Short answers, pulled from the story.
Classic warning signs include worsening constipation, blood in the stool, a decrease in stool thickness, loss of appetite, unexplained weight loss, and nausea or vomiting, particularly in people over 50. Around 50% of people with colorectal cancer report no symptoms at all, which is why screening is critical for early detection.
The American Cancer Society recommends colorectal cancer screening starting at age 45 for people at average risk. This replaced the previous guideline of age 50, changed in response to rising cases in younger adults. People at high risk, including those with a family history in two or more first-degree relatives, typically begin screening around age 40.
Between 75% and 95% of colorectal cancer cases occur in people with little or no elevated genetic risk. The most common causes are lifestyle factors including diet, obesity, smoking, heavy alcohol use, and lack of physical activity. Cancer develops through progressive mutations in genes including APC, TP53, and KRAS, combined with epigenetic changes that alter how those genes are expressed.
Treatment depends on the stage of the disease. Early-stage colorectal cancer may be curable with surgery alone, typically a partial colectomy. Stage III and Stage IV cancers usually require chemotherapy with agents such as fluorouracil, oxaliplatin, or irinotecan. Rectal cancer often involves radiation combined with chemotherapy before surgery. A subset of tumors with mismatch repair deficiency may respond to immunotherapy drugs such as pembrolizumab or dostarlimab.
The five-year survival rate in the United States was around 65% in 2014. Survival depends heavily on stage: people with tumor confined to the earliest layers have a five-year survival of approximately 90%, while those with distant metastases have a five-year survival ranging from under 5% to 31%. Early-detected colorectal cancers have survival rates about five times higher than late-stage cases.
Cases of colorectal cancer in adults under 50, called early-onset colorectal cancer, have increased sharply over the last decade across North America, Europe, Australia, and China. People aged 20 to 29 saw the steepest rise, with incidence increasing by 7.9% per year between 2004 and 2016. Researchers attribute the trend primarily to generational shifts in lifestyle and environmental factors rather than improved detection. By 2026, colorectal cancer had become the leading cause of cancer-related deaths among Americans younger than 50.