A PolyU study has found that 87% of nasopharyngeal carcinoma patients who received radiotherapy developed carotid atherosclerosis, thus placing them at higher risk of stroke.
Calvin, a former nasopharyngeal carcinoma (NPC) patient who was cured years ago, recently suffered a stroke. His family wondered whether the neck radiotherapy used in his previous treatment was a contributing factor. Now, a scientific study offers an answer.
There is a high prevalence of cervical lymph node metastasis in NPC patients, so neck radiotherapy is commonly used in the treatment process. However, ionising radiation in that therapy damages the carotid artery and could lead to the development of carotid atherosclerosis, which may result in cerebrovascular events such as transient ischemic attack and stroke.
With this possibility in mind, Dr Michael Ying, Prof. Yip Shea-ping and Dr Vincent Wu at the Department of Health Technology and Informatics conducted a study to investigate the differences in carotid atherosclerosis among post-radiotherapy NPC patients, type 2 diabetes mellitus (DM) patients, and healthy controls by using ultrasonography (a safe, non-invasive and cost-effective imaging modality).
The team evaluated and compared the degree of carotid atherosclerosis in 69 NPC patients treated with radiotherapy, 70 patients with type 2 DM and 76 healthy controls without both conventional cardiovascular risk factors and previous radiotherapy. Parameters (including carotid intima-media thickness, carotid arterial stiffness, presence of carotid plaque and carotid stenosis) were assessed using ultrasonography.
The results indicated that radiation-induced carotid atherosclerosis occurred in 87% of the post-radiotherapy NPC patients and was more severe than that in DM patients and healthy controls in terms of a stiffer carotid artery wall and a higher carotid plaque burden. "With a higher prevalence and severity of carotid atherosclerosis, the risk of having a stroke in post-radiotherapy NPC patients is doubled compared to non-irradiated controls," Dr Ying elaborated.
The study enhanced the understanding of potential variations between radiation-induced and spontaneous carotid atherosclerosis, which might offer a justification for assessing carotid atherosclerosis in routine follow-ups for NPC patients. Dr Wu recommended oncologists to well control and adjust the dose of radiotherapy when designing it so as to avoid unnecessary damage to the normal cells in the neck and surrounding areas. "In the four years after radiotherapy, NPC patients should undergo ultrasound carotid evaluation at least biennially," added Prof. Yip. ♦