Improved sentinel node visualization in breast cancer by optimizing the colloid particle concentration and tracer dosage

Abstract

Faint lymph uptake may hamper sentinel node (SN) identification by scintigraphy and subsequent gamma probe localization. The aim of the present study was to evaluate an adjustment in the colloid particle concentration and tracer dosage to optimize mammary lymphoscintigraphy. Scintigraphy was performed in 151 patients with a palpable breast carcinoma and clinically negative axilla: for the first 75 patients (group A) a standard labelling of 0.5 mg nanocolloid with 99Tcm was performed, for the subsequent 76 patients (group B) the labelling dilution volume was reduced from 4 to 2 ml. For both groups the volume of injection was 0.2 ml. Lymph node uptake was evaluated by a 4-step visual score (from 0 = absent to 3+ = very intense), and by count quantification of at 4 h in the first draining SN. The SN visualization rate increased from 93% (70/75) in group A (mean dosage 93.4 MBq, range 57-130 MBq) to 99% (75/76) in group B (mean dosage 106.5 MBq, range 74-139 MBq). The percentage of patients with uptake 3+ was significantly higher (P = 0.001) in group B (51% vs 35% in group A). SN counts were significantly higher for group B (P<0.001). The percentage of patients with less than 2000 counts/node diminished from 45% in group A to 9% in group B (P = 0.001). In group B (P = 0.033) more lymph channels (53% vs 35% in group A) were visualized and for a longer time (26% vs 4% at 4 h). Axillary drainage was seen in 96% in group A and 98% in group B whereas non-axillary drainage was observed in 19% and 25%, respectively. Intraoperative SN identification rate was 97% in group A and 100% in group B. SN metastases were found in 41% of group A and 47% of group B. It is concluded that enhancement of colloid particle concentration and adjustment of tracer dosage led to improved SN identification by substantial increase in lymph node uptake and lymph vessel depiction. A significant reduction of cases with faint SN uptake enables better surgical efficacy.