CHICAGO – Sentinel lymph node mapping is a safe, less extensive alternative to lymph node dissection in women with endometrial cancer regardless of the clinically suspected risk of metastases, suggest a pair of retrospective cohort studies reported at the annual meeting of the Society of Gynecologic Oncology.
“The role and extent of surgical staging in endometrial carcinoma is controversial. The various strategies range from no lymphadenectomy to a full lymphadenectomy dissection up to the renal vessels,” said Dr. Ane Gerda Zahl Eriksson, a surgical fellow in gynecologic oncology at the Memorial Sloan Kettering Cancer Center, New York.
“The use of SLN [sentinel lymph node] mapping is emerging as an acceptable approach for nodal assessment in endometrial carcinoma. However, as always when introducing a novel management strategy, we must be mindful not to compromise oncologic outcome or otherwise inflict harm on our patients by our approach,” she added.
Dr. Eriksson and colleagues assessed clinicopathologic outcomes according to nodal assessment approach among women with low-risk endometrial cancer, defined as that with endometrioid histology of any grade with myometrial invasion of less than 50%.
They compared 493 women who had selective lymph node dissection (LND) at the Mayo Clinic between 2004 and 2008 according to an institutional algorithm (complete pelvic and para-aortic lymphadenectomy to the renal veins in cases deemed at risk for nodal metastasis) with 642 women who had SLN mapping at the Memorial Sloan Kettering Cancer Center between 2006 and 2013 according to an institutional algorithm. The SLNs were evaluated by pathologic ultrastaging and were considered positive whether they had macrometastases, micrometastases, or isolated tumor cells.
Results showed that patients in the SLN cohort were more likely to have pelvic nodes excised (93% vs. 58%) and less likely to have para-aortic nodes excised (14% vs. 50%), Dr. Eriksson reported.
Markedly fewer lymph nodes were removed per patient with the SLN algorithm, yet it yielded a higher detection rate of stage IIIC1 disease (4.8% vs. 1.8%) and similar detection rates of stage IIIA/B and stage IIIC2 disease.
Patients in the SLN cohort were more than twice as likely to receive adjuvant therapy (27% vs. 12%). (Dr. Eriksson noted that patients in the SLN cohort who had positive nodes were offered the same adjuvant therapy options regardless of the amount of metastases found in the nodes.)
With a median follow-up of 2.1 years in the SLN cohort and 3.5 years in the LND cohort, the cohorts had statistically indistinguishable 3-year rates of freedom from isolated nodal recurrence (99.6% in each) and disease-free survival (94.9% and 96.8%).
“The application of the SLN algorithm does not appear to compromise oncologic outcome in this short follow-up. The value of SLN dissection or selective lymphadenectomy in patients with tumors equal to or less than 2 cm remains controversial,” Dr. Eriksson commented. “The clinical significance of disease detected on ultrastaging and the role of adjuvant therapy in these patients remains to be determined.”
“Prospective assessment of the SLN algorithm is needed and underway,” she concluded. “Our findings support the use of either strategy for endometrial cancer staging with no apparent detriment to the SLN algorithm.”
In the second study, investigators led by Dr. Jennifer A. Ducie, also a surgical fellow in gynecologic oncology at the Memorial Sloan Kettering Cancer Center, performed a similar analysis among women with intermediate-risk endometrial cancer, defined as that having endometrioid histology with any grade and at least 50% myometrial invasion, and high-risk endometrial cancer, defined as serous or clear cell carcinoma.
In the intermediate-risk group, there were 82 patients in the SLN cohort and 107 patients in the LND cohort. The groups had a similar detection rate of stage IIIC disease overall (35% and 28%), but the SLN cohort had a higher rate of detection of stage IIIC1 disease (32% vs. 11%) and the LND cohort had a higher rate of detection of stage IIIC2 disease (17% vs. 4%), Dr. Ducie reported.
In the high-risk group, there were 120 patients in the SLN cohort and 103 patients in the LND cohort. Patients in the SLN cohort were more likely to have pelvic nodes removed (98% vs. 85%) but had fewer nodes removed (11 vs. 30). Among patients who had para-aortic nodes removed, the SLN cohort was similarly as likely as the LND cohort to have positive nodes, but had a smaller median number positive (two vs. five). The rate of detection of stage IIIC disease overall (23% vs. 19%) and of the substages was statistically indistinguishable.