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Study: What causes cognitive impairments in breast cancer patients?


"Chemobrain" in breast cancer patients triggered by post-traumatic stress
Many breast cancer patients show slight impairments in their cognitive abilities, which is often associated with the side effects of chemotherapy. A team of researchers led by Dr. However, Kerstin Hermelink from the Breast Center of the Ludwig Maximilians University (LMU) has shown in a recent study that the impairment also occurs in breast cancer patients without chemotherapy. The cause is post-traumatic stress.

"Mild cognitive disorders in breast cancer patients can occur both with and without chemotherapy and are related to post-traumatic stress," the scientists report of their study results. The suspicion of a connection with the side effects of chemotherapy has not been confirmed. The so-called "Chemobrain" is therefore a myth. Rather, the impairments are a result of post-traumatic stress.

Changes in cognitive performance were examined
As part of their study, the scientists investigated the changes in cognitive performance in 166 women who had previously been newly diagnosed with breast cancer. The control group was made up of 60 women in whom a routine breast examination had shown no suspicion of cancer. All subjects were examined for post-traumatic symptoms on three appointments within one year using a clinical interview, and their cognitive functions were extensively tested using neuropsychological methods, the researchers report.

Impairments in all breast cancer patients
The scientists observed that minimal cognitive abnormalities appeared in the patients one year after breast cancer diagnosis. However, this applies both to patients after chemotherapy and to patients who had been treated without chemotherapy. In comparison with the participants in the control group, the breast cancer patients overall showed a slight, just verifiable decrease in their test performance. The abnormalities “were related to the strength of the post-traumatic symptoms and the effect of cancer on attention was no longer statistically significant when the effect of post-traumatic stress was taken into account,” the scientists report.

Response time minimally affected by chemotherapy
According to the researchers, chemotherapy has no far-reaching effects on cognitive abilities. "Only one noticeable neuropsychological result occurred exclusively in chemotherapy patients and had nothing to do with post-traumatic symptoms," the scientists report. A few months after the end of chemotherapy, the patients had shown somewhat longer reaction times in a computer-based test, in which they had to click as soon as a cross appeared on the screen. However, the minimal difference of an average of 19 milliseconds could have been caused by peripheral neuropathy, damage to the finger nerves by certain cytostatics and had nothing to do with cognitive functions, according to the study leader Hermelink.

Psychological factors of the triggers
Overall, the study results suggest that the disorders of cognitive functions in cancer patients are more likely to be attributed to psychological factors than to neurotoxic side effects of the treatment, the researchers write. "Our brain is not a machine that always functions the same, but it constantly changes its functioning and structure depending on what we do and experience," emphasizes the study director. The effects of the psychological stress on the cancer patients seem to be an almost logical consequence. "It would be strange if all the consequences of cancer for the psyche and interventions in life would leave the brain and cognitive functions without a trace," said Hermelink. In addition, "it is well proven that post-traumatic stress - not to be confused with normal everyday stress - intervenes deeply in the way the brain works."

Chemotherapy with no disadvantages on cognitive functions
In the current study, the scientists focused on the effects of post-traumatic stress, but insomnia, anxiety, depression and other factors could also play a role in cognitive impairments, according to the experts. Such factors have so far been neglected in research on cognitive disorders in cancer patients. For breast cancer patients, however, the current study results also contain good news, because the scientists emphasize that they do not have to reckon with neurotoxic effects of chemotherapy that inevitably damage their cognitive functions. (fp)

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