Can late lymphoscintigraphy be omitted in the sentinel node procedure in early-stage vulvar cancer?

In the Netherlands, the sentinel lymph node procedure protocol consists of preoperative lymphoscintigraphy combined with intraoperative blue dye for identifying sentinel lymph nodes in early vulvar squamous cell carcinoma. This study aimed at investigating the role of early and late lymphoscintigraphy.

From January 2015 to January 2019, early and late lymphoscintigraphies of 52 women were retrospectively analyzed. Lymphoscintigraphy was performed 30 minutes (early) and 2.5-4 hours (late) after vulvar injection of ^99m Tc-labeled nanocolloid. We calculated the concordance correlation coefficient (CCC) between number of sentinel lymph nodes detected on both images using the Lins concordance coefficient and correlated with clinicopathological data.

Thirty-four women had a midline tumor and 18 had a lateral tumor. Detection rates with early and late scintigraphy were 88.5% and 98.1%, respectively. Median number of detected nodes was 1.0 (0-7) and 2.0 (0-7). Good statistical correlation between number of sentinel lymph nodes detected on early and late imaging was found (CCC = 0.76) in most patients. In 18 women (35%) a mismatch occurred: a higher number of nodes was detected on late imaging. In 11 of 18 women re-injection was performed because no sentinel lymph nodes were visualized on early images. Late imaging and intraoperative detection showed a good statistical correlation (CCC = 0.61). One woman showed an isolated groin recurrence despite negative sentinel lymph nodes.

This study showed good statistical correlations between early and late scintigraphy in most patients. However, in 35% of women late scintigraphy detected more nodes. In case of poor visualization after the first scintigraphy, re-injection should be considered. Late scintigraphy is probably helpful in confirming successful re-injection and in showing deviating lymph flow in women with failed mapping after the first injection and successful re-injection. Because missing metastatic sentinel lymph nodes often leads to a poor prognosis, we prefer optimal correlations between imaging and intraoperative identification. Hence, late scintigraphy cannot be safely omitted.