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Background: Optimal dose and timing of lymphatic mapping (LM) for sentinel lymph node (SLN) biopsy for melanoma is unknown. This study compares outcomes of low-dose radiolabeled tracer LM on the same day (SD) of surgery with a higher dose the day before (DB) surgery.

Methods: All patients who underwent LM and SLN biopsy for melanoma from January 2009-December 2013 were retrospectively reviewed. Data collected and analyzed included: patient demographics, clinicopathologic characteristics of primary melanoma, dose and timing of LM injection, correlation of LM with operative findings, number SLNs identified, postoperative complications.

Results: 171 SLN biopsies for unique melanoma primaries were performed in 167 patients. 104 (60.8%) had LM performed the SD. The average dose of SD radiolabeled tracer was 0.61 mCi (0.4-4.2). The average dose for DB injections was 3.8 mCi (1.0-4.2). SLNs were identified in 168 (98.2%) biopsies. Mean number of SLNs removed was 2.0 (0-5) and 2.3 (1-8) (p>0.05) for SD versus DB LM. No drainage was seen in 2 SD LMs. Correlation between LM and operative findings was 98% and 97% for SD and DB, respectively. For head and neck melanomas, the correlation was 90.9% and 90.5% for SD and DB, respectively. Postoperative complication rates were the same between SD and DB LM (11.5% and 11.9%, respectively).

Conclusion:s: Higher-dose LM performed DB surgery corresponded with operative findings and did not increase the number of SLNs identified or rate of complications compared with low-dose, SD injection. DB injections offer increased scheduling flexibility without compromising surgical outcome.