Radiation oncology is a medical specialty that in many cases can be the single most effective method to treat gastrointestinal cancer. It may also be combined with surgery and/or chemotherapy to help increase its effectiveness.
Radiation therapy uses various forms of highly manipulated radiation, including high-energy x-rays to kill or shrink cancer cells, while preserving the normal surrounding tissue. It is often an option for someone who has early stage gastrointestinal 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: 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 gastrointestinal cancer 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 is used to treat primary liver cancers, pancreatic cancers, and bile duct cancers with promising long-term results. Since the treatment is so focused on the tumor, the chance of causing complications is minimal, and can be used for those who are not considered surgical candidates.
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 or 3-CRT is given in small radiation doses daily for a period of time and is often referred to as fractionated. In order to make the treatment conform to the tumor’s 3-dimensional shape and have the treatment distributed evenly to the selected tumor and node area, the radiation beam is also highly manipulated to modulate the radiation intensity, which is why it is called intensity-modulated. As a result, the precise therapy minimizes any potential complications.
- For rectal cancers and esophageal cancers, it is more effective when given along with chemotherapy before surgery. It can also be given after surgery for stomach and 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 nala sphincter function rather than having to use a colostomy bag after surgery. Similarly, it can also be the definitive non-surgical therapy of choice for some cancers of the esophagus.
- For patients with pancreatic cancer who are not candidates for Whipple surgery, IMRT or SBRT may be an option. IMRT or SBRT can treat the tumor with very high radiation doses in combination with a chemotherapy pill. These treatments offer patients hope that their local disease can be controlled, where previously, there weren’t any feasible options.
Brachytherapy/ “Liquid” Radioisotope Therapy
Radioisotopes, delivered to the tumor through the patient’s blood vessels, are another effective modality in the treatment of selected gastrointestinal tumors.
- Yttrium-90 (Y-90) is used to treat both primary liver cancers and cancers that have spread (metastasized) to the liver. In this technique, known as arterial radioembolization, Y-90 is delivered to the tumor through the liver arteries in the form of microspheres. The radiation then gets deposited near the cancer cells and kills them in a highly effective and safe manner.
- Another radioisotope therapy, known as Lutathera, uses Lutetium-177 in the form of a radiolabeled cell-targeted protein, which is injected into the patient’s bloodstream. This is used to treat neuroendocrine tumors of the stomach, pancreas, and intestinal tract.