Radiation Therapy for Colorectal Cancer
Written by: Dr. Prabhu
Colorectal cancer is the third most commonly diagnosed cancer in the United States. The large intestine is made up of the colon and the rectum. Approximately 28% of colorectal cancers arise in the rectum, accounting for 39,870 new cases of rectal cancer diagnosed in the United States in 2011.
The large intestine is one of the few body sites with an effective and widely available screening procedure to detect cancers at an earlier stage. Screening colonoscopy is generally recommended starting at age 50 with repeat procedures every 5 to 10 years depending on the findings at the time of colonoscopy. Specific recommendations for when to start colonoscopy and how often to have them depend on several factors such as age, family history, risk factors, and findings from colonoscopy procedures. Your primary care physician and gastroenterologist will be able to provide recommendations about screening colonoscopy specifically for you.
Cancers of the colon and rectum can be found on screening colonoscopy or can present with symptoms, such as rectal bleeding, weight loss, change in stool patterns or shape, or anemia (low blood count). Staging of these tumors involves looking at how deep the tumor extends into the colon or rectal wall and the whether the cancer has spread to nearby lymph nodes. This is typically assessed using imaging (such as CT or MRI) and/or ultrasound.
The management of these cancers can include surgery, chemotherapy, and radiation in different combinations. A team approach with your surgeon, medical oncologist, and radiation oncologist working together is key in achieving the best results with as little toxicity as possible.
Early stage cancers of the colon and rectum can sometimes be effectively treated with surgery alone. Treatment recommendations are different for higher stage cancers depending on location. Cancers of the colon that are higher stage are usually treated with surgery followed by chemotherapy. Higher stage cancers of the rectum are generally treated with radiation therapy given with chemotherapy before surgery, followed by additional chemotherapy given after surgery.
Radiation therapy for rectal cancer treats the rectal cancer itself and the surrounding “at risk” lymph node regions in the pelvis. The treatments are given daily, Monday through Friday, for approximately 5 and a half weeks. Surgery follows approximately 4 – 6 weeks after the completion of radiation therapy.
Your radiation oncologist will be able to give you more information about the specific treatment plan for you . He or she will work closely with your medical oncologist and surgeon to ensure that the best possible care is provided with the least amount of side effects possible.