| Summary: | 碩士 === 輔仁大學 === 應用統計學研究所 === 96 === Sensori-neural hearing loss (SNHL) is a common complication of radiation therapy in the upper head and neck region. To determine the relationship between the radiation dose to the inner ear and long-term hearing loss, in this thesis, we estimated the dose response relationship for SNHL using Lyman model. Patients with newly diagnosed AJCC Stage I–IV Nasopharynx carcinoma treated from 2000–2003 were identified. The records of 348 ears in 174 patients who received a pre-irradiation pure tone audiogram and follow up audiograms 36 months post-irradiation were included in the analysis. All patients were treated with conventional radiotherapy to 70-74.4 Gy and received cis-diamino-dichloro-platinum (CDDP) and 5-fluorouracil (5-FU) chemotherapy. Pre-treatment and post-radiotherapy audiograms at 1 year, 2 years, and 3 years were obtained. The audiograms included assessment of bone conduction thresholds at 0.25, 0.5, 1, 2, 4, and 8 kHz. We fitted the probability of developing late toxicity within 3 years with the radiation induced SNHL by using Lyman NTCP model. A maximum likelihood analysis yielded good estimates for the Lyman NTCP model parameters for the inner ear for the entire patient population.
Statistical analysis of the Lyman model was performed. Evaluation of goodness of fit and confidence intervals were conducted. The Lyman model parameters TD50(1) (the dose to the whole organ leading to a complication probability of 50%) was found to be 57, 56, 47Gy at 1st year, 2nd year and 3rd year post-radiotherapy at 8kHz and 65, 62, 50Gy at 4kHz. The volume dependence parameter n and the slope of the dose response relationship m were estimated to be nearly 0.02 and 0.85, respectively. The inner ear is a critical structure in patients with nasopharyngeal carcinoma. The dose to the inner ear should be carefully considered when planning radiation treatment in this region.
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