評估乳癌患者接受術後輔助性放射治療因胸廓形狀不同所造成肺部劑量的差異

Evaluation of the thorax shape effect on the lung dose for breast cancer patients receiving post-operative adjuvant radiotherapy

張家馨(Chia-Hsin Chang)

指導教授 ： 張寶樹

高雄醫學大學/健康科學院/醫學影像暨放射科學系碩士班/碩士(2016年)

摘要

早期乳癌患者通常接受乳房保留手術後，會再配合輔助性放射治療。常規乳癌放射治療使用切線照野技術做全乳房照射，為了提高治療範圍的均勻度與順形度並減少低劑量擴散，本科選擇用混合式強度調控技術(hybrid IMRT)作為乳癌的治療技術 。
過去文獻顯示使用影像學中的2D參數用來評估患側肺的劑量，但未有文獻針對胸廓曲度的影響作討論，因此本研究主要以胸廓曲度對於患側肺劑量的影響進行探討。收集80位癌症分期為T2N1以下、接受乳房保留手術的乳癌患者，排除需照射區域淋巴結的患者。因胸廓曲度無法直接測得，故定義一個替代胸廓曲度的測量值-HLD，再量測其他過去文獻曾提到的2D參數，與患側肺劑量進行統計分析。
使用SPSS 22版軟體，用皮爾森相關係數分析所收集到的資料，以p值＜0.05為有顯著的意義。結果得到2D參數與患側肺劑量作分析，胸廓曲度只有弱相關性，而最大肺距離(MLD)則有中強度相關性。
大多數的乳癌患者因胸廓曲度差異不大，因此對於患側肺的劑量影響不明顯。只有少數的漏斗胸患者因胸廓形狀類似駱駝峰，患側肺會接受到很高劑量，這類患者會建議使用多角度IMRT或VMAT。

關鍵字

全乳房照射 ； 胸廓曲度 ； 最大肺距離 ； 混合式強度調控技術

並列摘要

Adjuvant radiotherapy (RT) is usually given to patients with early breast cancer after breast-conserving surgery (BCS). The standard RT technique uses tangential fields to cover the whole breast. We use hybrid intensity modulated RT (hybrid-IMRT) for breast cancer RT to improve homogeneity and conformity, and decrease the scattering dose.
Previous studies showed that 2-demension (2-D) parameters of image can be used to evaluate the ipsilateral lung dose, but no research focused on the effect of thorax curvature (TC) on the ipsilateral lung dose. The current study evaluated the possible influence of TC on the ipsilateral lung dose. We collected 80 cases with pathological stage T2N1 or earlier and receiving BCS. Patients with supraclavicular LN coverage in RT field were excluded. Because of no direct way to measure TC, we defined an alternative method - hypotenuse lung distance (HLD) to measure TC. In addition, 2-D parameters were measured as well for statistical analyses of the ipsilateral lung dose.
SPSS 22 statistical software was used to conduct the Pearson correlation analysis. A p-value of less than 0.05 was defined as statistically significant. We found that TC had only a weak correlation with ipsilateral lung dose. On the other hand, the maximum lung distance (MLD) had a moderate correlation.
The difference of TC in most patients is not obvious, and it may have little contribution to the ipsilateral lung dose. However, a higher ipsilateral lung dose can be expected among cases with funnel chest. We suggest that multiple angles IMRT or VMAT should be used in these patients.

並列關鍵字

whole breast irradiation ； thorax curvature ； maximum lung depth ； hybrid-IMRT

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