MedicalResearch: What is the background for this study? What are the main findings?
Dr. Hermelink: Many breast cancer patients report problems of cognitive functioning that interfere considerably with their professional and private lives. In the last two decades, a number of studies have confirmed that subgroups of breast cancer patients show at least subtle cognitive impairment. Initially, the condition has entirely been attributed to chemotherapy effects and has therefore colloquially been named “chemobrain”. Meanwhile, however, cognitive impairment has also been found in patients who were managed without chemotherapy and, surprisingly, even in patients who had not yet received any systemic treatment at all.
Several hypotheses on the causation of cognitive impairment that occurs already pretreatment have been put forward; for instance, biological effects of the cancer itself might affect cognitive functioning, or there might be shared genetic vulnerability for cancer and cognitive impairment. None of these hypotheses have been empirically confirmed; thus, pretreatment cognitive impairment is as yet unexplained.
Our study was designed to investigate the effects of cancer-related post-traumatic stress on cognitive function in breast cancer patients before the start of treatment. Stress has a substantial influence on cognitive functioning, and post-traumatic stress disorder (PTSD) is associated with impairment of cognitive function. While the incidence of full diagnosis of stress disorder is low among breast cancer patients, many of these patients show symptoms of PTSD, with a peak shortly after diagnosis.
We did not find an elevated risk of overall cognitive impairment in pretreatment breast cancer patients compared with matched non-cancer controls; however, the cancer patients scored worse than the controls on a small fraction of the cognitive indices that were used. Performance on these indices was indeed robustly associated with PTSD symptoms.
Our results therefore indicate that pretreatment cognitive impairment in breast cancer patients may be largely caused by the stress of being diagnosed with cancer.