Study on the effect of PET/CT-guided nasopharyngeal carcinoma target delineation on the dose received by endangered organs

• Main Authors: Guang Huang, Shi-Ping Yang, Xian-Wei Wang, Yan-Hai Yin, Feng Chen, Ze-Tan Chen
• Format: Article
• Language: English
• Published: Editorial Board of Journal of Hainan Medical University 2019-08-01
• Series: Journal of Hainan Medical University
• Subjects: nasopharyngeal carcinoma; intensity-modulated radiation therapy; endangered organ; dose difference
• Online Access: http://www.hnykdxxb.com/PDF/201915/13.pdf

Objective: To compare the differences of radiation-induced doses between 18F-FDG-PET/CT and CT/MRI-guided target delineation in nasopharyngeal carcinoma in intensity-modulated radiotherapy. Methods: A total of 31 patients with locally advanced nasopharyngeal carcinoma receiving treatment in our hospital from December 2016 to December 2017 were studied in this research, and 18F-FDG-PET/CT and CT/MRI were used to guide the target delineation to develop an intensity-modulated radiotherapy plan(experimental group and control group). The dose differences between GTV and endangered organs in the two groups were compared. Results: Comparison of primary tumor volume: PET/CT was smaller than CT/MRI, and volumes of T3 and T4 were significantly different (P<0.001). Comparison of the two delineation plans, in terms of PGTV in Dmin, Dmean, and D95, the data of experimental group was smaller than that of the control group; in Dmax, the PGTV of the experimental group was larger than that of the control group with P<0.001 considered as a significant difference. In Dmin and Dmax, doses of experimental groups of the spinal cord were lower than those of the control group, showing a significant difference (P=0.022, 0.042); In Dmean, there was no difference between the two groups. In Dmax doses of an experimental group of the brainstem and parotid gland were significantly smaller than the control group (P=0.001, 0.047) while there was no difference between Dmin and Dmean. There was no difference between the two groups of Dmin, Dmean, and Dmax in the doses received by chiasm and temporal lobe. Conclusion: PET/CT guided target delineation is applied in the simultaneous dose adjustment of intensity-modulated radiation therapy in patients with advanced nasopharyngeal carcinoma. In primary lesion targets shown by MRI/CT, the tumor tissue of PET/CT concentration zone was given a higher dose with relatively smaller average dose and minimum dose in the overall tumor target area. Statistics also showed that the doses received by the spinal cord, brain stem, and parotid gland were reduced with no effect on the optic chiasm and temporal lobe. In the future, more studies should probe into the long-term effects of dose changes on lesion control and endangered organs.