When treating cancer, there are two primary treatment types: local treatments and systemic treatments. Local treatments are those that directly treat the tumor without affecting the rest of the body. This type of treatment is typically used for smaller tumors that are usually seen in earlier-stage cancers. Common types of local treatments are surgery, ablation, and radiation therapy. Systemic treatments are those that reach the entire body to target circulating and metastasized cancer cells wherever they are present. Common types of systemic treatments are chemotherapy, hormone therapy, and immunotherapy. [1]

Surgery with radiation and/or chemotherapy before or afterwards is often the primary treatment for rectal cancer. Like in colon cancer, the type of surgery performed for treating rectal cancer depends of the stage of the cancer. Early stage rectal cancers and pre-cancerous polyps are often removed during minimally invasive coloscopies. Another type of surgical treatment for rectal cancer is a transanal excision (TAE), which is utilized for early tumors that are small and located near the anus. Like a colonoscopy, this is a minimally invasive operation where the instruments are put in the rectum via the anus, the rectal wall is cut to remove the tumor and a margin of surrounding normal tissue, and then the rectal wall is closed. A transanal endoscopic microsurgery (TEM) is one that is similar to the TAE, except it is used for tumors that are located higher in the rectum and thus require a specialized magnifying scope. [2]

Tumors located in the upper part of the rectum, such most Stage II and Stage III cancers, are removing using a surgery called low anterior resection (LAR). In a LAR surgery, the entire part of the rectum with the tumor is removed and the colon is reattached to the rectum, ensuring that a colostomy bag will not be needed long-term. Tumors located in the middle and lower parts of the rectum, which are again often Stage II and Stage III tumors, require a surgery called a proctectomy, which is the removal of the entire rectum. This has to be done so that the lymph nodes near the rectum can be removed as well. The colon is then attached to the anus, bypassing the need for a long-term colostomy bag. For Stage II and Stage III cancers located in the lower part of the rectum, an abdominoperineal resection (APR) is often used, especially if the tumor has begun to grow into nearby muscles. APR requires the removal of the rectum, anus, and tissues around them, thus prompting the need for a permanent colostomy. [2]

Ablation is a treatment option that can be used on small tumors. It is commonly used when colorectal cancer has spread to create small masses in organs such as the liver and lungs. It is also helpful for patients that may not be ideal candidates for more invasive surgical techniques. [3] Ablation is a minimally invasive method where specialized probes are guided to the tumor using imaging techniques such as an ultrasound or CT scan, at which point the probe is used to “burn” or “freeze” the tumor, thereby killing the cancer cells. [4]

 Radiation therapy, or the use of high-energy rays to damage and kill cancer cells, is used for treating rectal cancer more often than colon cancer. The type of radiation used the most for colorectal cancer is external-beam radiation therapy (EBRT). In EBRT, a machine outside the body targets the cancer side and directs radiation towards this site to damage the cells there. [5] 

A common type of systemic therapy used to treat colon cancer is chemotherapy, which is a treatment where anti-cancer drugs are administered. These drugs travel through the bloodstream to eliminate cancer cells throughout the body. Chemotherapy may be given after surgery to kill remaining cancer cells (adjuvant chemotherapy), before surgery to try to shrink the tumor to make it easier to remove (neoadjuvant chemotherapy), and for treating the progression of advanced cancers. [6] Targeted therapies, like chemotherapies, are drugs that travel through the bloodstream to target cellular changes, such as growth factor changes, that are responsible for cancer growth. [7] Immunotherapy, a form of therapy that aims to help a person’s own immune system fight cancer, can be used to treat specific gene mutations that have made the cancer resistant to the patient’s immune system. [8]

References:

1.     Colorectal cancer treatment: How to treat colorectal cancer. https://www.cancer.org/cancer/colon-rectal-cancer/treating.html (accessed Jan 31, 2022).

2.     Rectal cancer surgery: Side effects of rectal surgery. https://www.cancer.org/cancer/colon-rectal-cancer/treating/rectal-surgery.html (accessed Feb 1, 2022).

3.     Ablation and embolization for colorectal cancer. https://www.cancer.org/cancer/colon-rectal-cancer/treating/ablation-embolization.html (accessed Jan 31, 2022).

4.     Molnar, H. Tumor ablation. https://www.hopkinsmedicine.org/interventional-radiology/procedures/tumor/#:~:text=What%20is%20Cancer%20Ablation%3F,needle% 0probe%20into%20the%20tumor. (accessed Jan 31, 2022).

5.     Radiation therapy for colorectal cancer: Radiation for colorectal cancer. https://www.cancer.org/cancer/colon-rectal-cancer/treating/radiation-therapy.html (accessed Feb 1, 2022).

6.     Colorectal cancer chemotherapy: Chemo for colon & rectal cancer. https://www.cancer.org/cancer/colon-rectal-cancer/treating/chemotherapy.html (accessed Jan 31, 2022).

7.     Colorectal cancer targeted therapy: Targeted drugs for colorectal cancer. https://www.cancer.org/cancer/colon-rectal-cancer/treating/targeted-therapy.html (accessed Jan 31, 2022).

8.     Immunotherapy for colorectal cancer: Immunotherapy for rectal cancer. https://www.cancer.org/cancer/colon-rectal-cancer/treating/immunotherapy.html (accessed Jan 31, 2022).