Sigmoid colon cancer develops in the S-shaped section of the large intestine, known as the sigmoid colon. This part of the colon connects the descending colon to the rectum, playing a role in storing stool before it is eliminated from the body. When abnormal cells within the lining of this segment begin to grow and multiply without control, it leads to the formation of a cancerous tumor.
Symptoms and Risk Factors
Sigmoid colon cancer often presents with several symptoms. Individuals may experience changes in their bowel habits, including diarrhea, constipation, or alternating patterns. Blood in the stool is another indicator, appearing bright red or making stools look dark brown or black. Persistent abdominal discomfort, such as cramping, gas, or pain, can also occur. Some individuals report a feeling that their bowel does not empty completely after a bowel movement.
Several factors increase the likelihood of developing sigmoid colon cancer, with age being a primary factor as risk increases for those over 45. A personal or family history of colorectal cancer or certain types of polyps also raises the risk. Inflammatory bowel diseases, such as Crohn’s disease or ulcerative colitis, are linked to a higher risk. Lifestyle elements like a diet high in processed meats, lack of physical activity, smoking, and excessive alcohol consumption are contributing factors. Certain genetic syndromes, including Lynch syndrome, also elevate the risk.
Diagnosis and Staging
Diagnosis typically begins with a colonoscopy, the primary tool for detection. During this procedure, a flexible tube with a camera is inserted into the colon, allowing a healthcare provider to inspect the lining for abnormalities like polyps or tumors. If suspicious areas are found, a biopsy (taking a small tissue sample) is performed. This sample is then examined under a microscope to confirm cancer cells.
After cancer is confirmed, imaging tests determine if it has spread beyond the sigmoid colon. A computed tomography (CT) scan of the chest, abdomen, and pelvis is used to check for spread to nearby lymph nodes or distant organs like the liver or lungs. The extent of spread is categorized through staging, using the TNM system. This system describes the Tumor’s size (T), involvement of nearby lymph Nodes (N), and presence of distant Metastasis (M).
The TNM classification is translated into a stage system (Stage 0 to Stage IV):
- Stage 0: Very early cancer confined to the innermost lining of the colon.
- Stage I: Cancer has grown into the colon wall but has not spread to lymph nodes or distant sites.
- Stage II: Cancer has spread further into or through the colon wall but remains localized to the colon and has not reached nearby lymph nodes.
- Stage III: Cancer has spread to nearby lymph nodes but not to distant organs.
- Stage IV: Advanced cancer that has spread to distant parts of the body, such as the liver, lungs, or ovaries.
Treatment Approaches
Treatment often involves a combination of approaches, with surgery as the most common initial step. The primary surgical procedure is a sigmoid colectomy, removing the cancerous section of the sigmoid colon along with a margin of healthy tissue. In some situations, such as bowel obstruction or perforation, a colostomy might be necessary. This creates an opening in the abdomen to divert stool into a bag outside the body and can be temporary or permanent.
Following surgery, chemotherapy is often employed, particularly for higher-stage cancers. This systemic treatment uses drugs to destroy remaining cancer cells, aiming to reduce recurrence risk. For advanced or metastatic sigmoid colon cancer, regimens like FOLFOX (folinic acid, fluorouracil, and oxaliplatin) are used to manage the disease. Chemotherapy can also help control symptoms and improve quality of life when the cancer has spread.
Beyond traditional chemotherapy, newer treatment options include targeted therapy and immunotherapy. Targeted therapies focus on specific molecules involved in cancer growth, often with fewer side effects than conventional chemotherapy as they affect cancer cells more specifically. Immunotherapy boosts the body’s immune system to fight cancer cells. These newer approaches are considered for specific types of advanced sigmoid colon cancer, especially when genetic mutations are identified in the tumor.
Prognosis and Post-Treatment Care
Prognosis for sigmoid colon cancer depends on the stage at diagnosis. For localized disease (confined to the colon), the 5-year relative survival rate is approximately 90%. If cancer has spread to nearby tissues, organs, or lymph nodes (regional disease), the 5-year relative survival rate is about 73%. When cancer has spread to distant organs (metastatic disease), the 5-year relative survival rate decreases to around 17%. These figures are statistical averages from large groups of people, and individual outcomes can vary based on factors like overall health and treatment response.
After initial treatment, ongoing post-treatment care monitors for recurrence and manages long-term effects. Surveillance includes regular follow-up colonoscopies, often scheduled at one, three, and five years after surgery for early-stage cancers. Regular doctor visits and blood tests, including the carcinoembryonic antigen (CEA) tumor marker test, also monitor for potential cancer recurrence. Some individuals may need to make long-term adjustments, such as dietary changes or managing an ostomy if one was created during surgery.