Leveling the playing field

If clinical trials are the best hope for advancing cancer treatment and saving or extending lives, then the stronger the clinical trial, the more grounded the hope.

Day after day, from all over the United States and the world, boxes of precious cargo arrive at the unassuming Radiological Physics Center (RPC) in the Department of Radiation Physics on the outskirts of the country’s largest medical center.

Inside the boxes are tiny opaque pellets called thermoluminescent dosimeters (TLDs) that measure a dose of radiation. Some of the TLDs are encased in anthropomorphic phantoms, back from an important mission: to gauge not only whether radiation machines used in cooperative clinical trials have been correctly calibrated, but also whether the participating institution can deliver a dose distribution as intended.

The 30 employees of the RPC — who include medical physicists and technologists, dosimetrists, computer systems analysts, graduate students, administrative support staff and visiting experts — know that their work affects patients far beyond their home base at MD Anderson.

Their efforts and expertise have, in fact, helped ensure the strength and applicability of clinical trial results for more than four decades, affecting patients all over the country and the world.

Impressive power demands strict monitoring

Since 1968, the National Cancer Institute has trusted the RPC to make sure the institutions that participate — or wish to participate — in clinical trials have the necessary radiation therapy equipment, personnel and procedures.

The long-running grant acknowledges the impressive power of radiation therapy techniques and the need to measure radiation output with corresponding precision to ensure patient safety.

Monitoring the machines at so many locations may seem a daunting task, but Geoffrey Ibbott, Ph.D., professor in the Department of Radiation Physics, and his team have several ways of accomplishing it. Their first line of duty involves sending out hundreds of boxes of TLDs a month.

The institutions position the TLDs under their radiation therapy machines, perform a set of prescribed tests, then pack them up and send them back. Once returned to Ibbott’s team, they’re tested to see if the output falls within accepted parameters.

If problems are found, the RPC has other ways of figuring out what’s wrong, Ibbott says. “We do onsite dosimetry reviews. We visit about 30 institutions a year. And we do record reviews for quality assurance.”

Because the goal is to help an institution resolve the problem, RPC staffers act as detectives to figure out why the machine isn’t calibrated correctly.

Between 1970 and 1980, the compliance rate for beam calibration among these institutions increased from about 70% to 90%. But as techniques have become more and more complex, discrepancies in other components of the treatment are more prevalent.

Mastery honed by research, experience

How do they keep up with the constantly evolving techniques to evaluate them?

“We read journals. We stay abreast of clinical activities, and we collaborate with the 10 or 11 groups that conduct clinical trials. We all stay up to date — we have to,” Ibbott says. “By monitoring in a number of ways and by knowing the processes inside and out, we try to avoid big problems that might occur because of an accumulation of small errors.”

Beyond the benefit to clinical trials, Ibbott knows that RPC employees help safeguard the treatment of all patients who receive radiation therapy as part of their cancer treatment.

“It’s a lot of responsibility, and we’re very aware of it,” Ibbott says. “We spend a lot of time making sure we find errors and correct them.”