Abstract P1-01-25: Sentinella® an Alternative for Conventional Scintigram and a Modality To Improve Intra-Operative Localisation of Sentinel Nodes in Breast Cancer

Abstract

Abstract Sentinel Lymph Node (SLN) biopsy is now a standard practice for staging of the axilla in early breast cancer. Access to nuclear medicine department and sentinel node imaging reamins an issue in number of hospitals in the UK and many parts of the word Sentinella® is a new portable imaging camera used intraoperatively to produce real time visual localisation of Sentinel nodes. Sentinella® was tested in a controlled laboratory environment at our centre and we report the first use of this novel technique in Breast cancer patients from UK. Methods: Sensitvity and spatial resolution of Sentinella® mobile gamma camera was compared with a CGC (conventional single headed gamma camera) normally used for sentinel node imaging. Spatial resolution was measured by calculating the full width half maximum (FWHM) of a line profile measured perpendicular to the image of a capillary tube filled with high activity concentration technetium-99m pertechnetate. Next a special simulator mimicking the axilla was planted with seeds containing radiocolloid Tc, mimicking lymph nodes. Seeds were placed at varying depths in the axilla. For each combination of depths and radioactivity images with Sentinella® and CGC were obtained. Sentinella® scans of the axilla was also obtained in 50 patients undergoing SLNB to correlate with the preoperative scintigrams and determine presence of any residual hot nodes after use of the standard hand held gamma probe.If hot areas suggesting residual lymph nodes were detected, further exploration was carried out until no further residual activity was noted. Results Sentinella® resolution is comparable with the CGC for objects close to the camera i.e. ∼ 5 cm, but reduces rapidly as you move away from the camera. For distances up to about 7 cm the Sentinella® with the blue collimator is more sensitive than the CGC. 68 Sentinella® images and 34 CGC images obtained from the simulated axilla. Sentinella detects high radioactivity (500 kBq) faster than CGC (1 vs 2.5min). In cases of low radioactivity (10kBq) Sentinella® was equally accurate and faster than cGC, when placed close to the skin. Identification of different number of beads with varying radioactivity was similar in Sentinella and CGC. Sentinella® scans correlated with all the lymphoscintigrams in demonstrating hot lymph nodes in all the 50 cases. Sentinella® scans demonstrated a serial decay in activity with removal of every hot node and its LED guided localisation helped in detecting residual nodes. Sentinella® picked up extra nodes in 5/50 cases (10%) after the axilla was found silent using hand held gamma probe.In 2/50 (4%) cases extra nodes found using Sentinella® had presence of cancer that led to a complete Axillary clearance Conclusion: The initial patient and laboratory data confirms the excellent sensitivity and specificity of the machine in localisation of radioactive nodes. This new imaging technique will increase our pick up of sentinel lymph nodes intraoperatively that are missed due to inadequate visualisation and provide an alternative to static scintigram imaging. This would be particularly useful in centres that do not have nuclear medicine facilities on site. Citation Information: Cancer Res 2010;70(24 Suppl):Abstract nr P1-01-25.