In-vivo detection of tumor-infiltrated axillary lymph nodes with a handheld beta-sensitive probe: a phantom study

Abstract

Sentinel node biopsy utilizing Technetium-99m-labeled sulfur colloid is rapidly becoming a standard part of the surgical treatment of breast cancer. Although this method is effective in identifying sentinel lymph node(s) in the axilla, the non-tumor-specific nature of colloids necessitates removal of the node(s) for subsequent analysis. Tumor-specific radiotracers, such as positron-emitting Fluorine-18-labeled Fluorodeoxyglucose (FDG), have been used with positron emission tomography (PET) to successfully stage breast cancer. Thus, the use of FDG with a handheld probe optimized for detection of beta particles could perhaps help identify cancer-infiltrated nodes during axillary dissection. In this study the ability of a new solid-state beta-sensitive probe to identify tumor- infiltrated lymph nodes was investigated in a phantom study. The axilla and tumor-infiltrated lymph nodes were simulated with gelatin phantoms containing FDG concentrations commonly reported from PET studies. FDG uptake in the organs of a patient was simulated with an anthropomorphic torso phantom. Following examination by the handheld probe, a PET image of the phantom was acquired. The results demonstrated that the probe was capable of identifying lymph nodes containing as little as 10 (mu) l of tumor. This amount of simulated tumor was too small to be detected by the PET scanner. This method, therefore, may be useful in intraoperatively identifying some tumor-infiltrated axillary lymph nodes not detected with PET; potentially increasing the efficiency of axillary dissection. Future clinical trials must be performed to assess the utility of this new technique.