Background: The combination of isosulfan blue (Lymphazurin) 1% and 99(m)Tc sulfur colloid (TSC) may improve the feasibility and accuracy of lymphatic mapping for colorectal cancer.
Methods: At laparotomy, 1 to 2 mL of isosulfan blue and 1 mCi of TSC were injected subserosally. Sentinel lymph node (SLN) designation was based on blue staining for isosulfan blue and increased radioactivity for TSC. Focused pathologic analysis of the SLNs and standard pathologic examination of the remaining specimen were performed.
Results: A total of 57 consecutive patients were studied (median age, 71 years; 27 men and 30 women). Mapping was successful in 100% of patients with isosulfan blue and in 89% with TSC (P =.47). Lymphatic mapping was accurate in 93% of patients with isosulfan blue versus 92% with TSC (P =.53). The combined accuracy was 95%. A total of 709 lymph nodes were found (12.4 per patient): 553 non-SLNs (5.6% nodal positivity) versus 156 SLNs (16.7% nodal positivity; P <.0001). Isosulfan blue detected 152 SLNs, TSC detected 100, and both modalities detected 96. Of the SLNs detected by isosulfan blue only, 10.7% had nodal metastases, whereas 19.8% of SLNs detected with both modalities had nodal metastases (P =.028). Nodal disease was detected in 41% of patients with invasive carcinoma. Metastases were detected only in the SLNs in 26% and only by micrometastases in 11% of these patients.
Conclusions: These data confirm the efficacy of isosulfan blue and TSC for SLN mapping in colorectal tumors. No significant difference with respect to feasibility or accuracy exists between isosulfan blue and TSC. The metastatic yield is significantly higher in SLNs identified by both modalities compared with isosulfan blue only.