Lee crunches number to battle prostate cancer

By Cathy Byrd

A merger of advanced mathematical techniques with cutting-edge computer technology may give doctors a powerful new weapon in the battle against prostate cancer.

Eva Lee, a scientist at Emory and the Georgia Institute of Technology, has developed a computerized expert system that would help radiation oncologists optimize placement of radioactive “seeds” for prostate brachy-therapy, a nonsurgical treatment that has been gaining popularity in recent years.

Beyond providing treatment more precisely tailored to each patient, the system targets escalated doses of radiation at tumor pockets and accounts for changes that occur in prostate volume during treatment. The system has the potential to improve tumor control and reduce uncomfortable side effects.

As a student, Lee struggled to choose between interests in both medicine and mathematics. Ultimately, her mathematical aptitude won out, but her interest in medicine drew her to look for applications of advanced techniques.

“The intricacy and complexity in radiotherapy treatment planning requires sophisticated mathematical modeling and advanced computational optimization techniques,” said Lee, an assistant professor of radiation oncology in the School of Medicine and of industrial and systems engineering at Georgia Tech. “This is a way I can contribute to the medical field even though I am not a physician. It’s a good collaboration.”

For the cost-conscious medical industry, the automated system dramatically reduces the time required to design radioactive seed treatment, allowing optimized plans to be created in minutes—and revised as the procedure continues.

“The system allows us to effectively manipulate the large number of variables involved, something that is far too complex for even the best human experts,” Lee said. “We can deliver better precision and create the optimal plan for each patient. This system should help cut the recurrence rate for prostate cancer and reduce toxicity to healthy tissue.”

Lee presented details of her treatment planning system recently at the annual meeting of the American Association for the Advancement of Science in San Francisco.

Prostate brachytherapy involves implantation of tiny radioactive seeds in the cancerous prostate. Continuous radiation from the seeds kills the cancer cells, allowing patients to avoid surgery that can produce such complications as incontinence and impotence.

To successfully treat the cancer, however, physicians must carefully design the radiation dose, balancing the high radiation levels needed to eradicate the cancer against the need to protect nearby tissue, including the urethra and rectum.

Further complicating treatment is the edema that occurs as needles are inserted to place the seeds.

Resulting changes in prostate volume can mean delivering too little radiation at the beginning of treatment and too much as the swelling subsides.

“It is very complicated to produce a successful implant,” explained Lee, who collaborated on the work with Macro Zaider, professor and head of brachy-therapy physics at Sloan Kettering in New York. “Proper coverage of the entire prostate is very important, but it can be very difficult to carry out the plan. The seeds cannot always be placed in the location you want, so you must be able to compensate for that. Our system allows real-time planning, and corrections can be made as you proceed.”

Ultrasound images of the patient’s prostate are used by the system to help determine optimal radioactive seed placement based on prostate volume, location of tumor pockets, radioactivity levels of the seeds, location of the urethra (which passes through the prostate) and regions of the organ that may be unreachable by placement needles.

Woven into the system are a dose-calculation engine, a modeling module, an optimization engine and a graphical evaluation tool.

“To the physician, this will be a black box,” Lee said. “They will not need to know what is going on with the mathematics. All they will have to do is tell the system what they want in the plan.”

Though the expert system is ready for commercialization, it will have to receive FDA approval before being made available to treatment centers.