A new study published in the Archives of Internal Medicine begins a debate challenging the conventional wisdom of early detection of breast cancerdefine. Frequent screenings may lead to over diagnose, picking up tumors that might have gone away without treatment.
Per-Henrik Zahl MD of the Norwegian Institute of Public Health conducting the study examined two groups of women aged 56 to 64 years. Around 120,000 women had mammograms every two years from 1996-2001. These were compared to another group of 110,000 women who had a single screening in six years. Results showed that invasive breast cancer was 22 percent higher in those frequently screened for detection.
Statistically, the two groups were almost identical. The education profile, kids and average family income matched. Considering the data, the cancer in both the groups should have been the same. A number of arguments have been put forward for the difference, one being hormone replacement therapy. However, the authors feel the explanations do not verify the large difference found in the two groups.
Screening does save lives but at a far more modest rate than universally believed. “If we are right, then this is a paradigm shift,” said Dr Zahl.
The findings prompted Dr Robert M Kalpan of the University of California to state in the editorial accompanying the study, “Our tendency was to dismiss it when we first read it, but the more we looked at it the more we thought it may be there is something to this.”
There are others who dispute the findings. Dr Alexis Willet from Breakthrough Breast Cancer said the study opens a series of curious questions, “It is not possible to predict whether early changes picked up by screening will progress.”
The study is controversial in nature and has caused quite a stir. Dr Chris Kagay, a clinical fellow at Harvard School of Medicine dismisses the theory “The authors are making a bold proposition about the natural history of breast cancer based on pretty limited evidence.”
While the authors said that it is possible that breast cancer can regress, the study does not provide a definitive answer. Robert A Smith, director of cancer screening at American Cancer Society said, “the conclusion that more than one in five invasive breast cancers is destined to regress without incident if not detected by mammography is nothing more than an over reaching leap of logic.”
The inputs are numerous. Autopsy studies show that many women die from other causes, blissfully unaware that they also had breast cancer. Dr Steven Narod, a leading breast cancer researcher at Toronto Sunnybrook Health Science Center said, “I do agree with them that the best explanation of the findings is that ten to twenty percent of the breast cancer disappeared on its own. I am still a bit skeptical that there’s alternative explanation but I think this one is worth paying attention to.”
The study is intriguing, raising a number of questions; especially that screening has only downsides. This simplistic half truth can be dangerous if it discourages women to have mammograms.
Dr Chris Kagay declares that “It’s important to remember that mammography saves lives. Suggesting that screening is not valuable or that these cancers detected will spontaneously regress is quite frankly dangerous if it convinces women that they don’t need to be screened.”
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