Ribociclib and Letrozole in Treating Patients With Relapsed ER Positive Ovarian, Fallopian Tube, Primary Peritoneal, or Endometrial Cancer

Inclusion Criteria

• Ability to understand and the willingness to sign a written informed consent document
• Post-menopausal
• Histologically confirmed recurrent ovarian, fallopian tube or primary peritoneal carcinoma or endometrial cancer in post-menopausal women; NOTE: pure clear cell and pure mucinous carcinomas are ineligible; platinum sensitive, platinum resistant and platinum refractory disease are eligible; no limitations in the number of prior regimens
• Patient has disease amenable to biopsy and is agreeable to undergo a biopsy; NOTE: under unusual circumstances, submission of ascites material may be acceptable if a biopsy is not possible; this exception will require approval by one of the study principal investigators
• Willing to provide tissue samples for ER and retinoblastoma (RB) staining
• Measurable disease by Response Evaluation Criteria In Solid Tumors (RECIST) criteria
• Tumors must stain positive for estrogen receptor (>= 10%) by immunohistochemistry (IHC)
• Eastern Cooperative Oncology Group (ECOG) performance status (PS) 0, 1, or 2
• Absolute neutrophil count (ANC) >= 1000/mm^3
• Platelet count >= 100,000/mm^3
• Hemoglobin >= 9.0 g/dL
• Total bilirubin = = 4 weeks from prior therapy completion (including radiation and/or surgery) to starting the study treatment
• Clinically stable CNS tumor at the time of screening and not receiving steroids and/or enzyme-inducing anti-epileptic medications for brain metastases
• Patient has any other concurrent severe and/or uncontrolled medical condition that would, in the investigator's judgment, cause unacceptable safety risks, contraindicate patient participation in the clinical study or compromise compliance with the protocol (e.g. chronic pancreatitis, chronic active hepatitis, active untreated or uncontrolled fungal, bacterial or viral infections, etc.)
• Clinically significant, uncontrolled heart disease or cardiac repolarization abnormalities and/or recent events including any of the following:
• History of acute coronary syndromes (including myocardial infarction, unstable angina, coronary artery bypass grafting, coronary angioplasty, or stenting) or symptomatic pericarditis within 6 months prior to screening
• History of documented congestive heart failure (New York Heart Association functional classification III-IV)
• Documented cardiomyopathy
• Left ventricular ejection fraction (LVEF) 160 mmHg or 110 at rest), by ECG or pulse at screening
• Inability to determine the QTcF interval on the ECG (i.e.: unreadable or not interpretable) or QTcF > 450 msec (using Fridericia's correction); NOTE: all as determined by screening ECG
• Patient is currently receiving any of the following medications and cannot be discontinued = = 30% of the bone marrow was irradiated
• Patient has had major surgery =< 14 days prior to registration or has not recovered from major side effects (tumor biopsy is not considered as major surgery)
• Known to be human immunodeficiency virus (HIV) positive (testing not mandatory)
• Patient has a known hypersensitivity to any of the excipients of ribociclib
• Patient is currently receiving warfarin or other Coumarin-derived anticoagulant for treatment, prophylaxis or otherwise; NOTE: therapy with apixaban, dabigatran, heparin, low molecular weight heparin (LMWH) or fondaparinux is allowed
• Participation in a prior investigational study within 30 days prior to enrollment or =< 5 half-lives of the investigational product, whichever is longer
• Patient has not recovered from all toxicities related to prior anticancer therapies to National Cancer Institute (NCI)-Common Terminology Criteria for Adverse Events (CTCAE) version 4.0 grade < 3 (exception to this criterion: patients with any grade of alopecia or neuropathy are allowed to enter the study)
• Patient with a Child-Pugh score B or C
• Patient has impairment of gastrointestinal (GI) function or GI disease that may significantly alter the absorption of the study drugs (e.g., ulcerative disease