Colorectal cancer

Colorectal cancer or colon cancer is a malignant disease caused by the presence of neoplastic cells (cancer cells) in the mucosa of the colon (innermost layer of the colon).

This is due to mutations in the DNA of the cells over many years. These mutated and malignant cells replicate to create a tumor than can have different size.

In many cases (up to 80%) the process starts with a polyp (abnormal cell proliferation) called adenoma that grow slowly over the years and can develop into cancer if it is not treated.

The malignant cells of the colon mucosa, with no treatment, may spread to other tissues of the colon and surrounding areas. They may also travel through the bloodstream to other organs such as the brain, lung, liver, etc. (blood metastasis) or may spread to the lymphatic system (lymphatic metastasis).

Colorectal cancer may be located in any part of the colon or the large intestine, including the ascending, descending, transverse, sigmoid or rectum.

It may be confined to only one part of the colon or be found in different parts simultaneously.

Colorectal cancer is the third most common type of cancer worldwide and the second cause of cancer-related deaths. It affects men and women in the same proportion.

The main symptoms of colorectal cancer include:

• Diarrhea or constipation.
• Tenesmus (frequent urge to evacuate the bowel).
• Blood in stool.
• Change in the stool caliber (they can be very narrow like a pencil).
• Abdominal pain.
• Weight loss of unknown cause.
• Fatigue (asthenia).
• Nausea or vomiting.

There are some risk factors that may increase the possibility of suffering colorectal cancer in the future:

• Environmental or lifestyle related
• Smoking
• Alcohol
• Diet with a high intake of processed meat and low in fruits and vegetables
• Lack of physical activity (sedentary lifestyle)
• Overweight and obesity
• Genetic or previous disorders
  • Family history of colorectal cancer
  • Family history of familial adenomatous polyposis and Lynch syndrome
  • Inflammatory bowel disease (Crohn or ulcerative colitis)
  • Radiation received in the abdomen or the pelvis for another cancer
  • Diabetics

Aged people or Afro-American people have a higher risk to develop colorectal cancer.

It is recommended to screen all people for colorectal cancer between ages 50 to 75 years.

For that matter, the following tests may be performed:

• Stool tests:
  • Guaiac fecal occult blood test (gFOBT).
  • Fecal immunochemical test (FIT).
  • Stool DNA test.
• Video colonoscopy (lower GI endoscopy): It is possible to take samples for a posterior analysis.
• Sigmoidoscopy: To study the final part of the colon where the possibility to find a cancer is higher.
• CT colonography.
• Diagnostic imaging: Barium enema, abdominal ultrasound, CT, abdominal X-ray.

A blood test is useful to detect the carcinoembryonic antigen (CEA), a tumor marker that is higher in the presence of colorectal cancer.

A fecal occult blood test every year or a colonoscopy every 2 years is recommended to screen people who are prone to develop colorectal cancer.

People with no risk factor should undergo screening starting at age 50 and repeat the test every 5 years until the age 75. For people over 75 the screening depends on their health status and the previous test results.

The colorectal cancer may be classified in stages based on the extent of the tumor. The extent of the cancer depends of the affected tissues from the inner to the outer ones (mucosa, submucosa, muscularis propria, serosa, lymph nodes and blood vessels).

A commonly used classification is Dukes (modified by Astel-Coller):

• Dukes A: Tumor confined to mucosa
• Dukes B1: Tumor growth into muscularis propria (no lymph node involvement)
• Dukes B2: Tumor growth through the serosa or intestinal wall (no lymph node involvement)
• Dukes B3: Tumor involves adjacent organs (no lymph node involvement)
• Dukes C1: Tumor growth into muscularis propria and spread to regional lymph nodes
• Dukes C2: Tumor growth through the serosa and spread to more than 4 regional lymph nodes
• Dukes C3: Tumor involves adjacent organs with lymph node metastasis
• Dukes D: Distant metastatic disease (liver, bones, lung)

The treatment for colorectal cancer depends on the size of the tumor, the stage, the location and the cell type:

• Surgery
• Immunotherapy
• Radiation therapy
• Chemotherapy
• Targeted drug therapy
• Palliative care

Surgery for early-stage colorectal cancer: If the tumor is confined to the mucosa or submucosa it is recommended a minimally invasive surgery:

• Remove polyps during a colonoscopy (polypectomy).
• Endoscopic mucosal resection.
• Laparoscopic surgery.

Surgery for advanced colorectal cancer: When the tumor growth into muscularis propria or intestinal wall:

• Partial colectomy: Remove of the affected part.
• Ostomy: Artificial opening in the abdominal wall to allow the pass of waste or urine.
• Affected lymph node removal.

Immunotherapy: Drugs used to help the immune system to detect and remove cancer cells.

Radiotherapy: X-ray and protons to destroy cancer cells.

Chemotherapy: It is usually administered after the surgery.

Targeted drug therapy: Used combined with chemotherapy or when the chemotherapy has not been effective.

Palliative care: To relief the pain and other symptoms of the cancer.