Probe firms find niche in sentinel node biopsy

Companies expect potential applications to increase

Since gamma probe technology first began to be developed in the late 1980s, manufacturers of these hand-held tools have had difficulty settling into a market niche. But this may be changing. In the area of oncology—particularly breast cancer—gamma probes are coming into their own as useful intraoperative tools that can determine whether a cancer has metastasized and limit invasive surgical procedures.

Probe developers such as Care Wise Medical Products of Morgan Hill, CA, Neoprobe of Dublin, OH, and U.S. Surgical of Norwalk, CT, have begun to catch a clinical trend of mapping the lymphatic system using gamma probes and radiopharmaceuticals to find the sentinel node, the main lymph node to which a tumor is draining. Once found, the sentinel node can be excised and tested for malignancy, and physicians can determine whether a particular cancer has begun to spread throughout the lymphatic system. Sentinel node biopsy helps clinicians determine a patient’s treatment, and can provide information that helps patients avoid more invasive lymphatic surgery.

The probe system consists of the probe itself and an analyzer unit. In a sentinel node biopsy procedure, patients are injected with a radioisotope, and after two to six hours, are taken to surgery. The surgeon runs the gamma probe over the skin, and the probe emits a sound as it scans areas where there has been radioisotope uptake. Different companies use different detector materials for their devices: Care Wise’s C-Trak unit uses sesium iodide in its detector head, while Neoprobe’s neo2000 and U.S. Surgical’s Navigator use cadmium zinc telluride. Most probes on the market range in price from $18,000 to $30,000.

Sentinel node biopsy using gamma probes has become the standard of care for melanoma treatment, and both mammography advocates and probe manufacturers hope that it will soon become the same for breast cancer. Gamma probes are primarily used for sentinel node biopsies of malignant melanomas and breast cancers, according to Rob Wise, manager of clinical research for Care Wise. But the market is open to a widening range of uses for the devices: Other potential applications include bone lesions, gastronomas, and vulvar, liver, pancreatic, and colorectal cancer. The probes can also be attached to devices that have PET capability.

Like other new technologies used in mammography, part of what is driving the gamma probe market is the nationwide focus on breast cancer. Increasing numbers of women under 40 are having mammograms, and physicians are detecting smaller cancers. Sentinel node biopsy is well-suited to small breast lesions, according to Scott DePierro, product director at U.S. Surgical. Patient initiative is also key: As women become more informed about their disease, they are seeking less invasive treatment options.

“Sentinel node biopsies are catching on,” said Dennis Bellett, clinical specialist at Neoprobe. “If (clinicians) aren’t doing this within the next year, they won’t be doing breast surgery. Since the information is so well distributed on the Internet, there are women now who are coming into doctors’ offices and requesting sentinel node biopsy.”

Increased interest in probe technology, particularly sentinel node biopsy, has begun to translate into increased revenues for probe developers. CareWise has seen its sales revenues double every year since 1994, when sentinel node biopsies using gamma probes were developed, Wise said. Neoprobe has seen an 81% increase in revenue for the first six months of 1999 over the same period in 1998, according to William Hirsch, Neoprobe marketing product manager. And U.S. Surgical has seen its lymphatic mapping business increase by 50% each year since 1997, DePierro said.