A phase II study of combined fulvestrant and everolimus in patients with metastatic estrogen receptor (ER)-positive breast cancer after aromatase inhibitor (AI) failure

Suleiman Massarweh, Edward Romond, Esther P. Black, Emily Van Meter, Brent Shelton, Vera Kadamyan-Melkumian, Mark Stevens, Richard Elledge

Research output: Contribution to journalArticlepeer-review

52 Scopus citations


Fulvestrant, which degrades ER, is used after AI failure in metastatic breast cancer but resistance develops quickly. We hypothesized that using everolimus to inhibit mTOR, a key signaling pathway in endocrine resistance, may delay fulvestrant resistance in patients and thus improve its efficacy. We conducted a phase II trial of combined fulvestrant and everolimus in postmenopausal women with disease progression or relapse after an AI. Primary endpoint was time to progression (TTP) and secondary endpoints included objective response rate, clinical benefit rate (CBR), safety, and biomarker correlates. Tumor blocks were collected and biopsy of accessible tumor was done for future biomarker analysis. Of 33 patients enrolled two were ruled ineligible after enrollment and were excluded from study analysis, for a total of 31 evaluable patients. Median age was 54 years (range 45-85). Prior therapy included tamoxifen (81 %), chemotherapy (71 %), with 26 % of patients having received 3 or more endocrine agents. Median TTP was 7.4 months (95 % CI 1.9-12.1) with an objective response rate of 13 % and CBR of 49 %. Of particular note, 32 % of patients exhibited de novo resistance to study treatment with disease progression as their best response. Most common adverse events (AEs) were elevated AST (87 %) and ALT (77 %), anemia (74 %), hyperglycemia (71 %), and hypercholesterolemia (68 %). Prominent clinical toxicities were mucositis (58 %), weight loss (48 %), and rash (42 %). Most AEs were grade 1 or 2 and largely reversible with infrequent need for everolimus dose reduction. To conclude, everolimus plus fulvestrant is effective after AI failure in heavily pretreated metastatic ER-positive breast cancer and has manageable toxicity. Further study of this combination is warranted in randomized studies. Since not all patients experience benefit, and in view of potential toxicities, biomarker examination is critical to help select patients most likely to benefit from this strategy in future studies.

Original languageEnglish
Pages (from-to)325-332
Number of pages8
JournalBreast Cancer Research and Treatment
Issue number2
StatePublished - Jan 2014

Bibliographical note

Funding Information:
Conflict of interests S.M. receives research funding from Novartis and Onyx–Bayer, and honoraria/consultation fees from Novartis. All remaining authors have declared no conflict of interest.

Funding Information:
Acknowledgments This work was supported by a grant from Novartis pharmaceuticals (S. M.). Presented in part at the 35th San Antonio Breast Cancer Symposium in 2012 (Cancer Res, December 15, 2012; 72(24 Supplement): P2-14-05, and at the 2013 American Society of Clinical Oncology Meeting, Chicago (J Clin Oncol 31, 2013, suppl; abstr 541). Registered under ClinicalTrials.gov number NCT00570921 and Investigational New Drug Application (IND) #79,103 (IND holder, S. M.).


  • Breast cancer
  • Endocrine resistance
  • Estrogen receptor
  • Everolimus
  • Fulvestrant
  • MTOR

ASJC Scopus subject areas

  • Oncology
  • Cancer Research


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