Contact: David Opon 312-202-5329 [email protected]
Radioactive Seeds Localize Biopsy Lesions
SAN FRANCISCO--About two years ago, a patient with a palpable mass in one of her breasts came to the Comprehensive Breast Cancer Center at the University of South Florida, Tampa, to have a sentinel node biopsy. As part of the standard biopsy procedure, she received an injection of radioactive technetium around the lesion so the lymph nodes draining the area could be identified and assessed. However, the surgeons were unsure where to make their incision to obtain a sample of the lesion itself, because although the lesion could be seen clearly on ultrasound, it was located deep in the breast and was difficult to feel.
Charles E. Cox, MD, FACS, who was performing the biopsy, decided to use the gamma probe that is used to find sentinel lymph nodes by detecting the radioactivity released by the technetium in the arm pit. Dr. Cox passed the probe over the breast, noticed a small amount of radioactivity emanating from the lesion itself, and surgically removed all the breast tissue containing the technetium. "We used the probe to find the radioactive material, and because it was concentrated around the lesion, we were able to take out the entire mass. The procedure worked like a charm," Dr. Cox, program leader of the breast cancer center, said.
The procedure worked so well, in fact, that Dr. Cox wondered if it could be applied to biopsies of nonpalpable breast masses. However, Dr. Cox soon realized that while radioactive material could be injected into a defined palpable mass, it would be unsuitable for nonpalpable lesions because the technetium might diffuse too widely and surgeons might remove more tissue than necessary.
Emilia Dauway, MD, a fellow in surgical oncology at the University of South Florida at that time, suggested inserting low-dose radioactive seeds adjacent to suspicious nonpalpable lesions. Dr. Dauway was mentored by Jay Friedland, MD, radiation oncologist, regarding seed technology. Dr. Friedland uses radioactive seeds for localized treatment of prostate cancer, which are easy to position and remain in place. There is little concern, about contaminating adjacent structures, since the seed is a self-contained radioisotope.
Drs. Cox and Dauway then began a pilot study of radioactive seed breast localization in 25 women. Results from that study, which were presented at the 1999 Clinical Congress of the American College of Surgeons, suggest that the surgeons have discovered an accurate, quick, and safe new way of taking biopsies from lesions in the breast.
The procedure also may be useful for biopsying lesions in other parts of the body as well. The seeds may simplify liver biopsies and colon biopsies, Dr. Cox said. "Instead of trying to find a liver lesion with ultrasound, which can be cumbersome, you can use the gamma probe, which is a very small and utilitarian tool. If you have a lesion embedded in the wall of the colon, you can remove that part of the colon laparoscopically using a laparoscopic radiographic probe," he said. In addition, radioactive seeds may be appropriate for biopsying growths in the brain and pancreas. "Actually any lesion anywhere in the body into which you can put a biopsy needle, you can prob- ably put a seed into," Dr. Cox said.
In the breast biopsy study, one seed--about the size of a grain of rice--was injected into each lesion. The seed was obtained from the pool of seeds that were set aside for, but not used in brachytherapy of a cancerous prostate gland. Already low in radiation dosage, the biopsy seed was allowed to decay until it was a third or a half of its original strength. The seed was inserted into a biopsy needle and injected into the suspicious mass.
The study indicated that radioactive seed localization was exceptionally precise. At the time of biopsy, surgeons were able to find the seed in every lesion they tested, and they removed the entire lesion in every case. The technique spared normal breast tissue. On average, surgeons removed less overall breast tissue (19.3 cm3 ) than they usually do with conventional needle local- ization biopsies (40.3 cm 3). Biopsies done with radioactive seeds took only 4.6 minutes on average to perform, and radiation exposure to the patient and members of the surgical team was minimal.
Radioactive seed localization was well tolerated by patients. Because the radioactive seed is completely contained within breast tissue, patients had no discomfort. The procedure also made it easy for surgeons to plan their biopsy incision, "because the gamma probe pinpointed exactly where the seed was located within breast tissue," Dr. Dauway said. "We could gauge the depth of dissection intraoperatively," she added, which decreased the amount of tissue loss.
Based on these findings, Drs. Cox and Dauway are spearheading a prospective randomized trial of radioactive seed localization in 200 patients with suspicious mammographic lesions. The objective of the trial is to compare the use of radioactive seeds with needle localization, the current standard for obtaining tissue samples from the breast. They also are designing protocols for clinical trials of the procedure for sampling tissue from the liver, colon, pancreas, and brain.
Dr. Dauway, assistant professor of surgery, at West Virginia University, has developed a new protocol that will evaluate the use of dual radioisotope scanning and cost analysis. This technique will allow the utilization of two radioisotopes (I-125 and technetium) enabling the surgeon to excise nonpalpable breast lesions localized with radioactive seeds and concurrent lymphatic mapping and sentinel lymph node biopsy. This study will be a multi-institutional trial.
Findings from these trials will determine whether Drs. Cox and Dauway have built "a better biopsy mousetrap," Dr. Cox said. Radioactive seed localization appears to be able to provide adequate samples for pathologic analysis without removing too much normal tissue. The technique also may be cost effective.
As Dr. Cox pointed out, researchers have been searching for improved ways of sampling breast tissue because of the enormous cost of screening for breast cancer. Mammography has increased the rate of detection of suspicious lesions in the breast. While all suspicious lesions need to be biopsied to determine if they are malignant, 70 percent of the lesions turn out to be benign.
Radioactive seed localization may prove to be less expensive than needle localization if it significantly reduces operative time. The technique also may save biopsy costs by eliminating the need for an Xray to validate that the entire lesion has been removed surgically. Rather than wait for a radiologist to examine an Xray of the biopsy sample, surgeons may be able to use the gamma probe to verify that the radioactive seed is in the specimen. According to Dr. Dauway, "If we know the seed came out and the seed was placed at the lesion, then we know we caught the lesion."
"We've been able to use the seeds fairly effectively in the pilot study," Dr. Cox said. "With the randomized prospective trial, we will have a concurrent series of cases comparing two procedures head to head and demonstrate if seed localization is specific enough and sensitive enough to locate lesions in the body."
Joining Drs. Cox and Dauway in their research endeavors were Douglas S. Reintgen, MD, FACS; Jay Friedland, MD; Claudia Berman, MD, Ni Ni Ku, MD; Robert Sanders; Timothy Yeatman, MD, FACS; Robert Falcone; and Steve Crawford.
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