Detection of melanoma micrometastases in sentinel nodes – The cons

Gamma probe and ultrasound guided fine needle aspiration cytology of the sentinel node (GULF) trial - overview of the literature, pilot and study protocol

BACKGROUND

Sentinel node (SN) biopsy (SNB) detects clinically occult metastases of breast cancer and melanoma in 20-30%. Wound infections, seroma and lymph edema occur in up to 10%. Targeted ultrasound (US) of the SN, (with fine needle aspiration cytology (FNAC) if appropriate) has been investigated as a minimally invasive alternative, but reported sensitivity rates are too low to replace SNB. Our hypothesis is that the use of a handheld gamma probe concomitant with US may improve sensitivity. Our aim is to provide an overview of the current literature on preoperative nodal staging of clinical N0 melanoma patients, report on a pilot, and present a study protocol for a minimally invasive alternative to the SNB: Gamma probe and Ultrasound guided Fine needle aspiration cytology of the sentinel node (GULF trial).

METHODS

The GULF trial is a multicenter open single arm observational trial. Newly diagnosed cT1b-4N0M0 cutaneous melanoma or cT1-3N0M0 breast cancer patients, aged >18 years, presenting for SNB are eligible. 120 patients will be included for preoperative targeted gamma probe guided US and FNAC of the SN. Afterwards all patients proceed to surgical SNB. Primary endpoint is the sensitivity of FNAC. Secondary endpoints include SN identification rate and the histopathological compatibility of Core Needle Biopsy and FNAC vs. SNB. Secondary endpoints were investigated in a pilot with 10 FNACs and marker placements, and 10 FNACs combined with Core Needle Biopsy.

RESULTS

A pilot in 20 patients showed that SN identification rate was 90%, supporting the feasibility of this technique.

DISCUSSION

There is broad experience with US (in combination with FNAC) prior to SNB, but sensitivity and specificity are too low to completely abandon SNB. Promising alternative techniques potentially will replace SNB in the future but more evidence is needed in the form of prospective studies. Accurate identification of the SN for US-FNAC has been proven feasible in our pilot. When adequate sensitivity can be reached, US-FNAC provides a minimally invasive alternative for the surgical SNB procedure.

TRIAL REGISTRATION

The GULF trial is registered in the Netherlands Trial Registry (NTR), ID: NRT5193 . May 1st 2015.

Accuracy of intraoperative pathological examination of SLN in cervical cancer

OBJECTIVE

Early cervical cancer patients with pelvic lymph node metastasis do not benefit from radical hysterectomy. Assessment of the SLN status is thus crucial before deciding to perform a radical hysterectomy as opposed to aortic dissection only followed by definitive radiation therapy. Accuracy of frozen section of SLN has been questioned and deserves further investigation.

METHODS

Stage IA-IB1 cervical cancer patients who underwent SLN then full pelvic dissection at the Claudius Regaud Cancer Center in Toulouse, France, were included.

RESULTS

At least one SLN was identified in all 94 patients. Bilateral detection rate was 80.8%. Ectopic drainage area was found in 19 patients (20.2%). Sentinel lymph node involvement was found in 11 patients (11.7%). Sensitivity and NPV of frozen section pathological examination for the detection of macrometastatic disease was 100%, sensitivity for the detection of macro and micrometastatic disease, excluding ITC, was 88.9%, and NPV was 98.8%. Micrometastasis and isolated tumor cells (ITC) undetected at frozen section examination were found in 1 patient (1.06%) and 2 lymph nodes (1.24%), and in 2 patients (2.13%) and 2 lymph nodes (1.24%), respectively. Final pathology sensitivity of SLN was 100% for both macro and micrometastatic disease, including ITC.

CONCLUSION

In our institution, intraoperative frozen examination of SLN accurately predicts the status of pelvic lymph nodes and is effective for selecting intraoperatively the group of patients who benefit from radical hysterectomy. In addition, our results suggest that patients with small tumors and bilateral detection of SLN can be spared full pelvic lymphadenectomy.

Assessment of proliferation markers in metastatic melanoma in sentinel lymph nodes

AIM

Some views on sentinel nodes for melanoma seem to cast doubt on the relevance of micrometastases in the sentinel nodes of patients with melanoma, suggesting that small metastases or isolated tumour cells can be ignored. Tumour dormancy has been proposed for their postulated lack of progression. The implication of the argument seems to be that minute metastases are inactive and therefore non-threatening, whereas larger ones are proliferative and therefore have aggressive potential.

METHODS

54 sentinel lymph nodes were studied with histologically identified micrometastatic melanoma using the protocol accepted by the European Organisation for Research and Treatment of Cancer melanoma group. These were studied with respect to metastasis size and by use of immunohistochemical markers of proliferation (MIB-1) and dormancy (p16).

RESULTS

The authors have demonstrated no correlation between the size of metastases and their proliferative activity. Very small metastases may not show proliferative activity, but this may be a reflection of the small number of assessable cells rather than a genuine reflection of the tumoural characteristics. Furthermore, the minute size of some of these metastases resulted in no residual tumour being present in adjacent sections. Where further sections did show more tumour, these small metastases were invariably p16 negative, suggesting dormancy was not the explanation for the lack of measurable proliferation. Occasionally, larger metastases, clearly not clinically insignificant, showed no proliferative activity presumably, considering their size, a transient phenomenon.

CONCLUSION

These findings suggest that variable phases in proliferation occur in metastases, and no conclusion of clinical insignificance can be made on the basis of small size.

Importance of tumor load in the sentinel node in melanoma: clinical dilemmas

There are two hypotheses to explain melanoma dissemination: first, simultaneous lymphatic and hematogeneous spread, with regional lymph nodes as indicators of metastatic disease; and second, orderly progression, with regional lymph nodes as governors of metastatic disease. The sentinel node (SN) has been defined as the first draining lymph node from a tumor and is harvested with the use of the triple technique and is processed by an extensive pathology protocol. The SN status is a strong prognostic factor for survival (83-94% for SN negative, 56-75% SN-positive patients). False-negative rates are considerable (9-21%). Preliminary results of the MSLT-1 trial did not demonstrate a survival benefit for the SN procedure, although a subgroup analysis indicates a possible benefit. A mathematical model has demonstrated 24% prognostic false positivity. SN tumor burden represents a heterogeneous patient population and is classified most frequently with the Starz, Dewar or Rotterdam Criteria. A completion lymph-node dissection might not be indicated in all SN-positive patients. Patients classified with metastases <0.1 mm by the Rotterdam Criteria have excellent survival rates. Ultrasound-guided fine-needle aspiration cytology is emerging as a staging tool for high-risk patients, but more research is necessary before this can change clinical practice.

Sentinel lymph node biopsy in melanoma patients

Appropriate surgical management of regional lymph nodes is critical in patients with cutaneous melanoma. The use of intraoperative lymphatic mapping and sentinel lymph node biopsy (SLNB) has increased significantly in the past decade. SLNB is performed as minimally invasive procedure that provides accurate staging of melanoma patients with no clinically detectable nodal disease. In many melanoma units across the world, it became the standard for detection of occult regional node metastasis in patients with intermediate-thickness primary melanoma. Use of SLNB in patients with thin melanomas is still under evaluation. Although SLNB has been established as staging procedure in melanoma patients, its therapeutic role is still not clear. Large-scale ongoing randomized trials should elucidate whether SLNB with complete lymphadenectomy has a survival benefit in melanoma patients with early lymph node metastases compared to 'watch-and-wait' policy (observation).

Expert opinion in melanoma: the sentinel node; EORTC Melanoma Group recommendations on practical methodology of the measurement of the microanatomic location of metastases and metastatic tumour burden

The sentinel node (SN) status has been recognised to be the most important prognostic factor in melanoma. Many studies have investigated additional factors to further predict survival/lymph node involvement. The EORTC Melanoma Group (MG) has formulated the following question: How should we report the microanatomic location and SN tumour burden? The EORTC MG recommends the following: the EORTC MG SN pathology protocol or a similarly extensive protocol, which has also been proven to be accurate, should be used. Only measure what you can see not what you presume. Cumulative measurements decrease the accuracy and reproducibility of measuring. The most reproducible measure is a single measurement of the maximum diameter of the largest lesion in any direction (1-D). If there is any infiltration into the parenchyma, this lesion can no longer be considered solely subcapsular. Reporting of the microanatomic location of metastases should be an assessment of the entire sentinel node, not only of the largest lesion. Multifocality reflects a scattered metastatic pattern, not to be confused with multiple cohesive foci, which fall under the regular location system. A subcapsular metastasis should have a smooth usually curved outline, not ragged or irregular. We recommend all pathologists to report the following items per positive SN for melanoma patients: the microanatomic location of the metastases according to Dewar et al. for the entire node, the SN Tumour Burden according to the Rotterdam Criteria for the maximum diameter of the largest metastasis expressed as an absolute number, and the SN Tumour Burden stratified per category; <0.1mm or 0.1-1.0mm or >1.0mm.

Sentinel node tumor burden according to the Rotterdam criteria is the most important prognostic factor for survival in melanoma patients: a multicenter study in 388 patients with positive sentinel nodes

SUMMARY BACKGROUND DATA

The more intensive sentinel node (SN) pathologic workup, the higher the SN-positivity rate. This is characterized by an increased detection of cases with minimal tumor burden (SUB-micrometastasis <0.1 mm), which represents different biology.

METHODS

The slides of positive SN from 3 major centers within the European Organization of Research and Treatment of Cancer (EORTC) Melanoma Group were reviewed and classified according to the Rotterdam Classification of SN Tumor Burden (<0.1 mm; 0.1-1 mm; >1 mm) maximum diameter of the largest metastasis. The predictive value for additional nodal metastases in the completion lymph node dissection (CLND) and disease outcome as disease-free survival (DFS) and overall survival (OS) was calculated.

RESULTS

In 388 SN positive patients, with primary melanoma, median Breslow thickness was 4.00 mm; ulceration was present in 56%. Forty patients (10%) had metastases <0.1 mm. Additional nodal positivity was found in only 1 of 40 patients (3%). At a mean follow-up of 41 months, estimated OS at 5 years was 91% for metastasis <0.1 mm, 61% for 0.1 to 1.0 mm, and 51% for >1.0 mm (P < 0.001). SN tumor burden increased significantly with tumor thickness. When the cut-off value for SUB-micrometastases was taken at <0.2 mm (such as in breast cancer), the survival was 89%, and 10% had additional non-SN nodal positivity.

CONCLUSION

This large multicenter dataset establishes that patients with SUB-micrometastases <0.1 mm have the same prognosis as SN negative patients and can be spared a CLND. A <0.2 mm cut-off for SUB-micrometastases does not seem correct for melanoma, as 10% additional nodal positivity is found.