Colon Cancer and Chemotherapy
Chemotherapy is a systemic treatment (travels throughout the body via the bloodstream) that often uses a combination of drugs to slow tumor growth and destroy cancer cells. Drugs may be administered orally or intravenously (through a needle in a vein). In some cases, chemotherapy drugs can cause an allergic or hypersensitivity reaction. These reactions, which may be severe and are triggered by an immune system response, can occur immediately or within hours or days of treatment.
Chemotherapy is often used as a first-line treatment for metastatic colorectal cancer to destroy cancer cells that have metastasized (spread). It also may be used prior to surgery (called neoadjuvant therapy) to shrink the tumor, may be administered following surgery (called adjuvant therapy), and may be combined with biological therapy (also called immunotherapy) and radiation therapy.
Newer combinations of chemotherapy drugs, such as FOLFOX (5-fluorouracil [5-FU], leucovorin, and oxaliplatin [Eloxatin]) and FOFIRI (5-fluorouracil [5-FU], leucovorin, and irinotecan [Camptosar]) may be used to prevent recurrence following surgery or to shrink the tumor prior to surgery.
A combination of chemotherapy drugs (5-fluorouracil [5-FU], leucovorin, and irinotecan [CPT11]), administered intravenously, is standard treatment for metastatic colorectal cancer. Side effects include diarrhea, mouth irritation (mucositis), low white blood cell count (e.g., neutropenia), and hair loss (alopecia).
Colorectal cancer with liver metastasis also may be treated using floxuridine (FUDR®) administered intra-arterially (i.e., through an artery). Side effects include nausea, vomiting, diarrhea, and inflammation of the intestine (enteritis).
In addition to chemotherapy drugs, blocking agents (e.g., cetuximab [Erbitux]) may also be used to treat metastatic colorectal cancer. These drugs prevent cancer cell receptors from receiving factors (e.g., epidermal growth factor) that cause cell growth, cell division, and additional metastasis. Blocking agents target specific cells so they usually do not cause systemic side effects. Side effects of these drugs include allergic reactions (e.g., difficulty breathing, hives, low blood pressure, rash).
Bevacizumab (Avastin) may also be used to treat advanced colorectal cancer. This medication prevents new blood vessels, which are necessary for tumor growth, from forming. It does not affect normal tissues that already have an established blood supply. Side effects include blood clots and high blood pressure, which can be controlled with medication.
Panitumumab (Vectibix) is the first entirely human monoclonal antibody approved by the Food and Drug Administration (FDA) to treat patients with metastatic colorectal cancer following chemotherapy. This medication is administered intravenously once every 2 weeks.
Regorafenib (Stivarga) is approved to treat colon or rectal cancer that has spreadafter treatment with other chemotherapy drugsand also to treat certain metastatic gastrointestinal stromal tumors (GIST)rare tumors of the GI tract. Side effects include fatigue, diarrhea, appetite loss, inflammation (of the mouth, throat, stomach, other organs of the GI tract) and infection. Severe side effects include liver damage, abnormal bleeding, skin rash and others.
In September 2015, the FDA approved the oral drug Lonsurf, which combines trifluridine and tipiracil to treat metastatic colorectal cancer that no longer responds to other chemotherapy drugs or biological therapy. According to the FDA, an international, randomized, double-blind study showed an improvement in survival time and in time to disease progression. Side effects include low blood cell counts (e.g., anemia, neutropenia, thrombocytopenia), fatigue, weakness, fever, loss of appetite, and gastrointestinal symptoms (e.g., diarrhea, nausea, vomiting, abdominal pain).