Colorectal Cancer

Colorectal cancer has several types depending on where it’s located. The most common type - adenocarcinoma - develops in the lining of the large intestine. Other types of colon cancer can develop in different parts of the digestive tract and can affect your hormone production, immune system, nervous system, muscles and other tissues. These types are very rare.

Adenocarcinomas of Colon & Rectum

More than 95% of colorectal cancers are adenocarcinomas, which start in mucous-secreting cells in the lining of the colon and rectum. They often begin as polyps (also called adenomas), which can be removed during colonoscopies before they become cancer. Adenocarcinomas typically start in the inner lining of the large intestine but can spread to other layers.

Rare Types of Colorectal Cancers

• Gastrointestinal carcinoid tumors - these slow-growing tumors form in neuroendocrine cells, which regulate hormone production. They account for about 1% of all colorectal cancers.
• Gastrointestinal stromal tumors (GISTs) - these tumors develop in nervous system cells that signal the bowel muscles to contract. GISTs are classified as sarcomas or cancers that begin in connective tissues like cartilage, fat, muscles and blood vessels.
• Primary colorectal lymphomas - these cancers develop in immune cells in the colon or rectum. They account for less than 1% of all colorectal cancers. Risk factors include having a suppressed immune system or inflammatory bowel disease.

Hereditary Types of Colorectal Cancers

While colorectal cancer isn’t generally hereditary, there are a small number of cases caused by gene mutations (changes) passed down in families. The two most common hereditary colorectal cancers are hereditary nonpolyposis colorectal cancer and familial adenomatous polyposis. 

• Hereditary nonpolyposis colorectal cancer (HNPCC) - also known as Lynch syndrome or cancer family syndrome, HNPCC occurs when very few or no polyps are found. Cancer often appears on the right side of the colon and occurs at a younger age than non-hereditary colon cancers.
• Familial adenomatous polyposis (FAP) - this rare type of colon cancer is caused by inherited changes in a gene that controls cell growth. It’s characterized by hundreds or thousands of colon polyps, sometimes appearing in the teenage years.

If you have a strong family history of colon cancer, especially in your first-degree relatives please contact your Mercy primary care doctor to discuss genetic testing for colon cancer no matter your age.   

While the exact cause of colon cancer is unknown, several factors can increase your risk of developing it. You can reduce some of these risk factors with diet and lifestyle changes.

Controllable Risk Factors

• Being overweight or obese
• Frequently eating red or processed meats
• Lack of physical activity
• Smoking (especially long-term)
• Heavy alcohol use

Non-Controllable Risk Factors

• Having a personal history of adenomatous polyps or colon cancer
• Having a family history of adenomatous polyps or colon cancer, including a parent, sibling or child who had colorectal cancer younger than age 45; two or more family members (parents, brothers, sisters or children) who had it at any age
• Inheriting gene mutations linked to colon cancer, such as HNPCC or FAP. Most people who inherit these conditions will get colon cancer if they’re not screened and treated.
• Being over age 50

Colon cancer doesn’t always cause symptoms, especially in the early stages. If you experience symptoms, they may include:

• A change in bowel habits, including persistent constipation or diarrhea
• Feeling like your bowel won’t empty completely
• Bleeding from the rectum with bright red blood
• Blood in the stool
• Cramping or abdominal pain
• Weakness and fatigue
• Unexplained weight loss
• Low red blood cell count (anemia) caused by blood loss through the rectum

Colon cancer screening tests can often detect colon cancer at its earliest stages when treatment is most likely to be successful. The most common colon and rectal cancer screenings are colonoscopies, sigmoidoscopies and high-sensitivity fecal occult blood tests (FOBTs). If your screening test shows a potential concern or you’re experiencing symptoms, your Mercy gastroenterologist may recommend diagnostic testing, which can include certain types of imaging tests, biopsies and laboratory tests.

Imaging tests are used in determining the staging and spreading of colon cancer. The types of imaging used to diagnose colon cancer may include:

• Diagnostic X-rays
• PET scans
• CT scans
• Pelvic MRIs

Biopsies are performed if colon or rectal cancer is suspected by screening or diagnostic tests. A biopsy is usually completed during a colonoscopy and often performed using the minimally invasive laparoscopic method.

Certain laboratory tests may be ordered to help determine if you have colon cancer. These blood tests can also be used to help monitor your cancer once diagnosed. The types of blood tests may include:

• Complete blood count (CBC)
• Liver enzymes
• Tumor markers

Colon cancer surgery is a common treatment for all stages of colorectal cancer. During surgery for colon cancer, lymph nodes are usually removed to determine whether they’re cancerous. Depending on the location and type of colorectal cancer, one or more surgeries may be performed. Mercy surgeons specialize in removing polyps and tumors and are skilled in the latest technologies and minimally invasive colorectal surgery techniques, including laparoscopic surgery and robotic-assisted surgery for colon cancer.

• Laparoscopic surgery uses a lighted tube (or scope) and small incisions to remove cancer or parts of the colon and rectum
• Robotic-assisted surgery offers enhanced precision and shorter recovery times for colon cancer surgeries.

Polypectomy & Local Excision

Some early-stage colon cancers can be removed during a colonoscopy. Both polypectomy and local excision can be performed during this procedure.

• Polypectomy is generally performed for early-stage colon cancer removal and is performed during the removal of polyps. This surgery uses a loop instrument is used to remove cancerous polyps from the colon wall.
• Local excision can treat cancers in the rectum (lowest part of your colon) by removing small cancers and some nearby healthy tissue from the colon or rectum.

Bowel Resection

Bowel resection, also called a colectomy, removes the diseased portion of the colon or rectum. The nearby lymph nodes are also removed during a bowel. resection in order to be tested for cancer. If possible, the two healthy parts of the colon or rectum are sewn together (also called anastomosis).

Colostomy

In many cases, patients will not need a colostomy after colorectal cancer surgery. However, there are instances in which the bowel cannot be immediately reattached and a temporary colostomy may be needed. A colostomy creates an opening on the outside of the body that collects waste in a pouch. 

Mercy radiation oncologists offer advanced radiation therapy treatments to precisely target cancerous tumors and may be used before or after colorectal cancer surgery. It’s also used as palliative therapy for people who can’t have surgery and need relief from discomfort caused by tumors. Types of radiation therapy for colorectal cancer include external radiotherapy and brachytherapy or internal radiation therapy.

External Radiation Therapy

External beam radiation therapy (EBRT) is a local cancer treatment and is most often used for patients with colon or rectal cancer. The different types of external radiotherapy used for colorectal cancers may include:

• Intensity-modulated radiation therapy (IMRT) – IMRT uses external radiation beams targeted to a tumor’s size and shape.
• Stereotactic radiotherapy (SRS) – SRS delivers high doses of radiation to extremely precise locations to protect nearby tissues. CyberKnife is a type of SRS that is often used for colon cancer by targeting complex cancer tumors that can’t be surgically removed with multiple high doses of radiation.

Internal Radiation Therapy

Internal radiation therapy, also known as brachytherapy, might be used to treat some types of rectal cancers. During brachytherapy, radioactive material is placed inside or near cancer tumors to target smaller treatment areas.

For some colorectal cancers, chemotherapy may be needed before or after surgery. Chemo drugs target cancer cells that grow and divide quickly. Chemo can be administered by infusion into your veins or orally to fight cancer throughout your body.

Immunotherapy is used in certain colorectal cancers to help improve treatment options. Many people who have taken immunotherapy medications have reported experiencing fewer side effects than traditional chemotherapies.

Targeted therapies are drugs that target gene and protein changes in cells involved with colorectal cancer. An example is monoclonal antibodies—substances made in a lab that can help your immune system find and attack cancer cells.