Tamoxifen在性激素敏感性乳腺癌的辅助治疗中非常重要，能够大幅降低复发率；然而，几乎50%的患者因副作用而无法坚持用药。本研究旨在研究内度酚指导下的降低剂量，是否能够减少副作用。本研究研究了具有烦人副作用和内度酚水平≥32 nM患者的降低剂量效果，并与仍然使用20毫克的患者进行了比较。使用功能评估癌症治疗-内分泌症状（FACT-ES）问卷，评估了激素症状和健康相关生命质量（HR-QOL），并在3个月后进行了评估。20名患者的剂量被降低，其中17名患者可评估副作用分析。在41%和65%的患者中，激素症状和HR-QOL分别观察到了>6分的临床意义改善。总体而言，剂量降低后，激素症状[5.7，95%置信区间（CI）-0.5-11.5]和HR-QOL（8.2，95% CI 0.9-15.4）显著且发生了临床意义上的改善。不降低剂量的患者（n=60）没有观察到这种情况。在21%的患者中，内度酚略微降低至16 nM阈值以下（12.8，15.5，15.8，15.9 nM）。内度酚指导下的降低剂量能够显著改善与tamoxifen相关的副作用和HR-QOL。近80%的患者的内度酚水平仍高于最保守的阈值。版权所有©2023年作者。由Elsevier Ltd.出版。保留所有权利。

Tamoxifen is important in the adjuvant treatment of hormone-sensitive breast cancer and substantially reduces recurrence; however, almost 50% of patients are non-compliant mainly due to side-effects. The aim of this study was to investigate whether endoxifen-guided tamoxifen dose reduction could lead to fewer side-effects.Effects of tamoxifen dose reduction were investigated in patients with bothersome side-effects and endoxifen levels ≥32 nM and compared to patients with side-effects who remained on tamoxifen 20 mg. Endocrine symptoms and health-related quality of life (HR-QOL) were assessed after 3 months with the Functional Assessment of Cancer Therapy-Endocrine Symptoms (FACT-ES) questionnaire.Tamoxifen dose was reduced in 20 patients, 17 of whom were assessable for side-effect analyses. A clinically relevant improvement of >6 points was observed in endocrine symptoms and HR-QOL in 41% and 65% of the patients, respectively. In total, there was a significant and clinically relevant improvement in endocrine symptoms [5.7, 95% confidence interval (CI) -0.5-11.5] and HR-QOL (8.2, 95% CI 0.9-15.4) after dose reduction. This was not seen in patients whose doses were not reduced (n = 60). In 21% of patients, endoxifen dropped slightly below the 16-nM threshold (12.8, 15.5, 15.8, 15.9 nM).Endoxifen-guided dose reduction of tamoxifen significantly improved tamoxifen-related side-effects and HR-QOL. Nearly 80% of patients remained above the most conservative endoxifen threshold.Copyright © 2023 The Authors. Published by Elsevier Ltd.. All rights reserved.