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Conventional medicine views all breast cancers in the same way: left untreated, tumors slowly grow and spread. A recent study of Norwegian women, however, suggests that as many as 25% of some invasive breast cancers might actually disappear all on their own.
U.S. researchers assessed the frequency of breast cancers diagnosed in four Norwegian countries before and after a mammography program began in 1996. Screening data for two groups of women ages 50-64 with similar risk were evaluated. One group had three mammograms in the six years after the initial screening program began. A comparison group was also followed for six years, but had mammograms only at the end of that period.
Assuming that all breast cancers found by screening remain or grow over time, researchers expected to show that both groups would have similar rates of breast cancer after the six-year follow-up period. Instead, the women who were screened during the six-year period had 22% more breast cancers than the comparison group. This suggests that some of the breast cancers in the comparison group spontaneously regressed during the follow-up period.
No one knows whether cancer may actually disappear; nor have these results been duplicated in other studies. But the implications are intriguing. If experts knew which cancers might “spontaneously regress,” careful monitoring might be prescribed for women diagnosed with those types of tumors. This watch-and-wait tactic would represent a complete departure from the current practice of treating all breast cancers with surgery, chemotherapy, and/or radiation. Some women could be spared the ordeal of treatment. Better yet, discovering why these cancers disappear would be a huge leap toward prevention.
Read more about this study in the New York Times article as well as the Archives of Internal Medicine abstract.
September 4, 2009