title: A phase II study of combined fulvestrant and everolimus in patients with metastatic estrogen receptor (ER)-positive breast cancer after aromatase inhibitor (AI) failure.
abstract: 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.
authors: The Department of Internal Medicine, University of Kentucky, Lexington, KY, USA, massarweh@uky.edu.
authors: Suleiman
authors: S
authors: Massarweh
authors: Edward
authors: E
authors: Romond
authors: Esther P
authors: EP
authors: Black
authors: Emily
authors: E
authors: Van Meter
authors: Brent
authors: B
authors: Shelton
authors: Vera
authors: V
authors: Kadamyan-Melkumian
authors: Mark
authors: M
authors: Stevens
authors: Richard
authors: R
authors: Elledge
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D018931:Antineoplastic Agents, Hormonal / Q000009:adverse effects / Q000627:therapeutic use; D000971:Antineoplastic Combined Chemotherapy Protocols / Q000009:adverse effects / Q000627:therapeutic use; D047072:Aromatase Inhibitors / Q000627:therapeutic use*; D001943:Breast Neoplasms / Q000188:drug therapy*; D004958:Estradiol / Q000009:adverse effects / Q000031:analogs & derivatives* / Q000627:therapeutic use; D000068338:Everolimus; D005260:Female; D000077267:Fulvestrant; D006801:Humans; D007166:Immunosuppressive Agents / Q000009:adverse effects / Q000627:therapeutic use; D008875:Middle Aged; D009364:Neoplasm Recurrence, Local / Q000188:drug therapy; D011960:Receptors, Estrogen / Q000378:metabolism; D020123:Sirolimus / Q000009:adverse effects / Q000031:analogs & derivatives* / Q000627:therapeutic use; D058570:TOR Serine-Threonine Kinases / Q000037:antagonists & inhibitors; D017211:Treatment Failure
chemical_list: D018931:Antineoplastic Agents, Hormonal; D047072:Aromatase Inhibitors; D007166:Immunosuppressive Agents; D011960:Receptors, Estrogen; D000077267:Fulvestrant; D004958:Estradiol; D000068338:Everolimus; C546842:MTOR protein, human; D058570:TOR Serine-Threonine Kinases; D020123:Sirolimus