breast cancer and race

I was reading some news reports on breast cancer today and one was linked to this press release from the M. D. Anderson Cancer Center at The University of Texas.

Despite modest overall improvements in breast cancer survival rates for women with advanced disease over the last two decades, the rates for black women have not improved and the difference in life expectancy between white and black women continues to widen, according to researchers at The University of Texas M. D. Anderson Cancer Center.

As a research scientist working in the area of breast cancer, I do try to keep up to date on the field but my focus is more on the drugs that kill cancer cells. The sociological aspect is not something I usually pay much attention to. However... this study really contained some conclusions that surprised me. I'm not sure if they're accurate--which is also something to mull over.

The study evolved as a follow-up to recent research of Sharon Giordano, M.D., assistant professor in M. D. Anderson's Department of Breast Medical Oncology, that found an overall improvement in the survival of Stage IV breast cancer patients enrolled in clinical trials at M. D. Anderson.

"We wanted to expand our research and look to a bigger subset of patients treated in the community to see if we would find similar results," says Shaheena Dawood, M.D., a Susan G. Komen Fellow in Breast Medical Oncology at M. D. Anderson. "We thought we would find that there was improvement in women with Stage IV breast cancer regardless if patients were white or black, with white women likely having better outcomes. Rather, over the decades, we found that black women's survival did not improve at all."

In those diagnosed with advanced breast cancer between 1988 and 1993, the median survival was 20 months in white women, compared to 17 months for black women, a one-year survival difference of 2.8%. In the women diagnosed between 1994 and 1998, a white breast cancer patient's median survival was 22 months versus 16 months in black patients, a one-year survival difference of 6.8%. In those diagnosed from 1999 to 2003, the median survival for white women was 27 months compared to 17 months for black women, a one-year survivor difference of 8.8%.

The info in the preceding section isn't anything new. You can read papers going back to the mid 90s discussing this stuff. The general conclusion was that for a variety of reasons, but low income being the main one, African-American women get worse health care and tend to present cancer cases at a later date, which makes for worse outcome. In other words, the delayed start of treatment means that the woman is more likely to die of cancer, and die quickly.

The following sentence highlighted in red is what really surprises me. I thought the paradigm of ethnicity and breast cancer had changed recently due to the new research into how HLA (Human Leukocyte Antigen) varies with race and expected outcome.

"We do not suspect that these statistics are due to the biology of the disease because we would not expect the biology to change over time. It's more likely due to socio-economic factors," says Giordano, the study's senior author. "While SEER data does not code for treatment, we hypothesize that lack of access to healthcare and to newer modalities for treatment of Stage IV breast cancer, such as targeted therapies like Herceptin and aromotase inhibitors, are two contributing factors for the growing disparity."

You see, as I understand it, African-American women tend to have a higher incidence of HLAs associated with cancer types that do not respond well to adjuvant therapy. I'll look into this because it's hard to believe that the group at University of Texas missed such an obvious thing. However the phrase "we would not expect the biology to change over time" just sounds so... well, dumb.

The reason is that it's not the biology that's changing but rather our ability to understand it. We used to think of breast cancer as a monolithic disease. Everyone got the same thing. Now we realise there's many subtypes and that the treatment for each type should be different. For example, typical treatment pre-surgery is some chemotherapy to shrink the tumor. It makes the surgery easier and also gives the doctor a better idea of how well the patient will respond to post-surgical chemo--which will influence how aggressive the surgical removal will need to be. If chemo is going to be ineffective, you'd better make sure everything is out--and that means removing more healthy tissue than would be ideal. It's a trade off. Now if you know the patient's tumor subtype does not respond at all to chemo, then you don't pretreat with chemo--and you know that you have to have surgery immediately.

Researchers have found that about twice as many ER-negative tumors in African-American women. They also discovered that high-grade tumors were much more common in African-American women than in white women, especially when the cancer was detected at an early stage. ER-negative tumors and high-grade tumors are both linked to poorer outcomes for patients. You can read more about this here. I don't know if that evidence is conclusive though and other studies have had different results. It's quite confusing when different research groups publish different results! You just don't know what to believe.

Here's another study showing a biological basis for the racial discrepancy in outcome. Since I'm sure the Texas group is aware of these findings, I wonder if there's been a sea change in the outlook of these studies. Maybe they've all been invalidated. If so, nobody told me!

Anyway, I'd best go back to looking up references and trying to sort this out.


SassyAssy said… least there is all this research and such on breast cancer. Maybe times have changed since mom died of ovarian cancer, but the research on ovarian was pretty limited back in 1997-2000. At least it appeared that way to my family.

I best not get started on endometriosis--the biggest cause of infertility in women and the most under-researched (and under-funded research) women's disease (my pet cause).
kenju said…
Dave, there was a blurb in our paper this morning saying that since the demise of HRT (hormone replacement therapy) the rates of breast cancer have gone down. I find that interesting - and I am vindicated for my long-held opinion on HRT - I refused to take it and now it has been shown that I was right. YAY!
tiff said…
It appears as though I'm a complete moron, because I kept waiting for the part about running to start ("race," as it were).

Cancer is such a complicated set of diseases, with such a tremendous diversity of causes and triggers, that I'm not surprised the emerging biology and our understanding of it would result in seemingly conflicting publications. Right now I'm working on many many different oncology clincial trials, and the types of infomation being pursued in them is going to be interesting and very difficult to tease apart.

Keep on figgerin' this stuff out Dave - one little step at a time gets us closer to whatever truths might be out there for your target.

Science rocks.
Pearl said…
Interesting post. Individual responses to a body attacking itself could take a while to sort out but sorting things apart methodically sounds like a good way to progress, as does educating people like you do.

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