Technical effects of adding 1 % lidocaine to technetium sulfur colloid for sentinel lymphatic mapping in early breast cancer: Analysis of data from a double-blind randomized controlled trial

Background: A practice standard in sentinel lymph node (SLN) mapping in breast cancer is intradermal injection of technetium-99m sulfur colloid (Tc-99m), resulting in significant patient discomfort and pain. A previous randomized controlled trial showed that adding lidocaine to Tc-99m significantly reduced radioisotope injection-related pain. We tested whether 1 % lidocaine admixed with Tc-99m affects feasibility of SLN mapping. Methods: Between January 2006 and April 2009, 140 patients with early breast cancer were randomly assigned (1:1:1:1) to receive standard topical 4 % lidocaine cream and intradermal Tc-99m (control) or to one of three other study groups: topical placebo cream and injection of Tc-99m containing sodium bicarbonate (NaHCO ₃), 1 % lidocaine, or both. All SLN data were collected prospectively. Results: Study groups were comparable for clinicopathological parameters. As previously reported, the addition of 1 % lidocaine to the radioisotope solution significantly improved patient comfort. Overall SLN identification rate in the trial was 93 %. Technical aspects of SLN biopsy were similar for all groups, including time from injection to operation, first SLN (SLN 1) gamma probe counts, ex vivo counts for SLN 1 and SLN 2, and axillary bed counts. SLN identification rates were comparable statistically: control (96 %), lidocaine (90 %), sodium bicarbonate (97 %), and sodium bicarbonate-lidocaine (90 %). The control group had a significantly higher SLN 2/SLN 1 ex vivo count ratio, and the number of SLNs detected was significantly reduced in the lidocaine versus no-lidocaine groups (p < 0.05). Conclusions: Addition of 1 % lidocaine to standard radioisotope solution for SLN mapping in breast cancer is associated with fewer SLNs detected, but it does not appear to compromise SLN identification.