A new study that looked at more than 287,000 women and took into account their mammogram habits showed that being overweight boosts the risk of getting advanced breast cancer for older women.

The leader of the study, Dr. Karla Kerlikowske, director of the Women Veterans’ Comprehensive Health Center at San Francisco Veterans Affairs Medical Center, told the media that women who are above their normal weight have higher levels of circulating estrogens, which promotes tumor growth. The study is expected to be published in the December the 3rd issue of the Journal of the National Cancer Institute.

In the past few years, it was believed that the increased risk for breast cancer for obese women may be due to their not getting screened adequately, or because their tumors are perhaps more difficult to detect on mammography, but these factors will be ruled out after this new study appears.

However, it seems that some breast cancers may naturally disappear without treatment, a study of women undergoing mammography suggests. Unbelievable as it is, some tumors that are not detected regress spontaneously. Even so, doctors can’t yet determine which tumors might regress and which might go on to be dangerous, so, therefore, the finding isn’t likely to change recommendations for mammography.

Doctor Jay Brooks, chairman of hematology/oncology at Ochsner Health System in Baton Rouge, told the media: "I am sure there are some that do regress. The problem is, we can't pick up those that are going to regress. It's one of the unanswerable questions." Cancer experts have long suspected that some cancers may grow and then simply shrink again and disappear, for unknown reasons. This new research appears to support that idea. The study was published in the November the 24th issue of the Archives of Internal Medicine.