Transport and retention of colloidal tracers in regional lymphoscintigraphy in melanoma: influence on lymphatic mapping and sentinel node biopsy

Sentinel node (SN) biopsy is a staging technique used to select patients for regional lymphadenectomy in melanoma. We compared the two most widely used radioactive tracers, Tc-99m-colloidal albumin (Tc-99m-CA) and Tc-99m-sulphur colloid (Tc-99m-SC), with respect to scintigraphy, success rate in gamma probe guided biopsy and absolute uptake in the SN. Scintigraphy was performed in six volunteers after simultaneous injection of the respective tracers in each leg. Comparison of uptake of both tracers showed a higher uptake on the Tc-99m-CA side. The scintigraphic count ratio of SNs labelled with Tc-99m-SC compared with Tc-99m-CA was 1 to 9-28. Next, 20 patients with biopsy-proven melanoma were randomized for injection of Tc-99m-CA Or Tc-99m-SC followed by SN biopsy. Within 20 min after the injection, focal uptake was seen in all cases of the Tc-99m-CA group but in only seven of the 10 patients in the Tc-99m-SC group (P < 0.05). Focal accumulations were seen in all patients of both groups after 2 h, Spill to non-SNs was seen in five of the Tc-99m-CA patients and three of the Tc-99m-SC patients. In all patients the SNs could be retrieved under the guidance of a gamma probe and blue dye. The uptake in the SN was significantly higher (P < 0.001) after the injection of Tc-99m- CA (0.92 +/- 0.40%) compared with Tc-99m-SC (0.34 +/- 0.34%). When dynamic scintigraphy is performed, Tc-99m-CA is preferable. SN uptake of Tc-99m-SC is less than that of Tc-99m-CA but this does not adversely affect the surgical procedure. (C) 1998 Lippincott Williams & Wilkins.