Pencil beam proton therapy: What to know

Pencil beam scanning, also called scanning beam, is the most advanced type of proton therapy. Only a few millimeters wide (the width of a pencil), pencil beam scanning is used to treat complex cancers with unparalleled precision. It’s used to treat head and neck, gynecologic, lung, prostate, breast, brain, liver, lymphoma, sarcoma and tumors in children. Proton therapy may also be used for tumors that recur in areas that have previously been treated with standard radiation therapy. “Pencil beam scanning is an intricate, personalized approach to proton therapy,” says Steven Frank, M.D., medical director of the MD Anderson Proton Therapy Center. “No two tumors are identical, so we customize the proton beam to target a patient’s unique tumor location, size and shape.” Pencil beam scanning builds on proton therapy’s success Pioneered at MD Anderson, pencil beam scanning uses a tumor’s location, shape and size to create a customized pattern of protons to precisely treat the tumor while avoiding nearby healthy tissue. With standard radiation therapy, energized particles called photons are used to destroy cancer cells. But surrounding normal tissues are also exposed to the radiation, increasing the risk of side effects. By using a different type of energy called protons, proton therapy is able treat the tumor while minimizing radiation exposure to the rest of the body. “There’s a low entrance dose when the beam enters the body and a low exit dose once the radiation has been deposited into the tumor,” says Albert Koong, M.D., Ph.D. However, pencil beam scanning takes the precision of proton therapy even further by shaping the area being treated, called the field, to...