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Does jointpoint analysis give true picture of cancer rates?

Cancer Rates CordaFriday, I wrote an article about statistics on foodborne illness. The Centers for Disease Control and Prevention issued a report and said some progress is being made in controlling foodborne infections, but much more needs to be done to protect people from illness.

Researchers from the CDC compared rates of infections in 2014 to 2006-2008 and during the last three years.

The research method reminded me of an article I wrote for The (Tacoma, Wash.) News Tribune when I wrote a senior consumer column.

The article, called "There Are Parts of the Cancer Story That Aren't Good News," was published on July 6, 2000. It questioned the use of jointpoint analysis, using changing trends over successive segments of time and the amount of increase or decrease within each time period instead of relying on overall trends.

Here's the article I wrote:

With more and more people I know getting cancer and dying from it, including my father, it's hard to believe cancer rates are declining. But that's the story coming from the cancer industry.

The rate of new cancer cases and deaths for all cancers combined as well as for most of the top 10 cancer sites declined between 1990 and 1997 in the United States, according to a report by the National Cancer Institute, American Cancer Society, North American Association of Central Cancer Registries, and Centers for Disease Control and Prevention, including the National Center for Health Statistics.

"It's exciting every year (to see the rates declining)," said Lynn A.G. Riess, health statistician for NCI. Riess is the principal author of "Annual Report to the Nation on the Status of Cancer 1973-1997, with a Special Section on Colorectal Cancer."

The report lumps all types of cancer and concludes that incidence rates - the number of new cancer cases per 100,000 persons per year - declined on average 0.8 percent per year between 1990 and 1997. It states cancer deaths declined a total of 0.8 percent for the same period.

The analysis features a new statistical technique called jointpoint analysis. Researchers use changing trends over successive segments of time and the amount of increase or decrease within each time period instead of relying on overall trends.

Dr. Julie Brody, executive director of the Silent Spring Institute in Newton, Mass., says most of the declines referred to in the report are because of people quitting smoking.

"It's wonderful people are giving up smoking," Brody said, but she thinks the "war on cancer" needs to address other areas besides smoking-related cancers.

Breast cancer rates are going up, she says, adding that women have a higher risk now than in any other generation of getting breast cancer and new approaches to breast cancer are an urgent priority.

The institute is looking for possible environmental factors that cause breast cancer, with the goal to preventing breast cancer. "More than 70,000 chemicals are used in commerce today," Brody said. "The vast majority have not been tested for health effects."

The Washington Toxics Coalition suggests looking at the huge increases in cancer rates since 1950 and comparing them to any decreases in recent years, says Shamra Harrison of the coalition.

All types combined, the incidence of cancer in the United States rose 49.3 percent between 1950 and 1991, reports biologist Sandra Steingraber in her book "Living Downstream." Some cancer rates may be going down, but these modest gains are swamped by cancers that show increases in both incidences and deaths, she writes.

Many state cancer registries are new, and they cannot look back across 50 years to analyze data, she says. Without a comprehensive national cancer registry - which the United States does not have - state registries must rely on an elaborate system of data exchange, Steingraber says. The NCI's Surveillance, Epidemiology, and End Results Program does not attempt to record all cases of cancer in the country but instead samples about 14 percent of the population.

Steingraber believes that chemicals should not be used in the environment until it is shown they will do no harm and that the least toxic alternatives should be used.

Environmental newsletter editor Peter Montague of Annapolis, Md., questions the trends reported of decreasing cancer rates. Many cancers remain undiagnosed unless an autopsy is performed, and autopsy rates have declined, he reports in the March 11, 1999, issue of Rachel's Environment & Health Weekly.

The cancer industry is playing a statistical game, he said, adding, "You can justify just about any conclusion you want with statistics. It's definitely a 'spin.'"

Cancer is caused by exposure to cancer-causing agents, some natural and many not, Montague says. He says he doesn't see much public policy discussion on reducing the public's exposure to cancer-causing chemicals in food, on the job, and in the environment.

It seems the CDC is using jointpoint analysis in its reporting of foodborne illness statistics. Although it's probably worthwhile to compare current rates of infections to what happened a few years ago, Americans certainly aren't being given an accurate picture on whether cases of foodborne illness are increasing substantially or moderately or decreasing.

The same is true of the cancer rates that I wrote about 15 years ago. And, the amazing thing is that newspapers and other media report these cancer figures every year without questioning the statistical method.

I guess the old saying is true: There are three kinds of lies: lies, damned lies, and statistics.

Copyright 2015, Rita R. Robison, Consumer Specialist


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