Reproducibility of lymphoscintigraphic drainage patterns in sequential 99mTc human serum albumin and 99mTc sulfur colloid studies: implications for sentinel node identification in melanoma

Selective lymphadenectomy, based on prior lymphatic mapping and sentinel node identification and excision, is now the standard management for intermediate-thickness melanomas in many cancer centers worldwide. At our center 99m-labeled technetium human serum albumin (HSA) scans are performed before the day of surgery in some patients with truncal lesions to detect multiple sites of lymphatic drainage. 99mTc sulfur colloid (SC) is then injected before the operation to delineate the sentinel node(s) for gamma-probe-guided excision. Our purpose was to retrospectively evaluate whether comparable diagnostic information resulted from lymphoscintigraphy performed with these 2 different agents.

All patients with melanoma who had dual sequential 99mTc HSA and 99mTc SC studies between January 1, 1996, and December 31, 1997, were reviewed.

Thirty-eight patients underwent paired HSA and SC imaging. Thirty-two patients had concordant scan findings. In all 6 discordant studies, 2 separate drainage areas were defined by HSA, but only 1 drainage area was defined by SC.

In 15.8% of dual studies (6/38 studies), discordant imaging results were obtained between HSA and SC. SC studies alone may result in nonvisualization of at-risk draining lymph node beds and hence failure to identify and excise all sentinel nodes. This could result in inaccurate staging, inappropriate therapy, and altered prognosis. A reduction in SC dose from 3 to 1 mCi was probably the most significant causal factor leading to these discrepancies, which suggests that the 3-mCi dose is preferable.