French researchers develop handheld probe for SLN detection

Jun 16, 2008

NEW ORLEANS - Researchers from France are making progress in the development and clinical utilization of a handheld gamma camera to perform lymphoscintigraphy for sentinel lymph node (SLN) localization in breast cancer.

The device is a lightweight (approximately 2.6 lb), preoperative, compact imaging probe dubbed POCI (preoperative compact imager).

"After the first successful proof-of-concept trials using the imaging probe, we decided to conduct a prospective study to quantify the clinical benefit of this device," said Dr. Khaldoun Kerrou, one of POCI's developers in the nuclear medicine department at Hôpital Tenon in Paris.

Kerrou presented details of the device and results of a prospective clinical study, which compared POCI with a conventional gamma camera, during the SNM annual meeting.

The study included 156 patients over a two-year period, beginning in January 2006. The sentinel lymph node protocol consisted of periareolar injections of 37 MBq technetium-99m sestamibi-labeled nanocolloids two hours before standard gamma camera lymphoscintigraphy, followed by imaging by the POCI device.

Acquisition time

The standard gamma camera acquisition time ranged between 15 and 30 minutes, while POCI acquisition time ranged between two and 18 minutes.

"The field-of-view of POCI, which is 13 cm², allowed us to move the POCI in the whole axillary area," Kerrou said. "[POCI] is not like a gamma camera image. You do not have to wait until the end to see the image; it is a real-time image, so you can see the acquisition."

For POCI detection, the entire axillary area was scanned with 10-second acquisition images. These examinations were conducted by two different nuclear medicine physicians blinded to each other's results. Physicians also were asked to screen the extra axillary area for sentinel lymph nodes using POCI in the preoperative setting.

The following day in the operating room, the surgeon, blinded to the results from both the gamma camera and POCI, first used POCI to perform intraoperative lymphoscintigraphy. After considering the previous results, the surgeon used the probe for sentinel lymph node biopsy.

In their analysis, the researchers reviewed the number and location of sentinel lymph nodes obtained by POCI and compared the results to the same information obtained the previous day with the POCI and the conventional gamma camera. "The acquisition times for all procedures were recorded and compared, and the data analyzed according to the normalcy of the distribution," Kerrou said.

Study results

The study included 156 patients, fulfilling the study design criteria. Of those patients, 129 patients (95%) showed axillary sentinel lymph nodes, eight (5%) patients showed no sentinel lymph nodes, and 17 patients (11%) showed extra axillary sentinel lymph nodes with axillary sentinel lymph nodes.

In comparing the conventional gamma camera with the POCI, Kerrou noted that none of the differences was statistically significant, but POCI was "significantly more sensitive to find more sentinel lymph nodes and radioactive axillary lymph nodes."

The conventional gamma camera detected a total of 206 sentinel lymph nodes, compared with 226 sentinel lymph nodes discovered by POCI. In the intraoperative exam, POCI detected a total of 180 sentinel lymph nodes.

SLN detection

After removal of the radioactive sentinel lymph nodes using a surgical probe, researchers asked the surgeon to search with POCI to see if any sentinel radioactive nodes were in the axillary area considered free by the surgical probe. This procedure was done with 125 patients.

"In this setting, POCI detected one residual axillary radioactive node in 20 (16%) of 125 patients," Kerrou said. "In one patient, it was the only mode with micrometastases." The surgeon subsequently changed the patient's treatment based on the finding.

The study found that the handheld POCI "is able to predict the number and localization of breast cancer sentinel lymph nodes," Kerrou concluded. "It is a promising tool, in my opinion, that can replace preoperative lymphoscintigraphy and compete -- as you have seen with the residual lymph nodes -- with the surgical probe, especially in the surgical center that does not have a nuclear medicine department."

By Wayne Forrest
AuntMinnie.com staff writer
June 17, 2008

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