Most colorectal cancers are found in the sigmoid colon, the portion of the large intestine that’s located just above the rectum. Most of these tumors grow slowly over several years, often beginning as small benign growths called polyps. Colorectal cancers can metastasize, or spread, to other organs, often the liver and/or lungs.


Are the most common type of colorectal cancers — more than 95% of colorectal cancers are adenocarcinomas. These are tumors that begin in the cells that line the interior of the colon and rectum.

Carcinoid Tumors

This common type of neuroendocrine tumor usually appears in the gastrointestinal system, particularly in the small intestine, rectum, stomach, colon, and liver. They grow so slowly they sometimes are called “cancer in slow motion.”

Gastrointestinal Stromal Tumors

“GISTs” are rare and usually start in the stomach, but can begin anywhere in the gastrointestinal tract.


This rare form of colon cancer accounts for only 0.5% of all colorectal cancers.

This list of common symptoms of colorectal cancer may also be caused by other conditions. A doctor must run tests to make a diagnosis.

  • Unintended weight loss
  • Fatigue
  • Vomiting
  • Change in bowel habits
  • Blood in the stool, which can look either bright red or almost black
  • Diarrhea, constipation, or feeling that the bowel does not empty completely
  • Stools that are narrower than usual
  • Frequent gas pains, bloating, feeling of fullness, or cramps

Colon cancer and rectal cancer are treated differently. Surgery for rectal cancer is often more complex than colon surgery, because the rectal area has nerves that control sexual and bladder function.

Advanced Minimally-Invasive Surgical Techniques

Some rectal cancers can be removed laparoscopically, which can reduce nerve damage and recovery time.

Radiofrequency ablation

A special probe uses tiny electrodes to kill cancer cells.


Also called cryotherapy, this treatment freezes and destroys cancerous tissue.

Targeted Therapies

These treatment techniques can target cancerous cells without damaging healthy tissue.

Stereotactic Body Radiation Therapy (SBRT)

This is an advanced radiosurgery device that uses computer technology to deliver highly focused radiation therapy.

Intraoperative Radiotherapy (IORT)

A treatment that delivers a high dose of radiation to the tumor during surgery. IORT reduces the exposure of healthy tissues to radiation and allows treatment of tumors that are considered inoperable.

Intensity Modulated Radiation (IMRT)

Another highly targeted technique which reduces radiation exposure of healthy tissue and can deliver radiation to difficult-to-reach areas.

3-D Conformal Radiation

A three-dimensional computer image of the tumor and surrounding healthy tissue is created from CT and MRI scans. This model allows radiation to be focused tightly on the tumor, so the surrounding normal tissue is not exposed to high doses of radiation.

Scientists are continually exploring how colorectal cancer is caused, developing improved colorectal cancer treatment, and gaining new knowledge about prevention.


New tests reveal the activity of genes in colon cancer tumors and can help predict which patients are at higher risk for the cancer to spread.


This research investigates natural or man-made chemicals thought to lower the risk of developing cancer. Researchers are conducting studies to determine if certain supplements, minerals and vitamins can reduce colorectal cancer risk. There is also some evidence that statins (cholesterol-lowering drugs) may help prevent colorectal polyps and tumors.

Earlier detection

Because any cancer can be treated more effectively if found at a very early stage, researchers continue to look for ways to improve screening methods and tests that detect blood in the stool or changes in the DNA of cells in the stool.

CT Colonography

This new technology is also called virtual colonoscopy and can detect colorectal polyps and cancers at an early stage.

Oncology San Antonio - cancer information

Multidisciplinary Cancer Treatment