Each treatment session lasts approximately 30 minutes, although this may vary depending on the tumor’s location and delivery plan. Most of the session is spent ensuring you are in the proper position before beam delivery. The actual time the beam is on is just a few minutes. The procedure is not painful, although some patients may experience discomfort from lying on the table and maintaining their body in the necessary position. Depending on the patient, proton therapy may last for several weeks. Usually patients are treated five days a week during that time and can expect to spend about an hour each day at the Cancer Center.