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

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, D, D, D, 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 4967(4789-5099) cGy, D 5447(5369-5589) cGy, D 5236(5171-5323) cGy, D 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 1341(1208-1385) cGy, V 48.06%(39.75%-48.97%), V 24.55%(21.58%-26.93%), V 18.40%(15.96%-19.16%); heart: D 339(138-640) cGy, V 1.10%(0%-6.14%), V 0.38%(0%-4.39%); spinal cord PRV: D 639(389-898) cGy). The skin doses were D 208.85(203.16-212.53) cGy, D 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.