Management of Malignant Melanoma of the Foot with Groin Lymph Node Involvement
For malignant melanoma of the foot with groin node involvement (Stage III disease), perform complete surgical resection of both the primary site and involved lymph nodes, followed by adjuvant systemic therapy for 52 weeks with either nivolumab, pembrolizumab, or—if BRAF V600E/K mutant—dabrafenib plus trametinib. 1, 2
Surgical Management
Primary Site Excision
- Wide local excision with margins based on Breslow thickness:
- ≤2 mm thickness: 1 cm margins
2 mm thickness: 2 cm margins 3
- For foot melanomas, margins may require modification to preserve function while achieving oncologic adequacy
Groin Lymph Node Management
- Complete therapeutic lymph node dissection is the standard of care for clinically evident groin node involvement 3
- Inguinal vs. ilioinguinal dissection decision:
- Superficial inguinal dissection alone: For clinically negative deep nodes on imaging
- Combined ilioinguinal dissection: For palpable nodes, radiologically positive disease, or multiple involved superficial nodes 4, 5
- Ilioinguinal dissection adds no significant morbidity but provides critical prognostic information and optimal regional control 5
Critical surgical principle: Removing only the tumor-bearing lymph node is insufficient—complete regional lymphadenectomy of the entire nodal basin is required 3
Adjuvant Systemic Therapy
BRAF Testing Required
Immediately obtain BRAF V600E/K mutation testing to guide adjuvant therapy selection 1, 6
For BRAF Wild-Type Disease (Stage IIIA-D)
Choose one of the following (no particular order): 1, 2
- Nivolumab for 52 weeks
- Pembrolizumab for 52 weeks
Both agents demonstrate:
- High-quality evidence for improved recurrence-free survival (RFS)
- Comparable efficacy (no head-to-head comparison exists)
- Similar toxicity profiles (~14% grade ≥3 treatment-related adverse events)
- Strong recommendation based on CheckMate 238 and EORTC 1325/Keynote 054 trials 1
Ipilimumab and high-dose interferon are NOT recommended for routine adjuvant use 1
For BRAF V600E/K Mutant Disease (Stage IIIA-D)
Choose one of the following (no particular order): 1, 2
- Nivolumab for 52 weeks
- Pembrolizumab for 52 weeks
- Dabrafenib plus trametinib for 52 weeks
Key decision-making considerations:
- Dabrafenib plus trametinib shows preliminary overall survival benefit (HR 0.57) and superior 12-month RFS (88% vs 75.4% for pembrolizumab) from COMBI-AD trial 1, 7
- However, higher toxicity: 41% grade ≥3 adverse events vs 14% for anti-PD1 agents, with 26% treatment discontinuation rate 1
- Anti-PD1 agents may provide better long-term durability based on curve shapes after treatment completion 7
- No validated biomarkers exist to guide selection between targeted therapy and immunotherapy 7
Important Caveats and Pitfalls
Stage IIIA with Minimal Nodal Disease
- Patients with microscopic sentinel node metastasis <1 mm were excluded from major adjuvant trials 1, 2
- These patients have relatively better prognosis and lower relapse risk
- Treatment should be individualized after discussing risk-benefit ratio, though both nivolumab and pembrolizumab are FDA-approved for this indication 1
Timing Considerations
- All patients in pivotal adjuvant trials underwent complete lymphadenectomy before systemic therapy 1
- This does not affect the strength of recommendations for these agents 1
Expected Morbidity
- Wound complications are common after groin dissection: expect lymphorrhea (universal), wound infection (~80%), and delayed healing (mean 46 days) 8
- Lymphedema rates: 6-15% in lower limbs with modern technique 9
- These complications do not differ significantly between inguinal and ilioinguinal approaches 4, 5
Prognostic Factors
Poor prognostic indicators include: 5
- Number of involved superficial lymph nodes (most significant)
- Presence of extracapsular spread
- Positive pelvic nodes (if ilioinguinal dissection performed)
- Advanced age
5-year overall survival for Stage III with groin involvement: 34-56% depending on extent of nodal disease 8, 5