I just read a really great post over at Jezebel called “We’ve Gotten a Little Too Good at Finding Breast Cancer“. I have to say, as a big Public Health nerd, I find their science and health reporting on this subject to be excellent. Their post discusses a study published last week in the Annals of Internal Medicine that shows that between 15-25% of the tumors identified via mammography would not have lead to metastatic cancer. Therefore the surgery, radiation or chemotherapy that followed their identification was not life-saving but rather unnecessary, invasive and expensive treatment.
The study, based in Norway, looked at 40,000 breast cancer cases from 1996-2005. It was designed to provide:
“Precise quantification of overdiagnosis of breast cancer (defined as the percentage of cases of cancer that would not have become clinically apparent in a woman’s lifetime without screening) due to mammography screening.”
So what do we do with this information? How do we process the idea that women are being routinely over-diagnosed and that annual screening may be too much, too soon? How do we do this when so many of us are shaking our heads and our fists that not enough is being done to save our friends, mothers, and sisters (not to mention ourselves) from this killer?
I think we take a step back and think about it. Here are a couple of points we should consider when we see headlines like this:
The study is valuable, but its applicability has limits. Norway is an extremely homogeneous society with a comprehensive and coordinated healthcare system. Neither of those two statements applies to the US. Also, the study is based on registry data. That means it’s based on the national Cancer or tumor registry. That is a great data set, but it exists in a silo. It looks at the incidence of cancer (for example) but not at it’s mortality. It doesn’t look at the myriad other things that play into someone getting a mammo and finding a lump.
The over-diagnosis argument isn’t new. There have always been a lot of false positives in this type of diagnostic technology. Ask your self, how many women do you know that have had a breast cancer scare? Probably quite a few. How many do you know that have actually had a breast cancer diagnosis? Hopefully far fewer. It’s intentional – isn’t it better to identify more potential cases and then rule the out those who are cancer-free through additional testing? The opposite would be to have a higher rate of false negatives, meaning that there would be more women who were told they were fine, when in fact they were not. If the goal is to prevent cancer deaths, false positives are necessary part of the screening equation.
What about those populations who are consistently under-diagnosed? This concept of over-diagnosis really applies to only one population and that’s rich, white women. While white women are more likely to be diagnosed with breast cancer, women of color are far more likely to die from it. Because (for one reason) those mammos and secondary tests are an excellent proxy measure for access to health care. For people who are on the fringes of the health care system or whose cultural beliefs prevent them from seeking routine screening, the concept of over-diagnosis is laughable. These women are chronically under-diagnosed, which is why their cancer is usually identified at a later stage of their disease’s progression and is likely to be fatal. These are preventable breast cancer deaths and we should fight like rabid wolverines to put an end to them.
Breast cancer treatment is rapidly changing. The role that genetic medicine now plays in treating breast cancer should not be underestimated. This technology couldn’t have played a significant part in this study because it didn’t exist when many of the patients were diagnosed. In fact, Jezebel ran a great post on the role of DNA testing and treatment options for breast cancer one day after publishing their take on the Norway study.
Cutting back on screening is dangerous. Educating physicians and empowering patients is smart. My friend just chose to have a double mastectomy and forgo chemo based on the pathology of her tumors. She was able to do this because she took the time to carefully research options and she had an excellent oncologist .
Anything that creates a sense of complacency or confusion around mammography and screening is scary to me. Why does it scare me? Because so many groups of women still choose not to get screened or are on the fringes of the system and have to fight for access. When we put out there a lot of “Is it even necessary?”, it may play a role in inhibiting those who are afraid to get a mammo or who are inclined to get screened but face barriers to access. And they are exactly the women who are at greatest risk of dying from breast cancer.
And preventable breast cancer deaths make Hulk angry.