Precision Cancer Medicines and Breast Cancer


by Dr. C.H. Weaver M.D. 9/2020

The purpose of precision cancer medicine is not to categorize or classify cancers solely by site of origin, but to define the genomic alterations in the cancer’s DNA that are driving that specific cancer. Precision cancer medicines can be used both instead of and in addition to chemotherapy to improve treatment. Precision cancer medicine utilizes molecular diagnostic testing, including DNA sequencing, to identify cancer-driving abnormalities in a cancer’s genome. Once a genetic abnormality is identified, a specific targeted therapy can be designed to attack a specific mutation or other cancer-related change in the DNA programming of the cancer cells. Precision cancer medicine uses targeted drugs and immunotherapies engineered to directly attack the cancer cells with specific abnormalities, leaving normal cells largely unharmed.By testing an individual’s breast cancer for specific unique biomarkers doctors continue to develop new precision medicines. Individuals not previously tested undergo genomic testing to determine whether newer precision cancer medicines are a treatment option

Genetic Mutations

Not all breast cancer cells are alike. They may differ from one another based on what genes have mutations. Molecular testing is performed to test for certain genetic mutations or the proteins they produce because the results can help select treatment including newer precision cancer medicines designed to attack specific colon cancer cells with specific genetic mutations.

HER2 status: The HER2 pathway is a biological pathway involved in cellular replication and growth. Approximately 20-25% of breast cancers over express the HER2 protein and are referred to as HER2-positive. Several precision cancer medicines target and block the HER2-protein, and are used for the treatment of both early-stage and more advanced HER2-positive breast cancer. (4) Treatment of HER2 + Breast Cancer in Depth....

Cyclin Dependent Kinase Inhibitors (CDK) interfere with cancer cells ability to multiply rapidly by blocking the activity of CDK enzymes, particularly CDK 4 and CDK 6 that help to regulate cell division. CDK inhibitors are usually combined with hormonal therapy, which works by preventing hormones from binding with their respective receptors on the cancer cells. (8)

BRCA mutations: About three percent of breast cancers are in people who inherited BRCA mutations. Mutations in the BRCA gene raise the risk of cancer because they make the body less likely to repair damage to its DNA, making the mutations that lead to cancer more likely. Poly ADP-ribose polymerase (PARP) inhibitors block enzymes involved in repairing damaged DNA. By disrupting a cancer cells’ ability to repair itself PARP inhibitors slow uncontrolled growth and replication of cancer cells.

  • Lynparza (olaparib) is the first PARP inhibitor approved for use in breast cancer. Lynparza was demonstrated to be superior to chemotherapy for treatment of HER2-negative advanced breast cancer patients who have a BRCA mutation.(11)

Checkpoint Inhibitors are a novel precision cancer immunotherapy that helps to restore the body’s immune system in fighting cancer by releasing checkpoints that cancer uses to shut down the immune system. PD-1 and PD-L1 are proteins that inhibit certain types of immune responses, allowing cancer cells to evade detection and attack by certain immune cells in the body. A checkpoint inhibitor can block the PD-1 and PD-L1 pathway and enhance the ability of the immune system to fight cancer. By blocking the binding of the PD-L1 ligand these drugs restore an immune cells’ ability to recognize and fight the lung cancer cells. A diagnostic test to measure the level of PD-L1 is available. (12,13)

Additional targets will continue to be identified and precision cancer medicines created to attack those targets. Patients should ensure they discuss the role of genomic testing and precision cancer medicines with their doctor and undergo molecular testing of their cancer tissue and potentially blood.


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  12. Keytruda®/Halaven® May Be Effective in Advanced Triple-Negative Breast Cancer
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