High-dose-rate remote afterloaders for intraoperatlve radiation therapy

AORN Journal,  Nov, 2007  by Song Gao,  Marc E. Delclos,  Lyvia C. Tomas,  Christopher H. Crane,  Sam Beddar

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Intraoperative radiation therapy (IORT) is single-fraction, external beam radiation treatment or high-dose-rate (HDR) brachytherapy that is administered at the time of surgery. In IORT treatment, a large-fraction dose of radiation is focused on a surgically exposed tumor or tumor bed while the surrounding healthy organs and tissues are either shielded by lead shields or displaced from the radiation field by gauze packing or retractors. The primary advantage of IORT is its ability to deliver a higher radiation dose to a tumor or tumor bed while minimizing radiation exposure of normal tissues.

In general, IORT is effective for tumors that might not be resectable or for which resection might be difficult, thus leaving close or positive margins. Specifically, IORT has been used to treat advanced or recurrent colorectal, gynecologic, genitourinary, pancreatic, and gastrointestinal cancers as well as primary, locally advanced cancers that have a low likelihood of cure with surgery alone. Intraoperative radiation therapy also is used as primary treatment for

* soft tissue sarcomas,

* retroperitoneal sarcomas,

* cancers in pediatric patients,

* head and neck cancers, and

* breast cancer.

It also is used for palliative treatment of hepatic colorectal metastases and cancers that recur in lymph nodes. (1,2)

Intraoperative radiation therapy can be delivered in several different ways. One of the most commonly used treatment methods is intraoperative electron beam radiation therapy (IOERT), which uses accelerator-produced electron beams. (3-6) Another method is high-dose-rate intraoperative radiation therapy (HDR-IORT) in which radioactive sources are used. (7-10)

A linear accelerator and shielded OR are needed for IOERT. For the HDR-IORT technique, the HDR afterloader unit is less expensive, but an existing shielded OR still is needed or the OR must be reconstructed with shields, which adds to costs. (10,11)

The overall concepts and treatment outcomes of IOERT and HDR-IORT are almost the same. A nonflexible, rigid cone applicator is used in the IOERT technique, however, so this technique is less feasible in sites containing narrow cavities such as

* the paranasal sinuses,

* sites deep in the inferior pelvis,

* subpubic locations,

* some lateral pelvic side walls,

* the anterior chest wall,

* the anterior abdominal walls, and

* the subdiaphragmatic area. (5,6,12)

Because HDR-IORT uses various sizes of flexible Harrison-Anderson-Mick (HAM) applicators, this treatment can be used for sites that are inaccessible with the IOERT technique.

Although the techniques in these two treatment methods are different, the methods are similar in that they supply high, effective radiation doses to the high-risk area while appropriate surgical procedures are used to protect adjacent sensitive structures. This article focuses specifically on HDR-IORT by reviewing the roles of IORT team members, discussing needed equipment and supplies, describing quality assurance processes, explaining the HDR-IORT treatment delivery procedure, and reviewing the post-treatment phase.

ROLES OF IORT TEAM MEMBERS

This multidisciplinary approach to cancer treatment combines surgery and HDR-IORT; consequently, staff members from both the Surgery and Radiation Oncology Departments are involved. The team consists of the surgeon, radiation oncologist, medical physicist, anesthesia care providers, and perioperative nursing staff members. Close collaboration between these members is essential to successfully implement an HDR-IORT program. Each team member, therefore, should clearly understand his or her own responsibilities and should be knowledgeable about the other practitioners' roles. (13)

SURGEON, In addition to performing the conventional surgical procedure, the surgeon works closely with the radiation oncologist to determine the size of the tumor or tumor bed to be treated. The surgeon is responsible for the entire procedure.

RADIATION ONCOLOGIST. During preoperative consultation, the radiation oncologist evaluates the patient and, jointly with the surgeon, determines if the patient is an appropriate candidate for the IORT procedure. During surgery, the radiation oncologist is responsible for determining the size of the radiation area, the appropriate applicator size to use, and the prescription of radiation doses. After the radiation oncologist places the applicator into the patient's cavity or onto the tumor bed, he or she connects the transfer tubes to the HAM applicator.

MEDICAL PHYSICIST. The responsibilities of the medical physicist include quality assurance (QA) of the HDR afterloader machine, the treatment planning system, and the remote monitoring system in the OR. The medical physicist generates the treatment plan, sets up the HDR afterloader machine for treatment, performs a radiation survey of the patient before and after treatment, delivers the radiation treatment, and documents the HDR-IORT procedure. The physicist also is responsible for ensuring that radiation emergency procedures are implemented if needed. The medical physicist visually inspect the equipment before initial use, and after completion of the surgical procedure, sends nondisposable supplies to the Central Processing Department.