Targeted Therapy for Colorectal Cancer

Targeted therapy drugs work differently than chemotherapy drugs by targeting specific changes in cells that cause colon or rectal cancer. These drugs can be used together with chemotherapy or by themselves. Currently, targeted therapies are only approved for the treatment of advanced (metastatic) stage IV colorectal cancer.

The epidermal growth factor receptor (EGFR) is a protein that can enable cancer cells to grow. 

Panitumumab (Vectibix^®) and cetuximab (Erbitux^®) are two targeted therapies that block EGFR, interfering with cancer cells’ ability to grow and proliferate. These drugs are used to treat some types of advanced colon and rectal cancer.

 These drugs have been shown to work better in patients who do not have mutations (changes) in any of the RAS genes (KRAS, NRAS, HRAS) or BRAF genes. Before beginning treatment with an EGFR inhibitor, the patient’s biomarkers will be tested to make sure that these drugs are only used when these mutations are not present.

The most common side effect of EGFR inhibitors is skin rash. To help relieve skin rash, it is recommended that you use sunscreen, keep your skin clean and moisturized, avoid direct sun exposure, and avoid using harsh skin products. Talk to your medical team about how to best manage any symptoms you may experience. Depending on the severity and type of rash developed, your doctor may reduce or delay the next dose of EGFR inhibitor.

If you are about to start or have recently started EGFR inhibitor therapy, a skin care sample kit is available to you. Please ask your healthcare professional how you can obtain one.

Vascular endothelial growth factor (VEGF) is a protein that helps cancer cells grow new blood vessels through a process known as angiogenesis. VEGF inhibitors (also known as angiogenesis inhibitors) block this process, causing blood vessels to shrink away from the tumour and starving it of oxygen and nutrients.

Bevacizumab (Avastin^®) is a targeted therapy that inhibits VEGF, blocking the growth and development of blood vessels. It is given together with chemotherapy to treat advanced colorectal cancer.

Mvasi^® and Zirabev^® are both biosimilars of bevacizumab (Avastin^®) that are available in Canada for the treatment of advanced colorectal cancer. Biosimilars are drugs that are highly similar to another original medication, in this case, bevacizumab. These two biosimilars are given in combination with chemotherapy to treat advanced colorectal cancer.

Encorafenib (Braftovi^®) is a targeted therapy that inhibits the function of the BRAF protein, which is involved in the growth of cancer cells. Encorafenib is given together with cetuximab (an EGFR inhibitor, see above) to people with advanced colorectal cancer.

Regorafenib (Stivarga^®) is a type of targeted therapy known as a kinase inhibitor. This drug targets the tyrosine kinase receptor proteins located on the surface of the cell. Regorafenib interferes with several kinase proteins at once – those that are involved in tumour growth and progression as well as blood vessel development (angiogenesis). Regorafenib is used to treated advanced colorectal cancer, usually once the cancer does not respond to other therapies.

Regorafenib is available in Canada for previously treated colorectal cancer, though it is generally not reimbursed.