評估三種不同治療計畫之鼻咽癌照射劑量比較與誘發甲狀腺癌危險度分析

Retrospective Evaluation on Dosimetric Comparison and Thyroid Cancer Risks for Three Treatment Planning System on Nasopharyngeal Carcinoma Irradiation

郭仕勳(Shih-Hsun Kuo) ； 顏亨軒(Heng-Hsuan Yen) ； 呂姿瑩(Tzu-Ying Lu) ； 黃旼儀(Ming-Yii Huang) ； 張寶樹(Pao-Shu Chang) ； 黃鈺婷(Yu-Ting Huang) ； 王鈞彥(Chun-Yen Wang)

《臺灣醫事放射期刊》 7卷1期 (2019/07) Pp. 17-26

https://doi.org/10.6717/JTMRT.201906_7(1).0003

摘要

回溯2010至2016期間接受放射線治療的鼻咽癌共37例治療計畫做為研究對象。利用順形指標、均勻指標及特定器官劑量等三項指標，評估不同治療計畫的優劣及不同腫瘤侵犯程度所造成的影響。Tomo Therapy® Treatment Planning System之順形指標為1.03±0.01，均勻指標為0.05±0.01及在危急器官劑量的比較，脊髓的最大劑量為2813.0±458.4 cGy及腦幹的最大劑量為3891.6±444.7 cGy皆為三種治療計畫中最佳。危急器官劑量在不同腫瘤大小之比較中，TNM腫瘤期別中，T分期的T4的治療計畫結果顯示視交叉所接受到的最大劑量3841.8±1526.1 cGy為最高。危急器官劑量在不同頸部淋巴結轉移程度之比較中，TNM腫瘤期別中，N分期的N3的治療計畫結果顯示甲狀腺所接受到的最大劑量6795.5±524.9 cGy為最高。在發生二次癌症危險度分析中，頸部淋巴結轉移程度對甲狀腺二次癌症危險度有顯著差異（p = 0.011 ＜ 0.05），其中N3的甲狀腺平均劑量高於其他的頸部淋巴結轉移程度。因為T4腫瘤較靠近腦幹，為增加腫瘤治療靶體積的包覆性，犧牲少部分體積的腦幹，造成有50.0%的治療計畫中腦幹最大劑量超過5000 cGy。在不同頸部淋巴結轉移程度的治療計畫，有97.3%的甲狀腺的最大劑量都超過4500 cGy但小於8000 cGy，可能是放射腫瘤醫師在勾畫治療計畫靶體積時會執行頸部淋巴結的預防性的照射。

關鍵字

鼻咽癌 ； 二次癌症的發生率 ； 順形指標 ； 均勻指標

並列摘要

The research participants comprised 37 NPC patients who received radiation therapy during the period between 2010 and 2016. Three indices: conformity index (CI), homogeneity index (HI), and organ-specific dose, were used to assess the advantages and disadvantages of three treatment plans and the influence of different levels of tumor invasion in the treatment plans. The organ at risk (OAR) doses were compared when the CI of the TomoTherapy® Treatment Planning System was 1.03±0.01, and the HI was 0.05±0.01. The maximum dose for spinal cord was 2813.0±458.4 cGy, and that for brain stem was 3891.6±444.7 cGy, which were the optimal doses in the three treatment plans. In the secondary cancer risk analysis, the difference between the three treatment plans for the thyroid cancer risk was significant (p = 0.013 ＜ 0.05). Moreover, the degree of neck lymph node metastasis exhibited significant difference regarding the thyroid cancer risk (p = 0.011＜ 0.05). Currently, cancer patients receiving radiation therapy have an increasingly high survival rate. Therefore, determining how to increase the coverage of the planning target area and reasonably reduce the dose administered to the non-target area, as well as how to reduce the incidence rate of secondary cancer and the deterministic effect, are worth investigating.

並列關鍵字

nasopharyngeal carcinoma (NPC) ； secondary cancer risk ； conformity index (CI) ； homogeneity index (HI)