Neuropathy: Help for 'A Scary Prognosis'
Network - Fall 2011
Patrick Dougherty, Ph.D., is passionate about finding the cause of pain.
A professor in MD Anderson’s Department of Pain Medicine, Dougherty and his research team explore why some chemotherapy patients develop chronic peripheral neuropathy, a common and
debilitating side effect of chemotherapy.
Several types of frontline cancer drugs cause patients to develop this condition — sensations in the hands and feet that range from numbness and tingling to severe pain. For some, this side effect lasts longer than three months, earning the label chronic.
“For example, 60% to 70% of patients on Velcade® (bortezomib) experience numbness in their hands or feet,” Dougherty says. “One-third of those experience pain, and a smaller percentage
develop chronic pain.
“Once you cross into the ‘chronic’ category, that’s a scary prognosis,” he says. “Our studies have shown that it’s rare for that pain to improve.”
Since he started his career, Dougherty has been intrigued by the biologic mechanisms that cause pain.
Why are some patients more susceptible to painful nerve damage that forces a choice between the most effective chemotherapy and a high quality of life after treatment?
A better way to gauge an important predictor
Dougherty is an authority on devising efficient ways of testing various types of pain response. He’s studied patients’ sensitivity thresholds to touch, pain, heat and cold.
He believes that a patient’s likelihood of developing chronic peripheral neuropathy is related to the density of nerve fibers in the epidural, or outer, layer of the skin. Chemotherapy damages these nerve fibers, and sometimes they don’t regenerate. Their loss leaves patients with chronic pain.
To assess a patient’s baseline density, though, has required a painful punch biopsy on the fingertip. Not surprisingly, patients have been reluctant to submit to this test before treatment.
So Dougherty has been searching for a quick, painless, but accurate, way of assessing the nerve-fiber density of patients before they begin treatment. Recently they’ve had success with an in vivo confocal reflectance microscope capable of high-resolution imaging of the skin. It’s noninvasive and painless.
“If we can look at scans of patients’ fingertips and see that they have relatively fewer nerve endings to begin with, we might tailor treatment to better protect these crucial nerves,” he says. “We want to choose the best dose to avoid toxicities.”
What drives him, Dougherty says, is first, the fact that patients who develop peripheral neuropathy may curtail their chemotherapy treatment, missing out on the ideal dose to wipe out the cancer.
“Second, if patients get neuropathy in their hands and feet, it may not go away and may be quite debilitating for them. It’s not enough just to survive,” he says. “Patients want a high quality of life.”
Best of all, Dougherty says, his research may eventually help all those affected by chronic peripheral neuropathy — for example, diabetics — not just cancer patients.