NEW YORK, April 08 (Reuters) -- One of the greatest conundrums in breast cancer research is that mammograms can help detect cancerous lumps in women in their 40s, but despite years of research, the tests have not conclusively been shown to save lives for younger women. Only in women over age 50 have regular breast x-ray exams been shown to definitely decrease cancer mortality.
Now, a new theory on the nature of breast cancer could explain this and other long-standing breast cancer mysteries, according to a report in the New York Times. The theory says that there are essentially three different types of breast cancer: one type develops and spreads within a matter of months; the second grows at a rate that could cause trouble in 5 to 10 years; and there is a third type that may take even longer to grow and metastasize.
A study by Dr. John Spratt, at the University of Louisville in Kentucky, found that the average time it took for a breast tumor to double in size was 260 days -- but the doubling times ranged from 10 days to 7,051 days.
According to that study, 13% to 17% of all breast cancers grow so quickly that they can spread in the time between mammograms, compared with 10% to 15% of tumors that grow so slowly they need only be removed. Any chemotherapy is unnecessary in those types of tumors because they are unlikely to have metastasized to other parts of the body, according to this theory. However, there is no way -- as of yet -- to determine what type of cancer has developed, or its likelihood of spreading.
Currently all women with breast cancer have the tumor removed, followed by chemotherapy or hormonal therapy to kill any cancerous cells that have moved to other parts of the body.
"Giving all those women adjuvant chemotherapy when the majority don't need it puts us in an awkward circumstance," said Dr. Samuel Hellman in the article. Women who don't need chemotherapy have to experience all the side effects of the treatment, and women who do need the treatment may get a "watered" down drug dosage that is not as effective, said Hellman, a radiologist at the University of Chicago, and a promoter of the new hypothesis.
"We end up with a poor mix in the middle," Hellman said.
The theory may explain why mammograms aren't useful in women under the age of 50. The test may pick up slow growing tumors that wouldn't necessarily be life-threatening for many years. And the same may be true for women over age 50. While mammograms have been shown to lower breast cancer mortality in that age group, the reduction has not been as dramatic as hoped.
Now, researcher are looking for cell markers, such as mutated genes or abnormal proteins that may help them distinguish slow growing breast cancers, from lethal, rapidly spreading tumors.
SOURCE: New York Times (April 1, 1997)
