1200 - Adjuvant Lymph Node Basin Radiation Therapy for Pathological Non-Responders to Neoadjuvant Immunotherapy in Clinically Node-Positive Cutaneous Melanoma

05:20pm - 05:25pm ET

Room 210

Presenter(s)

Jonathan Novinski, BA - Memorial Sloan Kettering Cancer Center, Middletown Township, NJ

J. Novinski¹, O. Cantillon¹, C. Ariyan¹, E. Bartlett¹, D. Bello¹, B. Givi², A. Shamseddine³, Y. Yu³, and C. A. Barker³; ¹Department of Surgery, Gastric and Mixed Tumor Service, Memorial Sloan Kettering Cancer Center, New York, NY, ²Department of Surgery, Head and Neck Service, Memorial Sloan Kettering Cancer Center, New York, NY, ³Department of Radiation Oncology, Memorial Sloan Kettering Cancer Center, New York, NY

Purpose/Objective(s):

Neoadjuvant immunotherapy (nIO) reduces the risk of recurrence in clinically node-positive cutaneous melanoma. Among patients with major or complete pathologic response, recurrence is rare and therefore adjuvant therapy is not warranted. However, among those with pathologic non-response (pNR) the value of additional treatment, including adjuvant lymph node basin radiation therapy (ALNBRT), is unclear.

Materials/Methods:

With IRB approval, we retrospectively analyzed a cohort of patients with clinically node-positive cutaneous melanoma that were treated with nIO and resection of regional metastases demonstrating pNR between 2019 and 2025. Patient, cancer, and treatment characteristics were extracted from the medical records and patterns of recurrence were assessed.

Results:

We identified 44 patients with pNR after nIO and resection of regional lymph node metastases. Two-thirds of patients were male. Median age was 61 (range, 24-79). Median number of nIO cycles was 2 (range, 1-7). Mean number of involved lymph nodes in surgical specimen was 3.8 (range 1-21), and mean size of involved nodes was 3.7 cm (range 0.1-9.2 cm). Extracapsular extension (ECE) was present in 22 (50%) of cases. Among 14 patients selected for ALNBRT (32%), all had high-risk pathologic features (as defined by TROG 02.01); these patients had significantly more involved nodes (mean 5.8 vs 2.9, p=0.04), of larger size (4.2 cm vs 3.5 cm, p=0.5), and significantly more often harbored ECE (83% vs 33%, p=0.003), compared to patients not selected for ALNBRT. Among patients selected for ALNBRT, distant and regional recurrence was observed in 7 (50%) and 1 (7%), respectively. Among those not selected for ALNBRT, distant and regional recurrence was observed in 15 (50%) and 8 (27%), respectively.

Conclusion:

Among patients with pNR to nIO for clinically node-positive cutaneous melanoma, ALNBRT was more often recommended for patients with high-risk nodal pathology at the time of surgery. Among those selected for ALNBRT, the risk of regional recurrence was <10%, while among those not selected for ALNBRT, the risk was 27%, in keeping with randomized trials conducted in the pre-nIO era. ALNBRT should be considered for patients with high-risk nodal pathology following pNR to nIO.