Characterizing isolated tumor cells in regional lymph nodes of early endometrial cancer.

ABSTRACT

OBJECTIVE: To examine the characteristics of isolated tumor cells (ITCs) in regional lymph nodes of early-stage endometrial cancer. METHODS: This is a retrospective cohort study examining the National Cancer Institute's Surveillance, Epidemiology, and End Result Program. The study population was 6472 women with non-metastatic, node-negative T1 endometrial cancer who underwent primary hysterectomy and surgical nodal evaluation. Multivariable binary logistic regression model was used to identify the independent characteristics for ITCs. Postoperative therapy according to ITCs status was also assessed with propensity score weighting. RESULTS: ITCs were seen in 111 (1.7%) cases. In a multivariable analysis, ITCs were largely associated with tumor factors including deep myometrial invasion (T1b versus T1a, 4.0% versus 1.0%, adjusted-odds ratio [aOR] 3.42, P < 0.001) and larger tumor size (>4 versus ≤4 cm, 3.0% versus 1.6%, aOR 1.55, P = 0.037). Moreover, women undergoing sentinel lymph node (SLN) biopsy had a higher likelihood of identifying ITCs compared to those undergoing lymphadenectomy (LND) 2.7% for SLN alone, 3.7% for SLN/LND, and 1.2% for LND alone (aOR ranged 2.60-2.99, P < 0.001). Women who had ITCs identified were more likely to receive postoperative therapy (81.8% versus 31.7%, P < 0.001), including external beam radiotherapy (EBT) alone (25.1% versus 3.2%) and chemotherapy/EBT (16.3% versus 1.9%). Similar associations were observed in the low-risk group (stage IA, grade 1-2 endometrioid, 78.4% versus 9.2%, P < 0.001), including EBT alone (35.3% versus 0.6%). CONCLUSION: This study suggests that a SLN protocol can identify more ITCs in the regional lymph nodes of early endometrial cancer. Deep myometrial invasion and large tumor size were associated with increased risk of ITCs. Postoperative therapy is offered more frequently in the setting of ITCs with variable treatment patterns, warranting further outcome studies and practice guidelines.