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Questions are answered about Radiation Therapy for Pituitary Adenomas. This section also offers explanations regarding treatment, effects and recovery from radiation therapy.
Preface: If radiation therapy has been recommended to you for treatment of a pituitary adenoma, you have probably already considered and/or tried other types of medical therapies or surgery with inadequate results. Remember, a tumor is a tissue mass, typically not normally present in the body. It can be either benign or cancerous. Pituitary adenomas are a type of benign tumor with many subtypes. Radiation therapy can be a very effective treatment for both hormonally active (such as Cushing’s disease or acromegaly) and inactive (“non-functioning”) pituitary adenomas. The decision to use radiation therapy should be balanced with an understanding of its associated risks. Treatment recommendations are tailored by specific type of pituitary tumor, size, boundaries of the tumor if large, response to initial therapies and other patient health concerns. Compiled here are common questions raised by patients with pituitary adenomas regarding radiation therapy.
Radiation therapy comes in many forms but all types of radiation therapy involve a planning process referred to as the “simulation.” The first part of the simulation is to establish a reproducible set up position that you will assume for each treatment. A mask or frame for your head will be custom made such that you will be able to get into the same position with great accuracy for each radiation treatment. The simulation session usually takes about one hour to complete and most commonly involves a CT scan or X-ray pictures of your head in the treatment position. These pictures are used to design the appropriate radiation beams for your treatment.
Daily treatments are usually about 10-15 minutes within the treatment room with most of that time allotted to setting you up accurately. Treatments are delivered by radiation therapists, highly skilled technologists who currently go through four years of training to obtain their radiation therapist license. The radiation beams are usually on for one to two minutes per day once the patient is in the correct position. Treatments are usually given daily, Monday through Friday, for five treatments per week. The total number of treatments most commonly ranges between 25-30 treatments, meaning a total of five to six weeks. Most centers have some amount of waiting time preceding treatment so it is best to be flexible and expect up to an hour’s time with each daily visit until you are familiar with your treatment center’s pattern.
Stereotactic radiosurgery (SRS) is a type of radiation therapy that delivers high dose radiation in a single treatment. The most commonly used form of SRS for pituitary tumors is known as “gamma-knife.” At Massachusetts General Hospital, SRS is given as either “proton beam” or “photon beam” radiation. SRS is a convenient treatment because it takes only one day and is frequently associated with a quicker response than the protracted alternative of daily radiation treatments over several weeks. However, SRS can also be associated with increased risk of side effects, such as injury to the nerves which transmit vision. Risk of injuries varies depending upon the nature of your tumor. Details of the size, shape and location of your pituitary adenoma determine which form of radiation delivery is best suited for you. If SRS has been recommended, then the risk of serious injury is felt to be very low.
Because a high radiation dose will be given at one setting, the highest precision is very important with SRS. A special head frame is used to keep your head still during treatment. Most people tolerate this treatment very well.
Radiation can decrease levels of one or more hormones produced by the pituitary gland. The risk of hormone deficiencies is very low immediately following radiation, but gradually increases over the years. Some patients develop hormone deficiencies a year or two after radiation, while others may have normal levels for 10 or 20 years and then develop low hormone levels. These deficiencies are treatable with replacement hormones. Because of this, it is important that you continue under close care with your endocrinologist. It is uncommon to develop injury to the brain or vision and even more rare to develop a radiation-induced tumor. All of these unlikely but serious events typically require years to occur.
At Mass General, proton radiation is also available and offers unique advantages to photon radiation in some conditions. Some common inquires about this resource are addressed below.
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