Risk of cerebrovascular events after neck and supraclavicular radiotherapy: a systematic review.

OBJECTIVE: Although low dose radiation therapy (RT) has been used to prevent re-occlusion of coronary arteries, it may also precipitate vascular damage. Specifically, irradiation to the neck is related to subsequent vascular wall thickening and atherosclerotic plaque formation. Several investigators, reporting patients with varied disease processes and using different methods, have described an increased risk of cerebrovascular events (CVEs) after RT to the neck for head and neck cancer, breast cancer, or lymphoma. Our purpose is to determine the rate and risk of CVEs in patients after receiving radiation therapy to the neck.
METHODS: We performed a pooled analysis of the published data to document the cumulative risk of subsequent stroke after RT to the neck. An extensive MEDLINE and PUBMED search yielded five articles involving 6908 patients describing institutional series or cohort analyses comparing the frequency of CVE in irradiated versus non-irradiated patients.
RESULTS: Sixty-six CVEs were reported in 2567 patients after neck RT, whereas only 12 CVEs were documented in 4119 non-irradiated patients. Crude risk of CVEs after neck RT was 2.6%, and was 0.29% in non-irradiated patients. This odds ratio of 9.0 was statistically significant (95% CI 4.9, 16.7; p<0.0001). Data for supraclavicular RT were more difficult to analyze given differences in populations and reporting between the three studies, but it appears a significant risk is unlikely.
CONCLUSIONS: Neck RT increases the likelihood of CVEs, but this risk must be reconciled with the benefits of the therapy in the specific clinical situation. For instance, consideration should be made to limiting neck RT where possible for breast cancer and lymphoma patients.