Abstract
1269
Aim: Although approved for clinical use by FDA and EMA in 2013 and 2014, respectively, 99mTc-Tilmanocept has been introduced in European countries since mid-2017. The aim of this study is to describe our preliminary results with this “next generation” radiotracer in melanoma patients scheduled for sentinel node (SN) biopsy. Materials and Methods: We prospectively analysed 32 patients who underwent SN biopsy using 99mTc-Tilmanocept as radiotracer. Median age was 55 (range: 34-72). Mean Breslow thickness was 1.6 mm (range 0.8-3.7). Nine patients presented at least 1 mitosis/mm2 (range 0-16). Eight melanomas were located in thorax, 7 in lower limbs and the remaining 6 in head, one in abdomen, 9 in lower limbs and 1 in the vulva. All of them were injected with 50 microgr 99mTc-Tilmanocept with a median dose of 90 MBq (range 46-140 MBq) in a volume of 0.4 ml. After tracer injection, all patients underwent lymphatic mapping within 4h. Operating room procedure started after 21-25 hours of tracer injection (two-day protocol). A conventional hand-held gamma probe and a portable gamma camera were used to locate the SNs.
Results: SN visualization was possible in all 32 patients. Dynamic study showed lymphatic channels in 28 out 32 patients (87.5%). Early planar images (15-30 min after injection) visualized lymphatic ducts in 31 of 32 patients (96.8) and at least 1 SN in all cases. Pre-operative images demonstrated 131 hot spots (4.1 per patient). During surgery, 76 SNs were retrieved (2.3/patient). In our two-day protocol, when injected dose was below 90 MBq (3 patients), SNs showed low radioactivity during surgery, and therefore, time to intraoperatively locate them was higher. However, when dose was increased between 90-111 MBq, no detection problems were reported by surgeons and surgical time was shortened. There were no adverse events. The 6 cases in the head and neck area were positively rated by surgeons because the easiness to depict the nodes in this complex area. Although the surgery time was longer than in other areas, every SN was well depicted even when located near the injection site.
Conclusions: 99mTc-tilmanocept successfully identified SNs in less than 30 minutes in our melanoma cases. However, its results can be hampered if a dose below 90 MBq is used in a two-day protocol. In our experience, although all cases were located, a slight dose increment allows a more comfortable procedure in operating room.