BRCA2-Positive Breast Cancer in a Woman With Down Syndrome

What happened, in summary

A 35-year-old woman with Down syndrome noticed a lump in her left breast. A biopsy confirmed invasive ductal carcinoma. Imaging at diagnosis showed no distant spread, and she underwent a left modified radical mastectomy with axillary lymph-node dissection. The surgical specimen measured about 2.5 cm, and cancer was found in 1 of 14 lymph nodes. Her tumor was strongly estrogen-receptor positive, progesterone-receptor negative, and HER2-negative.

She started endocrine therapy with an LH-RH agonist and tamoxifen. Twenty-three months after surgery, a supraclavicular lymph node became palpable, and scans showed metastatic disease in the lungs and multiple bones. She began paclitaxel plus bevacizumab and initially had a marked reduction in the enlarged lymph node.

Genetic testing later identified a germline BRCA2 pathogenic variant, leading to treatment with olaparib. The drug was briefly stopped and restarted at a lower dose after severe anemia. Tumor markers initially fell but later rose again, and eribulin was started after further progression. She subsequently developed extensive cancer spread through lymphatic vessels in both lungs and died 59 months after the breast operation.