But the study, published in the early online edition of the journal Critical Reviews in Oncology/Hematology, also argues that a diagnosis of dementia shouldn't discourage the use of cancer screenings and appropriate cancer treatments.
"As the population ages and as treatments improve, we're going to see more patients with both dementia and cancer," said lead author Claire Robb, assistant professor in the UGA College of Public Health. "And right now there are no guidelines for oncologists as to how to treat these patients."
Robb and her co-authors in the Senior Adult Oncology Program at Moffitt compared the outcomes of 86 cancer patients with cognitive impairment to a control group of 172 patients with cancer alone. They found that cancer patients with dementia survived an average of four fewer years.
Robb, who is also a researcher in the UGA Cancer Center, said that the reason for the disparity is unclear. She notes that the patients in both groups received similar treatment and that the survival gap persists even after controlling for age, tumor type and tumor stage.
But Robb pointed out that within the cognitively impaired group, there was a dramatic difference in survival time between those with mild cognitive impairment and those with moderate to severe impairment. People with mild cognitive impairment often have problems with thinking and memory yet can still live independently; those with moderate to severe dementia forget details about current events, lose awareness and have difficulty with basic tasks such as preparing meals or choosing proper clothing. The researchers found that while patients with moderate to severe dementia had an average survival time of eight months, those with mild dementia had an average survival time of nearly four and a half years.
"Some people would argue against treating patients with mild cognitive impairment because they're going to have a shorter survival," Robb said. "But, you know, 53 months, almost 4 and a half years, is a pretty significant amount of time to live."
The patients in the UGA/Moffitt study generally received the same treatment regardless of cognitive status, but other studies have found that patients with dementia often receive fewer cancer screenings and undergo less aggressive treatment. One study found that physicians were significantly less likely to recommend a mammogram for a woman with dementia than without, while another found that patients with dementia were twice as likely to have colon cancer reported only after death. Another study of breast cancer patients found that those with dementia were 52 percent less likely to have the tumor removed surgically, 41 percent less likely to undergo radiation therapy, 39 percent less likely to undergo chemotherapy and nearly three times more likely to receive no treatment.
"The fact that cognitively impaired patients seen in our Senior Adult Oncology Program received treatments similar to unimpaired patients while epidemiologic data show a marked difference in treatment provides food for thought," said study co-author Dr. Martine Extermann, associate faculty member at Moffitt. "Although this might reflect a referral bias in which those who volunteered to participate in the study are different from the general population, it might also indicate that such patients benefit from a specialized evaluation and management in a geriatric oncology program."
Robb emphasized that she does not advocate overly aggressive treatment for patients who are in the late stages of dementia, but urges the creation of guidelines to help ensure that cognitively impaired cancer patients receive appropriate treatment.
"People have thought about the impact of the aging population on rates of cancer and dementia, but not much attention has been paid to what happens when the diseases coincide," Robb said. "We're going to be seeing more cases like these, and, if anything, I hope our research raises awareness of this situation."