Introduction
Colorectal cancer is a malignant tumor that includes both colon cancer and rectal cancer, depending on where it starts. It arises from the inner wall of the colon or rectum, making it one of the most common and deadly forms of cancer worldwide. Most cases begin as benign polyps that may develop malignancy over time.
Globally, colorectal cancer (CRC) affects over 1 million people annually and accounts for hundreds of thousands of deaths.
Types
- Adenocarcinomas constitutes over 95% of the colorectal cancers.
- Rare types, including lymphomas, sarcomas, and neuroendocrine tumors.
Causes & Risk Factors
While the precise cause is unclear, uncontrolled genetic mutations in the cells lining the colon or rectum are central. Both genetic predisposition and environmental/lifestyle factors contribute:
- Environmental Factors:
- Age: Incidence rises sharply after age 50.
- Diet: High consumption of red and processed meats increases risk.
- Alcohol: Heavy alcohol intake (≥ 3 drinks/day) increases risk significantly.
- Smoking: smoking is linked to both adenomas and cancer, especially in the rectum.
- Genetic Predisposition:
- Family history: Having a first-degree relative with CRC doubles risk, rising further if multiple relatives are affected.
- Inherited syndromes: Lynch syndrome (HNPCC), FAP, and serrated polyposis syndrome significantly elevate lifetime risk; FAP often warrants preventive colectomy.
- Personal medical history: Prior polyps, inflammatory bowel diseases (Crohn’s, ulcerative colitis), and previous cancers (e.g., ovarian) raise CRC risk.
Signs & Symptoms
Around half of the cases are asymptomatic in early stages. Later, classic warning signs include:
- Blood in the stool (may be bright red or dark).
- Persistent change in bowel habits (diarrhea, constipation, or narrower stools).
- Abdominal pain, cramping, or bloating.
- Unexplained weight loss.
- Fatigue or anemia (especially in individuals over 50).
- Sensation of incomplete bowel emptying.
Complications
If untreated or detected late, Colorectal Cancer may:
- Spread (metastasize) to lymph nodes, liver, lungs, or other organs. Jaundice if the liver is affected, respiratory symptoms if lungs are involved may occur.
- Systemic symptoms like fatigue and cachexia.
- Bowel obstruction due to tumor growth.
- Perforation of the colon or rectum.
- Bleeding and iron-deficiency anemia.
Prevention
- Regular screening can help detect and remove polyps at earliest, preventing cancer development. Colonoscopy every 10 years starting at age 45 is the most effective prevention tool. Fecal occult blood testing and flexible sigmoidoscopy, are alternatives.
- Healthy diet emphasizing on intake of fiber, whole grains, fruits, vegetables and limiting red/processed meats, alcohol and smoking reduces risk.
When to Seek Medical Attention
Visit a healthcare provider promptly if you experience:
- Sudden or unexplained changes in bowel habits lasting more than a few weeks.
- New or persistent rectal bleeding.
- Unexplained weight loss or persistent fatigue.
- Abdominal pain, especially if severe or persistent.
- Diagnosis of iron-deficiency anemia without obvious cause.
Early detection and intervention are critical for improved outcomes. Anyone with symptoms or risk factors should discuss appropriate screening and prevention with a healthcare provider. Early evaluation, even under age 50 is advised if risk factors or symptoms are present.
Bibliography
[1] https://pmc.ncbi.nlm.nih.gov/articles/PMC5597496/
[2] https://pmc.ncbi.nlm.nih.gov/articles/PMC4874655/
[3] https://www.mayoclinic.org/diseases-conditions/colon-cancer/symptoms-causes/syc-20353669
[4] https://www.ncbi.nlm.nih.gov/books/NBK553197/
[5] https://pmc.ncbi.nlm.nih.gov/articles/PMC3170421/
[6] https://www.ncbi.nlm.nih.gov/books/NBK65938/
[7] https://www.cancer.gov/types/colorectal/hp/colorectal-prevention-pdq
[8] https://www.cdc.gov/colorectal-cancer/prevention/index.html