When colorectal cancer spreads

A common myth about colorectal cancer is that you don’t need to be screened if you don’t have symptoms. However, what’s lesser known is that colorectal cancer symptoms don’t always appear right away. The benefit of screening is catching the disease early, when it’s treatable and before it’s advanced or spreads to other parts of your body.

In the U.S., colorectal cancer is the second-leading cause of cancer-related death in men and women combined. The good news is that it has about a 90% survival rate when found early by screening tests, usually by a procedure called a colonoscopy.

“Undergoing a screening colonoscopy helps to prevent colorectal cancer because doctors can find and remove polyps or precancerous lesions in the colon or rectum before they develop into cancer or spread,” says Dr. David Bodkin, a board-certified oncologist/hematologist affiliated with the David & Donna Long Cancer Center at Sharp Grossmont Hospital.

The 4 stages of colorectal cancer

Colorectal cancer is thought to spread over time as it progresses through four stages:

Stages 0 and 1: Early stages when cancer is localized and usually has not grown beyond the inner lining of the colon or spread outside the colon.

Stages 2 and 3: May have regional spread, usually through the wall of the colon into nearby tissue and the lymph nodes.

Stage 4: Distant spread and is considered metastatic, which means it has traveled through the bloodstream or lymph system and formed new tumors in other organs or tissues. The most common sites are the liver followed by the lungs.

While the chances of colorectal cancer spreading or recurring typically increase as someone goes from stage 0 to 3, Dr. Bodkin notes other factors are also involved. He says it depends on the size and location of the tumor and how aggressive the biopsy tissue from the colonoscopy, or segment of the colon that’s taken out, looks to a pathologist's eye.

“Tumors are graded 1 to 3, with grade 1 looking like more normal cells to grade 3, which looks very different and is more aggressive,” Dr. Bodkin says. "We also send the specimen for DNA analysis and look for a dozen or so abnormal mutated genes that could lead to a poorer prognosis and greater chance of recurrence.”

Some tumors spread despite stage or size
In 2019, Stanford School of Medicine conducted a study of 3,000 colorectal cancer patients. They found that in most metastatic colorectal cancer patients, cancer cells had already spread and begun to grow in other parts of the body long before the primary tumor was clinically detectable. “This is an important study and does change our thinking and approach to metastatic colorectal cancer,” says Dr. Bodkin.

According to Dr. Bodkin, researchers and physicians thought that it took time for cancer cells to spread or travel through the body. “It appears from this study that 80% of the metastatic colorectal cancers had spread before the primary tumor was found, or prior to being clinically detected by symptoms, a colonoscopy, scan or other means,” he says. “Even minute cancers, measuring the size of a seed, could spread.”

The researchers traced the cause to a specific combination of gene mutations and molecular changes found almost exclusively in the metastatic cancer patients. “The upshot is early detection is even more important — as is doing molecular analysis to determine which cancers will be more aggressive behaving and require earlier and more aggressive treatments,” Dr. Botkin says.

Get screened
The most important step you can take to reduce your risk of colorectal cancer is to get screened starting at age 45. If you have a close relative with colorectal cancer or if you have Crohn's disease, ulcerative colitis or another inflammatory bowel disease, you may be considered high-risk and should talk with your doctor about whether you should be screened earlier.

Although many people don’t want to get screened because they incorrectly believe that colorectal cancer is not treatable, Dr. Bodkin says that couldn’t be further from the truth. Caught early, it’s often curable.

“New research is evolving all the time, and we’re increasingly learning more,” Dr. Bodkin says. “The focus now is on 'targeted' molecular or immune therapies where the body's own immune system can be strengthened and channeled to directly attack cancer cells, leaving other cells and areas of the body intact.”

Advanced technology, clinical trials and other comprehensive cancer care that supports the best outcomes can be found at Sharp Grossmont Hospital. “Prognosis and treatments are improving all the time for the better, and those with advanced cancer are living longer, full lives,” he says.

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