Author: Mary Anne Kenny
The risk of transient ischaemic attack (TIA) or ischaemic stroke is at least doubled by head and neck radiotherapy, a problem increasing in urgency as patients survive their malignancies longer, an Australian review of the literature has concluded. Besides case reports, the reviewers found 77 studies of stroke, TIA or rates of carotid stenosis in patients who had received radiation therapy for primary or secondary cancers of the head or neck region. The 17 epidemiological studies revealed that the procedures appear to “at least double” the relative risk of TIA or stroke, with the exception of adjuvant neck radiotherapy for breast cancer where no association was found.
Radiotherapy for breast cancer resulted in only the carotid artery only being minimally exposed to radiation, the authors reported in Stroke.
The evidence for radiation vasculopathy (defined as chronic occlusive cerbrovascular disease affecting medium- and large-diameter arteries) was strongest where the exposure occurred in childhood, but the exact magnitude of the increase was unclear due to heterogeneity in the studies.
Considering the 17 imaging studies, the reviewers found they repeatedly showed “an increased prevalence of haemodynamically significant carotid stenosis” when there was a history of head and neck radiotherapy. The most significant radiologic evidence implicating radiotherapy in TIA and stroke was the spatial distribution of the vascular disease itself, they said. “It signposts the [radiotherapy] field.”
Two theories of the pathogenesis of radiation vasculopathy were presented in the literature, they said. One was that it was an accelerated form of atherosclerosis and the other was that it was a distinct disease entity shaped by the initial radiation insult to the vasa vasorum. No trial had adequately assessed the medical treatment options, the reviewers said.
“Long-term prospective studies remain a priority as the problem is anticipated to rise with improvements in post [radiotherapy] patient survival,” they wrote.
Source: Stroke 2011; doi: 10.1161/STROKEAHA.111.615203.