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Tuesday, May 7, 2013

Breast cancer treatments and cognitive declines

As if women undergoing treatment for breast cancer don’t have enough problems, many of them claim to suffer from cognitive declines as a result of that treatment. But are these difficulties with memory and concentration directly caused by the treatment? A study by Patricia Ganz and her colleagues from the University of California, Los Angeles sets out to answer that question. According to this study, the good news is that chemotherapy does not appear to cause cognitive disfunction. The bad news is that radiation therapy does. Maybe.

The researchers recruited 189 women diagnosed with stage 0 through IIIA breast cancer. The patients were self-assessed for levels of depression as well as for cognitive function in four areas: memory, higher order thinking, language skills and motor-sensory perception. These evaluations occurred three times, at recruitment (and after chemotherapy and/or radiation but before the patients began any hormone therapy), six months later and six months after that. The patients were matched with data from 63 healthy controls.

Overall, about one fifth of the breast cancer patients complained of specific cognitive declines. Women were most likely to complain about memory problems if they had received radiation therapy, either with or without chemotherapy. Surprisingly, despite the expression 'chemo brain', women who only had chemotherapy did not seem to have these issues. 

I should point out that other studies have shown small cognitive deficits following chemotherapy. One group even observed changes in brain function that were visible on PET/CT scans, though that data has yet to be published. 

Personally, I don't find any of these studies to be particularly compelling, as I'll explain.

For one thing, study patients only underwent cognitive tests after chemotherapy and/or radiation. This means that we can’t compare the same women before and after they received treatment. Without that data point, it’s hard to be sure that the complaints represent true declines. Second, women with more cognitive complaints also suffered from more depression. This opens the possibility that any intellectual problems were symptoms of depression, rather than being caused by specific treatments. Finally, it’s difficult to argue that memory problems aren’t subjective when the assessments were all self-reported. These issues apply to most of the 'chemo brain' studies I looked at, not just this particular one.
So what’s the bottom line? Clearly, a large proportion of women are noticing problems with their memory and thinking abilities after receiving cancer treatment. At the very least, doctors should be prepared to discuss these symptoms with their patients. However, more experiments must be done before we know exactly what’s causing these problems.

Ganz, P., Kwan, L., Castellon, S., Oppenheim, A., Bower, J., Silverman, D., Cole, S., Irwin, M., Ancoli-Israel, S., & Belin, T. (2013). Cognitive Complaints After Breast Cancer Treatments: Examining the Relationship With Neuropsychological Test Performance JNCI Journal of the National Cancer Institute DOI: 10.1093/jnci/djt073.

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