Factors associated with successful bilateral sentinel lymph node mapping in endometrial cancer☆
Introduction
Sentinel lymph node (SLN) mapping has increasingly been recognized as an option for lymphatic assessment in patients undergoing surgical staging of endometrial cancer. In January 2014, the National Comprehensive Cancer Network Clinical Practice Guidelines were updated to include SLN mapping as a possible option for lymphatic assessment in experienced centers [1]. Despite this recognition, a number of controversies remain unsettled including optimal injection strategies and, most importantly, whether SLN mapping can be safely substituted for complete pelvic and para-aortic lymphadenectomy in patients that would otherwise be considered appropriate for a more comprehensive lymphatic assessment [2], [3], [4], [5], [6], [7].
Regardless of these overarching controversies, there is no dispute that a proportion of patients will not achieve successful lymphatic mapping with conventional SLN techniques. Depending on the published series, this rate ranges from 27 to 80% for failed bilateral SLN mapping [8]. Why do some patients fail to map? Lymphatic obstruction by tumor may be a factor. As demonstrated by Barlin et al., patients who fail to map have a higher rate of lymph node metastasis, presumably due to obstruction of lymphatic channels before reaching the sentinel node [9]. For this reason, side-specific lymphadenectomy has been recommended by some investigators for patients that fail to map on the ipsilateral side of the pelvis [10]. In spite of this, the majority of patients that fail to map likely do not have lymphatic metastases. If factors that predict patients at high risk for failed mapping can be identified, then strategies may be developed to increase the rate of successful mapping in this setting. Reducing the rate of failed mapping in patients without lymphatic metastasis has the potential to further mitigate the morbidity of completion lymphadenectomy — one of the primary advantages of SLN mapping in the first place [11], [12].
Other than lymphatic metastasis, factors influencing the rate of successful SLN mapping are largely unrecognized. The utilization of cervical injection and fluorescence imaging appear to have the greatest impact on the rate of successful mapping [8], [13], [14]. In a recent publication, we also identified that the benefit of fluorescence imaging with indocyanine green dye injection appears to be greatest in obese patients although no cutoff for preference was established due to a limited sample size [13]. After identifying these factors, we sought to determine whether other factors may influence mapping success. Given the potential influence of lymphatic obstruction caused by tumor infiltration, we hypothesized that other factors could also impair lymphatic drainage. As outlined below, we evaluated a number of factors divided into several categories that may impact failed mapping. These include patient demographic factors, tumor factors, surgeon factors, and lymphatic obstruction/inflammatory factors. Therefore, this study was conducted to evaluate the potential association of patient, tumor, and surgeon characteristics with lymphatic mapping success rate in women with endometrial cancer and complex atypical hyperplasia.
Section snippets
Sentinel lymph node mapping algorithm
Since September 2012, The Kelly Gynecologic Oncology Service at Johns Hopkins Hospital, Baltimore, MD has performed sentinel lymph node mapping as part of lymph node assessments for patients with endometrial cancer. Four gynecologic oncology surgeons with expertise in sentinel lymph node mapping techniques have participated in this program and contributed patients to a prospectively maintained database with institutional review board approval. Two surgeons were fellowship trained in sentinel
Results
During the study period, 111 patients underwent attempted sentinel lymph node mapping during robotic-assisted total laparoscopic hysterectomy for endometrial cancer or CAH. Demographic information can be found in Table 1. Most patients had grade 1 endometrioid tumors (48.6%) or CAH (16.2%) on final histology, although a significant percentage of type II cancers were also diagnosed (22.5%). Of the 79 patients with low risk disease based on preoperative sampling, 96% underwent frozen section
Discussion
Our understanding of the utility of sentinel lymph node mapping for endometrial cancer is growing rapidly but several questions remain unanswered. In the current analysis, we explored a number of factors that we hypothesized may impact the success of lymphatic mapping. As described in our previous report, the use of indocyanine green dye via cervical injection and fluorometrically-capable imaging remained the most important predictor of mapping success [13]. This is especially the case in obese
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Disclosure statement: The authors report no conflicts of interest. No industry or pharmaceutical support was obtained to conduct this research or produce this manuscript.