Standardized probe-directed sentinel node dissection in melanoma

Radiopharmaceutical agents appear to improve the accuracy of sentinel node (SN) identification in patients with early-stage melanoma, but the optimal radiopharmaceutical agent and its timing from injection to surgery remain controversial. We undertook this investigation to examine the utility of 3 methods of intraoperative lymphatic mapping with radiopharmaceutical-directed sentinel lymphadenectomy (LM/SL). We suspected that concurrent injection of radiopharmaceutical and blue-dye would lead to the greatest success of SN identification.

The study was composed of 247 consecutive patients who had American Joint Committee on Cancer stage I or II melanoma. Before LM/SL, all patients underwent cutaneous lymphoscintigraphy by 1 of 3 techniques: technetium 99m (Tc 99m) human serum albumin (HSA) injected at least 24 hours before LM/SL (124 patients), Tc 99m filtered sulfur colloid (SC) injected no more than 4 hours before LM/SL (same-day SC, 95 patients), or Tc 99m SC injected at least 18 hours before LM/SL (prior-day SC, 28 patients). At the time of LM/SL, isosulfan blue dye was injected alone (SC groups) or with a second dose of HSA (HSA group). A hand-held gamma probe was used to determine the radioactive (hot) counts of blue-stained and nonstained nodes, and the in vivo and ex vivo node-to-background count ratios of the nodes were compared.

Preoperative LS identified 299 drainage basins; LM/SL identified at least 1 SN in 119 (98%) of 121 basins using same-day SC, 142 (97%) of 146 basins using HSA, and 32 (100%) of 32 basins using prior-day SC. There was no difference (P = .62) in the accuracy rate between the 3 techniques. The total number of SNs was 463. Same-day SC yielded higher intraoperative node-to-background count ratios than did either of the other techniques (P < .0001). Same-day SC also had the greatest relative change in radioactivity between the blue sentinel node and the post-excision basin (P < .0001), and the highest rate of SNs that were both blue and hot (in vivo or ex vivo ratio > or = 2, P = .05).

LS and LM/SL performed on the same day with a single injection of filtered Tc 99m SC serves as the most useful method for probe-directed LM/SL. This technique demonstrated the highest in vivo and ex vivo count ratios, fall-off of radioactivity between the excised nodes and post-excision basin, and concordance between blue dye and hot nodes. It should be recommended as the method of choice for probe-directed LM/SL.