Factors influencing the identification rate of the sentinel node in breast cancer

Sentinel node biopsy is a widely accepted alternative to primary axillary lymph node dissection for ipsilateral nodal assessment in breast cancer. We have performed a retrospective chart review in 713 consecutive patients with primary, operable breast cancer who underwent sentinel node biopsy in order to identify factors that determine the sentinel node identification rate. Chi-squared test, univariate and multivariate analyses were used to evaluate the influence of different factors on the sentinel identification rate. Among the factors investigated, tumour size was correlated with sentinel lymph nodes detection rates (multiple logistic regression, P= 0.002). In addition, the patient's age showed to be a significant influencing factor (multiple logistic regression, P= 0.006). Body mass index and grade only exhibited a significant correlation with the identification rate in the univariate (P= 0.041, P= 0.025), but not in the multivariate analysis (P= not significant). All associations were found to be independent of the site of injection. Interestingly, surgeons with intermediate expertise (11-20 prior dissections) had the highest detection rates (P= 0.004). We conclude that sentinel identification rates are higher in larger tumours and in younger patients, independent of the injection site. Surgical experience in sentinel node dissection is not linearly correlated with higher identification rates.