Nodal basin recurrence following lymph node dissection for melanoma: implications for adjuvant radiotherapy

To analyze patterns of failure in malignant melanoma patients with lymph node involvement who underwent complete lymph node dissection (LND) of the nodal basin. To determine prognostic factors predictive of local recurrence in the lymph node basin in order to select patients who may benefit from adjuvant radiotherapy.

A retrospective analysis of 338 patients undergoing complete LND for melanoma between 1970 and 1996 who had pathologically involved lymph nodes was performed. Mean follow-up from the time of LND was 54 months (range: 12-306 months). Lymph node basins dissected included the neck (56 patients), axilla (160 patients), and groin (122 patients). Two hundred fifty-three patients (75%) underwent therapeutic LND for clinically involved nodes, while 85 patients (25%) had elective dissections. Forty-four percent of patients received adjuvant systemic therapy. No patients received adjuvant radiotherapy to the lymph node basin.

Overall and disease-specific survival for all patients at 10 years was 30% and 36%, respectively. Overall nodal basin recurrence was 30% at 10 years. Mean time to nodal basin recurrence was 12 months (range: 2-78 months). Site of nodal involvement was prognostic with 43%, 28%, and 23% nodal basin recurrence at 10 years with cervical, axillary, and inguinal involvement, respectively (p = 0.008). Extracapsular extension (ECE) led to a 10-year nodal basin failure rate of 63% vs. 23% without ECE (p < 0.0001). Patients undergoing a therapeutic dissection for clinically involved nodes had a 36% failure rate in the nodal basin at 10 years, compared to 16% for patients found to have involved nodes after elective dissection (p = 0.002). Lymph nodes larger than 6 cm led to a failure rate of 80% compared to 42% for nodes 3-6 cm and 24% for nodes less than 3 cm (p < 0.001). The number of lymph nodes involved also predicted for nodal basin failure with 25%, 46%, and 63% failure rates at 10 years for 1-3, 4-10, and > 10 nodes involved (p = 0.0001). There was no significant difference in nodal basin control in patients with synchronous or metachronous lymph node metastases, nor in patients receiving or not receiving adjuvant systemic therapy. Nodal basin failure was predictive of distant metastasis with 87% of patients with nodal basin recurrence developing distant disease compared to 54% of patients without nodal failure (p < 0.0001). On multivariate analysis, number of positive nodes and type of dissection (elective vs. therapeutic) were significant predictors of overall and disease-specific survival. Size of the largest lymph node was also predictive of disease-specific survival. Site of nodal involvement and ECE were significant predictors of nodal basin failure.

Malignant melanoma patients with nodal involvement have a significant risk of nodal basin failure after LND if they have cervical involvement, ECE, >3 positive lymph nodes, clinically involved nodes, or any node larger than 3 cm. Patients with these risk factors should be considered for adjuvant radiotherapy to the lymph node basin to reduce the incidence of nodal basin recurrence. Patients with nodal basin failure are at higher risk of developing distant metastases.