A complete guide to colorectal cancer symptoms, causes, and treatment

What is colorectal cancer?

Colorectal cancer (CRC) is classified into two types: colon cancer, which affects the largest part of the intestine, and rectal cancer, which affects the rectum—the final section of the large intestine.

Image Credit: Norgen Biotek Corp.

CRC usually develops gradually, taking months or even years to spread to other parts of the body. Due to this slow progression, early detection significantly increases the chances of successful treatment.

A major challenge with CRC is that symptoms are often mild or absent in the early stages, highlighting the importance of routine screening. Gaining a thorough understanding of this disease is a crucial first step toward adopting preventive measures to reduce its impact.

Common symptoms of colorectal cancer

Patients in the early stages of CRC typically have no symptoms or only mild symptoms. In the later stages of CRC, symptoms may vary depending on the tumor's size and location, but they often include:

Persistent changes in bowel habits

Individuals' bowel habits vary, and "normal" behaviors differ from one another. Bowel habits include how often someone has a bowel movement, as well as changes such as constipation, diarrhea, or differences in the size, shape, and consistency of stool.

Blood in the stool or rectal bleeding

Polyps and tumors can bleed for various reasons, including rupture of blood vessels in the gut lining, ulceration, inflammation and irritation of surrounding tissue, or physical injury from bowel movements caused by a blockage.

Abdominal discomfort, such as cramping or pain

Bloating and a persistent sense of fullness are possible symptoms. The location of the discomfort often varies based on the tumor’s position. In women, these symptoms may resemble menstrual pain and are frequently overlooked.

Unintended weight loss, fatigue, or weakness

A significant loss of weight (more than 10 pounds) in a short period of time, accompanied by a loss of energy, is a symptom of cancer and should be addressed immediately.

If you notice any of these symptoms, consult a doctor right away.

Image Credit: Norgen Biotek Corp.

Understanding the causes and risk factors of colorectal cancer

CRC results from genetic mutations that lead to abnormal cell proliferation. Some mutations are inherited, while others are caused by environmental or lifestyle factors.

Key risk factors

• Age: CRC primarily affects individuals over the age of 50. However, since the mid-1990s, there has been a 1–2 % increase in incidence among younger adults.^1,2 Alarmingly, rates in those under 50 have increased by 2.4 % each year, with mortality rising by 1 % each year.³
• Family history: Having a family history of CRC, especially in a first-degree relative, significantly increases the risk of developing the disease. Approximately one in every ten cases is linked to family history, highlighting the importance of early and regular screening for those at high risk.^1,4
• Diet: Consuming red and processed meats raises the risk of CRC, while a fiber-rich diet, such as one including whole grains, can help lower it. Studies have shown that consuming 300 milligrams of calcium daily (the amount found in a large glass of milk) can reduce the risk by 17 %.^{5, 6}
• Lifestyle: Lifestyle behaviors strongly influence CRC risk. Prolonged sitting increases the risk of colon cancer by 28–44 %. Other contributing factors include smoking and alcohol consumption. Alcohol, in particular, is associated with several types of cancer, including CRC.^7,8
• Medical conditions: Chronic inflammatory bowel diseases, such as Crohn's disease and ulcerative colitis, increase the risk of CRC. According to studies, long-term inflammation in the colon significantly raises this risk, highlighting the importance of routine screenings.⁹

Image Credit: Norgen Biotek Corp.

How is colorectal cancer diagnosed?

CRC is diagnosed using a combination of screening tests, diagnostic techniques, and laboratory analysis. Early detection is critical for improving outcomes and survival rates.

Patients will be asked to undergo the tests and procedures listed below based on their medical history, physical exam, and CRC screening test results.

Image Credit: Norgen Biotek Corp.

Colonoscopy

The gold standard for detecting polyps and cancers. A flexible tube equipped with a camera inspects the entire colon and rectum. A colonoscopy may include a biopsy or the removal of polyps.

Flexible sigmoidoscopy

Similar to a colonoscopy, but less invasive. It examines only the lower part of the colon and the rectum.

CT colonoscopy

No sedation is required for this minimally invasive colon imaging treatment. This method checks the large intestine for polyps, cancers, and other abnormalities. It uses computed tomography (CT) scanning technology to provide detailed, high-resolution 3D images of the colon and rectum.

Stool-based tests

The presence of blood in stool could be an indicator of CRC. Fecal occult blood tests (FOBT) and fecal immunochemical assays (FIT) can both detect blood in stool samples.

Blood tests

Blood tests cannot be used alone to diagnose CRC. However, they provide insight into a person's overall health and can detect abnormalities that may be related to the presence of cancer. Individuals suspected of having CRC are evaluated with a complete blood count, liver function tests, and kidney function tests.

Cell and tissue studies

When a tumor is discovered, the presence of certain mutations in the tumor cells can help determine the most effective treatment and therapy options for the individual.

Norgen Biotek offers researchers a variety of methods for isolating DNA and RNA from cell and tissue samples.

Tumor marker tests

Advanced approaches, such as RNA or DNA analysis, identify cancer-related genetic markers and support early tumor detection. Tumor markers can be found in blood, tissue, and other bodily fluids.

An abnormal level of a tumor marker may indicate CRC. Tumor marker tests are also used to monitor your response to cancer treatment.

Norgen Biotek provides cutting-edge technologies for liquid biopsy biomarker testing, ensuring accurate and reliable results.

How to prevent colorectal cancer

Prevention is crucial in reducing the occurrence of CRC. Individuals can significantly lower their risk by implementing effective measures.

Healthy diet

A nutritious diet is an effective way to reduce the risk of CRC. Increasing fiber intake from fruits, vegetables, and whole grains improves digestive health and lowers cancer risk.

At the same time, limiting the consumption of red and processed meats is important, as studies have linked excessive intake to a 29 % increased risk of colon cancer.¹⁰ Even small, consistent dietary changes can have a significant impact on CRC prevention.

Healthy lifestyle

Adopting healthy lifestyle habits is another important aspect of CRC prevention. Regular physical activity, such as 150 minutes of moderate exercise or 75 minutes of vigorous exercise per week, helps maintain a healthy weight and reduces cancer risk.¹¹

Similarly, limiting alcohol intake is essential, as excessive consumption has been linked to an increased risk of developing CRC.¹² Making these small but meaningful changes to your daily routine can have a significant impact on your long-term health.

Genetic testing for colorectal cancer

Individuals with a family history of CRC should consider genetic testing to identify inherited conditions such as Lynch syndrome or familial adenomatous polyposis (FAP), which significantly increase cancer risk.

Understanding these genetic predispositions allows for early and regular screenings, providing opportunities to detect and address cancer before it develops. Proactive genetic testing encourages individuals and families to better manage their health.¹³

Colorectal cancer screening

CRC should be conducted regularly to ensure early detection and prevention. The American Cancer Society recommends that individuals at average risk begin screening at age 45. Screening options include stool tests and visual exams such as colonoscopies.

These methods help detect and remove precancerous polyps, preventing cancer from forming. Early detection through screening significantly improves treatment outcomes.¹⁴

Things you may wonder

Who should be screened for colorectal cancer?

Screening should begin around age 45 for most people and earlier for those at high risk. Consult your doctor to determine whether you should start screening sooner.

What foods are linked to increased colorectal cancer risk?

Diets high in red or processed meats and low in fiber have been linked to an increased risk of CRC.

Are stool-based tests reliable?

Stool tests are useful for initial screening and can help detect early signs of cancer.

References and further reading

1. People. (2025). Cancer Is Increasing in Women, Decreasing in Men: ‘Something Broader Is Going On’. (online). Available at: https://people.com/cancer-82-higher-in-young-women-than-men-breast-colorectal-8775570 (Accessed 27 Mar. 2025).
2. CDC (2024). Family Health History and Cancer. (online) Cancer. Available at: https://www.cdc.gov/cancer/risk-factors/family-health-history.html.
3. People. (2025). This Refrigerator Staple Might Lower a Woman’s Risk of Colorectal Cancer, New Study Says. (online) . Available at: https://people.com/milk-might-lower-womans-risk-of-colorectal-cancer-study-8772735 (Accessed 27 Mar. 2025).
4. World Cancer Research Fund Network (2018b). Diet, nutrition, physical activity and colorectal cancer. Available at: https://www.aicr.org/wp-content/uploads/2020/01/colorectal-cancer-2017-report.pdf.
5. Jochem, C., et al. (2019). The Influence of Sedentary Behavior on Cancer Risk: Epidemiologic Evidence and Potential Molecular Mechanisms. Current Nutrition Reports. https://doi.org/10.1007/s13668-019-0263-4.
6. Wigle, R. (2025). This winter wellness trend can reduce your risk of cancer — but you have to keep it up. (online) New York Post. Available at: https://nypost.com/2025/01/09/health/lower-your-cancer-risk-with-this-winter-wellness-trend/ (Accessed 27 Mar. 2025).
7. Crohn's & Colitis Foundation (2024). The Risk of Colorectal Cancer in Crohn’s Disease and Ulcerative Colitis Patients. (online) Crohn’s & Colitis Foundation. Available at: https://www.crohnscolitisfoundation.org/patientsandcaregivers/what-is-ibd/colorectal-cancer.
8. American Cancer Society (2024). Colon Cancer Treatment, by Stage | How to Treat Colon Cancer. (online) Cancer. Available at: https://www.cancer.org/cancer/types/colon-rectal-cancer/treating/by-stage-colon.html.
9. National Cancer Institute (2023). Cancer of the Colon and Rectum - Cancer Stat Facts. (online) SEER. Available at: https://seer.cancer.gov/statfacts/html/colorect.html.
10. Omran, T.A., et al. (2024). Selection of optimal extraction and RT-PCR protocols for stool RNA detection of colorectal cancer associated immune genes. Scientific Reports, 14(1). https://doi.org/10.1038/s41598-024-78680-0.
11. Simkin, M., et al. (2012). Differences in the quantity of DNA found in the urine and saliva of smokers versus nonsmokers: implications for the timing of epigenetic events. Epigenomics, 4(3), pp.343–352. https://doi.org/10.2217/epi.12.24.
12. Alokail, M.S., et al. (2014). Increased TNF α, IL-6 and ErbB2 mRNA expression in peripheral blood leukocytes from breast cancer patients. Medical Oncology, 31(8). https://doi.org/10.1007/s12032-014-0038-0.
13. Vychytilova-Faltejskova, P., et al. (2023). Optimized procedure for high-throughput transcriptome profiling of small extracellular vesicles isolated from low volume serum samples. Clinical chemistry and laboratory medicine, (online) 62(1), pp.157–167. https://doi.org/10.1515/cclm-2023-0610.
14. Meng, W., et al. (2014). Abstract 889: MicroRNA-21-5p upregulation in urine samples serves as novel biomarkers for early stage renal cell carcinoma patients diagnosis. Cancer Research, 74(19_Supplement), pp.889–889. https://doi.org/10.1158/1538-7445.am2014-889.

About Norgen Biotek Corp.

Norgen Biotek: Advancing science with best-in-class, scientist-backed innovations

Norgen Biotek is a fully integrated biotechnology company that focuses on providing complete workflows for molecular biology sample preparation and analysis. With a diverse portfolio of over 600 products, the company delivers high-performance, user-friendly, and cost-effective solutions.

Scientifically driven, industry trusted

Norgen kits cover a broad range of applications from collection and preservation to isolation and purification. Our expert R&D team continuously develops cutting-edge technologies that set new industry standards for RNA, DNA, protein, and exosomal isolation, ensuring superior yield, purity, and integrity from even the most challenging sample types.

Unparalleled performance

At the heart of Norgen’s success is its patented Silicon Carbide (SiC) Technology. This proprietary resin exhibits uniform binding affinity for all RNA species, regardless of molecular weight or GC content. This ensures the full diversity of small and microRNA are captured while eliminating the need for phenol extraction. This innovative technology sets Norgen kits apart from others, positioning them as leaders in RNA purification.

Comprehensive solutions for any challenge

Norgen is committed to providing high-quality kits capable of processing a wide range of sample types, from ultra-low input samples such as liquid biopsies to highly impure samples like stool or soil. Our sample collection and preservation devices for stool and saliva simplify handling by rendering samples non-infectious by preventing microbial growth and inactivating viruses, while our blood and urine preservation solutions ensure the stability of highly vulnerable cell-free nucleic acids.

To meet varying research demands, we offer multiple isolation methods including, but not limited to high-throughput and automation-ready magnetic bead-based formats. Additionally, our multiple-analyte kits enable the simultaneous purification of RNA, DNA, and proteins, maximizing data extraction from a single sample.

Norgen offers an extensive variety of TaqMan qPCR kits designed for molecular diagnostic use, including lyophilized kits for easy shipping. Library preparation kits for both DNA and RNA samples are also available to support genomic applications. Norgen recently released their EXTRAClean technology, an innovative solution that minimizes background noise while providing high-purity RNA, significantly enhancing NGS performance.

Why choose Norgen?

• Scientist-Driven Innovation – Developed by leading experts in molecular biology
• Proven Quality & Reliability – ISO 9001 and ISO 13485 certified, indicating a commitment to selling high-quality products
• Global Presence – We ship to over 150 countries and have a network of 60+ distributors
• Award Winning – Norgen Biotek Corp. was honored with the 2021 Innovative Leaders Award, and recognized as the 2024 Rapid Star Award Winner in the PCR category.
• Innovative Products – Hold more than thirty issued and pending patents for products presenting solutions for all research & clinical applications

Driven by a mission to accelerate scientific discoveries, Norgen Biotek actively supports researchers by providing educational resources, technical workshops, and application notes. Their NorBlog serves as a hub for the latest scientific discoveries, protocol optimizations, and industry trends.

Explore Norgen Biotek’s innovative solutions today and take your research to the next level.

Sponsored Content Policy: News-Medical.net publishes articles and related content that may be derived from sources where we have existing commercial relationships, provided such content adds value to the core editorial ethos of News-Medical.Net which is to educate and inform site visitors interested in medical research, science, medical devices and treatments.