What is rectal cancer?
Rectal cancer is a type of cancer that develops in the cells of the rectum, which is the last portion of the large intestine that connects to the anus. Like colon cancer, rectal cancer typically starts as small growths called polyps on the inner lining of the rectum. Over time, some of these polyps may become cancerous, forming tumors that can grow and potentially spread to other parts of the body if not detected and treated early.
Rectal cancer shares many similarities with colon cancer, including risk factors, symptoms, and treatment approaches. However, because of its location in the lower part of the digestive tract, rectal cancer may present with specific symptoms and require specialized treatment strategies.
What are the risk factors for rectal cancer?
Risk factors for rectal cancer include:
- Age (most cases diagnosed in individuals over 50 years old)
- A family history of colorectal cancer or certain genetic syndromes (such as Lynch syndrome or familial adenomatous polyposis) increases the risk.
- Personal history of colorectal cancer or certain types of polyps (such as adenomatous polyps) increases the risk of developing rectal cancer.
- Certain lifestyle factors, such as a diet high in red and processed meats, low-fiber diet, sedentary lifestyle, obesity, smoking, and heavy alcohol consumption may increase the risk.
- Chronic inflammatory bowel diseases of the colon and rectum, such as ulcerative colitis or Crohn's disease, increase the risk of colorectal cancer, including rectal cancer.
What are the symptoms of rectal cancer?
Rectal cancer may not cause symptoms early on. Symptoms of rectal cancer usually happen when the disease is advanced. Symptoms of rectal cancer may include:
- A change in bowel habits, such as diarrhea, constipation, or a more frequent need to pass stool
- A feeling that the bowel doesn't empty completely
- Abdominal pain
- Rectal bleeding
- Narrow stool
- Unexplained weight loss
- Weakness or fatigue
How is rectal cancer diagnosed?
Rectal cancer diagnosis typically begins with a review of symptoms and medical history, followed by screening and diagnostic tests to confirm the presence of cancer. Early diagnosis is important, as rectal cancer detected in its early stages is often more treatable.
Diagnostic methods may include:
- Colonoscopy, which allows providers to examine the rectum and colon and remove tissue samples for biopsy
- Biopsy, where a tissue sample is examined under a microscope to confirm cancer and determine the cancer type
- Digital rectal examination, which allows the provider to check for abnormalities in the rectum
- Imaging tests, such as CT scans, MRI, or PET scans, to evaluate tumor size and determine whether the cancer has spread
- Endorectal ultrasound, which uses sound waves to assess how deeply the tumor has grown into the rectal wall
Once rectal cancer is confirmed, additional testing is used to determine the stage and grade of the cancer, which helps guide treatment planning.
Rectal cancer is graded based on how abnormal the cancer cells appear under a microscope. Lower-grade tumors tend to grow more slowly, while higher-grade tumors are more aggressive. Rectal cancer staging includes:
- Stage I: Cancer is limited to the inner layers of the rectum
- Stage II: Cancer has grown through the rectal wall but has not spread to lymph nodes
- Stage III: Cancer has spread to nearby lymph nodes
- Stage IV: Cancer has spread to distant organs, such as the liver or lungs
How is rectal cancer treated?
Determining a treatment plan depends on several factors including the stage of the cancer, the location and size of the tumor, the patient's overall health and preferences, and the expertise of the medical team. Treatment may involve a combination of surgery, radiation therapy, chemotherapy, targeted therapy, and immunotherapy.
Surgery
- Transanal Excision: This minimally invasive procedure is used for early-stage rectal cancer that has not spread beyond the inner layers of the rectum. The tumor is removed through the anus using specialized instruments. This technique is possible for low tumors within 8 cm of the anal opening.
- Transanal Minimally Invasive Surgery (TAMIS): TAMIS is a minimally invasive procedure used for early-stage rectal cancer that has not spread beyond the inner layers of the rectum. This technique is possible for mid-rectal tumors located between 5 and 15 cm from the anal opening.
- Low Anterior Resection (LAR): In this procedure, the portion of the rectum containing the tumor is removed, and the colon is reattached to the remaining healthy rectum. LAR is typically used for tumors without involvement of the anorectal sphincter muscles.
- Abdominoperineal Resection (APR): APR involves removing the entire rectum, anus, and surrounding tissues through incisions made in the abdomen and perineum. This procedure may be necessary for tumors located in the lower part of the rectum or for advanced cancers involving the anorectal sphincter muscles
Radiation Therapy: For some patients with locally advanced rectal cancer, high-energy X-rays are directed at the tumor and surrounding tissues from outside the body to destroy cancer cells and shrink the tumor. This treatment improves the success rate for surgery and reduces the risk of recurrence.
Chemotherapy: Chemotherapy may be used before surgery (neoadjuvant chemotherapy) to shrink the tumor and make it easier to remove, or after surgery (adjuvant chemotherapy) to kill any remaining cancer cells and reduce the risk of recurrence.
Targeted Therapy: Specialized medications may be used to target specific molecules or pathways involved in the growth and spread of cancer cells, particularly in tumors with specific genetic mutations (such as KRAS or BRAF mutations).
Immunotherapy: Specialized medications may be used to stimulate the immune system to recognize and attack cancer cells, particularly in tumors with high levels of microsatellite instability (MSI-H) or mismatch repair deficiency (dMMR).
Following treatment, the colorectal surgeon will provide ongoing monitoring and follow-up care to monitor the patient's progress, assess for any signs of recurrence, and address any postoperative issues or complications. The surgeon will work closely with other members of the multidisciplinary team to ensure comprehensive and coordinated care throughout the patient's journey.