Targeted Therapy & Immunotherapy
Some breast cancers have proteins or genetic changes that can be attacked with targeted drugs. The best-known example is HER2-positive breast cancer. Other targeted treatments are available for some cancers associated with BRCA mutations.
Immunotherapy works differently, helping the immune system recognize and attack cancer cells. It is useful for some women with triple-negative breast cancer.
These treatments depend on testing the cancer—and sometimes inherited genes—to identify characteristics that can be targeted.
HER2-Positive Breast Cancer
HER2-positive breast cancers have unusually high levels of a protein that promotes cancer growth.
The introduction of trastuzumab (Herceptin) dramatically improved treatment. For early HER2-positive breast cancer, trastuzumab can substantially reduce recurrence and improve survival.
Newer HER2-targeted treatments include antibody-drug conjugates, which combine an antibody that recognizes HER2 with a cancer-killing drug. Some of these treatments are now used not only for HER2-positive breast cancer but also for certain cancers with low or even very low levels of HER2.
The particular treatment depends on the cancer's stage, previous treatment, and response.
BRCA Mutations and PARP Inhibitors
Some breast cancers occur in women with inherited BRCA1 or BRCA2 mutations, which interfere with normal DNA repair.
PARP inhibitors, such as olaparib (Lynparza), exploit this weakness by blocking another DNA-repair pathway.
In the OlympiA trial, women with high-risk, HER2-negative early breast cancer and inherited BRCA mutations who received olaparib after standard treatment had fewer recurrences and better survival.
This is one reason inherited genetic testing can sometimes directly affect treatment choices.
Immunotherapy for Triple-Negative Breast Cancer
Triple-negative breast cancer lacks estrogen receptors, progesterone receptors, and excess HER2, so hormone therapy and HER2-targeted drugs do not work against it.
Pembrolizumab (Keytruda) helps the immune system recognize and attack cancer cells.
For high-risk early-stage triple-negative breast cancer, pembrolizumab may be combined with chemotherapy. The KEYNOTE-522 trial found that this approach reduced recurrence or progression and improved overall survival.
Pembrolizumab is also used for certain patients with metastatic triple-negative breast cancer, based partly on PD-L1 testing.
Immunotherapy can be effective but can also cause the immune system to attack healthy tissues.
Why Biomarker Testing Matters
Breast cancer is not a single disease. Testing can reveal characteristics that directly affect treatment.
ER, PR, and HER2 testing helps determine whether hormone or HER2-targeted therapy may work. BRCA testing can affect the use of PARP inhibitors, while PD-L1 testing can help guide immunotherapy in some metastatic triple-negative cancers.
A useful question is:
“Does my cancer have a characteristic that can be specifically targeted?”
Questions to Ask Your Doctor
Has my cancer been tested for the relevant biomarkers?
Is there a targeted therapy appropriate for my cancer?
Should I have inherited genetic testing?
How much benefit is the treatment expected to provide?
What are the important side effects?
Is immunotherapy appropriate for my cancer?
Learn More
An overview of HER2-targeted drugs and other targeted treatments for breast cancer.
Explains how trastuzumab targets HER2 and how it is used.
The major randomized trial of olaparib for certain women with high-risk, HER2-negative early breast cancer and inherited BRCA mutations.
A major randomized trial showing improved outcomes when pembrolizumab was added to chemotherapy for high-risk early triple-negative breast cancer.
Highlights advances in breast cancer treatment, including HER2-targeted therapy and newer approaches under study.