Triple Negative Breast Cancer (TNBC)

What makes it "triple negative"?

Breast cancers are tested for three receptors: oestrogen receptor (ER), progesterone receptor (PR) and HER2. "Triple negative" means all three tests come back negative. This matters because many effective breast cancer treatments target these receptors — so TNBC cannot be treated with tamoxifen, anastrozole (hormone therapies) or trastuzumab (Herceptin). Treatment relies primarily on chemotherapy.

Who is most affected?

TNBC accounts for around 15% of all breast cancers. It is more common in:

• Younger women (particularly under 40)
• Black women — TNBC is approximately twice as common in Black women as in white women
• Women with BRCA1 mutations
• Premenopausal women

Treatment

Chemotherapy is the primary systemic treatment for TNBC. It is often given before surgery (neoadjuvant), where it can shrink the tumour and help surgeons achieve better results. If cancer cells are still present in the surgical specimen after neoadjuvant chemotherapy, capecitabine is offered as additional treatment.

Immunotherapy has been a significant advance for TNBC. Pembrolizumab (Keytruda) is now approved alongside chemotherapy for early-stage, high-risk TNBC, and for some advanced TNBC cases. For BRCA-mutated TNBC, PARP inhibitors (olaparib, talazoparib) are highly effective.

Prognosis

TNBC tends to be more aggressive than other types, but it also tends to respond well to chemotherapy when it does respond. Some TNBC patients achieve complete pathological response (no cancer cells left) after neoadjuvant chemotherapy — and this predicts an excellent outcome.