Colorectal cancer is a malignancy that starts in the colon or rectum. Colorectal oncology is the medical field focused on the diagnosis, treatment, and care for individuals with this cancer. This cancer often begins as benign growths called polyps on the inner lining of the colon or rectum. Over several years, some polyps can become cancerous.
Early-stage colorectal cancer may not cause symptoms, making screening a primary tool for detection. When symptoms do occur, they can include changes in bowel habits, blood in the stool, and abdominal discomfort.
The CRC Oncology Team and Diagnosis
Effective management of colorectal cancer (CRC) involves a multidisciplinary team (MDT) of specialists who collaborate on patient care. This team includes:
- A surgical oncologist or colorectal surgeon to remove tumors.
- A medical oncologist to manage drug therapies like chemotherapy.
- A radiation oncologist to administer radiation treatment.
- A gastroenterologist to perform initial diagnostic procedures.
- A pathologist to analyze tissue samples and confirm the diagnosis.
The diagnostic process for CRC begins with a screening test like a colonoscopy. During this procedure, a doctor examines the colon and rectum with a flexible camera, removing any suspicious polyps. If a growth appears cancerous, a tissue sample is taken for a biopsy to confirm the diagnosis.
Once cancer is confirmed, imaging tests determine its extent. Computed tomography (CT) scans provide images of the abdomen and chest to see if the cancer has spread to organs like the liver or lungs. An MRI is used for rectal cancer to view the tumor’s relationship to nearby structures, while a positron emission tomography (PET) scan can detect cancer cells throughout the body.
Staging Colorectal Cancer
After diagnosis, the cancer is staged to describe its size and spread, which informs the treatment plan. The most common method is the TNM system, which stands for Tumor, Node, and Metastasis. “T” describes the size of the primary tumor and its growth into the wall of the colon or rectum. “N” indicates if the cancer has spread to nearby lymph nodes, and “M” signifies if it has metastasized to distant parts of the body.
These findings are combined to assign a stage from 0 to IV. Stage 0 (carcinoma in situ) means abnormal cells are only in the innermost lining of the colon or rectum. Stages I through III represent cancers that are more invasive but have not spread to distant organs. Stage I cancer has grown into the intestinal wall but not beyond the muscular layer, Stage II has grown through the wall but not to lymph nodes, and Stage III indicates spread to nearby lymph nodes.
Stage IV is the most advanced, meaning the cancer has metastasized to distant organs like the liver or lungs. The stage allows the oncology team to select therapies and predict a patient’s prognosis.
Core Treatment Modalities
Colorectal cancer treatment is based on three primary methods: surgery, chemotherapy, and radiation therapy. The combination and timing of these treatments depend on the cancer’s stage and location.
Surgery, the most common treatment for localized CRC, aims to remove the tumor, a margin of healthy tissue, and nearby lymph nodes. For colon cancer, this procedure is often a colectomy, where a portion of the colon is removed.
Chemotherapy uses drugs to destroy cancer cells throughout the body. As a systemic treatment, it travels through the bloodstream to reach cells that have spread beyond the primary tumor. It can be administered after surgery (adjuvant) to eliminate remaining cancer cells or before surgery (neoadjuvant) to shrink a tumor.
Radiation therapy uses high-energy rays to kill cancer cells in a specific area. This localized treatment is frequently used for rectal cancer because of the rectum’s fixed position in the pelvis. It is often combined with chemotherapy before surgery to shrink the tumor, which helps preserve organ function and reduces the chance of local recurrence.
Advanced and Targeted Therapies
Colorectal cancer treatment has evolved to include therapies that target specific characteristics of cancer cells, offering more personalized approaches. Targeted therapies are drugs that interfere with specific molecules involved in tumor growth and require the patient’s tumor to have the genetic marker the drug is designed to target. Common markers include mutations in genes like KRAS, BRAF, and abnormalities in the HER2 protein.
Immunotherapy is an approach that uses the body’s immune system to attack cancer cells. These treatments are particularly successful for tumors with biomarkers like high-frequency microsatellite instability (MSI-H) or mismatch repair deficiency (dMMR). These markers indicate the tumor cells have difficulty repairing DNA, making them more recognizable to the immune system.
For patients with advanced CRC, testing the tumor tissue for these biomarkers is a standard part of creating a treatment plan. These therapies represent a shift toward precision medicine and can offer new options for patients with advanced disease.
Survivorship and Ongoing Monitoring
After primary treatment, patients enter the survivorship phase, which focuses on recovery and long-term health. A structured follow-up plan is created to monitor for cancer recurrence and manage any lasting side effects.
This surveillance plan includes:
- Regular follow-up appointments with the oncology team.
- Blood tests to check for tumor markers, such as carcinoembryonic antigen (CEA).
- Regular imaging scans for a period of time.
- Colonoscopies to check for new polyps or cancers, typically starting one year after surgery.
The frequency of these tests depends on the initial cancer stage, treatments received, and individual risk factors.