Posted by dj on July 13, 2000, at 10:55:22
In reply to Re: Stress, Depression role of ADs, posted by stjames on July 13, 2000, at 1:12:00
Here's a well written piece on the interplay of enviroment and genetics from today's Boston Herald.
Environment causes more cancers than genes
by Michael LasalandraThursday, July 13, 2000
The environment, not genetics, plays the major role in causing most cancers, says a Swedish study some say sheds doubt on the role that mapping the human genome may have in wiping out the disease.
Genes account for only about one-third of all cancers, concludes the study in today's New England Journal of Medicine.
``Inherited genetic factors make a minor contribution,'' it says.
Cancer researchers say the findings are significant.
``I hope this will be a wake-up call for anybody who cares about cancer,'' said Julia Brody, executive director of the Silent Spring Institute in Newton, which has been studying environmental causes of breast cancer.
``To prevent cancer, we have to study the environment,'' she said.
Some cancers are more gene-based than others, the study says.
Genes account for about 42 percent of all prostate cancers, for example, while genetic factors cause about 27 percent of breast cancer cases, the study says.
The findings surpass earlier estimates that genes account for 10 percent to 20 percent of all cancers, said Paul Lichtenstein, an epidemiologist who led the study at the Karolinska Institute.
Still, the finding flies in the face of the idea that scientists ``will find solutions or cures to all diseases in the genes,'' he said. ``That won't be the case.''
Lichtenstein looked at 44,788 sets of twins in Sweden, Denmark and Finland. They studied both identical twins, who have the same genes, and fraternal twins, who are no more closely related than any other brothers and sisters, to analyze the importance of genetics in each type of cancer.
He stressed that the figures do not mean that someone whose identical twin has prostate cancer has a 42 percent risk of developing it, too.
The identical twin of someone with breast, colorectal or prostate cancer had an 11 percent to 18 percent risk of developing the same cancer before age 75, the researchers said.
The risk was only 3 percent to 9 percent for fraternal twins.
Those figures should go a long way toward dismissing the widespread belief ``that if your sister has cancer, you're doomed,'' said Dr. Robert N. Hoover of the National Cancer Institute.
Eric Lander, director of the Whitehead Institute's Center for Genomic Research, said the findings don't discount the potential of the genome mapping project.
``The fact that most cancers may depend on the environment doesn't mean that understanding the minority of genetic cases wouldn't teach us about the environmentally-caused cases,'' he said.
``If a quarter of cancer cases have genetic causes, that's more than enough to use to find the mechanism that may tell us what the environmental triggers are and how to prevent them.''
poster:dj
thread:40133
URL: http://www.dr-bob.org/babble/20000708/msgs/40318.html