Sentinel lymph node biopsy in endometrial cancer: description of the technique and preliminary results

Sentinel node biopsy for diagnosis of lymph node involvement in endometrial cancer

BACKGROUND

Pelvic lymphadenectomy provides prognostic information for those diagnosed with endometrial (womb) cancer and provides information that may influence decisions regarding adjuvant treatment. However, studies have not shown a therapeutic benefit, and lymphadenectomy causes significant morbidity. The technique of sentinel lymph node biopsy (SLNB), allows the first draining node from a cancer to be identified and examined histologically for involvement with cancer cells. SLNB is commonly used in other cancers, including breast and vulval cancer. Different tracers, including colloid labelled with radioactive technetium-99, blue dyes, e.g. patent or methylene blue, and near infra-red fluorescent dyes, e.g. indocyanine green (ICG), have been used singly or in combination for detection of sentinel lymph nodes (SLN).

OBJECTIVES

To assess the diagnostic accuracy of sentinel lymph node biopsy (SLNB) in the identification of pelvic lymph node involvement in women with endometrial cancer, presumed to be at an early stage prior to surgery, including consideration of the detection rate.

SEARCH METHODS

We searched MEDLINE (1946 to July 2019), Embase (1974 to July 2019) and the relevant Cochrane trial registers.

SELECTION CRITERIA

We included studies that evaluated the diagnostic accuracy of tracers for SLN assessment (involving the identification of a SLN plus histological examination) against a reference standard of histological examination of removed pelvic +/- para-aortic lymph nodes following systematic pelvic +/- para-aortic lymphadenectomy (PLND/PPALND) in women with endometrial cancer, where there were sufficient data for the construction of two-by-two tables.

DATA COLLECTION AND ANALYSIS

Two review authors (a combination of HN, JM, NW, RG, and WH) independently screened titles and abstracts for relevance, classified studies for inclusion/exclusion and extracted data. We assessed the methodological quality of studies using the QUADAS-2 tool. We calculated the detection rate as the arithmetic mean of the total number of SLNs detected out of the total number of women included in the included studies with the woman as the unit of analysis, used univariate meta-analytical methods to estimate pooled sensitivity estimates, and summarised the results using GRADE.

MAIN RESULTS

The search revealed 6259 unique records after removal of duplicates. After screening 232 studies in full text, we found 73 potentially includable records (for 52 studies), although we were only able to extract 2x2 table data for 33 studies, including 2237 women (46 records) for inclusion in the review, despite writing to trial authors for additional information. We found 11 studies that analysed results for blue dye alone, four studies for technetium-99m alone, 12 studies that used a combination of blue dye and technetium-99m, nine studies that used indocyanine green (ICG) and near infra-red immunofluorescence, and one study that used a combination of ICG and technetium-99m. Overall, the methodological reporting in most of the studies was poor, which resulted in a very large proportion of 'unclear risk of bias' ratings. Overall, the mean SLN detection rate was 86.9% (95% CI 82.9% to 90.8%; 2237 women; 33 studies; moderate-certainty evidence). In studies that reported bilateral detection the mean rate was 65.4% (95% CI 57.8% to 73.0%) . When considered according to which tracer was used, the SLN detection rate ranged from 77.8% (95% CI 70.0% to 85.6%) for blue dye alone (559 women; 11 studies; low-certainty evidence) to 100% for ICG and technetium-99m (32 women; 1 study; very low-certainty evidence). The rates of positive lymph nodes ranged from 5.2% to 34.4% with a mean of 20.1% (95% CI 17.7% to 22.3%). The pooled sensitivity of SLNB was 91.8% (95% CI 86.5% to 95.1%; total 2237 women, of whom 409 had SLN involvement; moderate-certainty evidence). The sensitivity for of SLNB for the different tracers were: blue dye alone 95.2% (95% CI 77.2% to 99.2%; 559 women; 11 studies; low-certainty evidence); Technetium-99m alone 90.5% (95% CI 67.7% to 97.7%; 257 women; 4 studies; low-certainty evidence); technetium-99m and blue dye 91.9% (95% CI 74.4% to 97.8%; 548 women; 12 studies; low-certainty evidence); ICG alone 92.5% (95% CI 81.8% to 97.1%; 953 women; 9 studies; moderate-certainty evidence); ICG and blue dye 90.5% (95% CI 63.2.6% to 98.1%; 215 women; 2 studies; low-certainty evidence); and ICG and technetium-99m 100% (95% CI 63% to 100%; 32 women; 1 study; very low-certainty evidence). Meta-regression analyses found that the sensitivities did not differ between the different tracers used, between studies with a majority of women with FIGO stage 1A versus 1B or above; between studies assessing the pelvic lymph node basin alone versus the pelvic and para-aortic lymph node basin; or between studies that used subserosal alone versus subserosal and cervical injection. It should be noted that a false-positive result cannot occur, as the histological examination of the SLN is unchanged by the results from any additional nodes removed at systematic lymphadenectomy.

AUTHORS' CONCLUSIONS

The diagnostic test accuracy for SLNB using either ICG alone or a combination of a dye (blue or ICG) and technetium-99m is probably good, with high sensitivity, where a SLN could be detected. Detection rates with ICG or a combination of dye (ICG or blue) and technetium-99m may be higher. The value of a SLNB approach in a treatment pathway, over adjuvant treatment decisions based on uterine factors and molecular profiling, requires examination in a high-quality intervention study.

Sentinel lymph node mapping in gynecological oncology

The intraoperative mapping of sentinel lymph nodes (SLNs) is part of the treatment strategy for a number of types of tumor. To retrospectively compare results from the mapping of pelvic SLNs for gynecological oncology, using distinct dyes, the present review was conducted to determine the clinical significance of SLN mapping for gynecological oncology. In addition, the present study aimed at identifying an improved choice for SLN mapping tracers in clinical application. Each dye exhibits demerits when applied in the clinical environment. The combination of radioisotopes and blue dyes was identified to exhibit the most accurate detection rate of SLN drainage of gynecological oncology. However, contrast agents were unable to identify whether a SLN is positive or negative for metastasis prior to pathologic examination; additional studies are required.

Sentinel lymph node assessment in endometrial cancer: a systematic review and meta-analysis

BACKGROUND

In the staging of endometrial cancer, controversy remains regarding the role of sentinel lymph node mapping compared with other nodal assessment strategies.

OBJECTIVE

We conducted a systematic review to evaluate the diagnostic accuracy and clinical impact of sentinel lymph node mapping in the management of endometrial cancer.

DATA SOURCES

We searched Medline, Embase, and the Cochrane Central Registry of Controlled trials for studies published in English before March 25, 2016 (PROSPERO CRD42016036503).

STUDY ELIGIBILITY CRITERIA

Studies were included if they contained 10 or more women with endometrial cancer and reported on the detection rate, sensitivity, and/or impact on treatment or survival of sentinel lymph node mapping.

STUDY APPRAISAL AND SYNTHESIS METHODS

Two authors independently reviewed abstracts and full-text articles for inclusion and assessed study quality. The detection rate, sensitivity, and factors associated with successful mapping (study size, body mass index, tumor histology and grade, injection site, dye type) were synthesized through random-effects meta-analyses and meta-regression.

RESULTS

We identified 55 eligible studies, which included 4915 women. The overall detection rate of sentinel lymph node mapping was 81% (95% confidence interval, 77-84) with a 50% (95% confidence interval, 44-56) bilateral pelvic node detection rate and 17% (95% confidence interval, 11-23) paraaortic detection rate. There was no difference in detection rates by patient body mass index or tumor histology and grade. Use of indocyanine green increased the bilateral detection rate compared with blue dye. Additionally, cervical injection increased the bilateral sentinel lymph node detection rate but decreased the paraaortic detection rate compared with alternative injection techniques. Intraoperative sentinel lymph node frozen section increased the overall and bilateral detection rates. The sensitivity of sentinel node mapping to detect metastases was 96% (95% confidence interval, 91-98); ultrastaging did not improve sensitivity. Compared with women staged with complete lymphadenectomy, women staged with sentinel lymph node mapping were more likely to receive adjuvant treatment.

CONCLUSION

Sentinel lymph node mapping is feasible and accurately predicts nodal status in women with endometrial cancer. The current data favors the use of cervical injection techniques with indocyanine green. Sentinel lymph mapping may be considered an alternative standard of care in the staging of women with endometrial cancer.

Sentinel lymph node mapping in early stage of endometrial and cervical cancers

BACKGROUND

The sentinel lymph node (SLN) is defined as the first chain node in the lymphatic basin that receives primary lymphatic flow. If the SLN is negative for metastatic disease, then other nodes are expected to be disease-free. SLN techniques have been extensively applied in the staging and treatment of many tumors, including melanoma, breast and vulvar cancers. This study aims to evaluate our technique in SLN mapping in early stage endometrial and cervical cancers.

MATERIALS AND METHODS

We scheduled a cross-sectional pilot study for patients undergoing staging surgery for endometrial and cervical cancer from November 2012 to February 2014 in Beheshti and Sadoughi Hospitals. Our SLN mapping technique included 1 h preoperative or intraoperative injection of 4 ml of 1% methylene blue dye in the tumor site. At the time of surgery, blue lymph nodes were removed and labeled as SLNs. Then systematic lymph node dissection was completed, and all of the nodes were sent for pathologic examination concerning metastatic involvement. All of the sentinel nodes were first stained with hematoxylin and eosin and examined. Those negative in this study were then stained with immunohistochemistry using anti-keratin antibody. Descriptive statistics, sensitivity, negative predictive values (NPV), false negative (FN) and detection rates were calculated.

RESULTS

Twenty-three patients including 62% endometrial and 38% cervical cancers enrolled in the study. Median of SLN count in the endometrial and cervical cancers was 3 and 2, respectively. Among endometrial and cervical cancers, detection rate of metastatic disease was 80% and 87.5%, respectively. The FN rate for this technique was 0 and the sensitivity and NPV are 100% for both endometrial and cervical cancers.

CONCLUSION

Considering the lower risk of metastases in early stage of both endometrial and cervical cancers, SLN technique allows for confident and accurate staging of cancer.