What is true regarding colon cancer?

Key Facts About Colon Cancer

Colon cancer typically begins as adenomatous polyps that slowly progress to invasive cancer, with screening recommended to begin at age 50 for average-risk individuals, not age 60. 1

Pathogenesis and Development

• Colon cancer typically develops from adenomatous polyps that slowly increase in size, followed by dysplasia and finally cancer 1
• The progression from adenoma to invasive cancer varies from 5 years or less to more than 20 years, with approximately 10% of adenomas progressing to carcinoma over 10 years 1
• 70-90% of colorectal cancer cases arise from premalignant adenomatous polyps 1

Staging and Classification

• Stage IIA colon cancer is defined as T3, N0, M0, which means the tumor has grown through the muscularis propria into pericolorectal tissues with no regional lymph node metastasis and no distant metastasis 1
• The TNM staging system is used for colorectal cancer, with T representing the extent of the primary tumor, N indicating lymph node involvement, and M indicating the presence of distant metastasis 1, 2
• Colon cancer is not classified as small cell or non-small cell - this classification is used for lung cancer, not colorectal cancer 1, 3

Symptoms and Presentation

• Symptoms of colorectal cancer include change in bowel habit, rectal bleeding, anemia, and abdominal pain 1
• Many patients with colorectal cancer have no symptoms until the cancer is advanced, which is why screening is so important 1
• Colon cancer does not typically present with rapid onset of symptoms; rather, it develops slowly over years 1, 4

Screening Recommendations

• The American College of Physicians recommends screening for colorectal cancer in average-risk adults starting at age 50, not age 60 1
• High-risk individuals should begin screening at age 40 or 10 years younger than the age at which the youngest affected relative was diagnosed 1
• Screening methods include stool-based tests (gFOBT, FIT), flexible sigmoidoscopy, and colonoscopy 1
• Screening has been shown to reduce mortality from colorectal cancer by enabling early detection and removal of precancerous polyps 1

Epidemiology and Risk

• Colorectal cancer is the second leading cause of cancer-related deaths among both men and women in the United States 1, 3
• The incidence of colorectal cancer has been declining in the United States by 2-3% per year over the past 15 years, though there has been an increase in younger individuals 1, 3
• 90% of colorectal cancer cases occur after age 50 1
• Environmental factors, particularly diet, account for approximately 90% of colorectal cancer cases, while genetic factors account for about 10% 1

Management Considerations

• After resection of malignant polyps or early-stage colon cancers, long-term surveillance is important for detecting new adenomas or metachronous cancers 4
• Proper pathological assessment of malignant polyps is crucial for determining the risk of residual disease and need for additional surgery 5
• Surgical resection remains the only curative treatment for colon cancer, with better outcomes when the disease is detected at an early stage 6