Is the risk of substantial LVSI in stage I endometrial cancer similar to PORTEC in the North American population? - A single-institution study.

OBJECTIVES: A pooled analysis of PORTEC-1 & 2 identified substantial lymphovascular space invasion (LVSI) in 4.8% of patients, which predicted for pelvic recurrence, distant metastasis, and overall survival. Our institution implemented the PORTEC three-tier system of LVSI reporting (absent, focal, or substantial). We aimed to quantify the incidence of substantial LVSI in a North American population and to correlate extent of LVSI with lymph node (LN) involvement.

METHODS: A retrospective review was conducted on patients with clinically uterine-confined, endometrioid type endometrial cancer who underwent surgical staging and were found to have pT1a-b disease. Binary logistic regression was used to assess predictors of LN involvement (defined as ITC, micrometastases, or macrometastases).

RESULTS: In total, 438 patients with pT1a-b disease were identified. In the overall cohort and in the subset meeting PORTEC-1 inclusion criteria (n = 195), no LVSI was present in 67.4% and 50.8%; focal LVSI was present in 16.7% and 24.1%; and substantial LVSI was present in 16.0% and 25.1%, respectively. Among patients who underwent surgical LN assessment (79.2%, n = 347), LNs were involved in 3.3% without LVSI, 7.5% with focal LVSI (OR 2.4), and 15.2% with substantial LVSI (OR 5.3) (p = .005), with a similar trend in the PORTEC-1 cohort. Extent of LVSI correlated with disease burden in LN metastases.

CONCLUSION: Our incidence of substantial LVSI was three to five times higher than reported by PORTEC and correlated with LN involvement. This questions the reproducibility of the three-tier LVSI reporting system and emphasizes the need for multi-institutional data outside PORTEC for confirmation of our findings.