Predicting nonsentinel lymph node involvement in stage I/II melanoma

Microscopic tumor burden in sentinel lymph nodes predicts synchronous nonsentinel lymph node involvement in patients with melanoma

PURPOSE

We and others have demonstrated that additional positive lymph nodes (LNs) are identified in only 8% to 33% of patients with melanoma who have positive sentinel LNs (SLNs) and undergo complete therapeutic LN dissection (cTLND). We sought to determine predictors of additional regional LN involvement in patients with positive SLNs.

PATIENTS AND METHODS

Patients with clinically node-negative melanoma who underwent SLN biopsy (1991 to 2003) and had positive SLNs were identified. Clinicopathologic factors, including extent of microscopic disease within SLNs, were evaluated as potential predictors of positive non-SLNs.

RESULTS

Overall, 359 (16.3%) of the 2,203 patients identified had a positive SLN. Positive non-SLNs were identified in 48 (14.0%) of the 343 patients with positive SLNs who underwent cTLND. On univariate analysis, several measures of SLN microscopic tumor burden, one versus three or more SLNs harvested, tumor thickness more than 2 mm, age older than 50 years, and Clark level higher than III were predictive of positive non-SLNs; primary tumor ulceration and number of positive SLNs had no apparent impact. On multivariable logistic regression analysis, measures of SLN microscopic tumor burden were the most significant independent predictors of positive non-SLNs; tumor thickness more than 2 mm and number of SLNs harvested also predicted additional disease. A model was developed that stratified patients according to their risk for non-SLN involvement.

CONCLUSION

In melanoma patients with positive SLNs, SLN tumor burden, primary tumor thickness, and number of SLNs harvested may be useful in identifying a group at low risk for positive non-SLNs and be spared the potential morbidity of a cTLND.

Prediction of Nonsentinel Lymph Node Involvement in Patients with a Positive Sentinel Lymph Node in Malignant Melanoma

Completion lymph node dissection (CLND) is routinely performed after metastatic melanoma is detected at sentinel lymph node (SLN) biopsy. Nonsentinel lymph node (NSLN) involvement is found in less than one-third of the cases. Possible predictors of NSLN involvement are examined. A retrospective review of 70 patients with a positive SLN biopsy for melanoma and drainage to one lymphatic basin was performed. The size of metastatic deposits was defined as macrometastases (>2 mm), micrometastases (≤2 mm), a cluster of cells (10–30 grouped cells) in the subcapsular space or interfollicular zone, or isolated melanoma cells (1–20 or more individual cells) in sub-capsular sinuses. Tumor stage, ulceration, SLN tumor burden, mitoses, number of positive SLNs, and total number of lymph nodes removed were examined as predictors of NSLN involvement after CLND. Two additional models based on SLN tumor burden and the number of nodes biopsied were designed. Nineteen patients (24.3%) were found to have NSLN metastases after CLND. Tumor stage, ulceration, SLN tumor burden, mitoses, number of positive SLN, and number of lymph nodes removed were not statistically significant. Residual disease at CLND stratified by SLN tumor burden was: isolated melanoma cells, 0; cluster of cells, 8 (38.1%); ≤2 mm, 5 (20.8%); and >2 mm, 6 (27.3%). A comparison of the means for the models was not predictive of NSLN involvement. None of the risk factors or models examined could predict nonsentinel lymph node involvement with melanoma. The SLN sample and minimal SLN metastatic disease when defined as isolated clusters of cells warrant further study as a potential indicator against CLND after positive SLN.

Prediction of non-sentinel node status and outcome in sentinel node-positive melanoma patients

AIMS

Sentinel lymph node (SLN) -positive melanoma patients are usually recommended completion lymph node dissection (CLND) with the aim to provide regional disease control and improve survival. Nevertheless, only 20% these patients have additional metastases in non-sentinel lymph nodes (NSLN), indicating that CLND may be unnecessary in the majority of patients. In this retrospective study, we (i) sought to identify clinico-pathological features predicting NSLN status, as well as disease-free (DFS) and -specific (DSS) survival and (ii) evaluated the applicability of previously published algorithms, which were able to define a group of patients at zero-risk for NSLN-metastasis.

METHODS

This analysis included 504 consecutive melanoma patients stage I and II who underwent successful SLN-biopsy (SLNB) at our institute between 1998 and 2005. Metastatic SLN were re-evaluated for tumor burden and categorized according to two different micro-anatomic classifications and the S/U-score (Size of the sentinel node metastasis > 2 mm/Ulceration of the primary melanoma) was assessed. DFS and DSS were calculated for all analyses.

RESULTS

Out of 504 melanoma patients stage I or II, 85 (17%) were SLN-positive and 18 of 85 (21%) were found with positive NSLN in the CLND specimen. Median follow-up was 31 months. Neither primary tumor characteristics (age, gender, Clark level, Breslow thickness, ulceration of the primary melanoma, site and histological subtype of the primary melanoma), nor features of the sentinel node tumor (number and site of draining lymph node basins, number of positive sentinel nodes and size of sentinel node tumor (< 2 mm vs. > or = 2 mm) were able to predict additional positive lymph nodes in the CLND specimen. Likewise the implementation of published algorithms was not able to identify patients at negligible risk for harboring NSLN metastases. Upon univariate analysis, disease-free survival in SLN-positive patients was correlated with Breslow thickness, sentinel node tumor size > 2 mm and S/U score. In respect to disease-specific survival the significant prognostic parameters were Breslow thickness, ulceration, sentinel node tumor size > 2 mm and the S/U score. After a median follow-up of 31 months recurrence rates (37% vs. 78%, p=0.02) and death from disease (24% vs. 50%, p<0.01) were significantly different in patients with SLN-metastasis only as compared to patients with NSLN-metastasis.

CONCLUSION

NSLN status cannot be predicted in this data analysis by using clinico-pathological characteristics. Therefore, CLND is recommended for all patients after positive SLNB pending the results of the second Multicenter Selective Lymphadenectomy Trial.

Clinical relevance of melanoma micrometastases (<0.1 mm) in sentinel nodes: are these nodes to be considered negative?

As only about 20% of sentinel node (SN) positive melanoma patients have additional non-SN lymph node involvement in the Completion Lymph Node Dissection (CLND) specimen, we tried to identify a SN positive patient group, which can be spared CLND. Micro anatomic analyses of metastatic SNs were performed to identify patient/tumor and/or SN factors predicting additional non-SN positivity as well as disease-free and overall survival. SN positivity was found in 77 of 262 stage I/II patients, included into a prospective database (10/97-5/04). Of 74 patients pathology material was available for re-evaluation. Micro anatomic analyses categorized topography of SN-metastases, Starz classification and amount of SN tumor burden. Additional non-SN positivity, DFS, OS and was calculated for all analyses. Mean Breslow thickness was 3.5 mm (0.8-12.0); mean FU was 35 (6-81) months. There was no additional non-SN positivity for SN-micrometastases <0.1 mm. Topography of SN involvement had no impact on OS. Estimated 5-year OS rates for the different groups of <0.1 mm, 0.1-1.0 mm and >1.0 mm SN tumor burden were 100%, 63% and 35% respectively. Distant metastases were exceedingly rare (1/16 = 6.3%) in <0.1 mm SN-positive patients. On multivariate analysis the SN tumor burden was the most important prognostic factor for DFS (P = 0.005) and OS (P = 0.03). Distant metastasis-free survival was identical (91%) to the 5-yr OS of SN negative patients, the estimated 5-yr OS was 100% for these patients and additional non-SN positivity was not observed. Therefore, our data suggest that patients with sub-micrometastases (<0.1 mm) in the SN may be judged as SN negative, as non-stage III, and are highly unlikely to benefit from CLND, which we no longer recommend.

Predictors of Nonsentinel Lymph Node Positivity in Patients with a Positive Sentinel Node for Melanoma

BACKGROUND

Patients found to harbor melanoma micrometastases in the sentinel lymph node (SLN) are recommended to proceed to complete lymph node dissection (CLND), although the majority of patients will have no additional disease identified in the nonsentinel lymph nodes (NSLNs). We sought to assess predictive factors associated with finding positive NSLNs, and identify a subset of patients with low likelihood of finding additional disease on CLND.

STUDY DESIGN

We queried our prospective melanoma database for patients from January 1996 to August 2003 with a positive SLN. Univariable logistic regression models were fit for multiple factors and a positive NSLN. To derive a probabilistic model for occurrence of one or more positive NSLN(s), a multivariable logistic model was fit using a stepwise variable selection method.

RESULTS

Of 980 patients who underwent SLN biopsy for cutaneous melanoma, 232 (24%) had a positive SLN; 221 (23%) followed by CLND. Of these patients, 34 (15%) had one or more positive NSLN(s). In multivariable analysis, male gender (odds ratio [OR] 3.6 [95% CI 1.33, 9.71]; p = 0.01), Breslow thickness (OR 4.58 [95% CI 1.28, 16.36]; p = 0.019), extranodal extension (OR 3.2 [95% CI 1.0, 10.5]; p = 0.05), and three or more positive sentinel nodes (OR 65.81 [95% CI 5.2, 825.7]; p = 0.001) were all associated with the likelihood of finding additional positive nodes on CLND. Of 47 patients with minimal tumor burden in the SLN, only 1 (2%) had additional disease in the NSLN.

CONCLUSIONS

These results provide additional data to plan clinical trials to answer the question of who can safely avoid CLND after a positive SLN. Patients with minimal tumor burden in the SLN might be the most likely group, although defining "minimal tumor burden" must be standardized. Serial sectioning and immunohistochemistry on the NSLN in any "low-risk" group must be performed in a clinical trial to confirm that residual disease is unlikely before avoiding CLND can be recommended.