Summary

Colon cancer, also known as colorectal cancer (CRC), is one of the most common and significant malignancies worldwide, accounting for nearly 10% of new cancer cases globally. It typically arises from the uncontrolled growth of abnormal cells in the colon or rectum and develops over several years through a combination of genetic predispositions and environmental factors such as aging, family history, dietary habits, inflammatory bowel disease, and lifestyle influences including alcohol consumption and smoking. Due to its high incidence and potential lethality, colon cancer remains a major public health concern, emphasizing the importance of early detection and effective treatment.
Early symptoms of colon cancer are often subtle or absent, which can delay diagnosis; however, signs such as changes in bowel habits, rectal bleeding, unexplained weight loss, and abdominal discomfort warrant prompt medical evaluation. Screening methods, including stool-based tests, flexible sigmoidoscopy, computed tomography colonography, and primarily colonoscopy, play a crucial role in identifying precancerous polyps and early-stage tumors, thereby improving patient outcomes. Diagnosis is confirmed through biopsy, with imaging used to assess disease spread.
Treatment strategies for colon cancer depend on the stage and individual patient factors and typically involve surgical resection, chemotherapy, and, less commonly, radiation therapy. Advances in personalized medicine, including targeted therapies and immunotherapy based on specific genetic and molecular tumor characteristics, are enhancing treatment efficacy and survival rates. Despite these improvements, recurrence remains a challenge, underscoring the need for ongoing research and vigilant follow-up.
Prevention efforts focus on modifiable risk factors such as diet, physical activity, smoking cessation, and alcohol moderation, which have been shown to reduce the risk of CRC. Additionally, hereditary syndromes like Lynch syndrome and familial adenomatous polyposis contribute to a smaller but significant proportion of cases, necessitating genetic counseling and tailored surveillance for affected individuals. Awareness campaigns targeting both clinicians and the public, especially younger adults experiencing early symptoms, are critical for timely diagnosis and improved prognosis.

Overview

Colon cancer is a significant global health concern, representing approximately 9.8% of new cancer cases worldwide as of 2008, making it one of the most common malignancies after cardiovascular diseases. The disease typically develops through a combination of genetic predispositions and environmental factors. Aging, personal and familial history of colorectal cancer (CRC) or adenomas, dietary habits, inflammatory bowel disease, and hereditary cancer syndromes are among the most important risk factors identified. Environmental influences such as alcohol consumption also contribute to CRC risk and mortality.
Early detection of colon cancer is crucial for improving outcomes. Screening strategies include stool tests, flexible sigmoidoscopy, computed tomography colonography, and colonoscopy, with colonoscopy serving as the confirmatory diagnostic procedure if initial tests yield positive or abnormal results. Imaging techniques like the double-contrast barium enema (DCBE) help visualize the colon and rectum by outlining them with barium during X-ray imaging, providing an alternative method for detecting abnormalities.
Treatment modalities depend on the stage and severity of the disease. Surgery remains a cornerstone of curative therapy, ranging from localized resection to more extensive procedures such as colectomy or diverting colostomy, particularly in advanced stages or when symptom relief is needed. Chemotherapy, administered intravenously or orally, is commonly employed to target cancer cells systemically and is often used as adjuvant or neoadjuvant therapy to improve patient outcomes. Emerging approaches focus on personalized therapy guided by biomarkers and circulating tumor DNA to tailor treatment and reduce recurrence rates, which remain a significant challenge despite early-stage diagnosis.
Raising awareness of the signs and symptoms of colon cancer is essential, especially among younger adults, to encourage timely medical evaluation and diagnosis. Clinicians are also urged to maintain vigilance for early indicators to improve detection rates in this population. Understanding the molecular pathways involved in CRC, such as the APC/Wnt/β-catenin pathway and various genetic mutations including those seen in hereditary syndromes like Lynch syndrome and familial adenomatous polyposis (FAP), further aids in risk assessment and management planning.

Signs and Symptoms

Colorectal cancer symptoms can vary widely among individuals and may not be apparent in the early stages of the disease. Initial symptoms are often subtle or absent because colorectal cancer typically begins as small polyps in the colon or rectum, which may not cause noticeable signs. As the cancer progresses, symptoms may become more pronounced and include diarrhea or constipation, changes in normal bowel habits, an urge to have a bowel movement without actual need, discomfort during bowel movements or when sitting, lower abdominal pain or cramping, bloating, changes in appetite, and rectal bleeding.
Unexplained weight loss is another potential early sign of colon cancer. This weight loss can occur gradually over time without any obvious changes in diet or physical activity and may serve as an important indicator for further medical evaluation. Persistent abdominal discomfort or cramps, which can range from mild to severe and do not necessarily correlate with bowel movements, may also be indicative of colorectal cancer.
Rectal bleeding is a common symptom and is thought to occur because blood vessels in larger polyps or cancers are fragile and prone to bleeding as stool passes through the colon or rectum. Although bleeding is often microscopic and not visible to the naked eye, it can sometimes be noticeable and warrants prompt medical attention. However, these symptoms are not exclusive to colorectal cancer; conditions such as hemorrhoids, anal fissures, irritable bowel syndrome, and inflammatory bowel disease can produce similar signs, making medical evaluation critical for accurate diagnosis.
Recent research indicates that certain symptoms like abdominal pain and rectal bleeding are more strongly associated with colorectal cancer in younger adults (aged under 50) compared to older adults. In fact, about 20% of younger patients with early-onset colorectal cancer reported one or more key symptoms—such as abdominal pain or rectal bleeding—within three months to two years before diagnosis. This highlights the importance of raising awareness among younger populations to seek medical care promptly if such symptoms arise.

Risk Factors

Colorectal cancer (CRC) risk is influenced by a combination of genetic, lifestyle, and environmental factors. Individuals exposed to certain risk factors have a higher relative risk (RR) of developing CRC compared to those unexposed. The most significant risk factors identified include aging, personal and familial history of CRC or adenomas, dietary patterns, inflammatory bowel disease (IBD), and hereditary colorectal cancer syndromes.

Genetic and Hereditary Factors

Hereditary colorectal cancer syndromes contribute to approximately 2% to 5% of all colon cancers, with Lynch syndrome and familial adenomatous polyposis (FAP) being the most well-known conditions. Lynch syndrome, caused by germline mutations in mismatch repair (MMR) genes such as MLH1 and MSH2, significantly increases lifetime CRC risk, which may reach up to 50% depending on the specific gene affected. This syndrome typically manifests with early-onset, right-sided colon cancers and is also associated with increased risk for other cancers including uterine, ovarian, gastric, and urinary tract cancers. Genetic testing is valuable for confirming diagnoses and guiding management strategies in affected families.
FAP, caused by mutations in the APC gene, is characterized by the development of numerous colonic polyps and almost inevitable progression to CRC if untreated. Variants include attenuated FAP, Gardner syndrome, and Turcot syndrome, each with distinct clinical features. Other hereditary polyposis syndromes such as MUTYH-associated polyposis (MAP), juvenile polyposis syndrome, Peutz-Jeghers syndrome, and serrated polyposis syndrome also contribute to inherited CRC risk. Familial aggregation of CRC, even without identified syndromes, suggests additional genetic loci influencing susceptibility.

Lifestyle and Environmental Factors

Lifestyle-related factors play a substantial role in CRC risk and are modifiable through behavioral changes. Smoking tobacco increases the risk of colorectal polyps and CRC, as well as mortality from the disease. Alcohol consumption is also linked to higher CRC incidence and related deaths, with risks consistent across sexes and colorectal sub-sites.
Dietary patterns affect CRC risk via mechanisms including metabolic dysfunction, inflammation, oxidative stress, and gut microbiota alterations. Diets high in processed meats and low in dietary fiber are associated with increased CRC risk, although evidence supporting dietary fiber’s protective effect is modest. Dietary fiber may reduce CRC risk by decreasing colonic transit time and limiting exposure to dietary carcinogens.
Physical activity exhibits a protective effect, with high levels of recreational activity linked to an approximate 20% relative risk reduction in CRC development. Physical activity also improves survival outcomes in CRC patients. Conversely, sedentary behavior is associated with increased CRC risk, reflecting societal shifts toward less physically demanding occupations and lifestyles.

Other Medical Conditions

Inflammatory bowel disease, which includes ulcerative colitis and Crohn’s disease, is a recognized risk factor for CRC due to chronic inflammation and dysplasia in the colon lining. Patients with IBD require earlier and more frequent CRC screening compared to the general population. It is important to distinguish IBD from irritable bowel syndrome (IBS), as IBS does not increase CRC risk.

Diagnosis

Diagnosis of colorectal cancer typically begins with screening tests aimed at detecting precancerous polyps or early-stage cancers in individuals without symptoms. When symptoms are present, diagnostic tests are employed to determine the cause. Colonoscopy is the most common and comprehensive diagnostic tool, allowing direct visualization of the entire colon and rectum using a flexible, lighted tube with a small camera called a colonoscope. If suspicious areas such as polyps or tumors are found during colonoscopy, they can be biopsied or removed during the procedure.
A diagnostic colonoscopy is performed when symptoms suggest colorectal cancer or when abnormalities are detected on other screening tests. This procedure requires thorough bowel cleansing beforehand and is often conducted with sedation to minimize discomfort. Unlike screening colonoscopies, diagnostic colonoscopies follow abnormal results from tests like stool blood tests or imaging studies, and insurance coverage may differ between screening and diagnostic exams.
Virtual colonoscopy, also known as computed tomographic (CT) colonography, is an alternative screening method that uses CT scanning to generate detailed images of the colon and rectum from outside the body. Patients undergo similar bowel preparation as for traditional colonoscopy but do not require sedation. Virtual colonoscopy is recommended every five years and has higher sensitivity for detecting cancerous changes, though it cannot remove polyps during the exam.
If a colorectal tumor is suspected or confirmed, further imaging tests such as CT scans or PET scans may be used to assess the extent of disease spread. CT scans provide detailed images of the lungs and other organs, while PET scans use a radioactive sugar tracer to identify cancer cells in the body, helping to detect metastases beyond the colon and rectum.
Biopsy is essential for confirming the diagnosis of colorectal cancer. During colonoscopy, tissue samples are taken from suspicious lesions. In some cases, part of the colon may be surgically removed to establish a definitive diagnosis, particularly when less invasive methods are insufficient.
Other diagnostic tools include flexible sigmoidoscopy, which examines the rectum and lower colon with a shorter scope and may be used for initial screening or symptom evaluation. This procedure also requires bowel preparation and may cause discomfort due to air insufflation but is less extensive than colonoscopy.

Treatment Options

Treatment options for colon cancer vary depending on the stage and location of the tumour, as well as the patient’s overall health and genetic characteristics of the cancer cells. A multidisciplinary team of doctors and healthcare professionals typically collaborates to determine the most appropriate treatment plan.

Chemotherapy

Chemotherapy is often used in conjunction with surgery, especially for stage II (with high-risk features), stage III, and metastatic colon cancers. Adjuvant chemotherapy, administered after surgery, typically lasts between 3 to 6 months and aims to eliminate any remaining cancer cells to reduce the risk of recurrence. The most commonly used regimens include FOLFOX (5-fluorouracil, leucovorin, and oxaliplatin) and CAPEOX (capecitabine and oxaliplatin), with adjustments made based on patient age and health status.
For stage II colon cancer, adjuvant chemotherapy is generally not recommended for low-risk patients but may be considered for those with stage IIB or IIC disease (tumours penetrating the visceral peritoneum or invading nearby organs) or other high-risk factors.
In metastatic colon cancer, chemotherapy options may be combined with targeted therapies or immunotherapy depending on molecular characteristics such as microsatellite instability-high (MSI-H) or mismatch repair deficiency (dMMR).

Radiation Therapy

Although radiation therapy is less commonly used for colon cancer than for rectal cancer, it may be employed in advanced cases to help prevent or relieve symptoms caused by the tumour, such as pain or obstruction.

Surgery

Surgery is the primary treatment for colon cancer, especially in cases where the cancer has not spread to distant sites. For stage 0 colon cancer, surgery usually involves local excision, such as a polypectomy performed during a colonoscopy, to remove the tumour along with a small margin of healthy tissue. For cancers beyond stage 0, a partial colectomy, which involves removing the section of the colon containing the tumour along with nearby lymph nodes, is the standard approach. Total colectomy is rarely needed and is mostly reserved for patients with multiple polyps or underlying conditions like familial adenomatous polyposis or inflammatory bowel disease.
Laparoscopic-assisted colectomy (LAC) and robotic-assisted surgery have become increasingly common, offering minimally invasive options that have shown comparable three-year recurrence and overall survival rates to traditional open colectomy.
In cases where the tumour has invaded surrounding organs or is considered bulky and difficult to remove completely, neoadjuvant therapy (chemotherapy or immunotherapy before surgery) may be employed to shrink the tumour and improve surgical outcomes. For advanced or metastatic colon cancer, surgery may also be used to alleviate symptoms or manage complications, although the goal may not always be curative.

Targeted Therapy and Immunotherapy

Targeted therapy drugs can be part of the treatment regimen for patients whose cancer cells have specific genetic or protein changes. For example, HER2-positive metastatic colorectal cancer may be treated with agents like trastuzumab in combination with tucatinib.
Immunotherapy, including drugs such as pembrolizumab, nivolumab, and dostarlimab, is an option for patients with MSI-H or dMMR metastatic colon cancer, particularly after standard chemotherapy has failed.

Prevention

Prevention of colorectal cancer (CRC) primarily involves adopting healthy lifestyle factors that have been shown to reduce risk. Multivariable analyses demonstrate that individual behaviors such as non-smoking, maintaining a healthy body mass index (BMI), consuming alcohol within recommended limits, following a healthy diet, and engaging in recommended levels of physical activity are each associated with a decreased risk of CRC. Specifically, non-smoking is linked to an odds ratio (OR) of 0.82, a healthy BMI to an OR of 0.71, recommended alcohol intake to an OR of 0.83, a healthy diet score to an OR of 0.70, and physical activity to an OR of 0.88, all indicating reduced risk. Moreover, combining these factors leads to progressively lower risks of colorectal, colon, and rectal cancer in a dose-response manner.
Physical activity plays a crucial role in CRC prevention. High levels of recreational physical activity are associated with approximately a 20% relative risk reduction in developing CRC and a 42% improvement in both all-cause and colon cancer–specific mortality after diagnosis. Conversely, sedentary behavior, such as prolonged occupational sitting, increases colon cancer risk by 44%, highlighting the importance of minimizing sedentary time in addition to meeting physical activity recommendations. This shift toward sedentary lifestyles, particularly in Western societies due to occupational changes, is a growing public health concern.
Diet

Prognosis

The prognosis of colon cancer largely depends on the stage at diagnosis, genetic factors, and the effectiveness of treatment strategies. Early detection significantly improves survival rates, as localized tumors (Stage I) are often small, confined to the inner layers of the colon wall, and highly treatable through surgical removal, which may be curative. In contrast, advanced stages, such as Stage II and beyond, indicate deeper tissue invasion or spread to nearby lymph nodes and organs, which complicates treatment and generally worsens prognosis.
Genetic factors play a critical role in the disease outcome. Lynch syndrome, the most common inherited colorectal cancer (CRC) syndrome, involves mutations in mismatch repair (MMR) genes and is associated with increased lifetime risks of colorectal and other cancers. Identification of pathogenic variants via prediction models like PREMM5, MMRpro, and MMRpredict can guide genetic evaluation and inform prognosis and management. Moreover, tumor testing for microsatellite instability (MSI) or deficient mismatch repair (dMMR) status is important for prognosis and treatment decisions, particularly in advanced or metastatic CRC cases.
Adjuvant therapies, including chemotherapy and radiotherapy, can improve outcomes by targeting residual microscopic disease and reducing recurrence risk. Preoperative radiotherapy, especially when employing advanced multiple field techniques, has been shown to lower postoperative mortality and improve survival in rectal cancer cases. Chemotherapy is also used to shrink tumors, alleviate symptoms, and prolong survival in advanced disease, though it is rarely curative in metastatic settings. Targeted therapies and immunotherapies, such as trastuzumab for HER2-positive tumors or immune checkpoint inhibitors for MSI-high cancers, have further enhanced prognosis in select patient populations.
Lifestyle factors and primary prevention also influence overall CRC risk and thus prognosis on a population level. Adherence to healthy dietary patterns and risk factor modification may reduce the incidence and improve long-term outcomes regardless of genetic predisposition. However, the increasing incidence of CRC, especially among younger populations, poses ongoing challenges to public health and underscores the importance of early detection and tailored treatment approaches.

Support and Resources

Managing colon cancer involves a multidisciplinary team of healthcare professionals who collaborate to provide the best treatment and care tailored to the individual patient. This team typically includes doctors, surgeons, oncologists, nurses, and other specialists who discuss and decide on the most appropriate treatment plan, which may include surgery, chemotherapy, or a combination of therapies. The treatment plan takes into account various factors such as the stage of cancer, the patient’s overall health, personal preferences, and goals of care, ensuring that patients are well-informed about their options, possible side effects, and the expected duration of treatment.
Current challenges in colon cancer treatment include limited tools for precisely selecting patients for adjuvant therapy, toxicity related to treatments, and only modest efficacy of some therapies. Emerging technologies, such as circulating tumor DNA, offer promise for improving personalized care and potentially transforming the standard treatment approaches for early-stage colon cancer.
Screening and early detection remain crucial components of support in colon cancer management. The United States Preventive Services Task Force recommends various screening strategies to identify colorectal cancer early, including stool tests, flexible sigmoidoscopy, computed tomography colonography, and colonoscopy, with colonoscopy often required to complete the screening process if initial tests are positive or abnormal. Raising awareness of key signs and symptoms, especially among younger adults who may be at risk for early-onset colorectal cancer, is essential. Both patients and clinicians need to be vigilant to facilitate timely diagnosis and improve outcomes.
Lifestyle factors also play a significant role in colon cancer risk reduction and patient support. Engaging in high levels of recreational physical activity is strongly associated with approximately a 20% relative risk reduction in developing colorectal cancer, as well as a significant improvement in survival among patients diagnosed with the disease. Conversely, a sedentary lifestyle, characterized by prolonged sitting and low physical movement, is linked to an increased risk of colon cancer, highlighting the importance of physical activity as part of ongoing support for prevention and recovery.

The content is provided by Jordan Fields, Front Signals