%A CHEN Gang, ZHANG Shunkang, SHEN Lei, SUN Liyun, ZHAO Yingwei, WANG Xin, WANG Huanhuan, LU Yue %T Comparison of three types of intensity-modulated radiotherapy plans for adjuvant whole breast and simultaneous tumor bed boost radiotherapy %0 Journal Article %D 2020 %J China Oncology %R 10.19401/j.cnki.1007-3639.2020.08.008 %P 611-619 %V 30 %N 8 %U {http://www.china-oncology.com/CN/abstract/article_1405.shtml} %8 2020-08-30 %X Background and purpose: Breast-conserving surgery (BCS) plus post-operative radiation therapy has become the standard of care for early stage breast cancer. This study aimed to design whole breast and simultaneous tumor bed boost radiation therapy plans by adopting 3 different types of intensity-modulated radiation therapy (IMRT) techniques, and to compare the dosimetric parameters involving target volumes, organs at risk (OARs) and other aspects of the three IMRT plans. Methods: Fifty female patients with early stage breast cancer (25 left and 25 right, respectively) treated with BCS during the year of 2018 in Department of Radiation Oncology, Shanghai Jiao Tong University Medical School Affiliated Ninth People’s Hospital Huangpu Branch, were randomly selected. Adjuvant whole breast and simultaneous tumor bed boost radiation therapy plans were designed by adopting forward-planned IMRT, reverse-planned IMRT and volumetric modulated arc therapy (VMAT) techniques. Conformity index (CI) and homogeneity index (HI) of target volumes, dosimetric parameters of OARs, including ipsilateral lung (V 5 , V 20 , V 30 ), heart (D mean , V 25 for left breast cancer, V 15 ), contralateral breast (D 2 , D mean ), single fraction minute (MU) and beam-out time of the three IMRT plans were compared, respectively. Further analysis was made to identify the effect of breast volume on IMRT plans. Results: CI of forward-planned IMRT, reverse-planned IMRT and VMAT for whole breast target volume were 0.69±0.09, 0.86±0.06, 0.79±0.07, respectively (pairwise comparison P<0.001). CI for tumor bed target volume were 0.71±0.15, 0.79±0.15 and 0.80±0.12, respectively (pairwise comparison, P=0007, P<0.001, P=0.624, respectively). HI of the three plans for whole breast target volume were 0.17±0.03, 0.13±0.03 and 0.18±0.03, respectively (pairwise comparison, P<0.001). HI for tumor bed target volume were 0.17±0.05, 0.07±0.01 and 0.10±0.02, respectively (pairwise comparison, P<0.001). Ipsilateral lung V 5 was 56.08±7.24, 46.08±5.48 and 57.82±6.64, respectively (pairwise comparison, P<0.001, P=0.079, P<0.001, respectively). V 20 was 27.96±2.57, 20.28±2.13 and 23.44±2.71, respectively (pairwise comparison, P<0.001, P=0.025, P<0.001, respectively). V 30 was 22.34±2.20, 15.40±2.37 and 16.42±2.82, respectively (pairwise comparison, P<0.001, P=0.006, P<0.012, respectively). Heart D mean for left breast cancer was 775.48±113.23, 584.20±223.04 and 634.24±174.38, respectively (pairwise comparison, P<0.001, P<0.001, P=0.045, respectively). Heart D mean for right breast cancer was 209.32±84.60, 125.56±41.65 and 200.80±49.74, respectively (pairwise comparison, P<0.001, P=0.524, P<0.001, respectively). Heart V 25 for left breast cancer was 8.20±1.73, 5.02±1.38 and 6.65±1.56, respectively (pairwise comparison, P<0.001, P<0.001, P=0.037, respectively). Heart V 15 for right breast cancer was 0 for all, and no further comparison was made. Contralateral breast D mean was 288.05±105.14, 108.25±56.47 and 123.59±73.79, respectively (pairwise comparison, P<0.001, P<0.001, P=0.023, respectively). Single fraction MU was 285.74±17.73, 1463.94±227.74 and 445.50±98.22, respectively (pairwise comparison, P<0.001). Beam-out time was 205.12±20.68, 343.26±37.59 and 138.06±13.53, respectively (pairwise comparison, P<0.001). A total of 50 patients were divided into small/large breast volume groups according to the mean breast volume (764.89 mL). Better dosimetric parameters of target volumes, fewer single fraction MUs and shorter beam-out time were found in small volume group. No statistical difference in OARs’ dosimetric parameters was found in the two groups. Conclusion: Reverse-planned IMRT and VMAT were better than forward-planned IMRT in the aspects of target volumes’ dosimetric parameters and protection of OARs. Reverse-planned IMRT was slightly superior to VMAT, and was recommended for younger patients with better tolerability and longer life expectancy. VMAT had both fewer single fraction MUs and shorter beam-out time, and was preferable for patients with older age and larger breast volume.