Factors affecting failed localisation and false-negative rates of sentinel node biopsy in breast cancer--results of the ALMANAC validation phase

BACKGROUND: Despite the widespread application of sentinel lymph node biopsy (SLNB) for early stage breast cancer, there is a wide variation in reported test performance characteristics. A major aim of this prospective multicentre validation study was to quantify detection and false-negative rates of SLNB and evaluate factors influencing them. METHODS: Eight-hundred and fourty-two patients with clinically node-negative breast cancer underwent SLNB according to a standardised protocol that used a combination of radiopharmaceutical 99mTc-albumin colloid and Patent Blue V dye. SLNB was followed by standard axillary treatment at the same operation in all patients. RESULTS: Sentinel lymph nodes (SLNs) were identified in 803 (96.1%) of 836 evaluable cases. The median number of SLNs removed per patient was 2 (range 1-9). There were 19 false negatives, resulting in a sensitivity of 263/282 (93.3%) and accuracy 782/803 (97.6%). SLNs were successfully identified by blue dye in 698 (85.6%), by isotope in 698 (85.6%), and by the combination of blue dye and isotope in 782 (96.0%) of 815 patients. Among 276 node positive patients, one or more positive SLNs were identified by blue dye in 251 (90.9%), by isotope in 246 (89.1%) and by the combination of blue dye and gamma probe in 258 (93.5%). Obesity, tumor location other than upper outer quadrant and non-visualisation of SLNs on the pre-operative lymphoscintiscan were significantly associated with failed localisation (p<0.001, p=0.008, p