I must admit that I smiled when I saw the findings from aÂ new studyÂ that suggested that 22-27% of breast cancers could actually go away by themselvesâ€”without treatment. I have been saying this for a long time, and it was nice to see it substantiated.This is another piece of evidence that â€œearly detectionâ€ is not always the way to prevent breast cancer deaths. It depends on the kind of cancer (there are at least six different types) as much as the timing. In this case, it appears that some of the cancers identified on mammography were so good they did not need to be found.
The findings come from an intriguing analysis of breast cancer screening data collected before and after four Norwegian countries started biennial screening mammography programs for women in 1996.
To study the impact this national screening program had on breast cancer incidence, a U.S. research group compared the number of invasive cancers that occurred over two consecutive six-year periods in two groups of women ages 50 to 64. One group of 119,000 women were offered mammography screening three times between 1996 and 2001 as part of the new program. The second group of 110,000 women was followed from 1992-1996, the six years prior to the start of the national screening program. These women were offered mammograms in 1997.
The researchers found that the incidence, or number of breast cancers found, rose substantially when the screening program was implemented. This is what they expected to see, because whenever a screening program is introduced all the cancers that would have been detected over the past few years are suddenly found. But then the incidence starts to level off, giving you a good sense of the actual rate of breast cancer in that population.
The rate seen in this group should have been the same as that seen in the group of women who were not screened. But that wasnâ€™t the case. Much to their surprise, the researchers found that the breast cancer rate was significantly lower in the group of women who had not been part of the screening program. In fact, the unscreened group had 22% fewer invasive cancers than the screened group. This led the researchers to conclude that the women in the unscreened group must have had cancers that had gone away by themselves or â€œdisappearedâ€ without any treatment at all.
This is the kind of study that I love because it challenges accepted truths and makes you really think about what we know about breast cancer. We used to believe that all cancers were the same: they slowly got bigger and then spread. Treatment was the same for everyone, too. Now we know that there are about six different types of breast cancer. One of these types is referred to as â€œalmost normalâ€ breast cancer. Could this be the type that will disappear on its own? Or does the tissue that surrounds the tumor change in a way that makes the cancer go away? Or could it be the immune system that is successfully fighting these cancers? We have no idea! But it gives us so much to think about! If we could figure out how to tell which cancers are the ones that might go away on their own, we could just watch them. And if we figure out what causes them to go away, that could help us to develop new breast cancer treatments. The ideas are swimming in my head!
What does it mean to you? Nothing right now. I will continue to get my mammogram every yearâ€”and you should, tooâ€”because we donâ€™t know if the finding is true and, even if it is, we have no idea which cancers will regress and which wonâ€™t. But I am happy that we now have a new path to explore in our continuous search for the truth!