Post-chemotherapy cognitive impairment
(also known as chemotherapy-induced cognitive dysfunction
, chemo brain
or chemo fog
) describes the cognitive
impairment that can result from chemotherapy
treatment. Approximately 20-30% of people who undergo chemotherapy experience some level of post-chemotherapy cognitive impairment. The phenomenon first came to light because of the large number of breast cancer survivors who complained of changes in memory, fluency, and other cognitive abilities that impeded their ability to function as they had pre-chemotherapy.
was recognized primarily in breast cancer
survivor and support groups
as affecting a subset of individuals treated with chemotherapy
, who attributed it to the effects of the medication taken to treat their cancers.
PCCI affects a subset of breast cancer
survivors, though the overall epidemiology
is not well known.
Although the causes and existence of post-chemotherapy cognitive impairment have been a subject of debate, recent studies have confirmed that post-chemotherapy cognitive impairment is a real, measurable side-effect of chemotherapy that appears in some patients. The details of PCCI's causes and boundaries are not well known, with more research on the subject required to understand and treat the condition. Bortezomib
is known to cause neuropathy
to the sensory
and peripheral nervous systems
that is reversible. In most cases there is no known way of reducing the effects of chemotherapeutic agents related to taxanes
-based compounds (oxaliplatin
is a notable exception to the latter category - though it does cause PCCI its effects can be buffered by infusion of calcium
and thought related to PCCI include the ability of the nerves to repair themselves, the ability of cells to excrete compounds, permeability of the blood-brain barrier
, damage done to DNA
including shortening of telomeres
and cellular oxidative stress
. Other theories suggest vascular
and the presence of the epsilon 4 version of the apolipoprotein E gene
PCCI is complex and factors other than the chemotherapeutic agents may impact cognitive functioning. Menopause, the biological impact of a surgical procedure with anesthesia, medications prescribed in addition to the chemotherapy, genetic predisposition, hormone therapy, emotional states (including anxiety, depression and fatigue), comorbid conditions and paraneoplastic syndrome may all co-occur and act as confounding factors in the study or experience of PCCI.
The systems of the body most affected by chemotherapy drugs include visual
and semantic memory
and motor coordination
. These effects can impair a chemotherapy patient's ability to understand and make decision regarding treatment, perform in school
and reduce quality of life
Breast cancer survivors who were treated with chemotherapy have to work harder to perform tasks than survivors whose treatment was surgical. A year after treatment the brains of cancer survivors treated with chemotherapy had physically shrunk while those of people not treated with chemotherapy had not.
Post-chemotherapy cognitive impairment comes as a surprise to many cancer survivors. Often, survivors think their lives will return to normal when the cancer is gone, only to find that the lingering effects of post-chemotherapy cognitive impairment impede their efforts. Working, connecting with loved ones, carrying out day-to-day tasks—all can be very challenging for an impaired brain. Although post-chemotherapy cognitive impairment appears to be temporary, it can be quite long-lived, with some cases lasting 10 years or more.
PCCI is seen as an important area of clinical interest due to the high rates of breast cancer, more aggressive dosing
of chemotherapeutic agents, the use of chemotherapy as an adjuvant to other forms of treatment and higher survival rates of patients. In some patients, fear of PCCI can impact treatment decisions. The magnitude of chemotherapy-related cognitive changes and their impact on the activities of daily living
Hypothesized treatment options include the use of antioxidants
, cognitive behavior therapy
and stimulant drugs such as methylphenidate
, though as the mechanism of PCCI is not well understood the potential treatment options are equally theoretical.
Modafinil, approved for narcolepsy, has been used off-label in trials with people with symptoms of chemobrain. Modafinil is a wakefulness promoting agent that can improve alertness and concentration. A University of Rochester study of 68 subjects had significant results. "We knew from previous studies that modafinil does alleviate problems with memory and attention, and were hoping it would do the same for breast-cancer patients experiencing chemo-brain, which it did," related the study's lead author Sadhna Kohli, Ph.D, a research assistant professor at the University of Rochester's James P. Wilmot Cancer Center.
Research on PCCI is limited, and studies on the subject have often been conflicting in results, in part due to differing means of assessing and defining the phenomenon, which makes comparison and synthesis difficult. Most studies have involved small samples, making generalization difficult, and there has been a focus on younger patients which makes conclusions about the largest group of cancer patients, the elderly
, difficult to draw.
The drug doxorubicin (adriamycin) has been investigated as a PCCI-causing agent due to its production of reactive oxygen species. It has been investigated in an animal model with mice.