Comparison of Significant Carotid Stenosis for Nasopharyngeal Carcinoma between Intensity-Modulated Radiotherapy and Conventional Two-Dimensional Radiotherapy

Abstract

Radiotherapy (RT) serves as the most efficient treatment for nasopharyngeal carcinoma (NPC) and can cause carotid stenosis. This work compared the incidence of significant carotid stenosis between intensity-modulated radiotherapy (IMRT) and two-dimensional conventional radiotherapy (2D-RT) for NPC and explored the risk factors. We retrospectively reviewed 233 cases with NPC who underwent carotid ultrasound post IMRT or 2D-RT from 2006 to 2015. The incidence of significant stenosis after RT was 19.3%. Significant stenosis was identified in 20 (14.6%) of 137 patients treated with IMRT and 25 (26.0%) of 96 patients with 2D-RT, respectively (p = 0.035). Multivariate logistic analysis indicated age (odds ratio = 1.054, 95% CI = 1.011-1.099, p = 0.014), radiation technique (IMRT) (odds ratio = 0.471, 95%CI = 0.241-0.919, p = 0.027) and time interval (odds ratio = 1.068, 95%CI = 1.033-1.105, p = 0.001) as independent predictors for significant carotid stenosis. Our study suggests that IMRT was associated with decreased incidence of significant carotid stenosis versus 2D-RT for NPC. Prevention and carotid ultrasound should be considered for older NPC survivors with longer interval from RT, especially those treated with 2D-RT.

Figure 1

Representative carotid color duplex scan of two patients. (A–D) was the carotid ultrasonography of one patient. For common carotid artery (CCA) of the right side (R): intimal-medial thickness (IMT) was 1.4 mm; internal carotid artery(ICA): occlusion; For L-CCA: IMT 1.0–1.4 mm, resistance index (RI) 0.74; ICA: occlusion; R- vertebral artery(VA): D 3.9 mm, RI 0.50; L-VA: D 4.4 mm, RI 0.56; (E,F) is the other. R-CCA: IMT 1.2 mm, RI:0.64; ICA: IMT 1.1 mm, RI: 0.61. external carotid artery (ECA): IMT 1.3 mm, RI 0.67. L-CCA: IMT 2.0 mm, RI 0.8. ICA: IMT 1.3 mm, RI 0.66. R-VA: D 3.4 mm, RI 0.65. L-VA: D 4.0 mm, RI 0.60. Note the carotid artery (stenosis arrowheads).