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Some Invasive Breast Cancers May Go Away on Their Own

Cancer researchers have known for years that in rare cases some cancers went away on their own. These were mostly seen as oddities.

But in a new study, published in The Archives of Internal Medicine, researchers suggest that even invasive cancers may sometimes go away without treatment and in larger numbers than thought possible.

Researchers examined invasive breast cancer rates among nearly 120,000 women age 50 to 64 that had a mammogram every two years over a six-year period. They compared the number of breast cancers detected with another group of about 110,000 Norwegian women of the same age and similar backgrounds who were screened just once at the end of the six-year period. It was thought cancer rates of the two groups would be equal. But the study found that women who hadn’t been regularly screened had 22 per cent fewer breast cancers.

Robert M. Kaplan, the chairman of the department of health services at the School of Public Health at the University of California, says the implications are potentially enormous. If the results are replicated, he said, it could eventually be possible for some women to opt for so-called watchful waiting, monitoring a tumor in their breast to see whether it grows. “People have never thought that way about breast cancer,” he added.

There are other explanations, but researchers say that they are less likely than the conclusion that the tumors disappeared on their own. The finding does not mean that mammograms caused breast cancer. Nor does it bear on whether women should continue to have mammograms, since so little is known about the progress of most cancers.

Dr. Steven Narod, a leading breast cancer researcher at Toronto’s Sunnybrook Health Sciences Centre, agreed the findings are persuasive. “I do agree with them that the best explanation of the findings is that about 10 to 20 per cent of the breast cancers … disappeared on their own,” he said.

Cancer Numbers Grow Worldwide

Cancer diagnoses around the world have doubled over the past 30 years according to the latest World Cancer Report by the International Agency for Research on Cancer (IARC). The report revealed that cancer will overtake heart disease as the world’s top killer by 2010, part of a trend that should more than double global cancer cases and deaths by 2030.

In 2007 there were 12 million new cancer cases worldwide – a record high. In 2000, the number was 10 million and in 1975 it was 5.9 million. The disease is growing fastest in low- and middle-income countries. Of the new cases last year, nearly half were in developing countries. Rising tobacco use in developing countries is believed to be a large reason for the increase, particularly in China and India, where 40 percent of the world’s smokers now live.

Cancer kills more people in poor countries than HIV, malaria and tuberculosis combined.

Pollutants in the womb can trigger adult cancers

Mouse moms exposed late in pregnancy to heavy doses of a carcinogen gave birth to pups that inevitably developed lymphomas and lung cancers, a new study shows. The malignancies generally didn’t show up until the offspring reached the human equivalent of adulthood.

In a new study, appearing in the December 15, 2008 issue of Toxicology and Applied Pharmacology, David E. Williams and his colleagues at Oregon State University determined the cancer risk among mice pups from exposures in the womb compared to any delivered through milk. Researchers discovered that sixty-five percent of mice that had encountered the carcinogen dibenzo[a,l]pyrene (DBP) in both the womb and their mother’s milk never reached 10 months old. Clean newborn mice sent to suckle from DBP-treated foster moms, by contrast, rarely developed cancer, much less died.

Although newborns exposed to DBP in the womb appeared healthy and fully developed, these pups began developing lymphomas within six weeks. By 12 weeks old (the equivalent of people in their 20s) mice were dying of cancer in rapidly increasing numbers. This demonstration “that very short early-life exposures can have major consequences is very important,” observes toxicologist Linda S. Birnbaum of the U.S. Environmental Protection Agency.