Overview

The purpose of this study is to explore the clinical utility of routinely measuring thymidine kinase activity (TKa) in HR+ metastatic breast cancer patients receiving treatment with any approved endocrine therapy either alone or in combination with any approved CDK4/6 inhibitor.

Eligibility

Inclusion Criteria:

• Pre- or post-menopausal HR+ metastatic breast cancer patients who are:
  • Group 1: scheduled to initiate 1st line combination therapy with an FDA-approved CDK4/6 inhibitor (palbociclib, ribociclib, or abemaciclib) and an FDA-approved endocrine therapy for pre- or post-menopausal HR+ metastatic breast cancer (mBC).
  • Group 2: scheduled to initiate second or later lines of therapy with an FDA-approved CDK4/6 inhibitor (palbociclib, ribociclib, or abemaciclib) with or without an FDA-approved endocrine therapy for pre- or post-menopausal HR+ mBC.
  • Group 3: currently receiving 1st line therapy with an FDA-approved CDK4/6 inhibitor (palbociclib, ribociclib, or abemaciclib) and an FDA-approved endocrine therapy for pre- or post-menopausal HR+ mBC.
  • Group 4: scheduled to initiate, or are currently receiving, 1st or 2nd line therapy of an FDA approved endocrine therapy (single agent) for pre- or post-menopausal HR+ mBC.

        NOTE: Patients that meet eligibility criteria for any of the above groups that are already
        enrolled in an ongoing clinical trial are eligible for co-enrollment to this observational
        study.
        Exclusion Criteria:
          -  Treatment including investigational agent or therapies
          -  Early breast cancer diagnosis
          -  Male breast cancer
          -  Currently receiving treatment for other active malignancy at time of registration
               -  EXCEPTIONS: Nonmelanoma skin cancer or carcinoma-in-situ (e.g. of cervix,
                  prostate)
          -  Inability to give written informed consent