Chemotherapy for Rectal Adenocarcinoma

Introduction:

The rectum is the last portion of the large intestine that connects the colon of the large intestine to the anus. Cancer that occur in the large intestine are called colorectal cancers. Colorectal cancer is the third most common cancer. 95 percent of rectal cancers are rectal adenosarcoma. Only 5 percent of other cancer types can be seen in the rectum.

What Is Rectal Adenocarcinoma?

Rectal cancer occurs when the rectal cells undergo mutation resulting in uncontrolled growth. There will be the growth of polyps in the inner layer of the rectum that develops into cancerous cells. Rectal adenocarcinoma can metastasize to other parts of the body. It is called invasive adenocarcinoma.

What Are the Causes of Rectal Adenocarcinoma?

The actual cause of rectal cancer is not clear. As age increases, the risk of getting rectal cancer also increases. It can also be seen in people with familial history of rectal cancer. Other causes of cancer are:

• Inherited gene mutation.

• Unhealthy diet.

• Increased alcohol use.

• Tobacco use and smoking.

• Lazy lifestyle.

• Diabetes.

• Hereditary.

• Obesity.

What Are the Symptoms of Rectal Adenocarcinoma?

There are few signs and symptoms during the early stages of rectal cancer. As cancer develops, the following signs and symptoms can be seen:

• Rectal bleeding.

• Blood in stools.

• Changes in bowel movements.

• Diarrhea or constipation.

• Narrow ribbon-like stools.

• Loss of weight.

• Fatigue and weakness.

• Pain in the abdomen.

• Abdominal bloating.

If the rectal cancer is metastasized or spread to other parts of the body, then symptoms depend on the site where the cancer has spread. The following symptoms can be seen in metastasized rectal cancer -

• Continuous cough.

• Weakness and fatigue.

• Pain in the bones.

• Breathlessness.

• Reduced appetite.

• Jaundice (yellow discoloration of skin and sclera of the eye).

• Swelling in hands and feet.

What Are the Types of Rectal Cancer?

There are mainly four types of rectal cancers.

• Rectal Adenocarcinoma - 95 percent of rectal cancers are rectal adenocarcinoma. They are cancers in the glandular tissues which produce mucous or digestive juices. Rectal adenocarcinoma starts as a growth or polyp in the mucosal wall that usually increases in size at a later stage.

• Gastrointestinal Stromal Tumors (GIST) - Cancer growth in the digestive systemaffects the nerve cells present in the walls of the organs which are present in the digestive system, including the rectum.

• Carcinoid Tumors - They are slow-growing tumors that can occur in the stomach, small intestine, and parts of the large intestine like the colon and rectum, appendix, etc.

• Lymphoma - Cancers in the lymphatic system or lymph nodes are called lymphoma.

What Are the Stages of Colorectal Cancer?

Depending on the extent of tumor growth in the rectum, rectal cancer is staged as follows-

• Stage 0 - The cancer cells are only seen in the mucosa lining the rectum.

• Stage 1 - The tumor starts to grow into the rectal wall from the mucosal lining.

• Stage 2 - The tumors extend into the tissues surrounding the rectum.

• Stage 3 - The tumor spreads to tissues outside the rectal wall and invades the lymph nodes.

• Stage 4 - The tumor spreads to other tissues and organs.

How Is Rectal Adenocarcinoma Diagnosed?

The following methods can diagnose rectal cancers -

• Blood Tests - Blood test shows an increase in the level of certain enzymes, which indicate cancer.

• Biopsy - A small amount of tissue from the tumor is removed and viewed under the microscope to know the stage and extent of cancer spread.

• Colonoscopy - A long, flexible tube is inserted into the rectum to check for changes in the tissue or mucosa, like polyps, growth, or swollen or inflamed tissues.

• Computed Tomography (CT) Scan - The use of a high amount of radiation and computer technology to get a cross-sectional image of the lower abdomen is produced to evaluate the cancer spread.

• Magnetic Resonance Imaging (MRI) - A three-dimensional image of the affected area is produced using a large magnetic field and computer technology.

• Ultrasound - Using high-frequency sound waves to produce echoes to create images of the internal organs.

• Positron Emission Tomography (PET) - Use of radioactive substances to know any abnormal growth in the tissues or organs.

What Are the Treatment Options for Rectal Adenocarcinoma?

The treatment option for rectal cancer depends on the extent of cancer spread and the stage of cancer. The treatment options include -

• Surgery Resection - Larger rectal cancers are surgically removed along with tumor margins and a part of the rectum to prevent a recurrence.

• Endoscopic Resection - Removes the polyps or the early-stage cancerous cells and tissues from the rectum. It is performed with a long thin tube with a camera and other instruments at the end of the tube. It is inserted through the anal opening. It is a less invasive method for removing cancerous cells.

• Immunotherapy - Using the body’s immune system to fight against cancer cells.

• Chemotherapy - Usage of higher dosages of drugs or a combination of drugs to kill the cancerous cells and reduce the growth of the tumor cells.

• Radiation Therapy - Use of radiation to kill cancer cells. There are two methods by which radiation therapy can be done. External beam radiation uses a machine to deliver the radiation, which is placed outside, and internal beam radiation or brachytherapy which uses radiation seeds that are inserted into the body to deliver the radiation.

• Targeted Therapy - Aims at a specific site to deliver the drug to prevent side effects of the drugs.

• Radiofrequency Ablation - Cancer cells are killed using special probes attached to electrodes.

• Cryosurgery - Abnormal cells are frozen using an instrument to prevent their growth.

What Are the Chemotherapeutic Drugs That Are Used to Treat Rectal Adenocarcinoma?

Chemotherapy can be done in two stages of treatment of rectal cancers. Neoadjuvant chemotherapy is used to shrink the tumor or cancer cells before the surgery for ease of removal of the surgery. Chemotherapy, along with radiation therapy, is sometimes used to shrink the tumor. Then adjuvant chemotherapy is administered after the surgical removal of the tumor. Adjuvant chemotherapy prevents the recurrence of cancer. Sometimes cancer cannot be removed entirely by surgical therapy. In such cases, chemotherapy, immunotherapy, radiation therapy, cryotherapy, and targeted therapy are used to reduce tumor growth and kill cancerous cells. In metastatic or stage 4 rectal adenocarcinoma, chemotherapy is used before and after the surgery. Some of the chemotherapeutic drugs that are used to treat metastatic rectal cancers are-

• Fluorouracil - It is the first line of drug therapy in rectal adenocarcinoma. It is administered by intravenous route. It is contraindicated in patients having bone marrow suppression.

• Oxaliplatin - Oxaliplatin has platinum-containing antineoplastic agents that are used to kill cancer cells. It is administered intravenously.

• Leucovorin - Leucovorin is a folic acid analogue. It helps to protect healthy or normal cells when other drugs like methotrexate kill cancerous cells.

• Capecitabine - Capecitabine stops cancer cell growth.

• Irinotecan - It is a topoisomerase-1 inhibitor that is used as an antineoplastic medication. It stops the growth of cancer cells.

• Cetuximab - It is an anticancer drug that inhibits the growth of cancer cells.

• Bevacizumab - Bevacizumab is administered intravenously, and it is used for treating a variety of cancer. It is also used as first-line drug therapy in colorectal cancer.

• Regorafenib - It is a multi-kinase inhibitor that is taken orally. It kills cancer cells.

• Panitumumab - It is used in patients who have metastatic rectal cancer. It is a monoclonal antibody.

Conclusion:

If the rectal adenocarcinoma is found at an early stage, then the prognosis for the cancer is good. The risk of developing rectal cancer can be reduced by regular exercise, eating more fruits and vegetables, avoiding red and processed meat, quitting smoking, and decreasing alcohol consumption. People with rectal cancer should be supported with nutritional intake, pain management, and mental support.