Subdermal re-injection:: a method to increase surgical detection of the sentinel node in breast cancer without increasing the false-negative rate

Purpose: The aim of this study was to evaluate in breast cancer whether subdermal (SB) re-injection improves surgical detection (SD) of the sentinel node (SN) in patients with negative lymphoscintigraphy on peritumoral ( PT) injection, without increasing the false-negative (FN) rate. Methods: Group I comprised 261 patients with invasive breast cancer > 3 cm and clinically negative axilla treated with primary chemotherapy. Axillary lymphadenectomy was performed in all of these patients. Group IA comprised 201 patients with PT injection, while group IB comprised 60 patients with SB injection in the tumour quadrant. Group II comprised 652 patients with breast cancer < 3 cm; in 73 of these patients with negative lymphoscintigraphy, SB re-injection was performed. For lymphoscintigraphy, 37 - 55 MBq Tc-99m-albumin nanocolloid in 1 ml was used for PT injection, and 18 MBq in 0.2 ml for SB injection. Five-minute images were obtained 2 h p.i. for PT injection and 20 - 30 min p.i. for SB injection. SD was performed 4 or 24 h p.i. Lymphoscintigraphic (LD), surgical and internal mammary (IM) detection rates were calculated. In group I, FN, negative predictive value (NPV) and accuracy ( A) were calculated. Statistical analysis was performed using the chi-square test. Results: In percentages, results were as follows: Group IA: SD: 84.1, FN: 13.6, NPV: 88.9, A: 78.6, IM: 14.5*. Group IB: SD: 90, FN: 0, NPV: 100, A: 90, IM: 1.7* (* p< 0.025). Group II: PT injection only: LD: 82.4, SD: 94; PT injection+ SB re-injection: LD: 90, SD: 98.5. SD was 97.8** in patients with positive lymphoscintigraphy and 58.5** when lymphoscintigraphy was negative (** p< 0.001). Conclusion: For correct staging, including extra-axillary drainage, peritumoural injection should first be performed. When the SN is not visualised, and only in those cases, SB re-injection should be performed, which increases the SD rate without increasing the FN rate.