Unfiltered sulfur colloid and sentinel node biopsy for breast cancer: Technical and kinetic considerations

Background: There are few clinical data on technical limitations and radioc olloid kinetics related to sentinel lymph node (SLN) biopsy for breast canc er. Methods: In 70 clinical node-negative patients, unfiltered Tc-99m sulfur-co lloid was injected peritumorally and cutaneous hot spots were mapped with a gamma probe. SLN biopsy was performed followed by axillary lymph node diss ection. Missed radioactive nodes (nodes not under hot spots) were removed f rom axillary lymph node dissection specimens and submitted separately; Results: At least one hot spot was mapped in 69 patients (98%) and SLNs wer e retrieved in 62 (89%). No radiolabeled nodes were found in five (7%) and only nodes not under hot spots were retrieved in three patients (4%). Resid ual nodes not under hot spots were retrieved in 17 patients (24%) in whom a t least one SLN specimen had been found. Diffuse radioactivity around the r adiocolloid injection site impeded identification of all radiolabeled nodes during SLN biopsy, and was responsible for one of two false negatives (20 node-positive patients; false-negative rate 10%). Hot spot radioactivity, n umber of radiolabeled nodes, and nodal radioactivity did not change with ti me interval from radiocolloid injection to surgery (0.75-6.25 hours). Conclusions: Although SLN localization rate is high, intraparenchymal injec tion may predispose to failure of radiocolloid migration, failure to identi fy SLNs because of high radiation background, and false-negative outcomes. Alternative routes of radiocolloid administration should be explored.