Background: Sentinel node biopsy has recently evolved as a means of staging the axilla in breast cancer with minimal surgical trauma. The aim of this prospective multicentre study was to identify factors that influenced the detection and false-negative rates during the learning phase.
Methods: Data on all 498 sentinel node biopsies performed between August 1997 and December 1999 in Sweden were collected.
Results: A sentinel node was found in 450 patients (90 per cent). Preoperative scintigraphy visualized 83 per cent of all sentinel nodes. The detection rate was higher with same-day injection of tracer than with injection the day before (96 versus 86 per cent; P < 0.01). Dye injected less than 5 min or more than 30 min before the start of the operation lowered the detection rate (less than 60 per cent versus more than 65 per cent; P = 0.02). The detection rate varied from 61 to 100 per cent between surgeons. The false-negative rate was 11 per cent. The presence of multiple tumour foci and a high S-phase fraction increased the risk of a false-negative sentinel node, whereas the number of operations performed by each surgeon was less important.
Conclusion: Training of the individual surgeon influenced the detection rate, as did timing of tracer and dye injection. The false-negative rate seemed to be related to biological factors.