Discordance in Biomarker Expression in Breast Cancer After Metastasis: Single Center Experience in India

Biomarker-estrogen receptor (ER), progesterone receptor (PR), and human epidermal growth factor receptor 2 (HER2/ neu) -discordance plays an essential role in the management and prognosis of patients with metastatic breast cancer. Rates of discordance have been previously reported around 12% to 35%, 30% to 50%, and 5% to 15%, respectively, in Western literature. Data are sparse regarding the same from developing countries, such as India.

We performed an ambispective review of paired biomarker status in patients with breast cancer-stage I, II, and III as per American Joint Committee on Cancer, 7th edition-who developed metastasis at recurrence (N = 103 patients). Biomarker status and clinical and radiologic parameters were documented at baseline and subsequent follow-up.

Discordance was present in 21.3% for ER, 29.1% for PR, and 15.5% for HER2/ neu receptor. In our cohort, 7.8% had positive to negative ER and 13.6% negative to positive. Whereas 21.4% had positive to negative PR, 7.8% had negative to positive PR. Approximately 6.8% had positive to negative HER2/ neu receptor and 8.7% negative to positive. In our cohort, 41 patients (40%) had single-site metastasis-bone, 15.5%; lung, 11.7%; nonregional lymph node, 7.8%; liver, 3.9%; and brain, 0.97%. More than one site of metastasis was present in 62 patients (60%). The most common sites of metastasis were visceral-lung and liver-followed by bone, nonregional lymph node, skin, and brain.

The current study demonstrated that metastatic disease evolution in breast cancer is characterized by change in the tumor biology, which leads to discordance in receptor status. Repeat biomarker studies at metastatic recurrence is warranted, especially if treatment plans include hormone and targeted therapy.