In the light of new mammography guidelines issued in 2009, one study has found that mammograms are doing shockingly little to stop cancers from being spread. Many more women are being over-treated for cancer. At the same time, two other studies have found that the change in mammogram guidelines could mean that doctors could miss cancers as often as 20 percent of the time.

Screening measures have long been a hallmark of American medicine in an effort to spot diseases early and often. The American Cancer Society suggests that women have mammograms annually starting at the age of 40. However, a government task force, the United States' Preventative Services Task Force issued new guidelines in 2009, saying that women should have mammograms every other year starting at the age of 50 and ending at the age of 74. For women at the age of 75 or older, the task force said that there was too little evidence for or against the benefits of screening.

Because of these changes in guidelines, two studies will be presented at the annual conference for the Radiological Society of North America, hoping to capture the effects of the new guidelines.

One study looked at the rates of mammograms conducted on women. Between the years of 2005 and 2009, the rate increased steadily. However, in 2010, there was a steep drop by 4.3 percent. That was particularly concerning because mammography rates were not even as high as doctors had hoped for 2009; that year, mammogram rates were 322.9 per 1,000 women, falling to 309.1 per 1,000 women the following year.

The study does not prove that the guidelines were the cause, but lead researcher Dr. David Levin believes that the pattern is fairly clear.

The study examined women aged 65 and over who were on Medicare. He says that he believes that some women may have been waiting an additional year between screenings. Other women over the age of 75 may have simply stopped receiving mammograms.

The second study examined 43,000 mammograms performed at a New York hospital. In general, mammograms caught 4.7 cancers for every 1,000 mammograms, though that number dropped to 2.7 cancers for every 1,000 mammograms performed on women in their forties.

However, women in their forties accounted for 20 percent of breast cancer cases. Because the new guidelines do not recommend mammograms for women under the age of 50, researchers worry that doctors could be missing as much as 20 percent of breast cancers. The task force said themselves that mammograms could provide a 15 percent reduction in the risk of death for women under the age of 50.

The study did not indicate whether the women in their forties who were diagnosed with breast cancer were at risk for death.

The panel states that the benefits of mammograms do not outweigh their risks.

Meanwhile, a third large study published by the New England Journal of Medicine says that 50,000 to 70,000 breast cancers a year - as many as a third - do not require treatment. The researchers say that as many as a million women are being treated for cancers that never would have threatened their lives.

However, because it is difficult to spot which "cancers" are malignant and life-threatening, the study says that many women are treated with chemotherapy and surgery that they do not actually need.

Mammograms spotted more than double the amount of early-stage breast cancer they spotted three decades ago - 112 to 234 cases for 100,000 women. However, the amount of late-stage breast cancer cases dropped by just 8 percent, suggesting a bit of overdiagnosis for early-stage cancers.

"The worst cancer is still going on, just like it always was," Archie Bleyer said to the Associated Press.