Colorectal Cancer: Screening and Treatment
Also known as: Colon Cancer, Rectal Cancer, Bowel Cancer
Overview
Colorectal cancer (CRC) refers to malignant tumors that develop in the colon or rectum. In the United States, it is the third most common cancer and the second leading cause of cancer death, with the American Cancer Society estimating more than 150,000 new cases diagnosed each year. It mostly affects people over 50, but it can occur at any age. When caught early, this cancer is highly treatable: the 5-year relative survival rate is above 90% for localized-stage disease.
Causes and risk factors
Several factors increase the risk of developing colorectal cancer:
- Age: risk increases as you get older, especially after 50 (screening is now recommended starting at 45)
- Family or personal history of adenomatous polyps or colorectal cancer
- Chronic inflammatory bowel disease (IBD): Crohn’s disease, ulcerative colitis
- Inherited genetic syndromes: familial adenomatous polyposis (FAP), Lynch syndrome
- A diet high in red and processed meats and low in fiber
- Obesity, physical inactivity, smoking, and moderate to heavy alcohol use
- Type 2 diabetes
Symptoms
The clinical signs of colorectal cancer are often late-appearing or easy to miss:
- Rectal bleeding or black, tarry stools
- Persistent changes in bowel habits: alternating diarrhea and constipation, changes in stool caliber
- Abdominal pain or recurring cramps
- A feeling of incomplete bowel emptying (tenesmus)
- Unexplained fatigue and unintentional weight loss
- Iron-deficiency anemia found on blood work
- A palpable abdominal mass (advanced stages)
Diagnosis
Doctors rely on several tests to confirm the diagnosis:
- Colonoscopy: the gold-standard exam, allowing direct visualization of the colon lining and biopsies
- Fecal immunochemical test (FIT): used as part of routine screening
- CT scan of the abdomen and pelvis and rectal MRI for staging
- Tumor marker testing (CEA) to check the effect of treatment and detect recurrence
Treatments
Colorectal cancer care relies on a multidisciplinary approach:
- Surgery: the main treatment for localized stages. It removes the affected colon or rectum segment along with nearby lymph nodes, and can often be done laparoscopically
- Chemotherapy: given after surgery (adjuvant) to lower the risk of recurrence, or for metastatic disease; regimens are typically based on oxaliplatin or irinotecan
- Radiation therapy: used mainly for rectal cancer, often before surgery to shrink the tumor
- Targeted therapies: bevacizumab, cetuximab, or panitumumab, depending on the tumor’s molecular profile (RAS, BRAF status)
- Immunotherapy: for tumors with high microsatellite instability (MSI-H)
- Supportive care: pain management, nutrition, and psychological support
Prevention
Several measures can significantly reduce colorectal cancer risk:
- Follow current screening guidelines: the USPSTF recommends colorectal cancer screening starting at age 45 through 75, using a stool-based test (FIT) every year, a colonoscopy every 10 years, or another approved option
- Eat a diet rich in fiber (vegetables, fruits, legumes) and low in processed meats
- Get regular physical activity: aim for 150 to 300 minutes of moderate activity a week
- Limit alcohol and avoid smoking
- Maintain a healthy weight and avoid abdominal obesity
- Get surveillance colonoscopies if you have a personal or family history of polyps
When should you see a doctor?
See a doctor promptly if you notice blood in your stool, a persistent change in bowel habits, unexplained weight loss, or unusual fatigue. Everyone ages 45 to 75 should get screened regularly, even without symptoms.
Sources
- American Cancer Society, colorectal cancer statistics, risk factors, and survival rates
- U.S. Preventive Services Task Force, official screening recommendations
- National Cancer Institute, U.S. colorectal cancer treatment and patient information
- National Cancer Institute, Colon Cancer Treatment (PDQ), surgery as the most common treatment for all stages, chemotherapy (oxaliplatin, irinotecan), targeted therapy (bevacizumab, cetuximab, panitumumab), and immunotherapy
- National Cancer Institute, Rectal Cancer Treatment (PDQ), radiation therapy given before surgery to shrink the tumor in rectal cancer
- National Cancer Institute, SEER Cancer Stat Facts: Colorectal Cancer, 5-year relative survival above 90% for localized-stage disease and age distribution of new cases
- National Cancer Institute, Tumor Markers List, CEA use to check treatment effect and detect recurrence in colorectal cancer
- National Cancer Institute, Physical Activity and Cancer, lower colorectal cancer risk and the 150 to 300 minutes per week activity recommendation
- Centers for Disease Control and Prevention (CDC), official U.S. colorectal cancer data and guidance