Colon Cancer
Colon cancer, also referred to as colorectal carcinoma when involving the colon specifically, is a malignant neoplasm arising from the inner lining of the large intestine. The pathogenesis typically begins with the transformation of normal colonic epithelium through a multistep process involving genetic and epigenetic alterations, such as mutations in the APC, KRAS, and TP53 genes, as well as microsatellite instability and chromosomal instability pathways. These changes lead to the progression from benign adenomatous polyps to invasive carcinoma. The disease exerts significant health impacts, including local invasion, obstruction, bleeding, and potential for distant metastasis, most commonly to the liver, lungs, and peritoneum. Colon cancer is a leading cause of cancer-related morbidity and mortality worldwide, with substantial implications for quality of life, healthcare resource utilization, and long-term survivorship.
Adenocarcinoma is the most prevalent type of colon cancer, accounting for the vast majority of cases. It originates from the glandular epithelial cells lining the colon and is characterized by the formation of abnormal glandular structures. These tumors can be further classified based on their histological features, including mucinous and signet-ring cell subtypes, each with distinct prognostic implications.
Mucinous adenocarcinoma is a variant of adenocarcinoma defined by the presence of abundant extracellular mucin constituting more than 50% of the tumor volume. This subtype tends to exhibit a more aggressive clinical course and is often associated with a higher frequency of microsatellite instability.
Signet-ring cell carcinoma is a rare and aggressive form of colon cancer characterized by the presence of tumor cells with prominent intracytoplasmic mucin displacing the nucleus to the periphery, giving a signet-ring appearance. This type is often diagnosed at an advanced stage and is associated with a poorer prognosis.
Medullary carcinoma is an uncommon histological subtype characterized by sheets of poorly differentiated tumor cells with prominent lymphocytic infiltration. It is frequently associated with microsatellite instability and may have a relatively better prognosis compared to other poorly differentiated carcinomas.
Colon cancer is one of the most commonly diagnosed malignancies globally, ranking third in incidence and second in cancer-related mortality according to the World Health Organization. The lifetime risk of developing colon cancer is approximately 4-5% in developed countries, with higher incidence rates observed in Western nations compared to Asia and Africa. The disease predominantly affects individuals over the age of 50, though incidence in younger populations has been rising in recent decades. Risk factors include advancing age, family history of colorectal cancer, hereditary syndromes such as Lynch syndrome and familial adenomatous polyposis, inflammatory bowel disease, dietary patterns high in red and processed meats, obesity, sedentary lifestyle, smoking, and excessive alcohol consumption. Five-year survival rates vary significantly by stage at diagnosis, exceeding 90% for localized disease but dropping below 15% for those with distant metastases.
The diagnosis of colon cancer involves a combination of clinical assessment, endoscopic evaluation, imaging, and histopathological confirmation. Initial suspicion often arises from symptoms such as rectal bleeding, altered bowel habits, unexplained iron-deficiency anemia, or incidental findings during screening. Colonoscopy remains the gold standard for direct visualization of the colonic mucosa, allowing for biopsy of suspicious lesions and polypectomy. Radiologic modalities such as computed tomography (CT) colonography and barium enema may be utilized when colonoscopy is incomplete or contraindicated. Staging is performed using contrast-enhanced CT scans of the chest, abdomen, and pelvis to assess for local invasion and distant metastases, while magnetic resonance imaging (MRI) and positron emission tomography (PET) may be used in select cases. Pathological examination of biopsy or resected tissue confirms the diagnosis and provides information on tumor type, grade, lymphovascular invasion, and molecular markers such as microsatellite instability or KRAS mutation status, which can inform prognosis and therapeutic decisions. Laboratory tests including carcinoembryonic antigen (CEA) levels may aid in monitoring response to therapy and detecting recurrence.
Capecitabine is an orally administered chemotherapeutic agent indicated for the treatment of colon cancer. It is a prodrug that is metabolized to 5-fluorouracil (5-FU) in the body, exerting its antineoplastic effects by inhibiting thymidylate synthase and thereby interfering with DNA synthesis and cell proliferation. Capecitabine is commonly used as monotherapy or in combination with other agents in the adjuvant setting following surgical resection, as well as for the treatment of metastatic disease. Its oral formulation offers a convenient alternative to intravenous 5-FU, and it is associated with a well-characterized safety profile that includes potential side effects such as hand-foot syndrome, gastrointestinal disturbances, and myelosuppression. Dosage and duration of therapy are tailored based on the stage of disease, patient tolerance, and treatment objectives.
| Structure | Generic Name | CAS Registry Number | Molecular Formula | Molecular Weight |
|---|---|---|---|---|
 | capecitabine (Rec INN; USAN) | 154361-50-9 | C15 H22 F N3 O6 | 359.35 |
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Colon Cancer
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