YO2 - A case of locally advanced breast cancer with biomarker conversion successfully treated with neoadjuvant chemotherapy-immunotherapy combination

Case summary

Biomarkers play an important role in breast cancer management, ranging from the traditional ER, PR and HER2 to newer biomarkers such as PD-L1 expression and BRCA status. Conversion of these markers might bring more treatment options. We hereby present a case of a 76-year-old female with a history of controlled hypertension. She was diagnosed with breast cancer, stage cT3N2M0, in which the core biopsy showed invasive carcinoma of no special type, grade III. Immunohistochemistry: ER (+) 10%, PR (-), HER2(-), Ki67 (+) 70%, PD-L1 (+) with CPS of 5%, the patient did not have BRCA germline mutation. We treated her with 2 cycles of Paclitaxel-Carboplatin chemotherapy, but the tumor increased in size from 6 cm to 8 cm with skin invasion, with no distant metastases. The patient was then switched to Docetaxel-Cyclophosphamide. Meanwhile, we performed re-biopsy of the tumor and re-test the biomarkers, which showed invasive carcinoma, ER (-), PR (-), HER2 (-), Ki67 55%, PD-L1 (+) with CPS of 12%. After 3 cycles of Docetaxel-Cyclophosphamide, the patient again had local progression and started to feel pain in the axilla with a fixed hard lymph node 4x5 cm in size. We then changed the treatment to Pembrolizumab-Doxorubicin-Cyclophosphamide with close monitor of the cardiac toxicities. The patient started to have response since the second cycle and after 4 cycles, she became operable by surgeon’s assessment. Finally, she successfully underwent modified radical mastectomy. In this hard-to-treat patient, the change from hormone receptor positive to triple negative subtype brought more treatment options of chemotherapy-immunotherapy combination. Besides, we also documented a change in PD-L1 expression after patient’s exposure to chemotherapy. Since the patient had progressed with 2 regimens, the subsequent treatment was not totally in neoadjuvant setting but more likely to be in advanced setting. Therefore, a CPS more than 10% gave us more confidence to use Pembrolizumab in this patient. In conclusions, physicians should be aware of the biomarker conversion, including PD-L1 expression, of breast cancer to maximize patients’ treatment opportunities.

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