Today’s radiation therapy options offer patients more colorectal cancer treatments than ever before.
Colorectal Cancer Overview
The colon and rectum are part of your digestive system. The colon is the first four to five feet of the large intestine and the rectum is the last five inches. Colorectal cancer typically grows slowly over a period of years, beginning as a polyp or small growth of tissue. It is the fourth most common cancer in both men and women after skin, prostate or breast and lung, with about 143,000 new diagnoses estimated for 2012 in the United States.
Risk factors for colorectal cancer include family history of the disease, polyps or growths on the inner wall of the colon or rectum, diets high in fat and low in fiber, ulcerative colitis or Crohn’s disease (both causing inflammation of the colon) and smoking. Common late stage symptoms include diarrhea, constipation, unexpected weight loss, nausea or vomiting, gas cramps, fatigue or blood in your stool.
Colorectal Cancer Treatment Options
Both colon and rectal cancers can be treated with surgery, chemotherapy, radiation therapy and targeted therapy. Oncologists may prescribe a combination of these colorectal cancer treatments depending on the stage and location of your disease.
Surgery is the primary treatment option for both colon and rectal cancer. In very early stage cases of colon cancer, polyps may be removed with the aid of a flexible colonoscope, which is inserted through the anus, avoiding cutting through the abdomen. Colonoscopy can also be used to remove small malignant polyps form the upper rectum. Small tumors in the lower rectum can be directly removed through the anus without a colonoscope. Early stage tumors can also be removed laparoscopically with three to four small incisions through the abdomen.
For colon cancer that is further advanced, your oncologist may recommend open surgery. In a colectomy, the surgeon removes the tumor along with a section of the colon on each side of it in case it contains any additional cancerous cells. Nearby lymph nodes are removed. The healthy colon ends are then sewn together. If reconnection is not immediately possible, your surgeon leaves an opening in the wall of the abdomen and connects the upper end of the intestine to a bag and closes the other end. This is called a colostomy and is usually a temporary situation. A permanent colostomy is only needed in one out of eight rectal cancer patients.
Your Medical Oncologist or Surgical Oncologist may recommend one of three different forms of chemotherapy. Neo-adjuvant or primary systemic chemotherapy is used before radiation or surgery to help shrink the tumor. Adjuvant chemotherapy is used after radiation or surgery to destroy any remaining cancer cells. Systemic chemotherapy circulates throughout the body via the bloodstream when the cancer is metastatic.
Tumors need new blood vessels for nourishment so that they continue to grow. Targeted therapy interferes with the blood supply, ensuring the colorectal cancer cells do not get the nutrition that they need and can no longer grow.
Colorectal Cancer Radiation Therapy
Radiation therapy, which uses high-energy x-rays to shrink and destroy tumors cells, is used in the treatment of both colon and rectal cancers. If you have colon cancer, radiation therapy may be used after surgery to destroy any remaining cancerous cells that may be left behind. In cases of rectal cancer, radiation therapy is typically administered before or after surgery and often in combination with chemotherapy.
Colorectal Cancer Radiation Therapy
There are two fundamental types of colorectal cancer radiation therapy. EBRT or External Beam Radiation Therapy delivers radiation from outside the body and IRT or Internal Radiation Therapy, also known as Brachytherapy, delivers radiation from a source implanted in the body near or at the tumor site. Which one is best suited for your particular situation depends on the size, location and stage of the tumor or tumors.
3D-Conformal Radiation Therapy and Intensity-Modulated Radiation Therapy (IMRT)
3D-Conformal Radiation Therapy and Intensity-Modulated Radiation Therapy (IMRT) are two forms of External Beam Radiation Therapy. During 3D-Conformal treatments, a device called a "multi-leaf collimator" will shape the individual radiation beams to “conform” to the shape of your tumor according to the data and instructions it receives from the system computer. IMRT uses thousands of radiation “beamlets” from many different angles to deliver a single dose of radiation. The intensity of the “beamlets” can change during the treatment session to modulate the dose, so that the tumor receives a very precise high dose of radiation, while minimizing damage to surrounding, normal tissue.
Before each session, a Radiation Therapist will carefully position you on the treatment table using a body immobilizer for precise body placement. Image guidance will be used to confirm the location of the tumor before the therapy begins. During your treatment sessions, the radiation delivery system will revolve around you, delivering the radiation according to the plan set by your Radiation Oncologist. Each treatment session lasts from 10 to 30 minutes. Typically, you will be scheduled for five sessions a week for four to six weeks. The sessions are pain-free and require no sedation so you can return to your normal activities right away.
High Dose-Rate (HDR) Brachytherapy
Two methods of delivering Internally Radiation Therapy for colorectal cancer are Interstitial and Endocavitary High Dose-Rate (HDR) Brachytherapy. With Interstitial HDR Brachytherapy, slim plastic tubes called catheters are passed through the perineal tissues to access the tumor site and deliver radiation from within the body. In Endocavitary HDR Brachytherapy the delivery device is inserted through the anus into the rectum. During treatment, a computer-controlled machine sends tiny radioactive pellets into each catheter to deliver the radiation at multiple depths and varying times. The overall treatment time at the tumor site is 10 to 20 minutes. Your colorectal cancer treatment plan may require one session or multiple sessions. The catheters are then removed so that no radioactive material remains in the body. You are free to resume normal activity right after each treatment.