Cancer deaths are declining, but there may be an asterisk

Cancer deaths in the United States are declining, and four million deaths have been prevented since 1991, according to the American Cancer Society’s annual report. report.

At the same time, the society reported that the number of new cancer cases had increased to more than two million in 2023, from 1.9 million in 2022. Cancer remains the second leading cause of death in the United States, after heart diseases. Doctors believe there is an urgent need to understand changes in the mortality rate, as well as changes in cancer diagnoses.

The Cancer Society highlighted three main factors in reducing cancer deaths: decreased smoking, early detection and greatly improved treatments.

Breast cancer mortality is one area where treatment 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 article reported receiving payments from companies involved in cancer therapies).

The paper, published Tuesday in JAMA, found that the breast cancer death rate had fallen to 27 per 100,000 women in 2019 from 48 per 100,000 in 1975. That includes metastatic cancer, which accounted for nearly 30 percent of the reduction of breast cancer. death rate.

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

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

“The biggest untold story about breast cancer is how much treatment has improved,” said Dr. H. Gilbert Welch, an oncology epidemiologist at Brigham and Women’s Hospital. “This is unequivocally good news.”

The American Cancer Society found increases in the incidence of many cancers, including those of the breast, prostate, uterus, oral cavity, liver (in women but not men), kidney, and colon and rectum in middle-aged countries. older adults. The incidence of melanoma also increased. The figures were adjusted for changes in population size.

Dr. William Dahut, the cancer society’s chief scientific officer, said that while the overall rate of colorectal cancer had continued to decline, he was concerned about an increase in one group: people under 55. In those younger people, society informs. , the incidence is now 18.5 per 100,000 and has increased by 1 to 2 percent annually 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 death among people under 50 years of age. It is now the leading cause in men under 50 and the second leading cause in women. Doctors can’t say why.

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

But colorectal cancer remains overwhelmingly a cancer of older people, among whom, among those over 65, it has been declining 3 percent a year, the cancer society says. Its incidence is now 155.4 per 100,000 and it is expected that 87,500 people will be diagnosed this year.

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

That sounds like a good thing: wouldn’t it be better to remove cancers before they become dangerous? The problem is that sometimes treatment may be unnecessary, because not all cancers are life-threatening or even noticeable. Some cancers never spread. Others, in fact, disappear. Others might have had a fatal outcome, but a person dies first from something else. But it can be impossible to distinguish harmless cancers from deadly ones, so they all receive treatment.

This situation is called overdiagnosis, but no one can say precisely how often it occurs. 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 occur, because they may be an artifact,” Dr. Etzioni said.

That’s the challenge cancer researchers now face.