Medical Mystery Baffles Southern Doctors

People who live in the middle South appear to have a heightened risk of allergic reactions to cetuximab, a chemotherapeutic drug.

After cetuximab's approval, the first three people treated at the University of North Carolina had severe reactions to the drug. Over time, doctors at Sarah Canon and Vanderbilt realized that an unusually high number of their patients were also reacting to the drug.

“After speaking with others, we realized that patients who lived on a line across North Carolina, Tennessee, northern Arkansas and southern Missouri had these adverse reactions to the drug,” said study leader Dr. Bert O’Neil, assistant professor of medicine, division of hematology and oncology at UNC. “So, we thought it appropriate to see what common bonds were there.”

Cancer researchers from UNC and Vanderbilt pooled their patients dating back to when the drug received approval from the Food and Drug Administration, in 2004. More than 140 patients from ongoing clinical trials (at Vanderbilt) and current clinical records (at UNC)
were reviewed for the presence of immediate, severe hypersensitivity reactions as well as pertinent demographics to determine this region’s rate of allergic reactions and to see if a profile of the potentially allergic patient was evident.

My first inclincation was to dismiss this as coincidence, but the rate of severe allergic reactions to cetuximab in the middle South is 22 percent. In the rest of the country, it's just two percent.

So what could explain it? Doctors figure it's a food or plant-based allergen. If the latter, they say that finding it could be extremely difficult. But is that necessarily true? It shouldn't be so hard to look at plant species distributions across the middle South and see if there's anything unique to the region.

In the meantime, the cetuximab's maker, Bristol-Myers Squibb, is working on a test to identify the mechanism of the reaction.

Weird. Not a cancer cluster, but a cancer drug sensitivity cluster? I've never heard of anything like that.

Scientists puzzled by severe allergic reaction to cancer drug in the middle Southern US [Press Release]

High Incidence of Cetuximab-Related Infusion Reactions in Tennessee and
North Carolina and the Association With Atopic History [Journal of
Clinical Oncology]
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Image: Louis Comfort Tiffany*