Three-fourths of people who had radiation therapy for nasopharyngeal cancer had narrowing or blockage of blood vessels in the neck, according to a report in the journal Cancer (Vol. 92, No. 9: 2357-2363).

While radiation is an effective therapy for cancer, it may also cause a narrowing of important blood vessels. This can cause to strokes and heart attacks.

Nasopharyngeal cancer affects part of the upper throat, and includes the adenoids. The typical treatment is radiation.

Radiation is given to both the tumor site and neck, so the carotid arteries are affected. The treatment is the same for other head and neck cancers.

Some doctors noticed an increase in strokes among these patients. But, before this study, none of the doctors considered that radiation might have caused the strokes.

This study was prompted by the lead author’s experiences with her father. Wynnie Wai-man Lam, MD, a radiologist at Prince of Wales Hospital in Hong Kong, said that her father suffered a series of strokes over a five-year period after he was treated for nasopharyngeal cancer.

Her father first passed out and hit his head. He had a brain scan, but it showed no abnormalities. When he fell again three years later, Lam looked deeper for a possible cause. She said an ultrasound test of blood flow called a Doppler revealed that her father had severe carotid artery stenosis (narrowing or blockage).

“He had no other risk factors for [heart disease],” Lam said. “He had no hypertension, no diabetes, and his cholesterol level was not high. He had been quite fit before his illness.

"I then realized that I had missed the carotid artery stenosis five years ago, and I thought radiation might be a contributing factor," she said. "I looked up the literature [but] nothing much had been said about radiation-induced carotid artery stenosis. I tried to convince our oncologists, and we started this project.”

Using Doppler, Lam and her colleagues examined the carotid arteries of 71 people who had nasopharyngeal cancer from four to 20 years earlier. They compared their findings to those in 51 people who had just been diagnosed with cancer and had not yet begun treatment.

Both groups of patients had similar diets and health habits. In the treatment group, 79% of the participants had stenosis, compared with 22% in the newly diagnosed group.

According to Lam, patients who have arterial damage often can’t connect their symptoms to the fact that they had radiation earlier. This makes early screening useful.

Lam and an American Cancer Society (ACS) expert both said the study shows the need to screen cancer survivors. Screening should continue for several years, they said.

Ivo Janecka, MD, ACS vice president of medical affairs and cancer control in the Florida division, called Lam’s paper “an important study.”

He said he believes nasopharyngeal cancer patients should be get a Doppler screening for carotid artery stenosis at the time of diagnosis. Depending on those findings, survivors should be checked again after cancer treatment.

“This is a simple, non-pain producing test to see where they stand,” he said. Patients who have “perfect vessels” could be rechecked one or two years later. Patients could take preventive measures, such as using aspirin, which can prevent strokes.

Those who already have risk factors that lead to heart disease and stroke, such as obesity and diabetes, or who already show signs of stenosis, may need to have the Doppler repeated more frequently, Janecka said. Because this is a new field of study, there are no guidelines yet, he said.