Colorectal cancer is often talked about as a single type of cancer encompassing both colon and rectal cancers. While they do share many similarities, it is important to know they also have distinct differences that impact the patient’s recommended treatment.

Understanding Colon Cancer and Rectal Cancer

The colon and rectum are parts of the digestive system. The colon is the longest section of the large intestine and is responsible for absorbing water and nutrients from food. The rectum makes up the last few inches of the large intestine and connects to the anus, or the opening to the outside of the body.

Where the cancer begins will determine whether it is classified as either colon cancer or rectal cancer. Understanding the specific locations of these cancers helps doctors determine what tests and treatments will be the most appropriate for you.

Treatment Approaches for Colon and Rectal Cancers

Your cancer care team will consider various factors such as the stage, location of the cancer in the colon or rectum, and your overall health when developing a personalized treatment plan. Most patients receive more than one therapy to complete the treatment process.

Related Read: How Does Colon Cancer Treatment Vary by Stage?

In some cases, the same drugs are used for both colon and rectal cancers. However, the types of surgery, approach to radiation therapy, and other aspects of treatment are often different. 

Surgery for Colon and Rectal Cancers

Surgery is the most common treatment for colon and rectal cancers. However, the type and stage of the cancer affect which surgical approach is most appropriate. These factors also influence when the surgery should take place. In some instances, surgery may be performed after other treatments, such as chemotherapy or radiation.

Colon Cancer Surgeries

The cancer is removed using one of the following surgical methods:

• Polypectomy: If a polyp is found in the colon or rectum that appears to be cancerous, it will be removed during a colonoscopy. The polyp will be tested to see if cancer is present. Your oncologist may recommend a follow-up colonoscopy to look for any other polyps, even if the cancerous polyp was entirely removed during surgery.
  
  Related Read: What Are Colon Polyps and Are They Cancerous
  
• Local excision: Early-stage colon cancer may be surgically removed without cutting through the abdominal wall. Instead, the surgeon may insert a tube with a cutting tool through the rectum into the colon to excise the cancer.
• Colectomy: This procedure removes a larger section of the colon and can be performed as open surgery or with a minimally invasive approach. The amount of the colon that needs to be removed will largely determine which approach can be used.

Rectal Cancer Surgeries

The type of surgery for rectal cancer depends on how close the tumor is to the anus. If polyps are found, your doctor may remove them with a polypectomy or an excision. However, some patients may require another type of rectal cancer surgery, such as: 

• Transanal endoscopic surgery (TEM): This method is used for larger cancers higher in the rectum that may be difficult to remove through local transanal resection. A specially designed magnifying scope is inserted through the anus into the rectum for the procedure.
• Low anterior resection (LAR): This procedure removes the section of the rectum containing the tumor and reconnects the colon to the remaining rectum. This surgery requires abdominal incisions, but a permanent colostomy is not necessary. Typically, this approach is used for some stage I, II, and III cancers located in the upper rectum.
• Proctectomy: This surgery involves removing the entire rectum to allow for a total mesorectal excision (TME), which removes all lymph nodes near the rectum. The colon will then be attached to the anus (a procedure called a colo-anal anastomosis) so that bowel movements can occur normally. This method is often used for some stage I and many stage II and III cancers located in the middle and lower rectum.
• Abdominoperineal resection (APR): Usually performed for stage II and stage III cancers in the lower to middle rectum, this procedure removes the rectum through abdominal incisions, as well as the anus and sphincter muscles through incisions around the anus. This type of surgery is often necessary if the cancer has spread to the sphincter muscle (the muscle that keeps the anus closed and prevents stool leakage) or the surrounding levator muscles that help control urine flow.

Chemotherapy for Colon and Rectal Cancers

Chemotherapy may be recommended, especially if the cancer was found at a later stage. Several chemotherapy drugs are available that treat both colon and rectal cancers. Common chemotherapies include: 

• Capecitabine (Xeloda)
• Irinotecan (Camptosar)
• Trifluridine and tipiracil (Lonsurf)
• FOLFOX, a combination drug that includes folinic acid, 5-Fluorouracil (5-FU), and Oxaliplatin (Eloxatin)

These drugs may be used alone or in combination with other systemic therapies such as targeted or immunotherapy.

Radiation Therapy for Colorectal Cancers

Radiation therapy uses high-energy rays to kill or damage abnormal cancer cells and reduce the size of cancerous tumors. While radiation therapy is sometimes used for colon cancer, it is a much more common approach in treating rectal cancer.

If or when you receive radiation therapy depends on the location of the tumor, whether the cancer has spread, and what was found during surgery. There are different types of radiation therapy used to treat colon and rectal cancer:

• External beam radiation therapy (EBRT): Beams of radiation are delivered to the tumor from outside the body, directly targeting the cancer site. If radiation is part of the treatment plan, it is used for both colon and rectal cancers. Most patients receive radiation therapy five days a week for several weeks. 
• Internal radiation (brachytherapy): This type of radiation is more common for rectal cancer. A device with radioactive material is placed in the rectum, delivering radiation directly to the area. Each session only takes a few minutes and is repeated over several weeks. 

Treating Colon and Rectal Cancer With Targeted Therapy

Targeted therapy is different from chemotherapy because it specifically targets cells with a genetic change that causes colon or rectal cancer to grow. To determine if a targeted therapy drug will be effective, the oncologist requests biomarker testing on the tumor tissue removed during a biopsy or surgery. Test results tell the cancer care team whether a targeted therapy drug that will slow the cancer's growth is available to include in the treatment plan.

Targeted therapies are more commonly used for advanced colon or rectal cancers. These drugs can be used in combination with other treatments, such as chemotherapy and immunotherapy.

Immunotherapy for Colon and Rectal Cancers

Immunotherapy drugs enhance the body's immune system to fight cancer. This treatment is commonly used for both colon and rectal cancers that exhibit certain genetic changes, such as dMMR (deficient mismatch repair) or MSI-H (microsatellite instability-high). Immunotherapy may also be an option for patients with advanced colon or rectal cancer, including tumors that have returned to distant areas in the body. 

The class of immunotherapy drugs used for colorectal cancer is called immune checkpoint inhibitors. These drugs block proteins known as checkpoints, produced by certain immune system cells, like T cells, as well as by some cancer cells. Checkpoints can prevent the immune system from responding properly, sometimes inhibiting T cells from killing cancer cells. By using an inhibitor, the body's ability to fight cancer cells is strengthened. 

Advances in Treatment & Emerging Therapies

Thanks to clinical research, significant advancements in the treatment of colorectal cancer are available today. These include biomarker testing and the development of new drugs that counteract specific characteristics of the cancer. Various screening methods also allow for the early detection of polyps, which are easier to treat. These advancements are helping patients, even those with advanced cancer, live longer, fuller lives.

Treatment for Colon and Rectal Cancers in Colorado

Remember, colorectal cancer can be successfully treated. It’s much easier when caught in its earliest stages. Be sure to get screened regularly and see your doctor if you receive any abnormal results.

If you were diagnosed with colon or rectal cancer, the specialists at Rocky Mountain Cancer Centers are here to help. Find a location in Denver, Boulder, Colorado Springs, and surrounding areas to schedule an appointment.