Limits of lymphoscintigraphy for sentinel node biopsy in women with endometrial cancer

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.

Recent Advances in Endometrial Cancer

Endometrial cancer is the most common gynecologic malignancy in the United States, with yearly rates continuing to increase. Most women present with early stage disease; however, advanced disease carries a grave prognosis. As a result, novel therapies are currently under investigation for the treatment of endometrial cancer. These advances include a better understanding of the genetic basis surrounding the development of endometrial cancer, novel surgical therapies, and new molecular targets for the treatment of this disease. This review explores the literature regarding these advancements in endometrial cancer.

Pericervical Injection of 99mTc-Nanocolloid Is Superior to Peritumoral Injection for Sentinel Lymph Node Detection of Endometrial Cancer in SPECT/CT

PURPOSE

Scintigraphic mapping of sentinel lymph node (SLN) is increasingly performed in patients with endometrial carcinoma although its routine clinical use is still under investigation. The purpose of this study was to compare preoperative SLN detection by means of SPECT/CT using pericervical (PC) versus hysteroscopic peritumoral (PT) injection.

PATIENTS AND METHODS

One hundred forty consecutive patients with endometrial carcinoma who underwent surgery and preoperative SLN SPECT/CT with Tc-nanocolloid were included. Seventy women received hysteroscopic injection at 3 PT sites, and 70 women received PC injection at 3-, 6-, 9-, and 12-o'clock positions. Each patient underwent SPECT/CT followed by modified radical hysterectomy with lymphadenectomy on the day after. Histopathological results were collected for validation.

RESULTS

Three hundred thirty-four SLNs were detected by SPECT/CT in 106 patients (mean, 3.15; range, 1-9). The detection rate after PC nanocolloid injection was 83% versus 69% after PT injection (Pearson χ test, P = 0.049). However, PT application resulted in a higher rate of para-aortic SLNs (PC: 60% vs PT: 38% of positive scans, P = 0.02). SPECT/CT yielded an overall sensitivity of 70% for the SLN detection in women with lymph node metastases with 3 false-negative cases. Failure to detect SLN was mostly associated with uptake in the reticuloendothelial system (liver, spleen, and bone marrow) or peritoneal diffusion in both cohorts. Negative scans after PT application often showed a minor to even failing injection depot.

CONCLUSIONS

Pericervical injection leads to a significantly better detection rate of SLN on SPECT/CT while reducing invasiveness of the injection procedure. Failure to detect SLN seems to be associated with major venous drainage.

Sentinel-node mapping in endometrial cancer patients: comparing SPECT/CT, gamma-probe and dye

OBJECTIVE

The aim of this study was to compare preoperative SPECT/CT with gamma-probe and methylene blue-dye (MBD) in the identification of sentinel lymph node (SLN) in early stage endometrial cancer.

METHODS

40 stage-I EC patients (66.7 ± 9.7 years) underwent preoperative lymphoscintigraphy. After about 3 h from Tc-99m-albumin nanocolloid cervical injection, all patients underwent SPECT/CT study. MBD was injected into the cervix just before surgery under general anesthesia. All patients underwent SLN biopsy, hysterectomy, bilateral salpingo-oophorectomy, and radical regional lymphadenectomy. SPECT/CT findings were compared to those of gamma-probe and MBD techniques.

RESULTS

In 2 patients no nodal migration was observed, neither with MBD nor radiotracer. Detection rate of at least one SLN was 90% (36/40 patients) with SPECT/CT, 88% (35/40) intra-operatively with gamma-probe and 80% (32/40) with MBD. Only in 7/40 patients a bilateral migration was obtained with all considered modalities. In particular, bilateral detection was achieved in 26 patients with SPECT/CT, in 24 with gamma-probe and in 10 patients with MBD. The concordance site between SPECT/CT and intraoperative gamma-probe was 73% (29/40 patients: 2 without migration, 21 bilateral and 6 monolateral SLNs); while concordance site with MBD was found in 40% (16/40: 8 bilateral, 6 monolateral SLNs, 2 without SLNs). Overall, 628 LNs were dissected (mean 18 LNs per patient). The median number of SLNs removed was 2 (mean 2.5 per patient). Out of 91 SLNs: 43 were "hot and blue (HB)", 10 were blue only and 38 were hot only. LN metastases rate was 16%: 9/90 SLNs (7 HB, 2 hot only) were positive for metastases in 6 patients. Four non-SLNs were found positive in 3 patients, and all presented concomitant positive SLNs. False negative rate was 0%.

CONCLUSIONS

SPECT/CT had the highest detection rate and achieved the highest rate of bilateral mapping, compared to gamma-probe and MDB. SPECT/CT had moderate concordance with gamma-probe, and it can help the intraoperative detection of SLNs providing important information about their anatomic location.

The sentinel node approach in gynaecological malignancies

This review discusses the state-of-the-art of sentinel lymph node mapping in gynaecological malignancies, including cervical cancer, endometrial cancer, and vulvar cancer, with an emphasis on new technological advances. For this objective, PubMed/MEDLINE was searched for relevant studies about the sentinel lymph node procedure in gynaecology. In particular, the use of preoperative lymphatic mapping with lymphoscintigraphy and single photon emission tomography/computed tomography (SPECT/CT) was identified in 18 studies. Other recent advances as hybrid tracers (e.g. ICG-^99mTc-nanocolloid) and intraoperative tools (portable γ-camera and 3D navigation devices) appear to also represent a useful guide for the surgeon during the operation. Concerning vulvar and cervical cancers, the sentinel lymph node procedure has been incorporated to the current guidelines in Europe and North America, whereas for endometrial cancer it is considered investigative.

Sentinel lymph node procedure in endometrial cancer: A systematic review and proposal for standardization of future research

OBJECTIVES

Sentinel lymph node (SLN) procedure could be an attractive solution to the debate on lymphadenectomy in endometrial cancer; however challenges to interpreting the literature include marked heterogeneity across studies, a wide variety of injection techniques and a lack of uniformly accepted definitions for important outcomes. We aim to critically appraise the published literature and streamline terminology and methodology for future studies in this field.

METHODS

We conducted a PubMed search and included all original research of endometrial cancer patients having undergone SLN procedure with an n>30. Data collected included injection technique, unilateral, bilateral, and para-aortic detection rates, and ultrastaging results. When different definitions were used for reporting outcomes, we recalculated the original study results according to our proposed definitions. Data was analyzed using descriptive statistics.

RESULTS

Seventeen studies met our inclusion criteria. Injection sites were categorized into cervical versus corporeal. Overall detection rates ranged from 60 to 100%; studies with n>100 all had overall detection rates of >80%. Bilateral detection rates were higher with a combination of two injection agents. Para-aortic mapping was most frequent after corporeal injection techniques (39%), and was higher after deep vs. standard cervical injection (17% vs. 2%). The proportion of metastatic lymph nodes diagnosed through ultrastaging was high (around 40%) and ultrastaging of SLN upstaged approximately 5% of patients. Retrospectively applying a surgical algorithm revealed a sensitivity of 95%, a negative predictive value of 99%, and a false negative rate of 5% (with only 9 false negative cases remaining in total).

CONCLUSION

Results of SLN research for endometrial cancer are promising. We believe that in future studies, uniform reporting is needed to improve our understanding of the safety and feasibility of SLN in EC. We propose 2 strategies: a checklist of elements to include in future reports and the standardization of key definitions.

Contribution of Lymphoscintigraphy for Sentinel Lymph Node Biopsy in Women with Early Stage Endometrial Cancer: Results of the SENTI-ENDO Study

BACKGROUND

This study was designed to evaluate detection rate and anatomical location of sentinel lymph node (SLN) at lymphoscintigraphy, to compare short and long lymphoscintigraphy protocols, and to correlate lymphoscintigraphic and surgical mapping of SLN in patients with early-stage endometrial cancer (EC).

METHODS

Subanalysis of the prospective multicenter study Senti-endo performed from July 2007 to August 2009. Patients with stage I and II EC received four cervical injections of 0-2 mL of unfiltered technetium sulphur colloid the day before (long protocol) or the morning (short protocol) before surgery. SLN detection used a combined technetium/patent blue labeling technique, and all patients had a systematic bilateral pelvic lymphadenectomy.

RESULTS

A total of 133 patients were enrolled in the study and 118 (94.5 %) underwent a lymphoscintigraphy. Of these 118 patients, 44 (37 %) underwent a short protocol and 66 (56 %) a long protocol (data on lymphoscintigraphy were not available in eight patients). Lymphoscintigraphic detection rate was 74.6 % (34 % for short protocol and 60.2 % for long protocol). No difference in the detection rate was observed according to lymphoscintigraphy protocol (p = 0.22), but a higher number of SLN was noted for the long protocol (p = 0.02). Aberrant drainage was noted on lymphoscintigraphy in 30.5 % of the patients. Paraaortic SLNs were exclusively detected using the long protocol. A poor correlation was noted between short (κ test = 0.24) or long lymphoscintigraphy (κ test = 0.3) protocol and SLN surgical mapping.

CONCLUSIONS

Our study demonstrates that preoperative lymphoscintigraphy allowed a high SLN detection rate and that long lymphoscintigraphy protocol was associated with a higher detection of aberrant drainage especially in the paraaortic area.

Surgical management of early endometrial cancer: an update and proposal of a therapeutic algorithm

In the last few years technical improvements have produced a dramatic shift from traditional open surgery towards a minimally invasive approach for the management of early endometrial cancer. Advancement in minimally invasive surgical approaches has allowed extensive staging procedures to be performed with significantly reduced patient morbidity. Debate is ongoing regarding the choice of a minimally invasive approach that has the most effective benefit for the patients, the surgeon, and the healthcare system as a whole.

Surgical treatment of women with presumed early endometrial cancer should take into account the features of endometrial disease and the general surgical risk of the patient. Women with endometrial cancer are often aged, obese, and with cardiovascular and metabolic comorbidities that increase the risk of peri-operative complications, so it is important to tailor the extent and the radicalness of surgery in order to decrease morbidity and mortality potentially derivable from unnecessary procedures. In this regard women with negative nodes derive no benefit from unnecessary lymphadenectomy, but may develop short- and long-term morbidity related to this procedure. Preoperative and intraoperative techniques could be critical tools for tailoring the extent and the radicalness of surgery in the management of women with presumed early endometrial cancer. In this review we will discuss updates in surgical management of early endometrial cancer and also the role of preoperative and intraoperative evaluation of lymph node status in influencing surgical options, with the aim of proposing a management algorithm based on the literature and our experience.

Isthmocervical labelling and SPECT/CT for optimized sentinel detection in endometrial cancer: technique, experience and results

OBJECTIVE

We evaluated the clinical feasibility of a new injection technique for sentinel detection in endometrial carcinoma (EC), transcervical subepithelial injection into the isthmocervical region of the myometrium. We compared detection of sentinel lymph nodes (SLN) by single photon emission computed tomography with CT (SPECT/CT) with planar lymphoscintigraphy.

METHODS

This is a unicentric prospective study. In all patients, transcervical injection of 10 MBq Technetium-99m-nanocolloid was performed into the isthmocervical myometrium without anaesthesia. After 40 (30-60) min, lymphoscintigraphy and SPECT/CT were performed. Patent blue was administered before surgery. The number and localisation of SLN detected in SPECT/CT and lymphoscintigraphy were recorded and compared to the SLN and non-SLN dissected intra-operatively.

RESULTS

Between August 2008 and March 2012, 31 patients with EC were enrolled. The new transcervical injection of labelling substances led to high intra-operative (90.3%) detection rates, pelvic bilateral (57%), para-aortic (25%). SPECT/CT significantly identified more SLN than lymphoscintigraphy (mean 2.2 (1-8) to 1.3 (1-7)) in more patients (29/31 (93.5%) to 21/31 (68%), p<0.01). If SLN were identified in one hemi-pelvis, the histological evaluation of the SLN correctly predicted lymph node (LN) metastases for this basin which led to sensitivity 100%, negative predictive value (NPV) 100%, and false negative results 0%.

CONCLUSION

Transcervical SLN marking in combination with SPECT/CT is easily applicable and leads to high physiologic detection rates in pelvic and para-aortic lymphatic drainage areas. Non-affected SLN truly predicted a non-affected LN basin. Combining both methods SLN dissection may be a safe and feasible staging technique for clinical routine in EC.

Preoperative detection of sentinel lymph nodes in endometrial cancer using SPECT/CT

We report the use of SPECT/CT in sentinel lymph node biopsy in endometrial cancer. The patient was a 54-year-old woman with the diagnosis of endometrial adnenocarcinoma, grade 2. Preoperative MRI and transvaginal ultrasound scans revealed tumor infiltrating more than 50% of the myometrium. The patient was qualified for total abdominal hysterectomy, bilateral salpingo-oophorectomy, and pelvic/paraaortic lymphadenectomy. Before the surgery, 2 cervical injections of the (99m)Tc-labeled nanocolloid (0.5 mCi) were administered and the SPECT/CT was performed using a standard dual-head gamma camera and a 6-slice spiral CT component.

Study of the sentinel node in endometrial cancer at early stages: preliminary results

AIM

To investigate the applicability of the sentinel lymph node biopsy technique in early stages of endometrial cancer.

MATERIAL AND METHODS

A prospective study that included consecutive patients with a histological diagnosis of clinical state I endometrial carcinoma was performed. Two doses of 2 mCi (74 MBq) of (99m)Tc-albumin nanocolloid were injected in the uterine cervix, and planar and SPECT-CT images were obtained at one hour, and at 24 hours if no migration of the tracer was observed. Methylene blue dye was also injected into the cervix immediately prior to the surgery. A gamma probe was used during the surgical procedure for sentinel lymph node identification. In all cases, a hysterectomy, double adnexectomy and pelvic lymphadenectomy were performed, carrying out a histological analysis (hematoxylin-eosin) of the sentinel lymph nodes and the lymphadenectomy specimen.

RESULTS

We included 19 patients, with a final diagnoses of endometrioid carcinoma (18 cases) and endometrial stromal sarcoma (1 case). At least one sentinel lymph node was identified in 17 of them (89.5% detection rate). Twenty-nine sentinel lymph nodes were identified during surgery, all of them negative for neoplastic infiltration. No metastatic invasion was found in the pelvic lymphadenectomy specimens as well.

CONCLUSIONS

The sentinel lymph node biopsy technique seems to be a reliable tool in nodal staging of endometrial cancer at early stages, with an acceptable detection rate and high histological correlation. The low prevalence of lymphatic spread in this group of patients and the encouraging results obtained could make the sentinel lymph node an alternative to routine complete lymphadenectomy.

[Current position of the sentinel lymph node procedure in endometrial cancer]

Lymph node status is a major prognostic element in endometrial cancer and affects the choice of adjuvant therapy. The sentinel lymph node (SLN) procedure is proposed as an alternative to lymphadenectomy. This review aims to assess its feasibility. To this end, 19 studies have been analysed. It appears that double detection (colorimetric and isotopic) is better than single detection, independent of injection site. Hysteroscopic injection is technically more difficult, yet can be done near the tumoral lesion. The cervical site does not accurately reflect the lymphatic drainage of the uterine body but is easier to access. SLN detection rate is notably identical between these two injections sites. Lomboaortic detection rate is lower for cervical injections than for endometrial ones. The myometrial site is also difficult to access (intraoperatively), due to same limitations as the hysteroscopic route, and can be deceiving (insufficient detection rate and high false-negative rate). The SLN allows for ultrastadification (micrometastases and isolated tumoral cells) with the development of new pathological techniques (serial sections and immunohistochemistry). Data on SLN in endometrial cancer is very heterogeneous in terms of methodology and populations studied. Despite being well-known, the SLN procedure in endometrial cancer remains in its feasibility stage. Its place in therapeutic strategies needs to be further explored and its potential benefit remains to be confirmed.

[Sentinel lymph node procedure and uterine cancers]

Lymph node metastases in cervical and endometrial cancer are major prognostic factors. Lymph-nodal involvement determines adjuvant therapy. As imagery is not reliable to diagnose lymph node status, pelvic +/- para-aortic lymphadenectomy remains the gold standard. These surgical procedures are, however, responsible for specific morbidity: lymphocele and lymphedema. Sentinel lymph node procedure could avoid lymphadenectomy and their complications in cervical and endometrial cancer with good negative predictive values. We present actual indications, procedure and results of sentinel lymph node procedures in cervical and endometrial cancer.

The role of sentinel node biopsy in gynecological cancer: a review

PURPOSE OF REVIEW

In early-stage vulvar, cervical and endometrial cancer, lymph node status is the most important prognostic factor. Surgical treatment is aimed at removing the primary tumor and adequately staging the regional lymph nodes. As morbidity of regional lymphadenectomy is high, sentinel node biopsy is a technique with potential for adequate staging with less treatment-related morbidity. This manuscript reviews its current role in vulvar, cervical and endometrial cancer.

RECENT FINDINGS

In early-stage vulvar cancer, level 3 evidence indicates that it appears to be safe to omit inguinofemoral lymphadenectomy in case of a negative sentinel node. However, false-negative results with fatal consequences do occur and are often attributable to procedural failures. For early-stage cervical cancer, level 3 evidence points to an acceptable false-negative rate of a negative sentinel node; clinical utility and safety remain to be established. The optimal technique of the sentinel node biopsy in endometrial cancer is currently unclear.

SUMMARY

In early-stage vulvar cancer, data suggest that sentinel node biopsy could be offered as a treatment option instead of routine inguinofemoral lymphadenectomy. However, more (long-term follow-up) data are needed to further appreciate real clinical benefits. It is emphasized that the procedure should be performed by a skilled multidisciplinary team, centralized in oncology centers and preferably within the protection of clinical trials. For cervical cancer, data are promising, but routine application cannot be recommended due to lack of data on clinical utility and safety. For endometrial cancer, studies on the sentinel node biopsy are still in feasibility stage.

A new multimodality technique accurately maps the primary lymphatic landing sites of the bladder

BACKGROUND

Pathoanatomic studies have failed to map accurately the primary lymphatic landing sites of the urinary bladder.

OBJECTIVE

To use single-photon emission computed tomography (SPECT) combined with computed tomography (CT) plus intraoperative gamma probe verification to map the primary lymphatic landing sites of the bladder.

DESIGN, SETTING, AND PARTICIPANTS

Clinical trial of 60 consecutive cystectomy patients at a single centre.

INTERVENTION

Flexible cystoscopy-guided injection of technetium nanocolloid into one of six non-tumour-bearing sites of the bladder for preoperative detection of radioactive lymph nodes (LNs) with SPECT/CT followed by intraoperative verification with a gamma probe. Backup extended pelvic LN dissection (PLND) for ex vivo detection of missed LNs.

MEASUREMENTS

Three-dimensional projection of each LN site.

RESULTS AND LIMITATIONS

A median of 4 (range: 1-14) radioactive LNs were detected per site and patient. Ninety-two percent of all LNs were found distal and caudal to where the ureter crosses the common iliac arteries. Eight percent were found proximal to the uretero-iliac crossing, none without simultaneous detection of additional radioactive LNs within the endopelvic region. Extended PLND resected 92% of all primary lymphatic landing sites; limited PLND resected only 52%. A few LNs may have been missed despite preoperative SPECT/CT, intraoperative gamma probe verification, and extended backup PLND.

CONCLUSIONS

Multimodality SPECT/CT plus intraoperative gamma probe show the template of the bladder's primary lymphatic landing sites to be larger than is often thought. PLND limited to the ventral portion of the external iliac vessels and obturator fossa removes only about 50% of all primary lymphatic landing sites, whereas extended PLND along the major pelvic vessels, including the internal iliac, external iliac, obturator, and common iliac region up to the uretero-iliac crossing, removes about 90%.