What are chemotherapy and targeted therapies?

When we talk about treating cancer, many people first think of chemotherapy. But what is it, really?

Chemotherapy is a type of medication that kills rapidly dividing cells by interfering with key steps in cell division.

These chemo drugs can’t tell the difference between tumor cells and healthy cells. This means that normal cells that also divide quickly can be affected by chemotherapy drugs — such as cells in your bone marrow, skin, hair follicles, the lining of your intestines, and more! This is the cause of many common chemo side effects, such as hair thinning.

Chemotherapy is considered a systemic therapy, because the drugs are injected into the bloodstream and circulate through the whole body.

Not all cancer drugs are chemotherapies. You might take some drugs called targeted therapies too. They may be given together, or with chemo. In those cases, targeted therapies can help chemo be more effective. 

How is chemotherapy used to treat colorectal cancer?

Chemotherapy can be used:

• As the primary treatment
• Before surgery or radiation to shrink tumors. This is called neoadjuvant chemotherapy
• After surgery or radiation to destroy any cancer cells that may be left over. This is called adjuvant chemotherapy
• Along with long course radiation for rectal cancer. This is called chemoradiation or chemo-RT

Will I get chemotherapy if I’m an early stage patient?

Most stage I CRC patients are unlikely to have any chemotherapy. 

Chemotherapy may be recommended for a small number of stage II patients, if you are ctDNA positive, or if your tumor has certain characteristics.

Learn more about ctDNA here.

All stage III patients are recommended to have chemotherapy, for either 3 or 6 month regimens. The most common regimens are FOLFOX and CAPOX.

The great majority of stage IV patients will receive chemotherapy. 

Read more about chemotherapy sequencing here.

What are targeted therapies?

Targeted therapies are drugs that block particular proteins or receptors that are important for cancer cells to grow. They can be given in combination with another targeted therapy, or chemotherapy. 

Examples include panitumumab (Vectibix) or cetuximab (Erbitux), which target the epidermal growth factor (EGFR) receptor. Other examples include bevacizumab (Avastin), which inhibits vascular endothelial growth factor (VEGF) signaling — which blocks tumors from growing new blood vessels. BRAF inhibitors like encorafenib (Braftovi) target and inhibit the BRAF V600E mutant protein.

Targeted therapies can be combined with chemotherapy. For example, EGFR inhibitors are commonly given to stage IV patients with wild type RAS/RAF tumors. Avastin is combined with chemo for people with left-sided or right-sided metastatic colorectal cancer.

How will I know if treatment is working — and how can I maximize my chances of success?

For most patients, first-line chemotherapy and targeted therapies are very effective at controlling cancer — meaning that tumors either stay the same size or shrink. These treatments are particularly effective for early stage cancer. 

So how do we know which drugs work to fight colorectal cancer? Chemo regimens are tested through extensive clinical trials. A chemotherapy regimen is a specific combination of medications given in a particular sequence. 

Through clinical trials we learn how chemo drugs work in large populations — but it can still be difficult to predict how you, as an individual, will respond to treatment. It depends on how similar your disease is to that of patients in the trial.

Luckily, with the help of biomarker testing, researchers are getting better and better at identifying which regimens work best in which patients. To learn more about biomarker testing and what it means for treatment, click here.

Your oncologist and healthcare team will check up with you on a regular basis. Scans, blood tests, and other exams can help your doctor determine how you are responding to treatment and plan out next steps.

Treatment can be rough. Following your oncologist’s recommendations and communicating with your healthcare team are the best things you can do to maximize your chances of successful treatment. Talk with your doctor about any unpleasant side effects you experience. Do your best to maintain a healthy weight, a healthy diet, and a healthy level of physical activity. These things will help you feel better, and may help your response to treatment. Listen to your body, and help support it as best you can!