Sentinel Node Mapping in Ovarian Tumors: A Study Using Lymphoscintigraphy and SPECT/CT

Abstract

Purpose: Ovarian cancer in the early stage requires a complete surgical staging, including radical lymphadenectomy, implying subsequent risk of morbidity and complications. Sentinel lymph node (SLN) mapping is a procedure that attempts to reduce radical lymphadenectomy-related complications and morbidities. Our study evaluates the feasibility of SLN mapping in patients with ovarian tumors by the use of intraoperative Technetium-99m-Phytate (Tc-99m-Phytate) and postoperative lymphoscintigraphy using tomographic (single-photon emission computed tomography/computed tomography (SPECT/CT)) acquisition.

Materials and methods: Thirty-two patients with ovarian mass participated in this study. Intraoperative injection of the radiopharmaceutical was performed just after laparotomy and before the removal of tumor in utero-ovarian and suspensory ligaments of the ovary just beneath the peritoneum. Subsequently, pelvic and para-aortic lymphadenectomy was performed for malignant masses, and the presence of tumor in the lymph nodes was assessed through histopathological examination. Conversely, lymphadenectomy was not performed in patients with benign lesions or borderline ovarian tumors. Lymphoscintigraphy was performed within 24 hr using tomographic acquisition (SPECT/CT) of the abdomen and pelvis.

Results: Final pathological examination showed 19 patients with benign pathology, 5 with borderline tumors, and 6 with malignant ovarian tumors. SPECT/CT identified SLNs in para-aortic-only areas in 6 (20%), pelvic/para-aortic areas in 14 (47%), and pelvic-only areas in 7 (23%) cases. Notably, additional unusual SLN locations were revealed in perirenal, intergluteal, and posterior to psoas muscle regions in three patients. We were not able to calculate the false negative rate due to the absence of patients with involved lymph nodes.

Conclusion: SLN mapping using intraoperative injection of radiotracers is safe and feasible. Larger studies with more malignant cases are needed to better evaluate the sensitivity of this method for lymphatic staging of ovarian malignancies.

Figure 1

Flowchart of the patient's selection.

Figure 2

Location of hot spots found using intraoperative gamma probing. The hexagons are locations of hot spots found in patients (n = 9) with tumor on the right side. The circles are locations of hot spots found in patients (n = 13) with tumor on the left side. The squares are locations of hot spots found in patients (n = 8) with tumor on bilateral sides.

Figure 3

Aberrant ovarian sentinel lymph nodes (SLN) in the sagittal and transverse SPECT/CT lymphoscintigraphy. (a) and (b): intergluteal SLN; (c) and (d): peri-renal SLN; and (e) and (f): psoas region SLN.

Figure 4

Planar lymphoscintigraphy in the (a) anterior and (b) posterior views show hotspots in the mid-abdomen and left pelvic side. SPECT/CT shows the exact location of these hotspots compatible with para-aortic and left internal iliac sentinel lymph nodes in the (c, d) transverse and (e, f) coronal views.