乳房保留手術後同步加強放射線治療: 強度調控放射線治療與螺旋斷層治療之治療計畫比較

Simultaneous integrated boost radiotherapy after breast conserving surgery of breast cancer: Treatment plannings comparised of intensity modulated radiotherapy and helical TomoTherapy

呂姿瑩(Tzu-Ying Lu)

指導教授 ： 陳佳如

共同指導教授 ： 黃志仁(Chih-Jen Huang)

高雄醫學大學/健康科學院/醫學放射技術學研究所/碩士(2012年)

摘要

本研究是比較逆算式強度調控放射線治療（Inverse Planned Intensity Modulated Radiation Therapy, ipIMRT）與螺旋式電腦斷層治療儀（Helical TomoTherapy, HT）兩種治療計畫，針對左側乳房保留手術（Breast -Conserving Surgery, BCS）後的乳癌患者，在同步加強放射線治療（Simultaneous Integrated Boost, SIB）方法治療時，兩種治療計畫在劑量分佈上之差異，並且探討身體特徵是否會對劑量分佈產生影響。
本研究共採用了36位接受BCS術後左側早期乳癌的患者（T1-2N0-1Mo），其同步加強劑量的計畫靶體積(boosted Planning Target Volume, PTVboost) 與乳房計畫靶體積(whole breast Planning Target Volume, PTVwb)同時分別給予60.2Gy和50.4Gy的劑量，分為28次治療。評估方式包括：高劑量包覆腫瘤的順形度（Conformity Index, CI）、腫瘤劑量分佈的均勻度（Homogeneity Index, HI）、腫瘤與心臟、患側肺部等不同劑量點及心臟、患側肺部的正常組織併發症機率(Normal Tissue Complication Probability, NTCP)等指標來評估兩種不同治療計畫之差異。另外，為了瞭解乳房型態對於評估結果的影響，亦量測每位病人的三項體型參數：（1）胸寬–胸厚比、（2）乳房體積與（3）胸骨到乳頭及乳頭到胸壁切線之角度，觀察其對腫瘤劑量分佈及心臟與患側肺部劑量分佈與NTCP之影響。
結果顯示HT在腫瘤的均勻度與順形度皆明顯優於ipIMRT（p<0.05），各劑量點皆較接近處方劑量，但在正常組織會有較多的體積接受到低劑量；而ipIMRT在正常組織的所接受到較高劑量的體積則較多。另外，HT在心臟與患側肺部的NTCP皆高於ipIMRT。身體特徵對於劑量的影響上，當胸寬-胸厚比值大於1.6時，ipIMRT的心臟NTCP約為胸寬–胸厚比值小於1.6的兩倍；而胸骨到乳頭與乳頭到胸壁的切線夾角大於91°時， HT患側肺部的NTCP約為夾角小於91°的2.7倍；另外，在乳房體積大小的比較，當PTVwb小於350c.c時，HT治療方法在患側肺部的NTCP是PTVwb大於350c.c的2.2倍。
總結，HT在腫瘤劑量分佈皆明顯優於ipIMRT，但在正常組織方面，會有較多的體積接受到低劑量。評估身體特徵對劑量的影響時，發現到胸寬-胸厚比值大小在利用ipIMRT治療方法時對心臟影響較明顯；而夾角與乳房體積大小對利用HT治療方法時，則對患側肺部影響較明顯。因此，在評估以何種放射線治療方法治療早期乳癌病患時，應多加考慮體型與低劑量對肺臟及心臟的影響，以免增加病人的副作用。

關鍵字

同步加強放射治療 ； 乳癌 ； 螺旋刀

並列摘要

Purpose:
The purpose of this study is to compare the radiation dose distribution inverse-planned intensity-modulated radiotherapy (ipIMRT) and helical TomoTherapy (HT) for breast cancer patients undergoing whole breast radiation with simultaneous integrated boost (SIB), which may be related to radiation-induced pneumonitis and cardiac mortality. To investigate whether some geometric/dosimetric indicators can be determined to estimate the normal tissue complication probability.
Material and methods：
Thirty-six patients with left breast cancer (clinical stage T1–2N0–1M0) were eligible for the trial. All patients generated their treatment planning from both HT and ipIMRT under the prescription of SIB technique. The whole breast and tumor bed were prescribed 50.4Gy and 60.2Gy, in 28 fractions, respectively. These parameters include conformity index（CI）、homogeneity index （HI）、different dose point and normal tissue complication probability. And three geometric parameters were measured for each patient: the thorax width/thickness ratio, breast volume and the angle of the nipple–sternum to nipple-chest wall.
Results：
The HI and CI were better in HT than in ipIMRT (p<0.001), and differenr dose points such as maximum dose、minimum dose and so on were more closer the prescribed dose. But there were more volume received lower dose（Ipsilateral lung V5Gy：HT about 71.7% vs ipIMR about 36.8%，p<0.001；Heart V5Gy：HT about 94.4% vs ipIMRT about 30.2%， p<0.001。）；there were more volume received more higher dose in ipIMRT（Ipsilaterla lung V20Gy：HT about 13.6% vs ipIMRT about 17.7%，p<0.001；Heart V30Gy：HT about 1.7% vs ipIMRT about 5.6%，p<0.001）. The NTCP was higher in HT than in ipIMRT. Three geometric parameters, the breast volume, angle and thorax width/thickness ratio, were the determining factors for evaluating the NTCP. Except, the breast volume, angle and thorax width/thickness ratio were the significant factor for evaluating the NTCP. When the thorax width/thickness ratio >1.6, the NTCP for heart will become double in ipIMRT；°the NTCP for ipsilateral lung of the angle>91°was 2.7times as great as the angle<91 in HT；the NTCP for ipsilateral lung of the breast volume<350c.c was 2.2 times greater than the breast volume>350c.c.
Conclusion:
Our results showed there were more volume received lower dose in HT. When the radiation oncologist judges which techniques is better to the patient, he should be think about the effect of the body characteristic and low dose carefully.

並列關鍵字

Simultaneous integrated boost radiotherapy ； breast cancer ； TomoTherapy

參考文獻

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