托架坐高角度对乳腺癌锁上腋顶区放疗肺受量的影响

目的探讨乳腺托架坐高角度对乳腺癌术后锁上腋顶光子野照射肺受量的影响。方法选取广州医科大学附属肿瘤医院放疗科收治的12例Ⅱ^Ⅲ期女性乳腺癌改良根治术后放疗患者,将其CT定位图像传输至3D-TPS行锁上腋顶区垂直前切野设计,每例患者分别作50 Gy和26 Gy两种剂量模式,并对0°、10°、15°、20°、25°和30°六种乳腺托架坐高角度分别作不同计划。采用Spearman秩相关分析探讨乳腺托架坐高角度与锁上腋顶野肺受量的相关性。结果 Spearman秩相关分析显示,乳腺托架坐高角度与肺受照体积(V照)成正相关(r=0.841,p=0.000,具有统计学意义)。不论50 Gy或26 Gy照射,Spearman等级相关分析均发现,乳腺托架坐高角度与肺V5、V13、V20、V30、a V5、a V13、a V20、a V30均成正相关(均p=0.000,具有统计学意义)。结论乳腺癌术后锁上腋顶光子野的肺受量随乳腺托架坐高角度的增加而逐级加大;故锁上腋顶野设计应注意乳腺托架坐高角度与肺受量的关系,在不影响放疗设野的条件下应尽可能减少乳腺托架坐高角度。

EFFECTS OF BREAST BRACKET AT HIGH- SITTING ANGLES ON LUNG DOSE IN SUPRACLAVICULAR AND TOP- AXILLARY FIELD AFTER RADIOTHERAPY IN PATIENTS WITH BREAST CANCER

Objective To investigate the effects of breast bracket at high- sitting angles on lung dose in supraclavicular and top axillary photon field in patients with postoperative breast cancer. Methods 12 cases with stage II- III breast cancer received radiotherapy after modified radical mastectomy in the Tumor Hospital of Guangzhou Medical University were selected. Their CT localization images were transmitted to 3D- TPS to design vertical- front cutting beam to supraclavicular and top axillary field with doses of 50 Gy and 26 Gy in each case. Different plans were designed with different high- sitting angles of breast bracket,including 0°,10°,15°,20°,25° and 30°. The Spearman rank correlation was used to analyze and probe relevances between high- sitting angles of breast bracket and lung doses of supraclavicular and top axillary field. Results Spearman rank correlation analysis showed that there was a positive correlation between high- sitting angles of breast bracket and irradiated lung volumes（ r =0. 841,p = 0. 000,with statistical significance）. Whether given with 50 Gy or 26 Gy irradiation,Spearman rank correlation analysis found that there were positive correlations between high- sitting angles of breast bracket and lung-dose indications including V5,V13,V20,V30,a V5,a V13,a V20 and a V30（ p = 0. 000,with statistical significance）. Conclusion Lung doses of supraclavicular and top axillary photon field increase gradually with high- sitting angles of breast bracket in patients with postoperative breast cancer. Thus,the design of supraclavicular and top axillary photon field should be paid attention to the relationship between high- sitting angles of breast bracket and lung doses. And it should reduce of breast bracket at high- sitting angles as much as possible under the condition of not affecting the design of radiotherapy fields.