Practical guidelines for optimal gamma probe detection of sentinel lymph nodes in breast cancer: Results of a multi-institutional study

Introduction. Multiple radioactive lymph nodes are often removed during the course of sentinel lymph node (SLN) biopsy for breast cancer when both blu e dye and radioactive colloid injection are used. Some of the less radioact ive lymph nodes are second echelon nodes, not true SLNs. The purpose of thi s analysis was to determine whether harvesting these less radioactive nodes , in addition to the "hottest" SLNs, reduces the false-negative rate. Methods. Patients were enrolled in this multicenter (121 surgeons) prospect ive, institutional review board-approved study after informed consent was o btained. Patients with clinical stage T1-2, N0, MO invasive breast cancer w ere eligible. This analysis includes all patients who underwent axillary SL N biopsy with the use of an injection of both isosulfan blue dye and radioa ctive colloid. The protocol specified that all blue nodes and all nodes wit h 10% or more of the ex vivo count of the hottest node should be removed an d designated SLNs. All patients underwent completion level I/II axillary di ssection. Results. SLNs were identified in 672 of 758 patients (89%). Of the patients with SLNs identified, 403 patients (60%) had more than 1 SLN removed (mean , 1.96 SLN/patient) and 207 patients (31%) had nodal metastases. The use of filtered or unfiltered technetium sulfur colloid had no impact on the numb er of SLNs identified. Overall, 33% of histologically positive SLNs had no evidence of blue dye staining. Of those patients with multiple SLNs removed , histologically positive SLNs were found in 130 patients. In 25 of these 1 30 patients (11.5%), the hottest SLN was negative when a less radioactive n ode was positive for tumor if only the hottest node had been removed the fa lse-negative rate would have been 13.0% versus 5.8% when all nodes with 10% or more of the ex vivo count of the hottest node were removed (P = .01). Conclusions. These data support the policy that all blue nodes and all node s with 10% or more of the ex vivo count of the hottest SLN should be harves ted for optimal nodal staging.