In the United States, colon cancer is the third most common cancer diagnosed in both men and women. As such, colon cancer screening is so important in the fight against this disease. Start a search to learn more about the diagnosis, staging and treatment processes of this disease.
Colon cancer also has the distinction of being the third leading cause of death from cancer among American men and women. It’s critical to know more about this cancer and what to keep your eyes out for in the early stages, as this could increase the chances of a better outcome if you’re diagnosed.
Your doctor will start by performing a thorough medical history focusing on your symptoms and family history. This is followed by a thorough physical examination, including a rectal examination.
Although there is no specific blood test for the diagnosis of colon cancer, your doctor may check your liver function tests and complete blood count. Colon cancer — especially if has spread to other parts of the body — or other medical conditions may adversely affect these tests.
Other diagnostic strategies for colon cancer may include imaging studies, such as double-contrast barium enema and virtual colonoscopy.
Staging of Colon Cancer
If diagnosed with colon cancer, you and your doctor will want to know the extent of your cancer. This is accomplished through a process called staging. This process helps determine which treatments are most appropriate for you. Abdominal, pelvic, chest CT scans, and biopsies are usually utilized in the staging of colon cancer.
Roman numerals ranging from 0 to IV are used to indicate the stages of colon cancer. They are:
- Stage 0: This is the earliest stage of colon cancer. The cancer has not grown beyond the mucosa (innermost layer of the colon).
- Stage I: The colon cancer has grown beyond the mucosa and into the submucosa (middle layer of the colon).
- Stage II: The colon cancer has grown beyond the mucosa and submucosa into the outer layers of the colon (muscularis propria and serosa).
- Stage III: The colon cancer has grown beyond the outer layers of the colon and to one to three lymph nodes. However, it has not spread to distant sites in the body.
- Stage IV: Also known as metastasis. As such, it is the most advanced form of colon cancer. The colon cancer has grown beyond all layers of the colon, spread to lymph nodes, and distant parts of the body, such as lungs, liver, bone, or brain.
There are several types of colon cancers. The most common type is adenocarcinoma, which accounts for 96 percent of colon cancers. Two subtypes of adenocarcinoma, mucinous and signet ring cell, deserve special mention because they tend to have a worse prognosis as compared to other types of adenocarcinoma.
Other less common types of colon cancer include:
- Carcinoid Tumors: Starts in the hormone-producing cells of the colon.
- Gastrointestinal Stromal Tumors: Starts in the interstitial cells of Cajal.
- Lymphomas: Namely a type of non-Hodgkin lymphoma that originates in the colon.
- Sarcomas: Namely leiomyosarcomas or cancers of smooth muscle.
The prognosis for your colon cancer is most commonly referred to as the five-year survival rate. For particular colon cancers, its stage at diagnosis determines the prognosis.
If left untreated, the complications of colon cancer may include:
- Bleeding, which can be visible from the rectum and leads to iron deficiency anemia;
- Blockage of the colon or bowel obstruction, or;
- A hole in the colon or bowel perforation.
These complications may be considered surgical emergencies and can become life-threatening.
Other potential complications of colon cancer include:
- Recurrence of cancer in the colon;
- Spread of cancer to other organs or tissues with subsequent dysfunction/failure, and;
- Diagnosis of second primary colon cancer.
The treatment of colon cancer depends on many variables, including the stage of cancer. The aims of colon cancer treatment are the removal of cancer, prevention of its spread, and reduction of any uncomfortable symptoms.
Colon cancer treatments come in two broad categories:
- Local Therapies: Treat colon cancer without affecting the rest of the body. These include surgery and radiation therapy.
- Systemic Therapies: Treat colon cancer using drugs. You can receive these drugs orally or directly into the bloodstream. These include chemotherapy, targeted therapy, and immunotherapy.
Surgery for colon cancer may include:
- Polypectomy: Removal of the cancerous polyp. Used for stage 0 and some stage I colon cancers.
- Local Excision: Removal of some tissue in the wall of the rectum. The rectum is the vault at the end of the colon. Used for stage 0 and some stage I colon cancers.
- Colectomy: Removal of the colon. Used for more advanced colon cancer (stages II through IV). There are two types: partial and total colectomy. All types of partial colectomy, as well as total colectomy, can be performed via minimally invasive laparoscopy or via a large abdominal incision. It may be accompanied by an ostomy, which can be temporary or permanent.
Radiation therapy is not commonly used in the treatment of colon cancer. Despite that, it may be useful in select cases, such as:
- Before surgery to decrease tumor size and allow for easier removal;
- During surgery to kill any residual cancer cells;
- After surgery to kill any residual cancer cells;
- To ease complications such as bleeding, bowel obstruction, or pain, and;
- To help treat metastatic colon cancer.
Side effects of radiation therapy may include:
- loss of appetite, and;
- Weight loss.
Most of these side effects resolve within several weeks after cessation of treatment.
Almost all individuals diagnosed with stage III colon cancer receive chemotherapy after surgery for a total of six to eight months. This is adjuvant chemotherapy.
Occasionally, chemotherapy with or without radiation therapy may be used before surgery to shrink the tumor and make it easier to remove. This is neoadjuvant chemotherapy.
Also, in individuals with stage IV disease, chemotherapy may be used to help ease symptoms by shrinking the tumor. It may even prolong life in these individuals.
Some chemotherapy drugs used to treat colon cancer include:
- 5-fluorouracil (5-FU);
- Irinotecan (Camptosar);
- Oxaliplatin (Eloxatin), and;
- Trifluridine and tipiracil (Lonsurf).
Side effects of chemotherapy may include:
- Hair loss;
- Mouth sores;
- Fatigue, and;
- Increased susceptibility to infections.
Targeted therapy involves drugs that specifically block or inhibit either the growth of cancer cells or the formation of new blood vessels. These two functions are crucial to the perpetuation of colon cancer. Specifically, targeted therapy can block:
- Epidermal Growth Factor Receptor (EGFR): A protein needed for cancer cell growth.
- Vascular Endothelial Growth Factor (VEGF): A protein needed for the formation of new blood vessels; also referred to as angiogenesis.
- Kinases: Several molecules that are responsible for both cancer cell growth and angiogenesis.
Examples of targeted therapy for colon cancer include:
- Cetuximab (Erbitux) and panitumumab (Vectibix), which target EGFR;
- Bevacizumab (Avastin) and ramucirumab (Cyramza), which target VEGF, and;
- Regorafenib (Stivarga), which target kinases.
Targeted therapy will sometimes work when standard chemotherapy drugs don’t. Plus, they often have different and less severe side effects compared to standard chemotherapy regimens.
Targeted therapy drugs can be used alone or in combination with surgery, radiation, and standard chemotherapy.
Immunotherapy focuses on drugs that have the potential to boost your immune system. This boost will hopefully lead to better recognition and destruction of colon cancer cells. Immunotherapy accomplishes this by blocking key proteins on immune cells, which boosts your immune response.
These drugs are known as “checkpoint inhibitors”. If your colon cancer is still growing, despite chemotherapy, you may be a candidate for a checkpoint inhibitor. Examples include pembrolizumab (Keytruda), nivolumab (Opdivo), and ipilimumab (Yervoy).
Side effects of this class of medications may include:
- Potentially life-threatening immune reactions;
- Rash, and;