Colorectral (colon) cancer is a cancer of the colon or rectrum and occurs primarily as people age. Additional risk factors include [2]:

• Inflammatory bowel disease such as Crohn’s disease or ulcerative colitis.
• A personal or family history of colorectal cancer or colorectal polyps.
• A genetic syndrome such as familial adenomatous polyposis or hereditary non-polyposis colorectal cancer (Lynch syndrome).

And lifestyle factors[1]:

• Lack of regular physical activity.
• A diet low in fruit and vegetables.
• A low-fiber and high-fat diet, or a diet high in processed meats.
• Overweight and obesity.
• Alcohol consumption.
• Tobacco use.

Symptoms may include [2]:

• A change in bowel habits (like skinny pencil-thin stools)
• Blood in or on your stool (bowel movement).
• Diarrhea, constipation, or feeling that the bowel does not empty all the way.
• Abdominal pain, aches, or cramps that don’t go away.
• Weight loss and you don’t know why.

In 2020, a new development in colorectal screening is that the CDC now recommends that you get a colonoscopy at age 45 now. This used to start at age 50 [3].

References and more info

1. CDC Colorectral risk factors
2. CDC Colorectral cancer symptoms
3. USPSTF changes recommended age for colorectal cancer screening to 45