April 27, 2001
Cancer: Heredity, Not Destiny
was her last visit with us. After dinner, I remember that she
remarked how much better she was feeling that day. My husband
and I knew she'd been seeing doctors for a possible malignancy.
Two weeks later our longtime family friend, Mary McLain, was diagnosed
with pancreatic cancer. A month after that she was dead -- killed
at age 76 by a disease that struck out of the blue, with no history
of similar cancer in her family.
Ounce of Prevention
| By Elizabeth Smoots, M.D.
Mary's story reminds me that most people who develop cancer have
no special genetic predisposition for the disease. We're all susceptible
to cancer, as frightening as the thought may seem. But many of
us tend to forget this possibility, or simply ignore it. Worse
yet, recent press about cancer-gene discoveries may be promoting
a fatalistic (and fallacious) attitude about cancer: You've either
got a cancer-causing gene and you're doomed, or you don't have
it and you're in the clear.
I recently read an article in the New England Journal of Medicine
(NEJM) that serves to dispel this popular myth. The study
sheds further light on the nature-versus-nurture debate and demonstrates
the importance of lifestyle choices in cancer development and
prevention. An editorial accompanying the article estimates 80-90
percent of all cancers arise from factors in our environment.
Fortunately, this is an area where we're in command. So shore
up your defenses with ammunition from the study.
Causes of cancer
Four times as large as any previous trial, the NEJM's
study of nearly 90,000 twins covered more than 10,000 cases of
the most common cancers in northern Europe. Researchers reported
that genetics accounted for a minority of the cancers, whereas
environmental exposures caused 58-82 percent of them. (In the
study, the exact number depended on the type of cancer.) They
concluded that our lifestyle is the "overwhelming" contributor
to cancer. This is good news for most of us.
Researchers reported that genetics accounted for a minority
of the cancers, whereas environmental factors caused
58-82 percent of them. They concluded that our lifestyle
is the "overwhelming" contributor to cancer.
The results do indicate that genetic factors, which we can't
control, may play a significant role in certain kinds of cancer.
For example, 42 percent of prostate cancer, 35 percent of colorectal
cancer, and 27 percent of breast cancer in the study had a genetic
Even for cancers with strong hereditary ties, however, the study
offers valuable insight. In people who had prostate, colon, or
breast cancer, researchers found that the risk of their identical
twin getting the same cancer was between 11 and 18 percent. For
fraternal twins -- no more alike than ordinary siblings -- the
risk was 3 to 9 percent. This indicates only a moderately increased
risk among close relatives of cancer victims, the researchers
say. In other words, just because you have cancer in the family
doesn't mean you'll get the disease.
Family history or no, the absolute best way to prevent cancer
is to replace risky lifestyle habits with healthier choices. When
I talked with Mary's daughter, Susan, we uncovered several factors
that may have contributed to Mary's illness. After having polio
as a child, Mary developed a permanent limp that impaired her
ability to exercise. She was overweight, despite a generally excellent
diet. And, in the past, she had smoked for about 15 years.
The older we get, the faster the years seem to fly by. So don't
put off the lifestyle changes that could improve both your quality
of life and your quantity of years. Here are my top cancer-prevention
only in moderation.
five to nine servings of antioxidant-rich fruits and vegetables
a plant-based diet emphasizing fiber-rich whole grains, beans,
and fresh produce; go easy on animal products, fat, and salt.
a healthy weight. Exercise at least 30 minutes most days of
your provider for regular cancer-screening exams.
you show warning signs of cancer, seek medical care immediately.
Send feedback on this article.
Elizabeth Smoots, M.D., F.A.A.F.P., is a board-certified family
physician in Seattle, Washington. A fellow of the American Academy
of Family Physicians, Dr. Smoots specializes in prevention and primary