Conditions: Breast Cancer
Keywords: aromatase inhibitor CA 15-3 Hormone receptor positive
Allocation: NA | Intervention model: SINGLE_GROUP
Enrollment: 3
Healthy volunteers: no

Brief summary:
The purpose of this research study is to study the effects of using aromatase inhibitor (AI) therapy intermittently on participants with breast cancer. AIs are a class of drugs used to treat breast cancer in postmenopausal women. They work by decreasing the level of estrogen, which is believed to stimulate the growth of tumor tissue. Breast cancer that progresses despite therapy with an AI is thought to have become resistant to AI therapy. There is scientific evidence to suggest that resistant breast cancer cells learn to grow at the very low levels of estrogen present on AI therapy, and that increasing estrogen levels even slightly by stopping AI therapy may inhibit the breast cancer cells.

Detailed description:
* This study involves treating participants with intermittent AI therapy. The AI will be stopped at the time they enter the study. We plan on monitoring a marker in the participants blood called CA 15-3 (or CA 27.29) every 4 weeks to help us make a decision of when to re-start treatment with letrozole (femara). This marker is known to rise when disease is progressing and drop when the disease is responding to treatment. We will be stopping and re-starting therapy based on the changes of CA 15-3 in the participants blood.
* In addition to bloodwork, the following tests and procedures will be performed on a monthly basis: medical history; physical examination and performance status.
* Every 8 weeks the following will be performed: Tumor assessment by physical exam (if possible); Chest x-ray or CT scan or chest; CT scans of abdomen and pelvis; and bone scan.

Arms:
arm 1: Letrozole 2.5 mg administered by mouth daily during each 28 day treatment cycle. Treatment is intermittent with possible breaks between each 28 day treatment cycle based on CA 15-3 or CA 27.29 levels. Letrozole is administered until the participant has disease progression as determined by RECIST (Response Evaluation Criteria In Solid Tumors), experiences severe side effects, or decides to stop treatment.

Interventions: intervention 1: Letrozole
Intervention descriptions: intervention 1: Treatment is intermittent with possible breaks between each 28 day treatment cycle if CA 15-3 or CA 27.29 level that has decreased by at least 50% of that individual patient's baseline or peak level on firstline letrozole or anastrozole therapy or has decreased into the normal reference range per institutional parameters. Letrozole or anastrozole therapy will be interrupted until CA 15-3 or CA 27.29 levels rise by at least 25% above trough CA 15-3 or CA 27.29 level. If the trough level is in the normal reference range then the CA 15-3 or CA 27.29 must rise into the normal reference range.

Protocol document: