Whether this mental "fogginess" is psychosomatic or reflects underlying changes in brain function has been a bone of contention among scientists and physicians.
Now, a new study led by Dr. Patricia Ganz, director of cancer prevention and control research at UCLA's Jonsson Comprehensive Cancer Center, demonstrates a significant correlation between poorer performance on neuropsychological tests and memory complaints in post-treatment, early-stage breast cancer patients — particularly those who have undergone combined chemotherapy and radiation.
"The study is one of the first to show that such patient-reported cognitive difficulties — often referred to as 'chemo brain' in those who have had chemotherapy — can be associated with neuropsychological test performance," said Ganz, who is also a professor of health policy and management at UCLA's Fielding School of Public Health and a professor of medicine at the David Geffen School of Medicine at UCLA.
The study was published April 18 in the online edition of the Journal of the National Cancer Institute
and will appear in an upcoming print edition of the journal.
Ganz and her colleagues looked at 189 breast cancer patients, who enrolled in the study about one month after completing their initial breast cancer treatments and before beginning endocrine hormone-replacement therapy (70 percent planned to undergo hormone therapy). Two-thirds of the women had had breast-conserving surgery, more than half had received chemotherapy, and three-quarters had undergone radiation therapy. The average age of study participants was 52.
Because cognitive complaints following cancer treatment have often been associated with anxiety and depressive symptoms, limiting confidence that "chemo brain" and similar difficulties reflect a cancer treatment toxicity, the researchers excluded women with serious depressive symptoms. They also took careful account of the cancer treatments used and whether or not menopause and hormonal changes could be influencing the cognitive complaints. A sample of age-matched healthy women who did not have breast cancer was used as a control group.
The researchers provided a self-reporting questionnaire to the women and found that those with breast cancer reported, on the whole, more severe complaints than normal; 23.3 percent of these patients had higher complaints about their memory, and 19 percent reported higher complaints about higher-level cognition (problem-solving, reasoning, etc.). Significantly, those breast cancer patients who reported more severe memory and higher-level cognition problems were more likely to have undergone both chemotherapy and radiation.
While earlier studies had not identified a consistent association between cognitive complaints and neuropsychological testing abnormalities, the UCLA research team found that even when patients reported subtle changes in their memory and thinking, neuropsychological testing showed detectable differences.
In particular, they discovered that poorer performance on the neuropsychological test was associated both with higher levels of cognitive complaints and with combined radiation-and-chemotherapy treatment, as well as with symptoms related to depression.
"In the past, many researchers said that we can't rely on patients' self-reported complaints or that they are just depressed, because previous studies could not find this association between neuropsychological testing and cognitive complaints," Ganz said. "In this study, we were able to look at specific components of the cognitive complaints and found they were associated with relevant neuropsychological function test abnormalities."
The findings are part of an ongoing study that seeks to examine the extent to which hormone therapy contributes to memory and thinking problems in breast cancer survivors, and this pre-hormone therapy assessment was able to separate the effects of initial treatments on these problems. Earlier post-treatment studies of breast cancer patients were difficult to interpret, as they included women already taking hormone therapy.
"As we provide additional reports on the follow-up testing in these women, we will track their recovery from treatment, as well as determine whether hormone therapy contributes to worsening complaints over time," Ganz said.