Lymphoseek shows promise in sentinel lymph node detection

Use of 99mTc-tilmanocept (Lymphoseek, Navidea Biopharmaceuticals) as a SPECT/CT agent can improve preoperative sentinel lymph node localization before surgical treatment for oral cavity squamous cell carcinoma (OSCC), according to a study published in the September issue of JAMA Otolaryngology – Head & Neck Surgery.

The findings suggest 99mTc-tilmanocept could be superior to elective neck dissection (END) or sentinel lymph node biopsy with current agents like sulfur colloid, the former being associated with considerable potential morbidity and the latter having false-negative rates up to 10 percent, according to Anna M. Marcinow, MD, and colleagues at The Ohio State University in Columbus.

“The sustained uptake and stable pattern of 99mTc-tilmanocept uptake within [sentinel lymph nodes] and its ability to be reliably detected and localized the day following injection may aid in overcoming the logistical challenges and inefficiencies often associated with [sentinel lymph node biopsy] procedures using agents such as 99mTc sulfur colloid,” wrote the authors. “Such agents often involve injection the same day as surgery, as well as more careful coordination and timing of nuclear medicine injection and imaging with relation to surgery.”

Current findings were based on an arm of an ongoing Phase III trial of Lymphoseek. A total of 20 patients with previously untreated, clinically and radiographically node-negative OSCC were treated at an academic tertiary referral center. All patients received a single dose of 50 µg 99mTc-tilmanocept injected peritumorally, and then underwent dynamic planar lymphoscintigraphy (LS) and fused SPECT/CT prior to surgery.

Primary tumors were excised, and radio-guided sentinel lymph node dissection and planned END were performed. Excised lymph nodes were evaluated for presence of metastatic disease.

Twelve of the patients (60 percent) had metastatic neck disease on pathologic examination, according to Marcinow and colleagues. All 12 had at least one sentinel lymph node positive for metastases and none had a positive END node without at least positive sentinel lymph node. 99mTc-tilmanocept thus yielded a 0 percent false-negative rate and a negative predictive value of 100 percent.

“The utility of SPECT/CT in this study was particularly evident in the preoperative localization of level I [sentinel lymph nodes]—an area that has proven challenging to assess because of the proximity of these lymph nodes to the primary site of disease and high levels of radioactive shine-through,” wrote Marcinow and colleagues.

More sentinel lymph nodes were detected with SPECT/CT than with planar LS (3.7 vs. 2.9 nodes, respectively), reported the authors. “Although the difference was not statistically significant, it is important to note that the single institutional site data are likely underpowered to detect such a difference.” They added that they did note improved correlation between results obtained from SPECT/CT images and intraoperative sentinel lymph node biopsy findings when compared with results obtained from planar LS images.