Risk of empty lymph node packets in sentinel lymph node mapping for endometrial cancer using indocyanine green

Objective: To determine whether the rate of sentinel lymph node (SLN) dissections that do not yield a lymph node on pathological analysis ('empty packet dissection') changes with increasing surgeon experience in the setting of patients undergoing minimally invasive hysterectomy and SLN mapping using indocyanine green dye for endometrial cancer.

Methods: All patients undergoing SLN mapping using indocyanine green dye at the time of minimally invasive hysterectomy for endometrial cancer or complex atypical hyperplasia were identified between January 2013 and September 2017 at our institution. All surgeons had prior experience performing SLN mapping for endometrial cancer using other methods. The rate of empty packet dissections and SLN counts were evaluated using a logistic regression model analysis.

Results: In total, 236 patients undergoing SLN mapping for either endometrial cancer (85%) or complex atypical hyperplasia (15%) were identified from a prospectively maintained database. When examining all six surgeons together, the percentage of empty packet dissections decreased with increasing number of procedures performed. Each additional procedure was associated with a 3.6% reduction in the odds of an empty packet SLN dissection. After adjusting for individual surgeons, each additional procedure was associated with a 4.9% reduction in the odds of an empty packet. The expected odds of an empty packet after 10 additional procedures decreased by 40.1% (95% CI 12.4% to 58.6%). The addition of two covariates (age and body mass index) did not contribute significantly to the model (likelihood ratio test: X²=2.75, p=0.25). The rate of empty packets appeared to stabilize after approximately 30 procedures. The number of SLNs removed did not change with increasing surgeon experience.

Conclusion: The rate of empty packet SLN dissections using indocyanine green dye decreases with increasing number of procedures. This stabilizes after 30 procedures, suggesting completion of a learning curve.