49: Risk Stratification of Sentinel Node Metastasis Disease Burden and Phenotype in Stage III Melanoma Patients

Friday, March 11, 2022

1:01 PM – 1:09 PM CST

Location: Chantilly East

Abstract Presenter(s)

Marc D. Moncrieff, MD FRCS(Plast.)

Professor of Plastic and Reconstructive Surgery
Norfolk & Norwich University Hospital
Norwich, United Kingdom

Disclosure: I do not have any relevant financial / non-financial relationships with any proprietary interests.

Participants should be aware of the following financial/non-financial relationships:

Marc D. Moncrieff, MD FRCS(Plast.): I do not have any relevant financial / non-financial relationships with any proprietary interests.

Introduction: The current AJCC classification system for stage III sentinel node positive (SN+) melanoma does not consider low-volume disease (< 1mm diameter deposit) frequently seen in the nodes. Removal of low-volume SN+ metastases at SNB may be therapeutic, obviating the risk of distant metastasis from the nodal disease, and this low-risk subgroup may not benefit from adjuvant systemic therapy.

Methods: A retrospective cohort study from a tertiary referral cancer center.

Results: 1377 adult patients were included, of which 238 (17.3%) were SN+. Increasing N-stage was associated with worse disease-specific survival (DSS) (p< 0.0001). The incidences of AJCC IIIA, IIIB and IIIC disease were 34.9%, 22.3% and 42.0%, respectively. For all survival endpoints (DSS, OS, DMFS and PFS), the IIIB and IIIC curves were statistically identical. Threshold analysis identified a SN+ maximum tumor deposit size (MTDS) cut-point of 0.45mm across all primary subgroups, except pT4b. The 5-year DSS for patients with SN+ ≤0.45mm was 94.5%, compared to 71.3% for SN+ >0.45mm (HR=1.07 [1.05-1.10]; p< 0.001). There was no significant secondary cut-point for DSS in the subgroup SN+ >0.45mm but those patients with extracapsular spread (ECS) had a significantly worse DSS (HR=2.27 [1.33-5.69]; p=0.007). All SN+ with ECS had a MTDS >0.45mm. A simplified, 3-tier staging system was devised according to MTDS and ECS status. There were 53 (27.5%) patients without ECS and SN+ ≤0.45mm who had the same DSS, OS, PFS & DMFS as N0 patients, from pT1b to pT4a (fig 1). It was not possible to classify the pT4b group, regardless of SN status, MTDS or presence of ECS.

Conclusions: Our data is consistent with the AJCC dataset results. It suggests that SN+ melanoma can be stratified by maximum tumor deposit size combined with ECS status, helping to identify the cohort of patients whose SNB is therapeutic and can be observed rather than offered adjuvant systemic therapy (~1 in 4 SN+ patients). The SN+ >0.45mm without ECS subgroup would benefit from alternative biomarkers to stratify their risk and treatment options. The future role of SNB for staging pT4b patients is debatable, given their overall poor prognosis.
Learning Objectives:
Identify low-risk AJCC stage III sentinel node positive melanoma patients who may not benefit from adjuvant systemic therapy and could be observed as if they were N0
Identify mid-high risk AJCC stage III sentinel node positive melanoma patients who should be referred on for adjuvant systemic therapy
Consider the utility of maximum tumor deposit size and extracapsular spread in sentinel node positive AJCC stage III melanoma patients for clinical decision-making