Robot and Radiation Offer New Alternative for Some Duke Cancer Patients
A robot is lending a "hand" to doctors at the Duke Comprehensive Cancer Center to deliver high-dose radiation therapy to patients during the middle of their surgeries.
The small boxlike device has been used for the past year to provide patients with a treatment known as intraoperative radiotherapy. The computer-controlled robot delivers a rice grain-sized bit of radioactive material to the site of a tumor while a patient is being operated on, helping reduce damage to normal tissue and organs. While the surgery occurs in a traditional operating room at Duke University Hospital, the radiotherapy is delivered in an adjacent specially built steel- and lead-lined room.
Duke is the only cancer center in the Southeast and one of only a handful of centers in the country offering the treatment. The nearest centers with similar technology are in Houston, New York City and Columbus, Ohio. A few other centers provide lower-dose intraoperative radiotherapy using a different radioactive material.
"Intraoperative radiotherapy provides a way to treat the tumor bed while minimizing harm to normal tissues," says Dr. Catherine Lee, a radiation oncologist at Duke University Medical Center. "For a select group of patients intraoperative radiotherapy is an important option to have."
In particular, certain patients with abdominal cancers might be candidates for this treatment, especially those with locally advanced rectal cancer, another cancer known as retroperitoneal sarcoma, or recurrent rectal or gynecologic cancers that haven't spread. The technique can only be used on patients whose tumors can be surgically removed.
"Generally these are people for whom intraoperative radiotherapy is part of a planned, multi-modality attack on the tumor," explains Dr. Edward Halperin, professor and chair of radiation oncology at Duke. "They are people in whom we use a combination of external beam radiation, chemotherapy, intraoperative radiotherapy and surgical resection."
In late April, Halperin and Dr. Greg Hulka, chief of pediatric head and neck surgery in otolaryngology, used intraoperative radiotherapy to treat a 5-year-old with a tumor in the nasal passages, the first use of the technique for a pediatric case at Duke.
Compared to other radiotherapy techniques, intraoperative radiotherapy permits higher intensity irradiation of areas that might harbor leftover cancer cells, since normal critical tissues can be moved out of the way or protected from damage.
With conventional external beam radiotherapy, a beam of ionizing radiation is aimed at the tumor, but necessarily passes through the skin and interceding normal tissues before hitting the cancerous area. While irradiation of normal tissues can be minimized by using careful treatment planning, it can never be completely eliminated when an external beam is used.
"With this procedure, we're able to avoid other tissues, the treatment is done at the time of the operation, and it's relatively quick," Halperin said.
Surgery is begun in a standard operating room adjacent to a small lead- and steel-lined room specially built for performing intraoperative radiotherapy. Once the tumor has been removed, the patient is wheeled into the treatment room, and channels in the robot are connected by narrow, flexible tubes to an "applicator" that is nestled against the area to be treated. When ready, the lead doors are closed and the robot goes through a series of checks to make sure all will go as planned.
During surgery, the radiation plan for the patient is finalized and stored on the laptop computer that controls the robot. Because the radioactive source, a grain of rice-sized bit of iridium-192, deposits most of its cell-killing energy within an inch of its location, the treatment plan is essentially a two-dimensional grid of pre-determined stopping points that will deliver the prescribed dose of radiation to areas where cancer cells might be hiding.
The radiation oncology, surgical and anesthesiology teams can adjust medications and anesthesia as needed as they wait outside the treatment room, carefully monitoring the robot and patient using adjustable video cameras and closed circuit televisions. If need be, the treatment program can be stopped to provide emergency medical treatment.
"Essentially in the time it takes to open the heavy door to the treatment room, the source will be back in the robot, and we can get in there to help the patient," says Halperin.
After the designated area has been treated and the source is safely back inside the robot, the doors are opened, and the patient is returned to the operating room to finish surgery. The whole process adds roughly two hours to the time patients spend under anesthesia.
The vast majority of cancer patients requiring radiation still will be treated with external beam radiotherapy instead of intraoperative radiotherapy, Halperin says. Because many patients with abdominal cancers are not candidates for surgery, the physicians expect only about two intraoperative cases per month. They also plan to conduct research using the robot.