3D-printed bolus ensures the precise postmastectomy chest wall radiation therapy for breast cancer
Xiran Wang, Jianling Zhao, Zhongzheng Xiang, Xuetao Wang, Yuanyuan Zeng, Ting Luo, Xi Yan, Zhuang Zhang, Feng Wang, Lei Liu
Abstract
Purpose To investigate the values of a 3D-printed bolus ensuring the precise postmastectomy chest wall radiation therapy for breast cancer. Methods and materials In the preclinical study on the anthropomorphic phantom, the 3D-printed bolus was used for dosimetry and fitness evaluation. The dosimetric parameters of planning target volume (PTV) were assessed, including D min , D max , D mean , D 95% , homogeneity index (HI), conformity index (CI), and organs at risk (OARs). The absolute percentage differences (|%diff|) between the theory and fact skin dose were also estimated, and the follow-up was conducted for potential skin side effects. Results In preclinical studies, a 3D-printed bolus can better ensure the radiation coverage of PTV (HI 0.05, CI 99.91%), the dose accuracy (|%diff| 0.99%), and skin fitness (mean air gap 1.01 mm). Of the 27 eligible patients, we evaluated the radiation dose parameter (median(min–max): D min 4967(4789–5099) cGy, D max 5447(5369–5589) cGy, D mean 5236(5171–5323) cGy, D 95% 5053(4936–5156) cGy, HI 0.07 (0.06–0.17), and CI 99.94% (97.41%–100%)) and assessed the dose of OARs (ipsilateral lung: D mean 1341(1208–1385) cGy, V 5 48.06%(39.75%–48.97%), V 20 24.55%(21.58%–26.93%), V 30 18.40%(15.96%–19.16%); heart: D mean 339(138–640) cGy, V 30 1.10%(0%–6.14%), V 40 0.38%(0%–4.39%); spinal cord PRV: D max 639(389–898) cGy). The skin doses in vivo were D theory 208.85(203.16–212.53) cGy, D fact 209.53(204.14–214.42) cGy, and |%diff| 1.77% (0.89–2.94%). Of the 360 patients enrolled in the skin side effect follow-up study (including the above 27 patients), grade 1 was the most common toxicity (321, 89.2%), some of which progressing to grade 2 or grade 3 (32, 8.9% or 7, 1.9%); the radiotherapy interruption rate was 1.1%. Conclusion A 3D-printed bolus can guarantee the precise radiation dose on skin surface, good fitness to skin, and controllable acute skin toxicity, which possesses a great clinical application value in postmastectomy chest call radiation therapy for breast cancer.