The cancer mortality rate in the United States has reached an important milestone: it has been declining for at least 25 years, according to a new report.

Smoking less result in fewer deaths. Advances in early detection and treatment also have a positive impact, experts say.

But that's not all good news. Obesity-related cancer deaths are on the rise and prostate cancer deaths are no longer declining, said Rebecca Siegel, senior author of the American Cancer Society's report released Tuesday.

Cancer is also the second killer of the nation. The company predicts that there will be more than 1.7 million new cases of cancer and more than 600,000 cancer deaths, in the United States this year.

There has been a lot of bad news lately about Death rate in the United States. In 2017, recent data released by the government resulted in an increase in deaths from seven of the top 10 causes of death. But cancer has been a kind of positive point.

The country's cancer death rate has increased until the early 1990s. Since then, it has dropped by 27% between 1991 and 2016, reported the Canadian Cancer Society.

Lung cancer is the main reason. Among cancers, it has long killed most people, especially men. But the lung cancer mortality rate has fallen by nearly 50% among men since 1991. This is a delayed effect of the decline in smoking that began in the 1960s, said Siegel.

David Spigel, senior scientist at the Sarah Cannon Research Institute, told CBS News that screenings and early detection also play a role in improving results.

"We know that there are more and more cancer screenings, such as breast cancers, which hopefully allow an early diagnosis of cancers for which it is possible to act." The same is true for colorectal cancer, "he said. "So it's probably a number of factors that lead patients to be diagnosed earlier, to be able to be helped earlier and to live longer now."

He pointed out that the number of new cancer diagnoses remains stable among women and is expected to decrease only slightly in men, even though mortality rates are falling.

"Another way of thinking about this is … a little less than 5,000 people in America will be diagnosed with cancer every day, sadly, that's true.And about 1,700 patients will die of cancer," he said. Spigelian.

The report has mixed news about Prostate cancer, the second leading cause of cancer death among men.

Prostate cancer mortality rate halved in two decades, but experts question whether the trend has changed after the 2011 decision by the US Task Force on Prevention Services to stop recommending screening systematic men using the PSA blood test. This decision was motivated by the fact that the test led to overdiagnosis and excessive treatment.

The prostate cancer mortality rate decreased between 2013 and 2016. Thus, although PSA testing revealed cases that did not really require treatment, they may have also Avoid some cancer deaths, suggests the report.

Of the most common types of cancer in the United States, all those with increased mortality rates are related to obesity, including pancreatic and uterine cancers.

Another is liver cancer. The number of liver cancer deaths has increased since the 1970s and, at first, most of this increase was related to hepatitis C infections, which spread among drug addicts. But now, obesity accounts for one-third of liver cancer death, and is more of a factor than hepatitis, Siegel said.

The growing epidemic of obesity in the country was identified as a problem in the 1990s. It may take decades to see how a risk factor affects cancer rates, "so we may only see the top of the iceberg in terms of the effect of the obesity epidemic on cancer, "Siegel said.

The historical racial difference in cancer mortality rates has decreased, but the economic gap is widening, especially for deaths that could be prevented through early detection and treatment, better nutrition, and reduced smoking. .

In the early 1970s, colon cancer mortality rates in the poorest counties were 20% lower than those in rich counties; now they are 30% higher. Cervical cancer deaths are twice as high among women in poor counties than among rich counties. And mortality rates for lung and liver cancer are 40% higher among men in poor counties.

Dr. Darrell Gray, deputy director of Ohio State University's Center for Cancer Health Equity, called the results "important, but not surprising."

"We have known for some time that race is a substitute for" other factors, such as poverty and the difficulty of getting – or paying for – doctor appointments, he said. declared.