Paraaortic sentinel lymph node detection in intermediate and high-risk endometrial cancer by transvaginal ultrasound-guided myometrial injection of radiotracer (TUMIR)

Abstract

Objective: We aimed to evaluate the accuracy of sentinel lymph node (SLN) mapping with transvaginal ultrasound-guided myometrial injection of radiotracer (TUMIR) to detect lymph node (LN) metastases, in patients with intermediate and high-risk endometrial cancer (EC), focusing on its performance to detect paraaortic involvement.

Methods: Prospective study including women with preoperative intermediate or high-risk EC, according to ESMO-ESGO-ESTRO consensus, who underwent SLN mapping using the TUMIR approach. SLNs were preoperatively localized by planar and single photon emission computed tomography/computed tomography images, and intraoperatively by gamma-probe. Immediately after SLN excision, all women underwent systematic pelvic and paraaortic lymphadenectomy by laparoscopy.

Results: The study included 102 patients. The intraoperative SLN detection rate was 79.4% (81/102). Pelvic and paraaortic drainage was observed in 92.6% (75/81) and 45.7% (37/81) women, respectively, being exclusively paraaortic in 7.4% (6/81). After systematic lymphadenectomy, LN metastases were identified in 19.6% (20/102) patients, with 45.0% (9/20) showing paraaortic involvement, which was exclusive in 15.0% (3/20). The overall sensitivity and negative predictive value (NPV) of SLNs by the TUMIR approach to detect lymphatic involvement were 87.5% and 97.0%, respectively; and 83.3% and 96.9%, for paraaortic metastases. After applying the MSKCC SLN mapping algorithm, the sensitivity and NPV were 93.8% and 98.5%, respectively.

Conclusion: The TUMIR method provides valuable information of endometrial drainage in patients at higher risk of paraaortic LN involvement. The TUMIR approach showed a detection rate of paraaortic SLNs greater than 45% and a high sensitivity and NPV for paraaortic metastases in women with intermediate and high-risk EC.

Keywords: Endometrial Neoplasms; Genital Neoplasms, Female; Lymph Node Excision; Sensitivity and Specificity; Sentinel Lymph Node; Surgery.

Fig. 1. Transvaginal ultrasound-guided myometrial injection of radiotracer. In the first step the needle penetrates through the anterior vaginal fornix, crossing the anterior myometrium and the endometrial cavity until reaching the posterior myometrium (A). Half of the volume of radiotracer is injected into the outer two-thirds of the myometrium (C). Then, the needle is partially removed, and the remaining volume of radiotracer is injected into the outer two-thirds of the anterior myometrium (E). (B) Needle crossing the endometrial cavity towards the posterior wall (red arrow). Discontinuous green line delimits the uterus. (D) Tracer accumulation (cyan asterisk) in the posterior wall of the myometrium. Discontinuous green line delimits the uterus. Green double-headed arrow indicates the endometrium. (F) Tracer accumulation (cyan asterisk) in the anterior and posterior walls of the myometrium. Discontinuous green line delimits the uterus. Green double-headed arrow indicates the endometrium.

Fig. 2. Flow chart of the patients included in the study and available for the analyses.

SLN, sentinel lymph node; TUMIR, transvaginal ultrasound-guided myometrial injection of radiotracer.

Fig. 3. Topography and lymphatic status of the SLNs identified in the different anatomical areas of lymphatic drainage (n=244) in the 81 patients with at least one SLN. (A) Number and percentage of SLNs retrieved per anatomic area. (B) Number and percentage of involved SLNs per anatomic area.

SLN, sentinel lymph node.