Randomized trial comparing overall survival of patients monitored with serum tumor marker directed disease monitoring (STMDDM) versus usual care in patients with metastatic hormone receptor positive breast cancer

Step 1 Pre-Randomization - Patients must have a diagnosis of hormone receptor positive (ER+ and/or PR+), HER-2 negative, metastatic (M1) breast cancer and must be receiving or plan to receive first-line systemic treatment for metastatic disease (systemic treatment is any treatment meant to treat the whole body such as endocrine therapy +/- targeted therapy +/- chemotherapy); patients must be registered to Step 1 between 14 days prior to and 60 days after start of first-line systemic treatment for metastatic disease; patients (women and men) must be >/= 18 years of age; patients must have been tested for all of the following breast cancer specific STMs after diagnosis of metastatic disease and within +/-14 days of initiation of first-line systemic treatment for metastatic disease: CEA (must be tested), CA 15-3 or CA 27.29 (at least one of these must be tested) and at least one of the tested STMs must have been >/= 2 x the institutional upper limit of normal at this time. Patients must have systemic radiographic imaging prior to initiation of systemic therapy or within 30 days of initiation of treatment for metastatic breast cancer and prior to Step 1 registration; modality of imaging is at the discretion of the treating physician; Patients must be willing to obtain disease monitoring (imaging and/or serum tumor markers) from a consistent facility in which the registering site has access to the results for the duration of the study intervention (312 weeks after Step 2 randomization); imaging and STMs do not need to be completed at the same facility; Patients with known cirrhosis, untreated B12 deficiency, thalassemia, or sickle cell anemia are not eligible as these could cause falsely elevated STM levels; patients with known brain metastases or leptomeningeal metastases are not eligible as they may require regular radiographic monitoring to assess treatment response; patients must not be currently enrolled or plan to participate in a first-line treatment trial for metastatic breast cancer with a defined monitoring schedule; patients who are able to complete questionnaires in English or Spanish must participate in patient-reported outcome (PRO) assessments as outlined in the protocol; patients must not be pregnant due to the potential harm to the fetus from radiation exposure from radiographic imaging. Patients must not have received prior systemic therapy for metastatic breast cancer, except for their current line of therapy. Step 2 Randomization - Patients must be tested for the breast cancer specific STMs that were tested prior to Step 1 Registration between 56 and 140 days after initiation of first-line systemic therapy for metastatic disease; CEA (must be tested), CA 15-3 or CA 27.29 (whichever was tested prior to Step 1); Testing all three STMs in encouraged but only two are required. Patients must plan to have the same two STMs tested for the duration that the patient is on protocol-specified monitoring; at least one of the STMs that was previously elevated must have decreased from the assessment at Step 1 by >/= 10% at this time. Patients must not have known progression since registration to Step 1. Patients must be registered to Step 2 randomization between 56 days and 140 days after the initiation of first-line systemic therapy for metastatic disease.this window is inclusive; patients may be registered to Step 2 on Day 56 or on Day 140. Patients must have been eligible for Step 1 in order to be eligible for Step 2 Randomization. Baseline questionnaires must be completed within 28 days prior to Step 2 randomization. (Note: Those patients who cannot complete the PRO questionnaires in English or Spanish can be registered to Step 2 without contributing to PRO research)