Standard radiation therapy uses X-rays. X-rays are electromagnetic waves that go through tissue, gradually losing energy as they move along. The highest dose of radiation is deposited about 0.5 centimeters (cm) to 3.5 cm deep in the body. Tumors are often located deeper than this range. This means a higher dose of X-ray radiation often gets delivered to the normal tissue in front of the tumor than to the tumor itself. As the X-rays exit the tumor, they keep depositing radiation in the healthy tissue beyond. For these reasons, X-ray radiation therapy can cause both short- and long-term side effects. Some of these side effects can seriously affect quality of life and health.
Protons are heavy charged particles that can be controlled to release their highest energy at a precise depth in the body. The radiation deposited by a proton beam increases gradually as it moves deeper into the body. Then, it suddenly rises to a peak, known as the Bragg Peak. Your team designs your treatment so the Bragg Peak conforms to your tumor. Right after the peak, the radiation dose falls to zero, sparing normal tissue on the far side of your tumor. Because proton therapy is so precise, your doctors may be able to give you a higher dose of radiation, which can be more effective in some cases.