Cancer deaths in the United States are declining, with four million deaths avoided since 1991, according to the American Cancer Society’s annual report. report.

At the same time, the company reported that the number of new cancer cases increased to more than two million in 2023, up from 1.9 million in 2022. Cancer remains the second leading cause of death in the United States, after heart disease. Doctors believe it is urgent to understand the evolution of the mortality rate as well as the evolution of cancer diagnoses.

The Cancer Society has highlighted three main factors contributing to the reduction in cancer deaths: reduced smoking, early detection and vastly improved treatments.

Breast cancer mortality is one area where treatment has had a significant impact.

In the 1980s and 1990s, metastatic breast cancer “was considered a death sentence,” said Donald Berry, a statistician at the University of Texas MD Anderson Cancer Center and author of a new study. paper on breast cancer with Sylvia K. Plevritis of Stanford University and other researchers (several authors of the paper reported receiving payments from companies involved in cancer therapies).

The paper, published Tuesday in JAMA, reveals that the breast cancer death rate fell to 27 per 100,000 women in 2019, compared to 48 per 100,000 in 1975. That includes metastatic cancer, which accounts for nearly 30%. reduction of breast cancer. mortality rate.

Breast cancer treatment has improved so much that it has become a more important factor than screening in saving lives, said Ruth Etzioni, a biostatistician at the Fred Hutchinson Cancer Center.

Mortality rates even declined among women in their 40s, who generally did not have regular mammograms, said Dr. Mette Kalager, professor of medicine at the University of Oslo and Oslo University Hospital, “indicating a substantial treatment effect,” she said. .

“The biggest untold story in breast cancer is improved treatment,” said Dr. H. Gilbert Welch, a cancer epidemiologist at Brigham and Women’s Hospital. “This is unambiguously good news.”

The American Cancer Society has noted an increase in the incidence of many cancers, including breast, prostate, uterus, oral cavity, liver (in women but not men), kidneys, as well as the colon and rectum. older adults. The incidence of melanoma has also increased. Figures have been adjusted for changes in population size.

Dr. William Dahut, the cancer society’s chief scientific officer, said that although the overall rate of colorectal cancer had continued to decline, he was concerned about an increase in one group: people under 55. In these younger people, the company reports. , the incidence is now 18.5 per 100,000 and has increased 1 to 2 percent per year since the mid-1990s, with 30,500 people expected to be diagnosed this year.

In the late 1990s, colorectal cancer was the fourth leading cause of cancer death among people under the age of 50. It is now the leading cause among men under 50 and the second cause among women. Doctors can’t say why.

“We don’t have a good explanation,” Dr. Dahut said. “We wave a lot. Is it a diet? Is it obesity? Is it something in the environment? Is this an in utero exposure?

But colorectal cancer remains predominantly a cancer that affects older people – among whom, among those over 65, it decreases by 3% per year, according to the cancer society. Its incidence is now 155.4 per 100,000, and 87,500 people are expected to be diagnosed this year.

Cancer researchers say that the more you look for cancer, the more you find. As screening becomes more and more sensitive, doctors are discovering more and more cancers.

This seems like a good thing: wouldn’t it be better to eliminate cancers before they become dangerous? The problem is that sometimes treatment can be futile, because not all cancers are life-threatening or even visible. Some cancers never spread. Others actually leave. Others could possibly have had a fatal outcome, but a person dies of something else first. But it may be impossible to distinguish harmless cancers from deadly cancers, so all are treated.

This is called overdiagnosis, but no one can say precisely how often it happens. With mammography, Dr. Berry said, estimates of overdiagnosis range from 0 to 50 percent.

“Increases in incidence are always concerning at first glance, but we need to understand why they are happening, as they could be an artifact,” Dr. Etzioni said.

This is the challenge facing cancer researchers today.

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