Isolated same-basin lymph node recurrence after precision lymph node excision for clinically evident melanoma metastasis.

9576 Background: While management of the nodal basin for melanoma has largely moved to observation for microscopic sentinel lymph node (SLN) metastasis, complete lymph node dissection (CLND) remains the current standard of care for melanoma patients with macroscopic, clinically detectable lymph node metastases (cLN). As CLND is associated with high surgical morbidity, we sought to study whether cLN may be safely managed by excision of only clinically abnormal nodes (precision lymph node dissection, PLND). Currently, a small subset of patients with cLN do not undergo CLND because of frailty or patient preference. We hypothesized that in these selected patients, PLND would provide acceptable regional control rates. Methods: Retrospective chart review was conducted at four academic tertiary care hospitals to identify melanoma patients who underwent PLND for cLN. cLN were defined as palpable or radiographically abnormal nodes. Recurrences were categorized as local/in-transit, same-basin lymph node, or distal lymph node/visceral. The primary outcome was isolated same-basin recurrence after PLND. Results: Twenty-one patients underwent PLND for cLN without synchronous distant metastases (characteristics of primary lesions summarized in Table). Reasons for forgoing CLND included patient preference (n=8), imaging indeterminate for distant metastases (n=2), comorbidities (n=4), loss to follow up (n=1), partial response to checkpoint blockade (n=1), or not reported (n=5). The inguinal node basin was the most common site (n=10), followed by the axillary (n=8) and cervical basins (n=3). A median of 2 nodes were resected at PLND, and 68% of resected nodes were positive for melanoma (median: 1, range: 1-3 nodes). Median follow-up was 23 months from PLND, and recurrence was observed in 28.6% of patients overall. Only 1 patient (4.8%) developed an isolated same-basin recurrence. The 3-year cumulative incidence of isolated same-basin recurrence was 5.3%, while risk of isolated local/in-transit recurrence or distant basin/visceral metastasis were 19.8% and 33.3%, respectively. Complications from PLND were reported in 1 patient (4.8%) and were limited to post-operative seroma and lymphedema. Conclusions: These pilot data suggest that PLND may offer acceptable regional disease control for cLN. Post-operative morbidity from PLND was also low, raising the possibility that PLND may provide adequate regional disease control without the morbidity associated with CLND. These data justify additional, prospective evaluation of PLND in selected patients.[Table: see text]