Patient-Derived Organoids for Guiding Neoadjuvant Chemotherapy in Bilateral Primary Breast Cancer: A Case Report.

Neoadjuvant chemotherapy (NAC) is the standard of care for locally advanced breast cancer, but the response to chemotherapy is unpredictable due to unknown information on the tumor drug sensitivity. Patient-derived organoids (PDOs) have recently been revealed to be a promising platform for assessing drug sensitivity in many cancers. A 46-year-old woman presented to the hospital due to an accidentally discovered mass in the left breast. Based on core-needle biopsies, pathologic examination showed invasive breast cancer in both breasts. In combination with immunohistochemistry, the patient was diagnosed with left breast cancer IIB with axillary lymphatic metastasis and right breast cancer IIA. The NAC with albumin-bound paclitaxel, epirubicin and cyclophosphamide was used. Although partial response was assessed overall, the left tumor did not lessen significantly; thus, organoids from bilateral breasts were cultured. After treatment with PDO-sensitive vinorelbine and carboplatin, partial response was achieved in the left compared with the initial tumor. Meanwhile, bilateral mastectomy was performed successfully, with pathological complete response achieved in the right. This typical case suggests that the PDOs from bilateral primary breast cancers can serve as a powerful tool to identify the sensitivity to NAC, thus providing novel treatment options at the patient-specific level.