Radiation oncology is a medical specialty that in many cases can be the single most effective method to treat colorectal cancers. It may also be combined with surgery and/or chemotherapy to help increase its effectiveness.
Radiation therapy uses high-energy x-rays and other forms of precisely targeted radiation, to kill cancer cells, while preserving the normal surrounding tissue. It is often an option for someone who has early-stage colorectal cancer, as well as for more advanced cancers. In the case where cancer has spread, radiation therapy can also help to relieve symptoms.
Radiation oncology offers different modalities of treatment, including Stereotactic Body Radiation Therapy (SBRT), fractionated Intensity-Modulated RadioTherapy (IMRT) or 3-Dimentional Conformal RadioTherapy (3DCRT), and brachytherapy with radioisotopes. A radiation oncologist who specializes in these types of cancers (colon, rectal, small intestinal and anal) evaluates each patient to determine the best course of treatment for the individual.
Stereotactic Body Radiation Therapy (SBRT)
This treatment uses a highly focused sharp radiation beam that targets only the tumor with increased accuracy within one millimeter. Therefore, an intense dose is given to the tumor itself in 2 to 5 sessions. It is also known as Stereotactic Radiosurgery (SRS) when it is given in a single session.
SBRT and SRS are completely noninvasive treatments and performed while the person is awake. SBRT can also be highly effective in treating isolated cancer recurrences or limited number of metastases, called “oligometastatic” disease.
Intensity-Modulated RadioTherapy (IMRT) or 3-Dimensional Conformal RadioTherapy (3DCRT)
This treatment is used for a number of gastrointestinal cancers, often combined with chemotherapy. The IMRT and 3-CRT are both given in small radiation doses daily for a period of several and are often referred to as "fractionated radiotherapy." In order to make the treatment conform to the tumor’s 3-dimensional shape and have the radiation dose distributed evenly to the selected tumor and node area, the radiation beam can also be highly manipulated to modulate the radiation intensity. The precise therapy avoids normal organs and minimizes any potential complications. This approach is known as intensity-modulated radiation therapy.
- For rectal cancers, this treatment is more effective when given along with chemotherapy before surgery. It can also be given after surgery for colorectal cancers when there are cancer cells left behind (“positive margins”).
- For anal cancers, the radiotherapy, along with chemotherapy, is used as the primary treatment instead of surgery, preserving the anal sphincter function rather than having to use a colostomy bag after surgery.