THURSDAY, Oct. 5, 2006 (HealthDay News) -- "Chemo brain," characterized by chronic problems with memory and attention, afflicts a sizeable minority of cancer survivors.
Now, researchers say the condition may be linked to brain metabolism and blood flow changes that can endure for more than a decade.
The new study, published in the Oct. 5 online edition of Breast Cancer Research and Treatment, should help refute the view that chemo brain is just a figment of patients' imaginations.
"Many women who have had chemo for breast cancer are suffering from cognitive problems for many years after their chemo is finished, and this is the first direct examination of the brain that identifies long-term, if not permanent, changes in brain metabolism related to those cognitive problems," said study lead author Dr. Daniel H.S. Silverman, of the department of molecular and medical pharmacology at the University of California's David Geffen School of Medicine in Los Angeles.
Although chemo brain has been spotted among survivors of other forms of cancer, such as lymphoma, Silverman's group focused on breast cancer patients because the disease is the second-leading cancer killer of American women after lung cancer.
Each year, more than 211,000 American women are diagnosed with breast cancer, the researchers noted, and anywhere from approximately 25 percent to 80 percent of those who undergo chemotherapy complain of later onset of cognitive difficulties.
Silverman stressed, however, that not every breast cancer patient who undergoes chemo suffers from chemo brain, and that many of those who do experience only mild symptoms.
"The impact tends to be relatively subtle," Silverman said. "These are not basic losses of cognition that are going to be noticed when doing easy things. It's more a question of being unable to maintain attention and concentrate when trying to accomplish demanding and high-functioning tasks."
Nevertheless, for some of those who experience this cognitive disruption, the impact can be debilitating. That's why Silverman and his colleagues looked for underlying mechanisms to better understand the condition.
Using positron emission tomography -- commonly known as PET -- the UCLA team scanned the brains of 21 former breast cancer patients who had had tumors surgically removed between five and 10 years prior to this study.
Sixteen of the women had undergone chemotherapy, while the remaining five had had surgery alone. Scans were also conducted for 13 women of similar age and backgrounds with no history of breast cancer or chemotherapy.
The researchers observed brain blood-flow patterns as participants engaged in short-term memory exercises lasting about 10 minutes. They also measured brain metabolism after the exercise.
Silverman's team found that the post-chemo patients experienced relatively large blood flow "spikes" to certain parts of the brain when performing the mental tasks. This group also executed the tasks 13 percent less well than the non-chemo and non-cancer groups.
As well, former chemotherapy recipients showed relatively low brain metabolism rates in the frontal cortex after the tasks were completed, the researchers noted.
Participants who had undergone both chemotherapy and hormonal treatments also showed about an eight percent drop in their resting metabolism in a region of the brain called the basal ganglia.
The basal ganglia is known to function as a bridge between thought and action, the researchers noted.
Putting all the facts together, Silverman's team said the task-related blood flow jumps in the brains of former chemotherapy recipients indicated increased brain activity. That may mean that the chemo group were starting from a neurological disadvantage -- working harder (and with less success) to complete the tasks than those who had never undergone such treatment.
"Chemo-brain symptoms are the single biggest impediment to the quality of life of long-term breast cancer survivors who are getting chemo at earlier and earlier stages and living longer, or even to full life expectancy," noted Silverman. "So, of course, this is discouraging news if you're trying to do something for the affected patients after the fact."
"But on the other hand," he noted, "these findings could ultimately be very encouraging in terms of trying to prevent this, because you could perhaps identify patterns of brain metabolism that could help steer individual patients toward therapy regimens that would be least harmful for them, or to terminate therapies before they cause permanent brain damage."
Dr. Claudine Isaacs, director of the clinical breast cancer program at Georgetown University, said the study was interesting but inconclusive.
"These are very provocative findings, and I think this is the way we need to go in terms of utilizing imaging studies to better understand the problem," she said. "But to know what all this means is another thing."
"The problem is that this is so multi-factorial," cautioned Isaacs. "There are so many things that go into this -- age-related influences, menopause -- and it's very difficult to tease out the different parts."
"It is also true," she added, "that other studies in this area have shown that a relative minority of patients are affected by this phenomenon, and that in substantial numbers, the problems resolve over time among those who are. So, the situation is not necessarily forever."
To learn more about chemo brain, visit the American Cancer Society.