The efficacy of sequential second-line endocrine therapies (ETs) in postmenopausal estrogen receptor-positive and HER2-negative metastatic breast cancer patients with lower sensitivity to initial ETs

Takayuki Iwamoto, Tomomi Fujisawa, Tadahiko Shien, Kazuhiro Araki, Kentaro Sakamaki, Takafumi Sangai, Yuichiro Kikawa, Shintaro Takao, Reiki Nishimura, Masato Takahashi, Tomohiko Aihara, Hirofumi Mukai, Naruto Taira

Research output: Contribution to journalArticlepeer-review

Abstract

Purpose: Second-line endocrine therapy (ET) for estrogen receptor (ER)-positive and human epidermal growth factor 2 (HER2)-negative metastatic breast cancer (MBC) is offered based on the response to first-line ET. However, no clinical trials have evaluated the efficacy and safety of secondary ETs in patients with poor responses to initial ET. This study evaluated the efficacy of second-line ET in ER-positive and HER2-negative postmenopausal MBC patients with low or very low sensitivity to initial ET. Methods: This multicenter prospective observational cohort study evaluated the response of 49 patients to second-line ETs in postmenopausal MBC patients with low or very low sensitivity to initial ET. The primary endpoint was the clinical benefit rate (CBR) for 24 weeks. Results: Of the 49 patients assessed, 40 (82%) received fulvestrant in the second line, 5 (10%) received selective estrogen receptor modulators, 3 (6%) received aromatase inhibitors (AIs) alone, and 1 received everolimus with a steroidal AI. The overall CBR was 44.9% [90% confidence interval (CI): 34.6–57.6, p = 0.009]; CBR demonstrated similar significance across the progesterone receptor-positive (n = 39, 51.3%, 90% CI: 39.6–65.2, p = 0.002), very low sensitivity (n = 17, 58.8%, 90% CI: 42.0–78.8, p = 0.003), and non-visceral metastases (n = 25, 48.0%, 90% CI: 34.1–65.9, p = 0.018) groups. The median progression-free survival was 7.1 months (95% CI: 5.6–10.6). Conclusion: Second-line ET might be a viable treatment option for postmenopausal patients with MBC with low and very low sensitivity to initial ET. Future studies based on larger and independent cohorts are needed to validate these findings.

Original languageEnglish
Pages (from-to)973-981
Number of pages9
JournalBreast Cancer
Volume27
Issue number5
DOIs
Publication statusPublished - Sep 1 2020

Keywords

  • Endocrine therapies
  • Estrogen receptor-positive
  • HER2-negative
  • Metastatic breast cancer
  • Resistance

ASJC Scopus subject areas

  • Oncology
  • Radiology Nuclear Medicine and imaging
  • Pharmacology (medical)

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