GTV Cochlea Distance to Predict the Feasibility of Dose Limiting in Cochlea Sparing during Intensity Modulated Radiation Therapy for Nasopharyngeal Carcinoma

Chao Zhang, Ling-xiang Liu, Wei-zhan Li, Wen Liang, Zhao-hui Chen, Xian-hai Huangand Juan Qi

Department of Radiation Oncology, Panyu Central Hospital, China Department of ENT, Panyu Central Hospital, China Department of Medical Affairs, Panyu Central Hospital, China

^*Correspondance to: Chao Zhang 

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Abstract:

Introduction: This study was to investigate factors related to dose limiting in cochlea sparing in IMRT with nasopharyngeal carcinoma, and to evaluate GTV-cochlea distance used to predict the feasibility of cochlea sparing. Methods: During April 2016 to April 2018 fifty one cases of nasopharyngeal carcinoma patients were enrolled, we designed a cochlea sparing plan (C-Plan) compared with non cochlea sparing plan (R-Plan). The dose radiated to the ipsilateral cochlea and contralateral cochlea was recorded. Among 102 cochleas of fifty one cases we measured and calculated its clinical T stage, GTV volume, PGTV dose and G-C distance in order to explore the relationship between these factors and dose to cochlea. Results: For all T stages, there was a significant difference with cochlea dose limited under 45 Gy between C-Plan and R-Plan (p=0.010). Univariate analysis revealed cochlea dose was associated with its clinical T stage, GTV volume, G-C distance and PGTV dose (p<0.05), multivariate analysis revealed that only G-C distance was related to cochlea dose (p<0.05), and ROC analysis suggested that regarding G-C distance the area under ROC curve was 0.827, the threshold of G-C distance for possible cochlea sparing to limit cochlea dose under 45 Gy was 15.3 mm. Conclusion: Our results demonstrated that the feasibility of cochlea sparing was associated with G-C distance, if G-C distance was more than 15.3 mm it was feasible to spare the ipsilateral or contralateral cochlea. This might help physicists and radiation doctors to make a judgment on whether or not the specific cochlea could be spared.

Keywords:

Cochlea sparing; GTV volume; GTV-cochlea distance; Intensity Modulated Radiotherapy (IMRT); Nasopharyngeal Carcinoma (NPC)

Cite the Article:

Zhang C, Liu L-X, Li W-Z, Liang W, Chen Z-H, Huang X-H, et al. GTV Cochlea Distance to Predict the Feasibility of Dose Limiting in Cochlea Sparing during Intensity Modulated Radiation Therapy for Nasopharyngeal Carcinoma. Clin Oncol. 2019;4:1665.