Older female cancer survivors are significantly more likely to suffer from long-term cognitive impairment after diagnosis and treatment when compared to their twin sibling with no history of cancer, a USC study found.
The risk was higher among survivors of gynecologic cancers and those who had treatments directly or potentially affecting ovarian functioning, according to the study published in the December issue of the Journal of Gerontology.
Findings suggest localized treatments that affect estrogen-producing areas may be associated with serious impairment of memory and thinking in older women, said co-author Margaret Gatz.
“This is not the result we expected,” said Gatz, a USC psychology professor. “We expected chemotherapy would have a larger effect. This surprised us deeply. The results showed that either surgery, radiation or pelvic cancer itself accounts for the increased risk of cognitive impairment.”
The study defined cognitive impairment as having significant problems in memory (such as not being able to remember three words over a short delay) and thinking (such as not being able to explain similarities and differences between pairs of common items), to the extent that the problems affected the management of daily life.
The association was strongest in women whose cancer treatment affected the pelvic area, resulted in ovary removal and/or when radiation was used in the pelvic area. The bulk of the women in the study were past menopause so the effect on estrogen production would not be as dramatic, yet cognition impairment was still significant.
The study seems to confirm that estrogen, even in older women, is important, Gatz said.
The next hypothesis Keiko Kurita, who is the lead author and a USC graduate student, will investigate for her dissertation is the role of ovaries, which produce estrogen, in cognitive performance.
“When we found that female, but not male, cancer survivors were at an increased risk for cognitive impairment compared to their co-twins, we were eager to uncover the reasons that might explain this,” said Kurita, who is advised by two of the study’s co-authors, Gatz and Beth Meyerowitz, a USC psychology professor who is corresponding author on the article. “On my dissertation project we will be examining the possible relation between cognitive functioning and ovarian removal, a research question that grew directly from the findings that we have just published.”
The study reviewed over 400 twin pairs who had participated in cognitive screening at least three years after one had ended cancer treatment.
Gatz, the USC Dornsife College’s Psychology Department chair and a foreign adjunct professor with the Karolinska Institutet in Stockholm, Sweden, is the one of the few researchers with access to the largest comprehensive twin registry in the world, the Swedish Twin Registry. The registry is a set of records on same-sex twins born between 1886 and 1925.
Studying twins statistically removes genetic or early childhood causes of both cancer and cognitive deficits, as twins usually possess similar genetic and early environmental influences. The comparison with cancer-free twins means the increased dysfunction cannot only be attributed to the normal aging process.
Cognitive effects on the twins were evaluated using a standardized mental status interview. The study was designed to rule out the short-term side effects of cancer treatment by separating the cognitive tests and the end of treatment by at least three years.
Per Hall of the Karolinska Institutet in Stockholm, Sweden, is also a co-author.
In a 2005 study, Gatz, Meyerowitz, Hall, and USC doctoral student Lara Heflin found long-term cancer survivors over age 65 were twice as likely to develop cognitive problems as individuals who had never been diagnosed with cancer. The study did not suggest a cause for the cognitive problems in cancer survivors.
Funding for this research came from the National Cancer Institute at the National Institutes of Health and the National Institute on Aging at the National Institutes of Health.
Contact: Eddie North-Hager at (213) 740-9335