BOSTON (AP) _ With her twin sister dying of a rare hereditary stomach cancer, Natasha Benn made to an extraordinary decision that put her family at the forefront of the new genetic medicine: She had surgeons remove her own, healthy stomach.
As an identical twin, she knew she was virtually certain to carry the same defective cancer gene as her sister. The rare cancer had taken Benn's mother at age 29, along with her grandmother, great-grandfather and great-aunt.
``It wasn't really a decision. It was something I had to do,'' said Benn, of Victoria, Canada, now 32 and cancer-free eight years later. ``It was something I had to do for myself and my family, so they didn't have to worry about me.''
Without stomachs, people lose weight and must eat smaller amounts more often. But the small intestine can still digest food fairly well.
Since her surgery, her older sister and three members of another family underwent the same pre-emptive operation and also spared themselves from the usually lethal disease. In fact, the approach was dramatically vindicated when the removed stomachs of the four patients were examined and found to have early traces of cancer.
Most of the patients were able to rely on a new genetic test that identified them as carriers of the broken gene.
All five cases _ reported Thursday in The New England Journal of Medicine _ underscore progress in the new and expanding field of genetic screening for cancer.
Genetic tests have already prompted some people to undergo pre-emptive surgery to remove breasts, ovaries, uteri, colons and thyroid glands.
In their study, an international team of investigators reported on Benn's family and another family from Detroit. The four others besides Benn, who were ages 22 to 40, saved themselves thanks to discovery of the cancer gene in 1998.
The gene, known as E-cadherin, makes a protein needed by cells to detect their surroundings properly. When the gene mutates and cannot make the protein, cells can break free and invade other body tissues as cancer, researchers believe.
Stomach cancer is the 13th most common cancer. But hereditary diffuse gastric cancer, the form in these families, accounts for no more than 1 percent to 2 percent of stomach cancers.
The broken gene gives a person an 80 percent chance of developing this stomach cancer.
An examination of the removed stomachs in all four of the cases after Benn found cancer that had gone undetected by other kinds of testing.
``We were astounded by what we found,'' said Dr. David Huntsman, the study's lead author at the British Columbia Cancer Agency in Vancouver, Canada. ``The stomachs looked completely normal, but when we looked at them carefully _ lo and behold _ all of them had minute cancers.''
It is not clear how long these patients might have lived without the surgery.
The researchers said people should consider such surgery when their families show a history of this particular cancer and gene testing reveals the mutations.
``If they waited for symptoms to develop, they probably would have suffered the same fate as their siblings _ which would be to die of a very aggressive stomach cancer,'' said Dr. Laurence McCahill, a cancer surgeon at City of Hope Cancer Center in Duarte, Calif. He co-wrote an accompanying editorial.
The operation, though, is major surgery. Around 1 percent to 2 percent of patients might die. Also, the patients had to change their eating habits.
Benn is satisfied with her decision. The new genetic test confirmed after the fact that she, too, carries the bad gene.
One other woman in the Detroit family had the surgery, like Benn, before the new genetic test was developed. The test later showed she did not carry the broken gene, meaning the surgery was unnecessary for her.
Her doctors said she is glad to know, at least, that her children will not carry the genetic risk.