WASHINGTON (AP) -- An American scientist says a London newspaper misinterpreted her study of a monkey virus in early polio vaccines when the paper said the virus had been proved ``cancer-causing'' and could be responsible for hundreds of cancer deaths.
``It is going one step farther than I am prepared to go,'' Dr. Janet S. Butel, a researcher at Baylor College of Medicine, said of the report in the London Sunday Telegraph.
``I don't think that the evidence is definitive that (the virus) causes those (human) tumors,'' Butel said. But she said the indirect evidence is getting strong.
Butel said studies have shown that the monkey virus is present in some human tumors and that it can cause cancer in animals. But more research is needed to nail down the role, if any, the virus may play in causing human cancers, she said.
The Telegraph article said the monkey virus that contaminated pre-1963 polio vaccinations was ``cancer-causing'' and might be responsible for hundreds of cancer deaths a year among people inoculated with the vaccine.
The newspaper based its report on Butel's study published last month in the Journal of the National Cancer Institute.
Butel said the story also was ``misleading'' when it blamed contaminated polio vaccine for the spread of the monkey virus. The virus may have infected humans from a variety of sources, and it may now be spread by human-to-human contact, she said. It's not known how the virus is spread.
``There is no evidence that the virus (found in some human tumors) came from the polio vaccine,'' she said. The monkey virus has been found in the tumors of people who were not even alive at the time the contaminated polio vaccine was used, she said.
In her study, Butel reviewed evidence from her research and from others' research about the spread and disease potential of a monkey virus called simian virus 40, or SV40. This virus was found to have contaminated a polio vaccine introduced in 1955. The contamination was only in vaccines used before 1963.
Butel said in the paper that ``the association of SV40 with human cancers is currently strong enough to warrant serious concern.'' But she said further studies are needed to prove whether the virus actually causes cancer in humans.
Butel's conclusions are similar to those expressed by experts attending a National Institutes of Health conference on SV40 held in 1997. A study by the National Cancer Institute, published last month in the Journal of the American Medical Association, concluded there has been no increase in a type of cancer that has been found in animals exposed to SV40.
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