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

PurposeTo investigate the values of a 3D-printed bolus ensuring the precise postmastectomy chest wall radiation therapy for breast cancer. Methods and materialsIn 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. ResultsIn 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%. ConclusionA 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.