Protecting the Patient during Radiation Therapy
By Stephanie Deming
Delivering radiation therapy effectively and safely requires a team effort. Cooperation is needed between skilled physicians, who prescribe the best treatment, and a host of other team members, who make sure that treatment is implemented correctly and that quality and safety checks are done meticulously.
According to Thomas A. Buchholz, M.D., professor in and chair of the Department of Radiation Oncology at The University of Texas MD Anderson Cancer Center, “You can be the greatest doctor in the world, but if you don’t have the greatest team, things can go wrong.”
Quality through teamwork
In addition to radiation oncologists, the radiation therapy team includes radiation physicists, who ensure that the treatment machines and treatment planning computers are working correctly; medical dosimetrists, who help translate the radiation oncologist’s prescription into a detailed treatment plan; and radiation therapists, who position patients on the treatment machines and deliver the radiation treatment.
The team members work together to develop and deliver a customized treatment plan for each patient. For radiation therapy to be successful, the treatment plan must strike an appropriate balance between maximizing the number of tumor cells killed and minimizing damage to normal tissue. However, careful treatment planning is not sufficient—it is also critical that the treatment planning computers and treatment machines function correctly so that patients receive the planned radiation therapy.
According to Dr. Buchholz, the incidence of medical errors with radiation has been very low nationwide. “However, if something goes wrong, it can be devastating,” he said, adding that every member of the radiation therapy team must be aware of the potentially serious consequences of errors. “We have teamwork to assure that everything is done perfectly,” said Dr. Buchholz. “Quality in radiation therapy is paramount. Radiation oncology is a specialty that prides itself on taking these quality steps, and we at MD Anderson have very much been part of that for decades.”
Radiological Physics Center
For more than 40 years, MD Anderson’s Radiological Physics Center (RPC) has been overseeing the quality of all radiation therapy delivered in U.S. National Cancer Institute (NCI)–sponsored clinical trials, including trials conducted at MD Anderson. According to Geoffrey Ibbott, Ph.D., director of the RPC, “We started in 1968, when the NCI decided that there needed to be a quality assurance mechanism to make sure that patients who were treated with radiation in their clinical trials were getting the correct radiation doses.” Today, the RPC works with approximately 1,800 institutions, including about 200 outside the United States.
The RPC runs four formal programs for institutions that are members of the cooperative study groups that participate in NCI-sponsored clinical trials:
Credentialing program. Credentialing is done to ensure that institutions wishing to participate in specific NCI-sponsored trials involving advanced radiation therapy techniques can treat patients according to the protocol’s specifications. The RPC uses a number of credentialing approaches. The simplest is to ask physicians at the participating institution to fill out a questionnaire to demonstrate their understanding of the protocol. A more in-depth approach is to mail the institution a set of computed tomography scans for a hypothetical patient, showing the tumor and surrounding normal tissues. Using the information from these scans and following the treatment protocol, the institution designs an appropriate treatment plan, which is then checked by the RPC. For the most complicated trials, the RPC mails the institution an anthropomorphic phantom—a model of part of the human body, such as the pelvis, thorax, or head and neck—that can be placed on a treatment machine and irradiated. Phantoms contain sensors, called thermoluminescent dosimeters (TLDs), that measure the amount of radiation received. The institution creates a treatment plan for the phantom according to the protocol specifications, irradiates the phantom, and mails the phantom back to the RPC, which analyzes the TLDs to determine whether radiation was delivered correctly.
Annual treatment machine audits. Every year, the RPC checks all the treatment machines at the centers participating in NCI-sponsored clinical trials to make sure that the radiation beams are calibrated correctly—in other words, to make sure that the amount of radiation the institution thinks is being delivered by the machine is what is actually being delivered. The RPC mails TLDs to the participating institutions, which then position and irradiate the TLDs as instructed and mail them back to the RPC for analysis. According to Dr. Ibbott, about 15% of the institutions checked each year have at least one beam whose delivered dose disagrees with the expected value.
Site visits. Physicists from the RPC travel to 30–40 institutions a year for on-site evaluations. During the day, while patients are being treated, the RPC physicists review the institution’s quality assurance programs and check some of its patient treatment records to make sure that the institution is consistent in the way it applies its calculations. Each evening, after patient treatments are finished, the RPC physicists spend 4–6 hours checking the treatment machines. At about 70% of institutions, RPC staff find a discrepancy in the treatment machine measurements during the site visit. These discrepancies are generally minor but occasionally are large enough to affect the quality of treatment. “Institutions usually respond very quickly and are very concerned about our findings,” said Dr. Ibbott.
Audits of treatment records. Finally, the RPC reviews patient treatment records for some of the cooperative groups that take part in NCI-sponsored clinical trials to make sure that institutions are accurately reporting how they treated patients and accurately delivering the intended doses. These audits turn up documentation errors (e.g., someone writes “5,400 cGy” instead of “4,500 cGy”) in about 25% of cases and dosing errors in about 10% of cases.
When RPC staff find problems at an institution, they notify the radiation physicist and, if the problem may have resulted in serious consequences for patients, the radiation oncologist. The cooperative study groups—and, through them, the NCI—are also notified of the findings. In the case of major problems, which fortunately are extremely rare, membership in a study group may actually be revoked, meaning that an institution can no longer participate in NCI-sponsored trials.
In addition to these formal programs, the RPC offers informal assistance to institutions participating in NCI-sponsored clinical trials. For example, radiation physicists at other institutions may ask the RPC to double-check complicated treatment plans. “Often, they ask us if we’ll send an extra set of TLDs even though it’s not the right time of the year, but they have a new machine that they want to have checked independently before they start treating patients,” said Dr. Ibbott. “We strongly encourage that.”
To help institutions that don’t participate in NCI-sponsored trials, the RPC has a sister program, Radiation Dosimetry Services (RDS), which is also based at MD Anderson and can help these institutions for a modest fee. According to Dr. Ibbott, “Nearly 1,000 radiation therapy departments took advantage of that service last year. There is some overlap between the two groups of customers—we have a number of clinical trial participants who think that TLDs once a year isn’t often enough, so they’ll buy another set at the midpoint from RDS. And then there is a completely separate set of customers who just take advantage of RDS’s service.”
MD Anderson also serves as a national resource for quality in radiation therapy through a number of educational programs. Twice a year, MD Anderson offers “Introduction to Physics and Administrative Aspects of Radiation Oncology for Administrative Staff,” a 2.5-day course that draws attendees from all over the country who want to learn how to establish and maintain a high-quality radiation treatment facility. MD Anderson’s School of Health Professions offers bachelor of science degrees in medical dosimetry and radiation therapy; the most recent graduating class included 35 students in those programs. MD Anderson’s radiation physics faculty also teach 1-and 2-week Continuing Medical Education short courses on medical dosimetry throughout the year. The RPC plays a major educational role as well: the RPC trains graduate students in radiation physics, and in fact most of the anthropomorphic phantoms that the RPC uses were designed by radiation physics graduate students during their training.
“We have a very conservative stance on quality,” said Dr. Buchholz, “and we’re educating people on how to do this right.”
For more information about the Radiological Physics Center or Radiation Dosimetry Services, please call 713-745-8999.
Other articles in OncoLog, October 2010 issue: