- 期刊
閃避海馬迴的全腦放射治療：比較傳統二維及強度調控治療與非共平面弧形治療的計劃品質和治療效率
Whole-Brain Radiotherapy with Hippocampal Sparing: The Comparison of Plan Quality and Treatment Efficiency Using 2D and Volumetric Modulated Arc Therapy and Intensity-Modulated Radiotherapy Techniques
摘要
針對腦部腫瘤轉移的全腦放射治療已極為普遍，但據統計有11%的全腦放射治療患者在一年內會發生痴呆或記憶力喪失等嚴重的神經學症狀，如能適當抑低海馬迴劑量將有效減輕神經毒性並降低副作用。因此我們設計了非共平面弧形治療的方式，並與文獻的強度調控治療及傳統雙側對照的方式做整體的比較。五十位患者均進行核磁共振影像檢查以圈畫出正確的海馬迴位置，全腦靶區的定義即為大腦減去海馬迴外加7 mm的體積，給予劑量為30 Gy共12次治療，設計傳統雙側對照並阻擋海馬迴及眼球的治療方式，還有非共平面強度調控治療及非共平面弧形治療等三種治療計畫進行各項劑量參數及治療效率的比較。以全腦靶區的劑量包覆及劑量均勻度而言，非共平面強度調控治療及非共平面弧形治療的計畫95%劑量以上所占體積分別是96.7%及97.3%，傳統雙側治療則僅有75.7%。對於海馬迴的平均等效生物劑量分別是4.6 Gy，9.3 Gy，7.8 Gy。在此研究中發現即使閃避海馬迴，非共平面弧形治療仍能達到足夠的劑量包覆及維持劑量均勻度，相對傳統雙側對照，雖然海馬迴劑量夠低，但全腦靶區的劑量涵蓋不足。另外，非共平面弧形治療除了可以合理抑低該區劑量，同時總治療時間在六分鐘以內，此臨床計畫的前期研究也觀察到患者確實可以減緩神經退化。
並列摘要
Whole-brain radiotherapy (WBRT) is the most widely used treatment option for patients with multiple brain metastases, but 11% of long-term brain metastases survivors (＞12 months) treated with WBRT develop severe dementia. RTOG 0933 is a Phase II clinical trial that aims to explore the hypothesis that sparing the hippocampus during cranial irradiation may mitigate radiation-induced neurocognitive toxicity. Although hippocampal-sparing is a big challenge in whole-brain radiotherapy, we discovered some special techniques to approach. The preliminary experience report will be presented in this study. Fifty patients with brain metastases were selected and the hippocampus was contoured on T1-weighted MRI axial sequences. Planning Target Volume (PTV) was defined as whole brain exclusive of the hippocampus plus 7 mm. 2D bilateral fields and non-coplanar VMAT and IMRT treatment plans with prescription dose of 30 Gy in 12 fractions were generated independently for evaluation purpose. The hippocampus volume was 4.2 cm^3 in average, hippocampal avoidance volume occupying 0.31% of the whole-brain planning target volume. For PTV coverage, V_(95%) were 75.7%, 96.7% and 97.3% in average for 2D, IMRT, and VMAT respectively. For hippocampus sparing, equivalent biological mean dose were 4.6 Gy, 9.3 Gy and 7.8 Gy for 2D, IMRT, and VMAT respectively. Target coverage and dose homogeneity were acceptable in IMRT and VMAT plans, but 2D plans cannot perform well. VMAT plans provided more dose fall-off gradient in hippocampus than IMRT plans and VMAT plans delivery time were within 6 minutes. Preclinical evidence suggests that sparing the hippocampus of therapeutic doses of radiation may mitigate neurognitive decline.