What to Expect During Radiation Treatment

Radiation treatment must be individualized for each patient depending on the size and location of their cancer. In order to tailor radiation treatment to meet the specific needs of individual patients, the radiation process involves several components, including consultation, simulation, treatment planning, and finally, the actual treatment.


The consultation is an important visit that allows both you and the radiation oncologist to gain more information. During the consultation, the radiation oncologist will obtain a medical history and perform a physical examination. Many patients find it helpful to prepare for the consultation by bringing x-rays, medical records, a list of medications, insurance information, and referral forms.

During the consultation, the radiation oncologist may communicate a great deal of information in a short period of time. You may find it useful to prepare a list of questions prior to the consultation to assure they are all answered. You may also find it beneficial to bring another person to the consultation to help understand the information from the physician.

After the consultation, the radiation oncologist may order additional tests, await results of other pending tests or consultations, or obtain additional records and reports. Multidisciplinary care is increasingly important for optimal cancer care, therefore the radiation oncologist will typically communicate with any other treating physicians to determine the appropriate course of treatment. In addition, the radiation oncologist will likely send a complete report of their evaluation to the referring physician and any other physicians requested by the patient. Once all of the necessary information has been gathered and the treatment team has communicated, a decision may be made to use radiation treatment. At this point, the radiation oncologist will discuss the treatment plan and alternatives with you and will present a consent form for you to sign prior to treatment. It is important to read and understand the consent form prior to signing it.

CT Simulation

After the initial consultation and decision to use radiation treatment, the next session is usually a planning session, which is called a simulation. Simulation is used to determine the radiation treatment fields and most of the treatment planning. Of all the visits to the radiation oncology facility, the simulation session may actually take the most time.

The CT simulator does not deliver radiation treatment, but instead allows the radiation oncologist and technologists to see the area to be treated. Images are obtained and transferred to the planning system where a virtual 3-dimensional image of the patient is created and the treatment delivery plan is developed.

For the simulation session, temporary marks are made on your skin with magic markers to identify the treatment areas. The room is periodically darkened while the treatment fields are being set. Alignment is critical during simulation and is facilitated by lasers mounted on the wall and ceiling. Special individually constructed immobilization devices may be used to help achieve this alignment. While you may see red lines of light, the low energy lasers are for alignment purposes only and you will not feel burning or anything else from the laser light.

Once the aspects of the treatment fields are set, the technologist will take special simulation x-rays representing the treatment fields. In most centers, the patient is given multiple “tattoos,” which mark the treatment fields and replace the marks previously made with magic markers. These tattoos are not elaborate and consist of no more than pinpricks followed by ink, appearing like a small freckle. Tattoos enable the radiation technologists to set up the treatment fields each day with precision, while allowing you to wash and bathe without worrying about obscuring the marks that indicate where treatment will be delivered.

Sometimes several simulation sessions are necessary in order to optimize treatment and are often performed prior to planned “boost” or “reduced field” treatments as part of the overall treatment plan.

Treatment planning

Several steps occur after simulation and prior to treatment; however, you do not need to be present during most of these procedures. The simulation x-ray may be used to design special lead alloy blocks that are used to block normal tissues from the effects of radiation. These lead alloy blocks are placed on a plastic tray and will be attached below the head of the linear accelerator, the machine that emits the radiation, prior to each treatment. These blocks are designed to minimize the amount of radiation that is delivered to normal tissues, while maximizing the dose to the cancer site. You may need to return after simulation and prior to treatment to verify the placement of these blocks and accuracy of the treatment plan.

During treatment planning, the technologists also perform special calculations to help assure that the proper radiation dose will be delivered. Computerized treatment planning may facilitate these calculations. Computers have become extremely sophisticated in planning radiation therapy delivery. Some computers are even capable of extremely complex three-dimensional representation of the treatment area and surrounding normal tissues. If such computerized planning is necessary, the patient may be asked to have a special CT scan (a special type of x-ray device with a donut shaped opening).

It may take several days for treatment planning to be completed after simulation and prior to treatment. After all treatment planning is complete, radiation therapy treatments are ready to begin.

Radiation treatment

Radiation treatment is usually given in another room separate from the simulation room. The treatment plans and treatment fields that result from the simulation session are transferred over to the treatment room, which contains a linear accelerator focused on a patient table similar to the one in the simulation room. The treatment plan is verified and treatment started only after the radiation oncologist and technologists have rechecked the treatment field and calculations, and are thoroughly satisfied with the “setup”.

During radiation treatment, you must lie very still on the treatment table while the radiation beam is targeted to the exact area of the tumor. The machine and treatment table may rotate up to 360 degrees if the treatment requires the radiation to hit the tumor from all angles. The technologists will not be in the room during the treatment, but they will be monitoring the treatment via a video camera and an audio connection with the treatment room. You will not feel the radiation as it is being delivered.

Radiation therapy is generally given once a day, five days a week, usually at the same time each day. Occasionally, treatment is given less frequently or twice a day. The number of treatments depends on multiple factors and varies from 5-10 to 40 or more, which means that treatment may last anywhere from one to eight weeks or more. Radiation treatments are generally given as outpatient treatments and involve relatively little time each day. While the first few visits might last for an hour or more, typically a daily radiation treatment will take about 15-30 minutes in the treatment room and the actual treatment only lasts a few minutes. It is important not to miss treatments. Extending treatments beyond the recommended time period may reduce the chance of controlling the cancer.

The following is a general overview of radiation therapy, covering:
Techniques for Delivering Radiation Therapy
What to Expect during Radiation Treatment
Side Effects of Radiation Therapy
Prevention and Management of Radiation Side Effects
Frequently Asked Questions