Omitting Preoperative Lymphoscintigraphy Does Not Decrease Sentinel Lymph Node Detection Rate in Vulvar Cancer

Sentinel lymph nodes in vulvar cancer can be detected in a variety of ways. A method described in GOG-173 involves injection of technetium-99m and isosulfan blue intraoperatively. Lymphoscintigraphy, for which the technetium-99m is injected preoperatively, became required two years into the study due to unpublished evidence that lymphoscintigraphy improved intraoperative sentinel lymph node localization. Despite this amendment, the need for preoperative lymphoscintigraphy has been questioned. The primary objective of this study was to determine the detection rate of sentinel lymph nodes in vulvar cancer when preoperative lymphoscintigraphy is omitted. The secondary objective was to compare the sentinel lymph node detection rate when lymphoscintigraphy is omitted to the rate reported in GOG-173, in which preoperative lymphoscintigraphy was performed. The tertiary objective was to determine lymphoscintigraphy cost at one institution. Patients with vulvar cancer who underwent sentinel lymph node dissection at a single institution from 2008 to 2016 were identified. All but one patient had intraoperative peritumoral injection of both technetium-99m and patent blue dye. Patients were excluded if preoperative lymphoscintigraphy was performed. Information on demographics, pathology, and outcomes were collected. Descriptive statistics were used for patient demographics, tumor characteristics, and the detection rate. A 1-sample proportion test was used to compare our detection rate to data available from GOG-173. Percentages were rounded to the nearest whole number. Current procedural terminology codes were used to estimate lymphoscintigraphy cost. Fifty patients were identified and 32 patients were deemed eligible for the study. The sentinel lymph node detection rate was 97% per patient, which was not statistically different from the rate of 92% reported in GOG-173 (p = 0.347). It was determined that lymphoscintigraphy cost $5,288.22 per imaging study. In this study, omitting preoperative lymphoscintigraphy did not decrease sentinel lymph node detection rates when compared to GOG-173. Furthermore, there is a substantial cost associated with lymphoscintigraphy, although this cost may vary between institutions