Sentinel lymph node mapping in endometrial cancer: an analysis of parameters affecting detection rate in SPECT/CT

Objectives SPECT/CT after pericervical injection of technetium-99m-nanocolloide was shown to be suitable for sentinel lymph nodes (SLN) mapping in endometrial cancer. Aim of our study was to analyze factors affecting successful SLN detection in SPECT/CT such as imaging findings, patient characteristics and tumor biology in a large cohort of patients.

Methods 141 consecutive patients referred for surgery of endometrial cancer were included in this retrospective analysis. All patients received pericervical injection of technetium-99m-nanocolloide (mean 243 MBq) followed by SPECT/CT of abdomen and pelvis (mean 4:41 h p.i.). Total hysterectomy and lymphadenectomy was performed on the next day. Acquisition parameters, patient characteristics, SPECT/CT findings and histopathological results were collected. Mann-Whitney U test was used for statistics.

Results The overall scintigraphic SLN detection rate was 81%. SLN detection failure was frequently associated with high bone marrow and sometimes peritoneal/abdominal radioactivity (p=0.005 and p=0.24 respectively). Liver/spleen uptake on its own was not predictive of detection failure, but even more often present in case of successful detection (70% vs. 84%). There was a trend for high BMI in case of missed SLN detection (p=0.054). Lymph node (LN) involvement did not seem to affect SLN detection since 13/16 cases were detected on SPECT/CT. Paraaortic SLN detection was associated with a somewhat higher injected activity (mean 259 vs. 236 MBq; p=0.014). No significant influence on SPECT/CT results was found for parameters tumor histology and stage, patient age and the time gap between injection and imaging.

Conclusions Venous drainage as indicated by bone marrow uptake was the most important factor associated with SLN detection failure thus meticulous application of the radiotracer is crucial in endometrial cancer. Remarkably, presence of LN metastases did not seem to influence SLN detection rate.