A new multisite study funded by the National Institute on Aging will examine whether co-occurring Alzheimer disease and stage 4 breast or prostate cancer alters pain perception, potentially leading to undertreated cancer pain.

The five-year project, led by primary investigators Ronald Cowan, MD, PhD, professor of Psychiatry and Behavioral Sciences at Vanderbilt University Medical Center, and Todd Monroe, PhD, associate professor at The Ohio State University College of Nursing, will study thermal and pressure pain thresholds as well as central sensitization to pain in 264 people across three groups: those with stage 4 breast or prostate cancer only, those with Alzheimer disease only, and those with both stage 4 breast or prostate cancer and Alzheimer disease.

According to the researchers, a considerable number of older adults will suffer from cancer and co-occurring Alzheimer disease, but it’s unclear how the combined diagnoses alter pain perception and reporting. If pain processing is altered, it may increase the risk for undertreatment of metastatic cancer pain, reduce the likelihood for pain to be detected upon injury and predispose the patient to increased suffering at the end of life.

Previous fMRI studies have suggested patients with Alzheimer disease may have a stronger perception of pain or a difference in the kind of pain they experience, but they often don’t report it.

“The results showed that people thought patients with Alzheimer didn’t have much pain, so nurses and doctors weren’t treating it or asking about it, and they didn’t give much pain medication,” said Cowan. “People thought that since patients with Alzheimer didn’t complain of pain, they weren’t really having any. We think they have a longer duration of untreated pain, or they may not be able to recognize and label pain, but it could still be affecting them.

“That’s why this study looks at people who should be expected to have pain due to bone metastases from their cancer.”

Researchers at both sites will study pain perception using two psychophysical measures of pain: a small heat stimulus delivered to part of the palm and a pressure device. Researchers will ask the patient to report when they first feel pain and to rate whether the pain is mild or moderate. Patients will also be asked to report how unpleasant each level of pain is to better understand their emotional response.

If pain perception proves stronger in patients with co-occurring cancer and Alzheimer disease, interventions targeting the parts of the brain that are altered may provide relief. Standard pain relief measures may also be more readily used.

“The results of this study might lead to interventions, but they also might just lead to changes in the policies and procedures for the staff who are taking care of these patients. We’re hoping to educate the people who assess pain, which are commonly the nurses and doctors who are treating these patients. We want them to know if pain is present, it may not be reported, and that they should investigate to make sure they’re providing proper treatment. We can’t assume that people aren’t having pain if they don’t necessarily complain of it,” said Cowan.