Therapeutic Advances in Medical Oncology (Feb 2021)

High-dose tamoxifen in high-hormone-receptor-expressing advanced breast cancer patients: a phase II pilot study

  • Yanhong Su,
  • Yarui Zhang,
  • Xin Hua,
  • Jiajia Huang,
  • Xiwen Bi,
  • Wen Xia,
  • Xinyue Wang,
  • Zhangzan Huang,
  • Chenge Song,
  • Yongyi Zhong,
  • Yanxia Shi,
  • Shusen Wang,
  • ,
  • Wei Fan,
  • Zhongyu Yuan

DOI
https://doi.org/10.1177/1758835921993436
Journal volume & issue
Vol. 13

Abstract

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Background: Tumor progression following endocrine therapy is considered to indicate resistance to endocrine drugs due to a variety of mechanisms. An insufficient dose of endocrine drugs is one of the causes for treatment failure in some patients with high hormone-receptor (HR)-expressing advanced breast cancer. This study aimed to explore the efficacy of high-dose tamoxifen (TAM) treatment in patients with advanced breast cancer with highly expressed HR. Materials & methods: This was a single-arm, phase II pilot study that enrolled patients with advanced breast cancer with high HR expression (estrogen receptor ⩾60% and/or progesterone receptor ⩾60%) following routine endocrine therapy. All enrolled patients received a high-dose of TAM (100 mg/day) until disease progression. The primary endpoint was progression-free survival (PFS). The secondary endpoints included objective response rate (ORR), clinical benefit rate (CBR), overall survival (OS), and safety. Exploratory endpoints included the predictive value of 16 α- 18 F- 17 β-fluoroestradiol quantitative positron emission tomography/computed tomography ( 18 F-FES PET/CT) for treatment efficacy. Results: A total of 30 patients were enrolled between September 2017 and February 2019. The median PFS was 6 months [95% confidence interval (CI) 4.9–7.1] and the median OS was 15.6 months (95% CI 8.3–22.9). Five patients experienced a partial response (PR) and none experienced a complete response (CR), with an ORR of 16.7% and CBR of 33.3%. No severe adverse events were observed. Lesions with 18 F-FES maximum standardized uptake value (SUVmax) ⩾4 had a significantly longer PFS [median 9.2 months, (95% CI 6.9–11.6)] compared with lesions with a 18 F-FES SUVmax <4 [median 4.8 months, (95% CI 3.9–5.6); p = 0.022]. Conclusion: A high-dose of TAM is effective and safe for patients with advanced breast cancer with high HR expression. 18 F-FES SUVmax values may predict the local clinical benefits of high-dose TAM . Trial Registration: [ClinicalTrials.gov identifier: NCT0304565]