Patients with Comorbid Cancer and Dementia More Likely to Die

January 5, 2009

Researchers found that the stage of cancer at diagnosis was significantly less likely to relate to mortality in patients with preexisting dementia.

As the size of the elderly demographic in the United States increases, we will likely see a corresponding increase in the incidences of dementia and cancers. Researchers recently reported that the stage of cancer at diagnosis was significantly less likely to relate to mortality in patients with preexisting dementia.

Using the Surveillance, Epidemiology, and End Results-Medicare (SEER) database, investigators conducted a retrospective cohort study of 106,061 patients aged 68 years or older who had received a diagnosis of breast, colon, or prostate cancer. They stratified patients according to the presence/absence of a previous dementia diagnosis and assessed their overall mortality risk (including cancerous and noncancerous causes).

A preexisting dementia diagnosis was observed in 7% percent of sampled patients. Patients with dementia had significantly lower survival rates compared with patients without dementia, and most of the excess deaths were attributable to noncancerous causes. Approximately 33% of patients with dementia died within 6 months of receiving a cancer diagnosis, compared with 8.5% of patients with no cognitive concerns. In dementia patients with breast or colon cancer, a more advanced stage of cancer at diagnosis accounted for less than 17.0% of the excess mortality. None of the excess deaths in those with prostate cancer could be explained by cancer stage at diagnosis. Researchers concluded that in patients with all three cancer types, preexisting dementia attenuated the relationship between stage at diagnosis and survival.

“What we found was that older people with preexisting dementia have a very high rate of death from noncancer causes in the years after the diagnosis,” said coauthor James S. Goodwin, MD, director of the Sealy Center on Aging at the University of Texas Medical Branch in Galveston. “Whether you screen those people or not, whether you diagnose that cancer earlier or not, is going to have less impact on an older person with dementia because they are going to be dying anyway, before the cancer has a chance to kill them.”

According to Dr. Goodwin, this tips the risk/benefit balance. He suggested that there might be little reason, for example, to pressure a reluctant elderly woman with dementia to undergo a mammogram. The agitation and stress the beneficial procedure induces in a patient who may erroneously view it as an assault outweigh the advantages of finding a cancer that is not likely to cause her eventual death.

Dr. Goodwin said that his study did not address which, if any, particular screening techniques “may do more harm than good” and instead focused only on whether there was less benefit to screening elderly patients with dementia for cancer. “For these older patients, the relationship between stage at diagnosis and overall survival was much less than in older patients without dementia.”

One of the fastest growing causes of death over the course of the study was the dementia itself, noted William Dale, MD, PhD, chief of the Section of Geriatrics & Palliative Medicine at the University of Chicago Medical Center in Illinois. The ability to diagnose dementia improved over the years for which the data were collected. Patients were progressively receiving a diagnosis while the disease was in its earlier stages.

“Most of their data is likely related to those with later-stage dementia, and there is no severity measure of dementia available with this data,” said Dr. Dale. He cautioned that investigators “need to be very careful in applying these findings to those with earlier and less severe forms of cognitive impairment.” He added that a diagnosis of dementia in the 1990s is likely to be very different from today’s diagnosis, which is more likely to consist of early dementia or mild cognitive impairment.

One concern is that, based on these findings, a physician might be encouraged to view a patient with comorbid cancer and mild dementia as an unsuitable candidate for screening or aggressive treatment. These results, said Dr. Dale, would not be applicable to an individual with an early form of cognitive impairment who receives a diagnosis of aggressive cancer in 2008. “Keeping this in mind, I think their results apply very well to those patients with more obviously advanced forms of dementia,” he added.

In addition, Dr. Dale thinks it is reasonable to consider combining cognitive impairment assessment for elderly patients with decisions about cancer screenings and treatment. He noted that while busy oncology practices often overlook a dementia diagnosis in patients, there are at least two reasons why it is important that clinicians make such an assessment. “One is that dementia itself lowers life expectancy and might impact your decision to screen for cancer,” and the other is that “Dementia…affects the care burden and adherence to treatment. Going through surgery, chemotherapy or radiation is an even harder burden for someone with dementia and their caregivers, and knowing this in advance is crucial to optimizing therapy.”

Arch Intern Med

Raji MA, et al. Effect of a dementia diagnosis on survival of older patients after a diagnosis of breast, colon, or prostate cancer. . 2008;168:2033-2040.

Author Kurt Ullman is a freelance health and medical writer based out of Indianapolis.