A Patient's Guide to Understanding Colorectal Cancer

Colorectal cancer (CRC) is a complex disease, but understanding its fundamental aspects can empower you to have more informed and productive conversations with your oncologist. This guide provides an overview of the key topics in colorectal cancer care, from diagnosis to survivorship.

What Are the Different Types of Colorectal Cancer?

Colorectal cancers are classified by the cells they originate from. The vast majority of cases are adenocarcinomas, but a small percentage are other, more rare types.

Adenocarcinomas:

• This is the most prevalent type, accounting for over 95% of CRC cases.
• It starts in the cells that line the colon and rectum and produce mucus.

Other Rare Types of Colorectal Cancer:

• Lymphomas: Cancers that begin in immune system cells and can sometimes start in the colon or rectum.
• Carcinoid Tumors: A type of neuroendocrine tumor that develops from hormone-producing cells in the gut lining.
• Gastrointestinal Stromal Tumors (GISTs): A rare type of soft tissue sarcoma that can originate anywhere in the gastrointestinal tract.
• Squamous Cell Carcinomas: Tumors that originate in the squamous cells, which are flat, thin cells found in some parts of the lower rectum and anal canal.
• Sarcomas: Tumors that start in the connective tissues of the body, such as the muscle or blood vessels in the colon wall.

Most colorectal cancers are considered "sporadic," meaning they occur in people with no family history of the disease. However, a small percentage are linked to inherited genetic syndromes.

How Is Colorectal Cancer Staged?

Staging describes the extent of the cancer's spread. It's a crucial tool that helps doctors determine the best treatment plan and predict the prognosis. The staging system typically uses a scale of 0 to 4, with the T (tumor), N (nodes), and M (metastasis) system providing more detail.

• Stage 0: Non-invasive cancer, also known as carcinoma in situ.
• Stage 1: The tumor has grown into the inner layers of the colon or rectal wall.
• Stage 2: The tumor has grown through the wall of the colon or rectum but has not spread to nearby lymph nodes.
• Stage 3: The cancer has spread to nearby lymph nodes.
• Stage 4: Metastatic colorectal cancer, meaning it has spread to distant parts of the body, such as the liver or lungs.

What Is the Role of Genetics, Such as Lynch Syndrome, in Colorectal Cancer?

Genetic factors play a significant role in about 10% of colorectal cancers. Lynch syndrome, also known as hereditary nonpolyposis colorectal cancer (HNPCC), is the most common hereditary CRC syndrome. It is caused by a mutation in a mismatch repair gene (e.g., MLH1, MSH2, MSH6 or PMS2). These genes normally help repair cell damage. A mutation significantly increases a person's risk of developing CRC and other cancers, such as endometrial cancer. Genetic testing can determine if you carry one of these mutations, which may influence your screening and treatment plan.

Colorectal Cancer Diagnosis: What Tests Are Used?

A definitive diagnosis of colorectal cancer is made through a biopsy, where a small tissue sample is taken during a colonoscopy and examined by a pathologist.

Discussing the benefits of colonoscopy in an interview with CURE, Dr. Usman Shah said, “When we think about screening, there are two potential benefits that we pay attention to. One is, of course, early detection. If you can diagnose colon cancer or rectal cancer at an earlier stage, the prognosis is that much better.

“But the other thing to also know is, when we think about colonoscopy, it can serve not just as early detection, but early prevention, or prevention in general. And the reason for that is most colorectal cancers will begin as a benign polyp that will ultimately have the risk of turning into cancer over about seven to 10 years.

“If we can intervene on that polyp with removing it through a colonoscopy, we can actually decrease the risk of that cancer ever developing in the first place. The colonoscopy can serve both as early detection but actually prevention as well. But there are certainly other less invasive or noninvasive methods that may still serve as early detection but not necessarily prevention.”

Shah is a medical oncologist at Overlook Medical Center, phase 1 and gastrointestinal oncology medical director.

Additional tests help classify the cancer, including:

• Carcinoembryonic Antigen (CEA) Test: This blood test checks for the presence of a tumor marker that can sometimes be elevated in people with CRC. It is often used to monitor a patient's response to treatment and check for recurrence, but not for initial diagnosis.
• Molecular/Biomarker Testing: Tests on tumor tissue can identify specific genetic mutations, such as those in the KRAS, NRAS and BRAF genes, and can also check for microsatellite instability (MSI). This information helps doctors choose the most effective targeted therapies and immunotherapies.

What Are the Available Colorectal Cancer Treatment Options?

Treatment plans are highly individualized and often involve a combination of therapies.

• Surgery: This is often the first step to remove the tumor and nearby lymph nodes. Depending on the cancer's location and size, options include a partial colectomy (removing part of the colon) or a proctectomy (removing the rectum).
• Radiation Therapy: This therapy uses high-energy rays to kill cancer cells. It is more commonly used for rectal cancer, often before surgery to shrink the tumor and make it easier to remove.
• Chemotherapy: These powerful drugs are used to kill fast-growing cancer cells throughout the body. Chemotherapy may be given before surgery to shrink a tumor (neoadjuvant) or after surgery to destroy any remaining cancer cells (adjuvant).
• Targeted Therapy: This treatment targets specific characteristics of cancer cells, such as proteins that promote growth, with less harm to normal cells. It may include therapies that block specific proteins like EGFR or VEGF.
• Immunotherapy: This treatment harnesses the body's own immune system to fight cancer. It is often used for metastatic CRC with specific genetic markers, like high microsatellite instability.

How to Manage Side Effects in Colorectal Cancer Treatment

Treatments can have various side effects, such as fatigue, nausea or nerve pain. Discussing potential side effects with your care team and having a plan to manage them is crucial for maintaining your quality of life. Strategies may include medication adjustments, dietary changes, gentle exercise, or complementary therapies such as acupuncture or massage. Communicating openly with your care team about new or worsening side effects ensures timely support and interventions.

Emotional Well-Being During and After Colorectal Cancer Treatment

A cancer diagnosis is emotionally challenging. Many patients benefit from support groups, therapy, or connecting with others who have gone through a similar experience. Mindfulness practices, journaling, meditation or creative outlets can help manage stress and anxiety. It's normal to experience a range of emotions, and seeking professional help is a sign of strength, not weakness.

What Does Colorectal Cancer Survivorship Mean?

After active treatment ends, the focus shifts to survivorship. This includes regular follow-up appointments, monitoring for recurrence and maintaining a healthy lifestyle. Survivorship also involves managing long-term side effects, addressing other health conditions, and restoring energy and strength. Patients may develop a survivorship care plan with their oncology team to guide ongoing health decisions.

Understanding Colorectal Cancer Recurrence

Even after successful treatment, there is a risk of recurrence. This can be a local recurrence, in the same area as the original tumor, or a distant recurrence, known as metastatic disease. Staying in close contact with your oncologist is essential for long-term monitoring. Being aware of symptoms, following routine imaging and lab tests, and discussing risk-reduction strategies, including lifestyle changes and preventive medications, can help detect recurrence early. Emotional support for coping with the possibility of recurrence is equally important.

Editor's note: This guide is designed to be a starting point. Your personal experience will be unique. By using this information as a foundation for your discussions, you can partner with your oncologist to make the best decisions for your health.

This article is for informational purposes only and is not a substitute for professional medical advice. Please contact your healthcare team with any questions or concerns.

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