Brachytherapy accelerated partial breast irradiation (APBI) is well tolerated, but reported acute toxicities including moist desquamation rates range from 7% to 39%. Moist desquamation is correlated to long-term skin toxicity and high skin dose is the main risk factor. This study uses radiochromic films for in vivo skin dosimetry of low dose rate (LDR) APBI brachytherapy and prediction of skin toxicity. Patients participating in a clinical trial assessing skin toxicity of LDR seed brachytherapy were included in this study. Following the seed implantation procedure, patients were asked to wear a customized oval shaped radiochromic film on the skin projection of the planned target volume (PTV) for 24 h. Exposed films were collected, and maximum point doses were measured. In addition, maximum doses to a small skin volume (D0.2cc) were calculated on the pre- and post-implant CT-scan. Acute skin toxicities (redness, pigmentation, induration and dermatitis) were scored by the treating physician for 2 months during follow-up visits. Skin dose measurements and acute toxicity were available for 18 consecutive patients. The post-implant calculated maximum skin doses (D0.2cc), 60.8 Gy (SD ± 41.0), were on average 30% higher than those measured in vivo (Dmax-film), 46.6 Gy (SD ± 19.3), but those values were highly significantly correlated (Spearman's rho 0.827, p < 0.001). Also, dermatitis and induration were significantly correlated with higher in vivo measured and post-implant calculated skin dose. Pre-implant dosimetry was not correlated with measured or post-implant skin dose or side effects. Radiochromic films can reliably diagnose excess dose to the skin during the first 24 h and predict skin toxicity, which enables preventative measures. Trial registration: Nederlands Trial Register (www.trialregister.nl), NTR6549, the trial was registered prospectively on 27 June 2017. ABR number: NL56210.078.16.

中文翻译：

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放射致变色片体内剂量测定法可预测近距离放射治疗局部乳房照射的急性皮肤毒性风险。

近距离放射治疗加速局部乳房照射（APBI）耐受性良好，但据报道急性毒性（包括潮湿的皮肤脱屑率）为7％至39％。潮湿的脱皮与长期的皮肤毒性有关，高剂量的皮肤是主要的危险因素。这项研究使用放射致变色膜对低剂量率（LDR）APBI近距离放射疗法进行体内皮肤剂量测定，并预测皮肤毒性。参与评估LDR种子近距离放射疗法皮肤毒性的临床试验的患者包括在该研究中。植入种子后，要求患者在计划的目标体积（PTV）的皮肤投影上佩戴定制的椭圆形放射致变色膜24小时。收集曝光的胶片，并测量最大点剂量。此外，最大剂量可达到较小的皮肤体积（D0。在植入前和植入后CT扫描中计算2cc）。在随访期间，治疗医师对急性皮肤毒性（发红，色素沉着，硬结和皮炎）进行了2个月的评分。皮肤剂量测量和急性毒性可用于连续18位患者。植入后计算的最大皮肤剂量（D0.2cc）为60.8 Gy（SD±41.0），比体内测量的最大皮肤剂量（Dmax-film）平均为46.6 Gy（SD±19.3）高30％，但这些值高度相关（Spearman's rho 0.827，p <0.001）。另外，皮炎和硬结与体内测量的较高和植入后计算的皮肤剂量显着相关。植入前的剂量测定与植入后的皮肤剂量或副作用无关。放射致变色膜可以在最初的24小时内可靠地诊断出皮肤过量，并预测皮肤毒性，从而可以采取预防措施。试验注册：Nederlands试验注册（www.trialregister.nl），NTR6549，该试验已于2017年6月27日进行了预先注册。ABR号：NL56210.078.16。