Abemaciclib plus trastuzumab with or without fulvestrant versus trastuzumab plus standard-of-care chemotherapy in women with hormone receptor-positive, HER2-positive advanced breast cancer (monarcHER): a randomised, open-label, phase 2 trial.

BACKGROUND: Patients with HER2-positive breast cancer who have received two or more previous therapies for advanced disease have few effective treatment options. The monarcHER trial aimed to compare the efficacy of abemaciclib plus trastuzumab with or without fulvestrant with standard-of-care chemotherapy of physician's choice plus trastuzumab in women with advanced breast cancer. METHODS: This phase 2, three-group, open-label trial was done across 75 hospitals, clinics, and medical centres in 14 countries. Eligible patients were women aged 18 years or older, who had hormone receptor-positive, HER2-positive advanced breast cancer with unresectable, locally advanced, recurrent or metastatic disease, Eastern Cooperative Oncology Group performance status of 0 or 1, and who had previously received at least two HER2-targeted therapies for advanced disease. Patients were randomly assigned 1:1:1 to the abemaciclib, trastuzumab, and fulvestrant (group A), abemaciclib and trastuzumab (group B), or standard-of-care chemotherapy and trastuzumab (group C). Oral abemaciclib 150 mg 12 hourly was administered on days 1-21 of a 21-day cycle, intravenous trastuzumab 8 mg/kg on cycle 1 day 1, followed by 6 mg/kg on day 1 of each subsequent 21-day cycle, and intramuscular fulvestrant 500 mg on days 1, 15, and 29 and once every 4 weeks thereafter. Standard-of-care chemotherapy was administered as specified by the product label. Randomisation was by a computer-generated random sequence by means of an interactive web-response system and stratified by number of previous systemic therapies for advanced breast cancer and measurable versus non-measurable disease. The primary endpoint was investigator-assessed progression-free survival in the intention-to-treat population, first testing group A versus group C and, if this result was significant, then group B versus group C. Safety was assessed in all patients who had received at least one dose of study treatment. This trial is registered at ClinicalTrials.gov (NCT02675231) and is ongoing for long-term survival follow-up. FINDINGS: Between May 31, 2016, and Feb 28, 2018, 325 patients were screened, of whom 237 eligible patients were enrolled and randomly assigned to groups A (n=79), B (n=79), and C (n=79). Median follow-up was 19·0 months (IQR 14·7-25·1). The study met its primary endpoint, showing a significant difference at the prespecified two-sided α of 0·2 in median progression-free survival between group A (8·3 months, 95% CI 5·9-12·6) and group C (5·7 months, 5·4-7·0; HR 0·67 [95% CI 0·45-1·00]; p=0·051). No difference was observed between median progression-free survival in group B (5·7 months, 95% CI 4·2-7·2) and group C (HR 0·94 [0·64-1·38]; p=0·77). The most common grade 3-4 treatment-emergent adverse event in groups A, B, and C was neutropenia (21 [27%] of 78 patients, 17 [22%] of 77, and 19 [26%] of 72). The most common serious adverse events were: in group A, pyrexia (three [4%]), diarrhoea (two [3%]), urinary tract infection (two [3%]), and acute kidney injury (two [3%]); in group B, diarrhoea (two [3%]) and pneumonitis (two [3%]); and in group C, neutropenia (four [6%]) and pleural effusion (two [3%]). Two deaths were attributed to treatment: one due to pulmonary fibrosis in group B and one due to febrile neutropenia in group C. INTERPRETATION: The combination of abemaciclib, fulvestrant, and trastuzumab significantly improved progression-free survival versus standard-of-care chemotherapy plus trastuzumab while showing a tolerable safety profile. Our results suggest that a chemotherapy-free regimen might potentially be an alternative treatment option for patients with hormone receptor-positive, HER2-positive advanced breast cancer. FUNDING: Eli Lilly and Company.

Abemaciclib, a potent cyclin-dependent kinase 4 and 6 inhibitor, for treatment of ER-positive metastatic breast cancer.

CDK 4/6 inhibitors have given patients with estrogen receptor (ER)-positive/HER2-negative (ER+/HER2ࢤ) advanced metastatic breast cancer important new therapeutic options. Abemaciclib is different to the other two licensed and approved CDK 4/6 inhibitors, palbociclib and ribociclib, both in dosing schedule (continuous vs intermittent) and toxicity profile (less neutropenia, more diarrhea), yet the magnitude of clinical benefit seen in first- and second-line studies is very similar. One of the key issues for clinicians is when to use these therapies. Ultimately, the biggest impact of abemaciclib could be in the adjuvant setting if the current MONARCH-E trial in high-risk node-positive patients is positive. The emerging biomarker work in the early breast cancer setting (i.e., neoMONARCH) may determine which tumors are most sensitive to abemaciclib.

Fulvestrant plus anastrozole or placebo versus exemestane alone after progression on non-steroidal aromatase inhibitors in postmenopausal patients with hormone-receptor-positive locally advanced or metastatic breast cancer (SoFEA): a composite, multicentre, phase 3 randomised trial.

BACKGROUND: The optimum endocrine treatment for postmenopausal women with advanced hormone-receptor-positive breast cancer that has progressed on non-steroidal aromatase inhibitors (NSAIs) is unclear. The aim of the SoFEA trial was to assess a maximum double endocrine targeting approach with the steroidal anti-oestrogen fulvestrant in combination with continued oestrogen deprivation. METHODS: In a composite, multicentre, phase 3 randomised controlled trial done in the UK and South Korea, postmenopausal women with hormone-receptor-positive breast cancer (oestrogen receptor [ER] positive, progesterone receptor [PR] positive, or both) were eligible if they had relapsed or progressed with locally advanced or metastatic disease on an NSAI (given as adjuvant for at least 12 months or as first-line treatment for at least 6 months). Additionally, patients had to have adequate organ function and a WHO performance status of 0-2. Participants were randomly assigned (1:1:1) to receive fulvestrant (500 mg intramuscular injection on day 1, followed by 250 mg doses on days 15 and 29, and then every 28 days) plus daily oral anastrozole (1 mg); fulvestrant plus anastrozole-matched placebo; or daily oral exemestane (25 mg). Randomisation was done with computer-generated permuted blocks, and stratification was by centre and previous use of an NSAI as adjuvant treatment or for locally advanced or metastatic disease. Participants and investigators were aware of assignment to fulvestrant or exemestane, but not of assignment to anastrozole or placebo. The primary endpoint was progression-free survival (PFS). Analyses were by intention to treat. This trial is registered with ClinicalTrials.gov, numbers NCT00253422 (UK) and NCT00944918 (South Korea). FINDINGS: Between March 26, 2004, and Aug 6, 2010, 723 patients underwent randomisation: 243 were assigned to receive fulvestrant plus anastrozole, 231 to fulvestrant plus placebo, and 249 to exemestane. Median PFS was 4·4 months (95% CI 3·4-5·4) in patients assigned to fulvestrant plus anastrozole, 4·8 months (3·6-5·5) in those assigned to fulvestrant plus placebo, and 3·4 months (3·0-4·6) in those assigned to exemestane. No difference was recorded between the patients assigned to fulvestrant plus anastrozole and fulvestrant plus placebo (hazard ratio 1·00, 95% CI 0·83-1·21; log-rank p=0·98), or between those assigned to fulvestrant plus placebo and exemestane (0·95, 0·79-1·14; log-rank p=0·56). 87 serious adverse events were reported: 36 in patients assigned to fulvestrant plus anastrozole, 22 in those assigned to fulvestrant plus placebo, and 29 in those assigned to exemestane. Grade 3-4 adverse events were rare; the most frequent were arthralgia (three in the group assigned to fulvestrant plus anastrozole; seven in that assigned to fulvestrant plus placebo; eight in that assigned to exemestane), lethargy (three; 11; 11), and nausea or vomiting (five; two; eight). INTERPRETATION: After loss of response to NSAIs in postmenopausal women with hormone-receptor-positive advanced breast cancer, maximum double endocrine treatment with 250 mg fulvestrant combined with oestrogen deprivation is no better than either fulvestrant alone or exemestane.

BOLERO-2 - will this change practice in advanced breast cancer?

The benefit of endocrine therapy has always been limited by the eventual development of acquired resistance. For the first time, clinical research has identified a therapeutic agent, everolimus, that targets the mammalian target of rapamycin (mTOR), which in combination with the aromatase inhibitor exemestane can substantially reduce the risk of disease progression and seemingly circumvent endocrine resistance. The magnitude of the benefit represents a quantum shift in how we should use endocrine therapy in future, and potentially defines a new standard of care in this setting.

Combinations of endocrine and biological agents: present status of therapeutic and presurgical investigations.

There is an increasing rationale to develop effective combinations of endocrine agents with novel therapeutics that target aberrant signal transduction pathways in estrogen receptor-positive breast cancer. Acquired resistance to endocrine therapy is associated with an increase in peptide growth factor signaling that results in crosstalk activation of estrogen receptor, and various signal transduction inhibitors (STI) can target these pathways to inhibit hormone-resistant growth. In experimental models of hormone-sensitive breast cancer, combinations of endocrine agents with STIs provide significantly greater growth inhibition than either alone, delaying the emergence of resistance. There are now several trials assessing the efficacy of combinations of tyrosine kinase inhibitors with various endocrine agents in the tamoxifen-resistant/second-line setting, together with five randomized phase II/III trials in the first-line setting. Similar work is ongoing with both farnesyltransferase inhibitors and mTOR antagonists where there are strong preclinical data to suggest additive or synergistic effects for either of these agents in combination with tamoxifen or estrogen deprivation therapies. More recently, presurgical studies with biological primary end points are being utilized as an alternative approach to investigate whether combined endocrine/STI therapy is a more effective strategy than endocrine therapy alone. This article reviews the rationale and current status of clinical trials in this area as well as the challenges that lie ahead for the development of these therapeutic combinations for breast cancer.