Background: Sentinel lymph node (SLN) mapping has become the standard of care for axillary staging in women with early-stage breast cancer. The purpose of the study was to investigate the hypothesis that nonvisualization of SLN on lymphoscintigraphy (LSG) predicts a subset of patients at risk of having a substantial burden of axillary tumor as evidenced by higher rate of lymph node involvement.
Study design: We retrospectively reviewed the records of 1,500 patients who underwent dual-tracer SLN mapping for breast cancer between 1999 and 2004. LSG were reported as negative or positive.
Results: Ninety-one percent had axillary SLN(s) identified on LSG imaging. In 133 of 134 (99.3%) patients with a negative LSG, SLN(s) was identified intraoperatively either by blue dye or hand-held gamma detection. SLN was positive in 28.4% of LSG nonvisualized group and was positive in 29.1% of LSG visualized group (p>0.05). A significantly higher percentage of women older than 50 years of age had nonvisualization of SLN (p<0.0001). Body mass index (calculated as kg/m2) was >30 in 42.5% of LSG nonvisualized group and in 26.3% in LSG visualized group (p<0.0001).
Conclusions: Failure to demonstrate axillary uptake by LSG appears to be related to technical factors and patient-related factors, such as body mass index and older age, but does not adversely affect SLN identification. The equivalent rate of positive SLNs in patients with a positive or negative LSG supports the null hypothesis that "failure to visualize" on LSG does not identify a subset of patients at higher risk of being axillary lymph node positive.