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

doi:10.3389/fonc.2022.964455

3D-printed bolus ensures the precise postmastectomy chest wall radiation therapy for breast cancer

Front Oncol. 2022 Sep 2:12:964455. doi: 10.3389/fonc.2022.964455. eCollection 2022.

Authors

Xiran Wang¹, Jianling Zhao², Zhongzheng Xiang¹, Xuetao Wang², Yuanyuan Zeng¹, Ting Luo^{1

3}, Xi Yan^{1

3}, Zhuang Zhang⁴, Feng Wang^{1

3}, Lei Liu^{1

3}

Affiliations

¹ Department of Head and Neck and Mammary Oncology, West China Hospital, Sichuan University, Chengdu, China.
² Department of Radiotherapy, West China Hospital, Sichuan University, Chengdu, China.
³ Clinical Research Center for Breast, West China Hospital, Sichuan University, Chengdu, China.
⁴ State Key Laboratory of Oral Diseases, West China Hospital of Stomatology, Sichuan University, Chengdu, China.

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, V₅ 48.06%(39.75%-48.97%), V₂₀ 24.55%(21.58%-26.93%), V₃₀ 18.40%(15.96%-19.16%); heart: D_mean 339(138-640) cGy, V₃₀ 1.10%(0%-6.14%), V₄₀ 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.

Keywords: 3D-printed bolus; PMRT; breast cancer; dosimetry; radiation dermatitis.