前列腺癌影像導引放射治療擺位誤差之劑量評估

The Dosimetric Impact of Daily Setup Error with Image-Guided Radiotherapy for Prostate Cancer

李雅雯(Ya-Wen Li) ； 林招膨(Jao-Perng Lin) ； 陳俊佑(Chun-You Chen) ； 李良明(Liang-Ming Lee) ； 林克勳(Ke-Hsun Lin) ； 溫玉清(Yu-Ching Wen) ； 蕭智豪(Chi-Hao Hsiao) ； 林雍偉(Yung-Wei Lin) ； 陳秋萍(Chiu-Ping Chen) ； 周志成(Chih-Cheng Chou) ； 吳思遠(Szu-Yuan Wu)

《放射治療與腫瘤學》 21卷4期 (2014/12) Pp. 305-315

https://doi.org/10.6316/TRO/201421(4)305

摘要

目的：前列腺癌放射治療，治療間（inter-fraction）的器官變動和形變，會造成每天治療劑量之改變。本研究應用影像導引放射治療（imaged-guided radiation therapy, IGRT）之離線重新計算劑量和線上重新校正擺位之方式來執行全體積調控弧形治療（volumetric modulated arctherapy, VMAT），評估擺位誤差（set-uperror）對臨床靶體積（clinicaltarget volume, CTV）、計畫靶體積（planning target volume, PTV）包覆率和周圍危急器官（organat risk）之劑量影響。材料與方法：本研究為回溯性實驗，時間為西元2011年5月至2013年4月，收集12位前列腺癌病患，應用Elekta Synergy X-ray cone beam computed tomography system執行校正靶體積定位之影像導引放射治療，總治療劑量為75.6Gy。IGRT輔以VMAT，擷取每分次的空間座標之再計算劑量後，以Python程式加總。CTV、PTV之包覆率和周圍危急器官之劑量是被重新評估的，因實際之絕對劑量是重新計算、堆疊在每分次之空間座標上，與原始計畫做比擬。結果：所有病患的平均位移誤差在左右、頭尾、前後各為：2mm±1mm、3mm±3mm、4mm±3mm。系統誤差在左右、頭尾、前後各為：0.8mm、2.0mm、1.6mm。隨機誤差在左右、頭尾、前後分別為：1.2mm、1.7mm、2.1mm。重新計算之CTV劑量包覆率由100%降至96%、PTV包覆率由97.5%降至86.9%，周圍危急器官，在統計上則不具顯著之改變。故影像導引是必須的，雖然CTV劑量包覆率由100%降至96%，但PTV包覆率由97.5%降至86.9%，達統計上之顯著改變。結論：IGRT對前列腺癌輔以VMAT是有益的，不僅能降低每分次間之擺位誤差。對於危急器官和腫瘤之具體劑量，更能精確評估，並獲得更佳之腫瘤控制率與較少之併發症，也期望在未來裡，能有更新的隨機臨床試驗驗證。

關鍵字

影像導引放射治療 ； 全體積調控弧形治療 ； 擺位誤差 ； 臨床靶體積 ； 計畫靶體積

並列摘要

Purpose: In prostate radiation therapy, inter-fractional organ motion/deformation has posed significant challenges on reliable daily dose delivery. To evaluate the set-up errors and dose impact at clinical target volume (CTV), planning target volume (PTV) coverage and critical organ with cone beam computed tomography (CBCT), image-guided radiation therapy (IGRT), volumetric modulated arc therapy (VMAT); off-line re-optimization and online re-positioning have been used clinically. Materials and Methods: Between 2011 and 2013, 12 patients with prostate cancer were treated with IGRT to a dose of 75.6 Gy with daily correction of the target position based on Elekta Synergy X-ray cone beam computed tomography system, image-guided radiation therapy practiced with VMAT. We captured each space coordinates in every fraction with dose redistribution to form a new dose distribution with the Pyton software. The real dose with recalculation and stacking with new three dimensional coordinates from each fraction were compared with initial plan. The dose at CTV, PTV coverage and critical organ were reevaluated. Results: The average shift of ML (medial-lateral), CC (cranio-caudal) and AP (anterior-posterior) were 2 mm±1 mm, 3 mm±3 mm and 4 mm±3 mm. The calculated systematic errors in ML, AP and CC direction were 0.8 mm, 2.0 mm and 1.6 mm. The calculated random errors in ML, AP and CC direction were 1.22 mm, 1.7 mm and 2.1 mm. The coverage of CTV and PTV with recalculation were significantly decreased from 100% to 96% and 97.5% to 86.9% respectively. There was no statistical difference in the dose to organ at risk. IGRT will be necessary in our study. Though CTV coverage decrease from 100% to 96%, but the PTV coverage decrease from 97.5% to 86.9% reaching statistical significance. Conclusions: IGRT would be beneficial for prostate cancer treatment with VMAT really. CBCT image guide VMAT in radiotherapy to prostate cancer not only shortened the treatment time but also decreased the uncertainty of set-up within each fraction. The specific dose to critical organs and tumor would be more exact compared with radiotherapy without IGRT. The less side effect and better tumor control might be expected in the future after proof of new randomized clinical trial.

並列關鍵字

Image-guided radiation therapy (IGRT) ； Volumetric modulated arc therapy (VMAT) ； Set-up errors ； Clinical target volume (CTV) ； Planning target volume (PTV)