Radiolabeled sentinel node biopsy: collaborative trial with the National Cancer Institute

The objective of this study was to maximize the success rate of sentinel node (SN) localization in breast cancer patients with the tracer that demonstrated the highest initial success during a preliminary evaluation. Altogether, 145 patients with operable invasive breast cancer and clinically negative lymph nodes were studied. Technetium 99m (99mTc)-sulfur colloid was injected into the breast parenchyma surrounding the invasive cancer or the biopsy cavity. Variable volumes of tracer, amounts of 99mTc, and duration of time between injection and surgery were evaluated. A hand-held gamma detector was used at surgery to locate and guide resection of all radioactive sentinel nodes (SNs), including those that were extraaxillary. A conventional lymphadenectomy was then performed in all cases. Based on previous studies, unfiltered sulfur colloid provided a higher success rate of SN identification than the other tracer types. Further evaluation with 99mTc-sulfur colloid demonstrated that increased volume increased the success rate of SN identification. An injection volume of 8 ml resulted in a success rate of 98%. SNs were not exclusively located in the axilla: In 8.6% of cases SNs were removed from an internal mammary location. The overall accuracy of patients with SNs resected was 98.4%, and the false-negative rate was 4.4%. It was concluded that (1) unfiltered 99mTc-sulfur colloid at a volume of 8 ml resulted in a high success rate for SN identification; (2) a significant number of the SNs were extraaxillary in location; and (3) the accuracy of the SNs for determining whether regional metastases had occurred was high. The U.S. National Cancer Institute is funding a randomized phase III clinical trial to evaluate SN resection compared to conventional axillary lymphadenectomy in clinical node-negative breast cancer patients. Major endpoints of this trial include long-term regional control and survival.