Can SLN mapping replace lymphadenectomy for surgical staging of early-stage EEC?

Researchers from the KK Women’s and Children’s Hospital, Singapore found that sentinel lymph node (SLN) mapping is an acceptable and safe alternative to routine lymphadenectomy in the surgical staging of early-stage endometrioid endometrial cancer (EEC).

Complete lymphadenectomy has been considered the standard of care for evaluating LN status in EC. However, it is associated with surgical morbidity, such as long-term complications of lymphoedema and lymphocyst formation, the researchers pointed out.

“SLN mapping has been developed as an alternative to complete lymphadenectomy for the surgical staging of early-stage, uterine-confined EC to reduce the morbidity of lymphadenectomy and has been demonstrated as a safe and feasible alternative,” they added.

The researchers retrospectively evaluated 203 women with clinical and radiological FIGO* stage I EEC undergoing staging surgery (THBSO** with/without pelvic lymph node dissection [PLND] and/or para-aortic lymph node dissection). Of these, 109 underwent SLN mapping while 94 had PLND. [Obstet Gynecol Int 2023;doi:10.1155/2023/9949604]

Compared with the PLND group, the SLN group had a markedly shorter operative time (median 129 vs 162 minutes), less blood loss (median 100 vs 300 mL), and shorter postoperative hospital stay (3 vs 4 days; p<0.001 for all).

There were no significant differences between the SLN and PLND groups in terms of the number of operative complications (12.8 percent vs 23.4 percent; p=0.05). LN metastases detection rates were also comparable between groups (4.6 percent vs 7.4 percent; p=0.389), as were disease-free survival (median 13 months; p=0.538) and overall survival (median 13 months; p=0.333).

The SLN group had numerically lower rates of cervical stromal involvement (9.2 percent vs 20.2 percent; p=0.076), lymphovascular space invasion present (7.3 percent vs 12.8 percent; p=0.196), and positive peritoneal washings (2.8 percent vs 9.6 percent; p=0.08) than the PLND group, but the between-group differences were not significant.

The comparable results imply that SLN mapping appears to be noninferior to standard lymphadenectomy in terms of oncological outcomes, the researchers noted. “Our centre’s experience and results with SLN mapping successfully reproduce comparable surgical and oncological outcomes to those reported in literature.”

Shifting to SLN mapping

SLN mapping with ultra-staging has been shown to increase LN metastases detection and improve staging, with indocyanine green being the tracer of choice owing to its superiority to methylene blue and radiocolloid in terms of detection rate. [Gynecol Oncol 2017;147:528-534; Gynecol Oncol 2014;133:506-511; Gynecol Oncol 2017;146:405-415]

The SENTOR study found SLN mapping to be a feasible alternative for surgical staging of high-risk EC, with 96-percent sensitivity, 4-percent false-negative rate, and 99-percent negative predictive value for detection of nodal metastases in patients with high-grade EC at an increased risk of nodal metastases. [JAMA Surg 2021;156:157-164] Another study showed that SLN biopsy can accurately detect LN metastases in high-grade EC. [Am J Obstet Gynecol 2021;225:367.e1-367.e39]

“[T]he current focus of research is shifting to the use of SLN mapping in high-grade EC … [Findings from these studies] suggest that SLN biopsy may replace routine lymphadenectomy in high-grade ECs,” said the researchers.

“We recognize that our main limitation was the short median duration of follow-up (14–15 months) and the size of or study population, which may have affected the comparison of operative complications and long-term complications such as lymphoedema,” they noted. Longer term follow-up and studies with larger cohorts are thus recommended.