Case Study: Treating HR+ and HER2- Breast Cancer

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In the second case study of the series, moderator Adam M. Brufsky, MD, PhD, describes a 63 year-old woman presenting with thickening of the outer left breast and an enlarging mass. The thickening began a year earlier and the enlargement began within the past month, Brufsky notes.

The patient experiences slight dyspnea on exertion but does not have bone pain. Upon further examination, a 6 cm mass with slight dimpling and underlying skin contraction was noted on the left breast. A PET-CT scan was performed which confirmed the presence of the left breast mass and found multiple areas of metastatic disease in her thoracic/lumbar spine and hips. However, there were not any areas that suggested impending fractures of her long bones.

A biopsy was performed and found the patient was strongly ER-positive, with an H-score of 300, indicating that 100% of the cells were intensity 3+ for ER, notes Brufsky. Additionally, the patient was PR-positive and HER2-negative by both IHC and FISH with a ratio of 1.02.

For this patient, Sara Hurvitz, MD, would initially begin treatment with a bone-stabilizing agent. Following this, if a physical examination does not indicate a local issue, treatment with an endocrine therapy would be appropriate. If the examination showed the potential for the breast mass to break through the skin or if there was severe pain, Hurvitz recommends a more aggressive treatment with radiation along with an aromatase inhibitor and fulvestrant.

In a similar situation, Hope S. Rugo, MD, notes seeing a pathological complete response with an aromatase inhibitor in a patient whose tumor had eroded through the skin. Erring on the side of caution, Joyce A. O'Shaughnessy, MD, would administer the 500 mg dose of fulvestrant in combination with an aromatase inhibitor, regardless of local issues.

Another option for this patient would be to seek a clinical trial investigating the CDK 4/6 inhibitor palbociclib, notes Rugo. This trial is enrolling patients who have not had prior systemic treatments for ER-positive breast cancer. In this phase III trial, patients with ER-positive, HER2-negative advanced breast cancer are randomized to either letrozole alone or in combination with palbociclib.