Dosimetric Comparation between Two Positions （Prone Versus Supine） for Breast-Conserving Postoperative Radiotherapy: A Meta-Analysis

Objective To investigate the dosimetric differences between prone position and supine position for breast cancer radiotherapy after breast-conserving surgery. Method Strict inclusion and exclusion criteria was drew up. We searched the databases including the Cochrane Library （Issue 1, 2014）, PubMed, FMJS, EMBASE, CHKD, CNKI, WanFang Data and VIP from inception to July 25, 2014. Dosimetric comparisons of targets and organs at risk for breast-conserving postoperation radiotherapy between two positions were included. Standardized mean difference and 95% confidence interval were computed by using statistical software RevMan5.2. Results 17 trials involving 542 patients were included. Meta-analysis of these trials showed that: ①Radiation exposure of ipsilateral lung SMD=-4.36, 95%CI （-5.41,-3.31）, P<0.000 01 and heart SMD=-0.24, 95%CI（-0.4,-0.09）, P=0.002 in patients after breast-conserving surgery were dramatically lower in the prone group than supine one. ②Target homogeneity was significantly better in the prone position SMD=0.42, 95%CI（0.24,0.60）, P<0.001, but the planning target volume coverage did not differ between the two positionsSMD=-0.18,95%CI（-0.39,0.04）, P=0.11. ③There were no differences in target coverage of axillary nodal regions（ANL）for levels I SMD=-7.49, 95%CI（-15.24,0.26）, P=0.06 and ⅡSMD=-5.38,95%CI（-11.31,0.56）, P=0.08 between the prone and the supine positions, while the target coverage of ALN level Ⅲ was dramatically inadequate in the prone position （SMD=-1.14, 95%CI（-1.61, -0.67）, P<0.001）. Conclusions The use of prone radiotherapy resulted in the improved target homogeneity and greater sparing of ipsilateral lung and heart than supine position in patients after breast-conserving surgery. Unfortunately, prone radiotherapy provided inadequate axillary nodal coverage.