Breast cancer is the most commonly diagnosed malignancy in women worldwide. In the United
States, an estimated 230,480 new cases of invasive breast cancer were diagnosed in 2011,
with 39,520 breast cancer deaths. In 40-80% of women with node-positive disease at
diagnosis, their breast cancer will recur. When distant metastases occur, median survival
is 18 to 36 months from time of recurrence. Among the 60-70% of women with HR+ breast
cancer, 40-60% of them will benefit from endocrine therapy. Endocrine therapy has shown
to yield similar survival rates in hormone-sensitive disease as compared to chemotherapy;
although response rates are lower and responses develop more slowly. Endocrine therapy is
considerably less toxic than chemotherapy, and is therefore the preferred treatment
option for patients with HR+ disease.
Endocrine therapy represents the foundation of treatment for HR+ metastatic and locally
advanced breast cancer. Multiple compounds in varying classes exist, and those most
widely used include the selective estrogen receptor modulators (SERMs), aromatase
inhibitors (AIs), and the selective estrogen receptor down-regulators (SERDs). Although
the utility of these drugs is well established, as many as 50% of women with HR+ breast
cancer will fail to respond to endocrine treatment. Moreover, those who do respond will
inevitably develop acquired resistance.
Fulvestrant is the first drug which acts as a pure estrogen receptor (ER) antagonist
without known agonist effects. It competitively binds to the ERs with an approximately
100 times greater affinity than that of tamoxifen. Fulvestrant promotes the degradation
of ERs and subsequently prevents ER-mediated gene transcription.
Everolimus (RAD001) is an oral derivative of rapamycin that is an m-TOR inhibitor. At
cellular and molecular levels, everolimus acts as a signal transduction inhibitor.
Everolimus selectively inhibits mTOR (mammalian target of rapamycin); a key and highly
conserved serine-threonine kinase which is present in all cells and is a central
regulator of protein synthesis and ultimately cell growth, cell proliferation,
angiogenesis and cell survival. mTOR is the only currently known target of everolimus.
In oncology, everolimus has been in clinical development since 2002 for patients with
various hematologic and non-hematologic malignancies as a single agent or in combination
with antitumor agents, including cytotoxic chemotherapeutic agents, targeted therapies,
antibodies and hormonal agents.
Patients will be randomized (1:1) to receive everolimus or placebo with fulvestrant after
consideration of stratification factors of performance status (0 vs. 1), measurable
disease (yes vs. no), and prior chemotherapy for metastatic disease (yes vs. no).
Patients will be evaluated for disease response every 12 weeks, and treated until disease
progression or unacceptable toxicity or withdrawal of consent for a maximum of 12 cycles
(48 weeks).
Patients with no evidence of progressive disease who remain on study after completing 12
cycles are unblinded and continue to receive fulvestrant alone (if originally randomized
to placebo) or in combination with everolimus (if originally randomized to everolimus) at
the same dose and schedule. Patients will continue to be evaluated for disease response
every 12 weeks and continue until disease progression or unacceptable toxicity.