The cornerstones of colon and rectal cancer treatment are surgery, radiation, and chemotherapy.
For patients who have tumors with specific genetic traits or protein changes, doctors may also turn to two newer types of treatment: targeted therapy and immunotherapy.
Decisions largely depend on the extent, or stage, of the cancer — whether it is present only in the inside lining of the colon or rectum, has grown deeper into those tissues, or has spread to other parts of the body.
As with other cancers, people with early-stage colorectal cancer (a term that encompasses both colon and rectal cancer) generally have the best outcomes.
Patients with stage 1 colon cancer, also called “localized” because it hasn’t spread beyond the middle layers of the colon or rectum, have a five-year relative survival rate of around 91 percent; people with stage 1 rectal cancer are at 90 percent.
Those numbers drop to 14 percent and 17 percent for patients with stage 4 cancers, which may have spread to lymph nodes or other organs. (1)
Surgery Is Often the First Option
Surgery is the main treatment for many early-stage colon cancers and most rectal cancers.
Doctors can remove some early-stage colon and rectal tumors, as well as precancerous growths called polyps, using minimally invasive techniques that don’t require cutting into the abdomen.
For a procedure called a colonoscopy, the doctor threads a colonoscope — a long, thin, flexible tube with a tiny video camera at the end — through the anus.
Doctors use cutting tools inserted through the colonoscope to remove tumors or polyps.
For a large tumor confined to the colon, the surgeon will perform an operation called a colectomy.
For most colon cancer treatment, this procedure involves removing affected parts of the colon along with a small margin of healthy tissue.
Nearby lymph nodes are also removed for examination.
In an open colectomy, the surgeon makes a long incision in the abdomen to reach the colon.
A less invasive technique, called laparoscopic-assisted colectomy, uses many small incisions — one for a laparoscope (a camera similar to a colonoscope) and others for long, thin surgical instruments.
After removing a section of colon, the surgeon reconnects the cut ends.
But if the tumor has blocked the colon, the surgeon may be unable to reattach the ends immediately after colectomy.
Instead, the surgeon makes an opening in the abdomen, called a stoma, for waste to pass out of the body from the colon or the small intestine and into an airtight plastic pouch. (2)
If the cancer has spread to only a few spots in the lungs or liver, surgeons may be able to remove them or use other methods to kill cancer cells or block blood flow to them, such as cryosurgery (freezing with a metal probe). (3)
Radiation Therapy May Play a Role
Radiation therapy, which relies on high-energy X-rays or other types of radiation to destroy cancer cells, is less commonly used for colon cancer than for rectal cancer.
It is often combined with chemotherapy to boost its effects.
For instance, doctors might use radiation and chemotherapy together to shrink a large tumor so it’s easier to remove surgically.
Radiation may also be used before or after surgery to help lower the risk of cancer recurrence. (4)
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Chemotherapy Is a Go-To Treatment
Doctors use chemotherapy drugs to kill colon and rectal cancer cells or stop their spread.
Chemotherapy, together with radiation, may be administered before surgery for rectal cancer to reduce the size of tumors, or after surgery to kill any cancer cells left behind.
It can also be used to shrink tumors in other parts of the body, relieving symptoms.
Chemotherapy drugs may be given orally or intravenously (IV) to a localized area, reducing side effects.
The chemotherapy drugs in most widespread use for colorectal cancer include:
- fluorouracil (Adrucil)
- capecitabine (Xeloda)
- irinotecan (Camptosar)
- oxaliplatin (Eloxatin)
To get the best results, these drugs are frequently used in combination, and sometimes with targeted therapy. (5)
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Targeted Therapy Is Next-Gen Medicine
Targeted therapy, used in combination with chemotherapy, is another type of medicine-based treatment for colon cancer and rectal cancer. These therapies are used for metastatic colon cancer that cannot be treated with surgery or radiation.
Researchers have made progress understanding the biochemistry of colorectal cancer and identifying gene and protein changes unique to cancer cells — creating targets for a new generation of drugs.
Targeted drugs may have fewer side effects than chemotherapy, or different and less severe ones.
Targeted drugs that home in on a protein in cancer cells called VEGF (vascular endothelial growth factor), which helps tumors form new blood vessels, include:
- bevacizumab (Avastin)
- ramucirumab (Cyramza)
- ziv-aflibercept (Zaltrap)
Other targeted drugs that may treat some advanced colon cancer and rectal cancer by focusing on the protein EGFR (epidermal growth factor), which helps cancer cells grow, include:
- cetuximab (Erbitux)
- panitumumab (Vectibix)
A targeted drug called a kinase inhibitor focuses on kinases — proteins that carry signals to the cancer cell’s control center. These include:
- regorafenib (Stivarga)
- encorafenib (Braftovi) (6)
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Immunotherapy Is Helping Some Patients
Immunotherapy, which harnesses the power of the body’s own immune system to attack cancer cells, has shown great promise for the treatment of certain advanced cancers, such as melanoma and non-small-cell lung cancer.
Immunotherapy has so far had a more limited impact on the treatment of colorectal cancer. But for the subset of patients whose cancer cells have specific genetic changes, immunotherapy appears to have real potential.
For instance, 15 percent of patients with colorectal cancer and 4 to 5 percent of patients with metastatic colorectal cancer have tumors with a high level of microsatellite instability (MSI-H), or changes in one of the mismatch repair (MMR) genes. (7)
Immunotherapy drugs called checkpoint inhibitors can be very effective in treating these patients.
Two immunotherapy drugs, pembrolizumab (Keytruda) and nivolumab (Opdivo), target PD-1, a protein on the immune system’s T-cells that normally prevents them from attacking other cells in the body.
By blocking PD-1, these drugs free T-cells to attack MSI-H tumors.
Another checkpoint inhibitor, ipilimumab (Yervoy), achieves a similar goal by blocking the T-cell protein CTLA-4.
Researchers continue to explore other immunotherapy treatments, such as vaccines, in pursuit of new ways to beat colorectal cancer. (8)