The number of deaths due to cancer in the United States has fallen steadily over the last 30 years, with the steepest declines occurring among the younger age groups, said researchers, who suggested improvements in prevention, detection and treatment are largely responsible for the gains across the board, but because of the way disease statistics are presented, most people remain unaware of this good news.

The report appears as an advanced online paper this week in Cancer Research, a journal of the American Association for Cancer Research. The first author was Dr Eric Kort, who completed the study while working as a research scientist at the Van Andel Research Institute in Grand Rapids, Michigan.

Kort told the press that:

“Our efforts against cancer, including prevention, early detection and better treatment, have resulted in profound gains, but these gains are often unappreciated by the public due to the way the data are usually reported.”

Kort and colleagues wrote that much of what is published about cancer deaths follows the common practice of reporting an overall, age-adjusted figure that “heavily emphasizes the experience of older, higher mortality age groups”.

They suggested such practice may be hiding the shifts in lifetime cancer death rates emerging first in younger groups.

So, for this study, they looked at cancer death rates registered in the US since 1955 and assessed trends according to age at death, the period when people were born, the period when they died, and the type of cancer they died from.

The results showed that:

  • Since the early 1950s, age-specific cancer death rates have been falling steadily, starting first with children and young adults, and then eventually across all age groups.

  • Apart from lung cancer, much of this falling trend has taken place despite the fact that numbers of cases (incidence) has remained steady.

  • From the middle to the end of the 20th century, for people born between 1925 and 1934, then between 1935 and 1944, and so on, every ten years until 1995, there has been a lower risk of cancer death in each birth decade compared to the previous decade for nearly every age group.

  • The youngest age groups have experienced the steepest decline at 25.9 percent per decade, but even the oldest groups have experienced a 6.8 percent per decade decline.

The researchers concluded that:

These findings suggest that improvements in cancer detection, treatment, and/or prevention have reduced the risk of cancer death across the life span for individuals born in the last three quarters of the 20th century.”

The public is confused, suggested the researchers, because we hear more about incidence rates, which continue to rise across most types of cancer, and “mortality proportions”, and because bodies like the World Health Organization predict that deaths from cancer will overtake deaths from heart disease by 2010.

However, all of these are right, said Kort, but these are not the questions that they addressed, and the WHO statistic, while correct can be misleading, especially if you are not used to the language of epidemiology.

Dr Richard Severson, a cancer epidemiologist and associate chair of the Department of Family Medicine and Public Health Sciences at Wayne State University explained why.

“Proportional mortality” looks at what happens in groups of 100 and is based on the reasonable assumption that everyone will die of something, eventually.

“So you take 100 deaths and calculate, based on death certificates, what those people have died from,” said Severson.

So, while cancer will overtake heart disease as the main cause of death by 2010, this reflects the fact that deaths to heart disease have been falling at a faster rate than cancer deaths.

And while it’s true that the number of people diagnosed with cancer (incidence) has been rising and continues to rise, the fall in death rates across all age groups shows the effect of better screening and treatment.

“In childhood cancer particularly, we’re able to do amazing things with leukemia and lymphoma that used to be a death sentence but now we are curing many of these cancers,” said Severson.

“The Decline in U.S. Cancer Mortality in People Born since 1925.”
Eric J. Kort, Nigel Paneth, and George F. Vande Woude.
Cancer Res. 2009 69: 6500-6505.
Online publication date: August 15, 2009.
DOI: 10.1158/0008-5472.CAN-09-0357

Additional source: American Association for Cancer Research.

Written by: Catharine Paddock, PhD