Improved sentinel lymph node localization in patients with primary melanoma with the use of radiolabeled colloid

Background. The purpose of this study was to determine whether the sentinel lymph node (SLN) localization technique, which uses blue dye and ^99mTc-labeled sulfur colloid, provides advantages over blue dye alone in the management of patients with stages I and II cutaneous melanoma. Methods. The records of 626 consecutive patients with melanoma who underwent lymphatic mapping and SLN biopsy between 1991 and 1997 at the M.D. Anderson Cancer Center were reviewed. Lymphatic mapping was performed with isosulfan blue dye alone (n = 252) or in combination with ^99mTc-labeled sulfur colloid accompanied by a hand-held gamma probe (n = 374). SLNs were defined as those that stained blue or demonstrated increased focal radiotracer uptake. Results. SLN identification rates improved from 87% (dye alone) to 99% (dye and colloid) (P < .0001) with the combined technique in all anatomic sites examined. The mean number of SLNs harvested from each basin was significantly greater in the patients mapped with dye and colloid (1.74 vs 1.31; P <. 0001). Occult metastatic disease was identified in 17.5% of all patients and did not significantly differ between groups. In 92% of patients who had at least one positive SLN and were mapped with both agents, lymphatic metastases were identified in the SLN that contained the greatest radiotracer uptake. In 19% of cases the first blue SLN harvested did not contain the greatest radiotracer uptake. Conclusions. SLN identification is enhanced by the addition of radiolabeled sulfur colloid and intraoperative use of the hand- held gamma probe and may identify SLNs missed by the blue dye alone. These data support the combined use of radiolabeled sulfur colloid and blue dye in lymphatic mapping procedures to improve the nodal staging of stages I and II melanoma.