Cancer: A Progress Report
For: The Gold Standard, March 2002
Every year a report on cancer goes out to the nation,
compiled by experts at the National Cancer Institute, the Centers
for Disease Control and Prevention, and other agencies. This year's
report, like previous ones, had some good news. Apart from cancers
caused by tobacco, notably lung cancer, we are not in the middle
of a cancer epidemic. In fact, the rate of new cancer cases and
deaths from cancer in the U.S. declined in the 1990s. But it pays
to look closer. Cancer is, in fact, not one disease, but many.
How they keep track of cancer
In keeping track of cancer, scientists speak of incidence
(new cases diagnosed among a given number of people in a given period)
and mortality rate (deaths among
a given number of people in a given period). When incidence goes
up, it may be hard to tell why, but sometimes it's because of some
new method for detecting a particular cancer. Thus, between 1988
and 1992, when PSA testing came into wide use, the incidence of
prostate cancer rose—but that was because the new test found
otherwise hidden disease. Of course, increased or decreased incidence
may also be caused by some change in the environment or in people's
habits. For example, the increase in smoking is responsible for
the huge upsurge in lung cancer incidence and deaths during the
past half century. On the other hand, the mortality rate may fall
because of a drop in incidence, or because of some new medical advance:
deaths from cervical cancer declined dramatically because the Pap
test came into wide use, beginning in the 1940s. For the first time,
doctors could diagnose this cancer early and cure it.
Highlights of the new report
The new report, covering through 1998 (the latest
year for data), shows that, as has been true for some time, the
four cancers that affect the most Americans—and kill the most—are
lung, colorectal, breast, and prostate cancers: 56% of all cancers
diagnosed in 1998 were one of these four, and they accounted for
almost 53% of the cancer deaths that year. Looking at most of these,
you'll see a mix of good and bad news:
• Lung cancer: This remains the biggest cancer killer of both men and women (except Hispanic women, who died of breast cancer more often than lung cancer). The incidence of lung cancer in men is declining, as is the mortality rate. And while the incidence in women has leveled off, the death rate is still increasing—because so many women started smoking after the 1940s. To date there's no practical screening test for lung cancer that has been shown to save lives.
• Prostate cancer: Since 1994 the death rate has declined, possibly due to improved treatments. It is difficult to evaluate the changing incidence of prostate cancer because of the fluctuation in the use of the PSA test for screening.
• Breast cancer: This is still the most common cancer among women, but more women die each year from lung cancer. Breast cancer incidence increased among women aged 50 to 74, probably because of wider use of mammography, which detects hidden disease. But the death rate among white women has declined steadily since 1989 and dramatically since 1995. The mortality rate remained stable among black women in the 1990s.
• Colorectal cancer: The incidence declined between 1985 and 1995 and then stabilized. The death rate has declined. The latter may be attributed to better diagnosis and treatments.
The news, however, is not good for every type
of cancer. For example, the incidence of melanoma, the most serious
type of skin cancer, increased—perhaps due to increased awareness
and screening. And the death rate from melanoma among white men
also increased. Also, the death rates for non-Hodgkin's lymphoma
and esophageal cancer rose between 1992 and 1998 (though the death
rate from esophageal cancer has decreased dramatically for black
men and women). Though these cancers do not contribute greatly to
the total number of cancer cases and deaths in this country, it
serves as a reminder that cancer comes in many varieties—and
that there is still much work to be done in understanding, preventing,
and treating cancer.
How can you guard against cancer?
• If nobody used tobacco, the total incidence and death rate from cancer would fall by about one third. It is a tragedy of our time that so little has been done to eliminate tobacco use.
• A diet rich in fruits, vegetables, and grains is known to help prevent cancer. Indeed, if a plant-based diet were the norm, cancer incidence might fall by yet another third.
• Maintaining a healthy weight is another good step: being obese contributes to cancer risk, especially breast cancer. Nobody knows why this is so, but the alarming increase in obesity in the U.S. and other countries may well cause cancer incidence to rise.
• Finally, get screened. If you're a woman 50 or older, have a mammogram every year. Get Pap tests on a regular schedule. Talk with your doctor about screening for colorectal cancer—and for prostate cancer if you're a man. See our November issue for our guide to these and other preventive services.
UC Berkeley Wellness Letter, December 2001
