The Impact of Dynamic Parotid Volume Changes and Body Weight Loss on Dose Distributions for Patients with Nasopharyngeal Cancer Receiving Intensity-Modulated Radiation Therapy

腮腺體積變化和體重減輕對於鼻咽癌病患接受強度調控放射治療劑量分布的影響

賴家玄(Chia-Hsuan Lai) ； 陳妙芬(Miao-Fen Chen) ； 洪照雄(Chao-Hsiung Hung) ； 劉國基(Kuo-Chi Liu) ； 王文弘(Wen-Hung Wang) ； 陳文政(Wen-Cheng Chen)

《放射治療與腫瘤學》 17卷2期 (2010/06) Pp. 113-123

https://doi.org/10.6316/TRO/201017(2)113

摘要

目的：對於鼻咽癌而言，強度調控放射治療已成為具展望的新治療方法，可以提供良好的腫瘤包覆並且有意義的保留腮腺的功能。本研究目的在於量化對於顯著的體重減輕與否對腮腺體積的縮小的影響以及腮腺體積的縮小對於腮腺的劑量分布的影響。
材料與方法：從2003年2月到2005年10月，共收集了30個病人。13個病人有顯著的體重減輕。在每個病人接受的劑量到達41.4Gy到46.8Gy的時候，會讓病人再做一次電腦斷層模擬攝影，獲得第二組用來做治療計畫的電腦斷層影像，做出第二個強度調控放射治療的治療計畫（新治療計畫）。另外，在假設沒有第二組用來做治療計畫的電腦斷層影像的情形之下，對於原來的電腦斷層影像，我們也會做出另一個治療計畫（新混合型治療計畫）。
結果：病人身體輪廓的縮減和體重減輕有高度相關。不管體重有無顯著的減輕，腮腺體積都會縮小。在比較“新治療計畫”和“新混合型治療計畫”的劑量分布之後，我們發現兩者在腫瘤目標的包覆上並沒有顯著的劑量差異。但是在腦幹，脊髓以及兩側的腮腺則發現在新混合型治療計畫有顯著的劑量增加。進一步分析發現，當病人體重有顯著的減輕時，脊髓，腦幹，右側的腮腺及高劑量區在PTVCTV1的比例則有顯著增加。當病人體重沒有顯著的減輕時，腦幹和脊髓的劑量會增加但腫瘤的劑量包覆仍是符合要求的。
結論：腮腺體積在強度調控放射治療的過程中會有顯著的縮小，即使病人沒有顯著的體重減輕。對於用強度調控放射治療來治療鼻咽癌，第二組電腦斷層影像以及新的治療計畫是需要的。

關鍵字

鼻咽癌 ； 強度調控放射治療 ； 腮腺 ； 體重減輕 ； 放射治療計畫

並列摘要

Background: Intensity-modulated radiation therapy (IMRT) has become the new promising treatment of nasopharyngeal cancer (NPC) in terms of providing excellent tumor coverage with significant sparing of the parotid glands. In this study, we intend to quantify the importance of the volume shrinkage of parotid gland and its influence on the dose distribution of parotid glands among patients with or without significant body weight loss.
Material and Methods: From Feb. 2003 to Oct. 2005, 30 patients with NPC were enrolled into this study. 13 patients suffered from significant body weight loss (＞6% of their origin body weight at the end of the 4th week of the entire RT course). A 2nd plan CT scan images were acquired after every patient had received 41.4 to 46.8 Gy of prescribed dose. A second IMRT plan was generated for the cone-down treatment. However, we also created a 2nd plan (Hybrid 2nd plan) for the 1st CT images to assume if no 2nd plan CT images were available.
Results: The reductions of body contours are highly correlated with the body weight loss of the patients. The parotid glands decrease in size no matter the patients had significant body weight loss or not. When comparing the dosimetric effects of Hybrid and New 2nd plan, there were no significant dosimetric differences of target coverage. However, increases in the doses of normal tissue such as brainstem, spinal cord, left and right parotid glands were noted. In the subgroup analysis, there were significant increase of spinal cord, brainstem, R't parotid gland doses and hot spots in PTV(subscript CTV1) for patients with significant body weight loss. For patients without significant body weight loss, there were increases of spinal cord and brainstem doses but the target dose coverage remained satisfactory.
Conclusions: We conclude that the volume of parotid glands decreased significantly during the course of IMRT even in patients without significant body weight loss. A 2nd plan CT and a new 2nd IMRT plan based on the new CT scan are needed for the IMRT treatment of NPC.

並列關鍵字

Nasopharyngeal neoplasm ； Intensity-modulated radiotherapy ； Parotid gland ； Weight loss ； Radiotherapy planning