Assessment of Carotid Vasculitis in Head and Neck Cancer Patients following Individual Proton/Photon Radiation Therapy and Combined Therapy Using 18F-FDG PET/CT Imaging

Introduction: Head and neck cancers (HNC), a prevalent class of malignancies, occur at the oral cavity, major salivary glands, hypopharynx, and more. Photon radiotherapy (RT) with surgery or chemotherapy is the standard treatment for HNC, but it can be toxic to nearby tissue. Previous studies have demonstrated that proton RT, an alternative approach, reduces the incidence of inflammatory complications via greater precision, fewer beams, and lower doses to normal tissue. These studies leveraged PET/CT with an 18F-FDG radiotracer to evaluate RT-induced vasculopathy. Both RT types can result in a range of cardiovascular complications such as carotid vasculitis and vasculopathy that necessitate surgical interventions like carotid endarterectomy and carotid stenting, which can lead to infection, strokes, bleeding, and restenosis. Thus, we aim to assess via 18F-FDG PET/CT whether a combined proton and photon RT therapy approach modulates these effects in HNC patients, offering valuable insights into mitigate carotid vasculitis via radiotherapy strategies.

Methods: HNC patients who underwent proton and/or photon RT in combination with chemotherapy at the University of Pennsylvania between February 9, 2010, and January 6, 2020 were the subjects of a retrospective study. Following the application of the exclusion criteria, 18F-FDG-PET/CT scans for 26 HNC patients (9 proton RT, 10 photon RT, 7 with combined proton and photon RT) were obtained for before RT and 5-10 months after RT. All subjects underwent 18F-FDG-PET/CT imaging 60 minutes after 5.0 MBq/kg 18F-FDG injection. Delta global SUVmean was determined by taking the difference between the global SUVmean measured 5 to 10 months after radiation therapy and the baseline global SUVmean for both the left common carotid (LCC) and right common carotid (RCC). OsiriX MD was utilized to analyze 18F-FDG uptake in the RCC and LCC. Wilcoxon’s rank-sum test was performed to compare the pre- and post-RT scans’ global SUVmean. p-Value < 0.05 was considered statistically significant.

Results: In the LCC, delta SUVmean was lower in the proton group (0.213 ± 0.26) compared to the combined RT group (0.56 ± 0.35, p = 0.032), and delta SUVmean was lower in the photon group (0.278 ± 0.21) compared to the combined RT therapy group (0.56 ± 0.35, p = 0.048). In the RCC, delta SUVmean was also lower in the proton group (0.10 ± 0.31) compared to the combined RT group (0.31 ± 0.09, p = 0.040), and delta SUVmean was also lower in the photon group (0.245 ± 0.19) compared to the combined RT therapy group (0.44 ± 0.13, p = 0.031).

Conclusion: The results indicate that combined proton and photon therapy causes significantly more inflammation in both the RCC and LCC of HNC patients compared to individual proton and individual photon therapy. Future studies should consider conducting longer follow-up scans and clinical data related to vasculitis. A limitation of this study is the small sample size, which will be improved in future studies.

Publication History

Article published online:
05 February 2024