左侧乳腺癌改良根治术后切线野放疗中心脏最大距离预测心脏剂量探讨

目的 探讨用切线野心脏最大距离(MHD)来预测左侧乳腺癌心脏照射剂量的可行性。方法 以2010—2011年在我院行辅助性左胸壁切线野放疗的40例左侧乳腺癌改良根治术后患者为研究对象,对每位受试对象用3D TPS计算MHD,全心脏、冠状动脉左前降支、左心室及心前区D_mean以及对侧乳腺组织厚度和胸骨至体表厚度。用曲线拟合方法分析MHD与上述各D_mean相关性,R2>0.8为可靠性非常好。结果 40例患者中MHD在1.14~5.34 cm之间^(2.67±0.98) cm]。MHD与全心脏D_mean的拟合一次、二次和三次方程的R2值分别为0.869、0.875和0.883(3个P=0.000),与心前区D_mean的分别为0.777、0.799和0.813(3个P=0.000),与左心室D_mean的分别为0.598、0.601和0.633(3个P=0.000),与冠状动脉左前降支D_mean的分别为0.418、0.470和0.472(3个P=0.000)。心脏各D_mean不受身体脂肪厚度影响。结论 该模型提示MHD是预测左侧乳腺癌切线野放疗中全心脏、心前区D_mean的可靠指标。

Use of maximum heart distance to evaluate heart dosimetry for tangential field radiotherapy in left-sided breast cancer after modified radical mastectomy

Objective To assess the value of maximum heart distance (MHD) in predicting the dose of tangential field heart irradiation in left-sided breast cancer. Methods A total of 40 left-sided breast cancer patients who were given adjuvant tangential field irradiation on the left chest wall after modified radical mastectomy in our hospital from January 2010 to December 2011 were selected in this study. For each patient, the following parameters were derived using three-dimensional treatment planning system:MHD, mean dose (D_mean) to organs at risk including the whole heart, left anterior descending (LAD) coronary artery, left ventricle (LV), and anterior myocardial territory (AMT), thickness of the contralateral breast tissue, and thickness from the sternum to the body surface (measuring body fat). The relationship between MHD and each D_mean was analyzed by curve fitting equation. The reliability of R2>0.8 represented a good correlation. Results The MHD of 40 patients was between 1.14 and 5.34 cm (2.66±0.16 cm). The R2 values of first-, second-, and third-order curve fitting equations were 0.869, 0.875, and 0.883, respectively, between MHD and whole heart D_mean(all P=0.000);0.777, 0.799, and 0.8133, respectively, between MDH and AMT D_mean(all P=0.000);0.598, 0.601, and 0.6333, respectively, between MHD and LV D_mean(all P=0.000);and 0.418, 0.470, and 0.4723, respectively, between MHD and D_mean of the LAD coronary artery (all P=0.000). The D_mean of all the heart compartments was not affected by the body fat thickness. Conclusions MHD is a reliable predictor of the mean dose to organs at risk (whole heart and AMT) in tangential field radiotherapy for left-sided breast cancer.