2ⁿᵈ Edition of the Cancer R&D World Conference 2026

Abstract

Background: Although Merkel cell carcinoma (MCC) often spreads to lymph nodes, there is limited research on indications for nodal radiotherapy (NRT). Our objective is to find the optimal radiotherapy nodal volumes for MCC.

Methods: Data (Mar/1982 - Feb/2015) from six institutions from Canada, France and Australia was combined with individual patient data from a PubMed search of the English and French literature. A 949-patient aggregated database was built. The primary outcome was nodal recurrence, with overall survival as a secondary outcome.

Results: In total, 939/949 patients were evaluable, 50.8% of which were male, with a median follow-up of 21 (range: 0-272) months, and a median age of 73 (range: 31-96) years, with 77.5% (728/939) having clinically localized cancer (stage I and II). Among irradiated new (previously untreated) patients, all stages, 53% received NRT, 34.9% (80/229) no NRT and 11.8% (27/229) unknown if NRT was given. For recurrent cases, 94.7% (18/19) had NRT while 5.3% (1/19) did not. There were 682 new patients with clinical stage I or II: nodal recurrence was 16% (8/50) with NRT, 40.1% (250/624) without NRT and 1.2% (8/682) uncertain if NRT was given (P=0.0001, chi-square test with Yates correction [cstYc]). 5-year Kaplan-Meier cause- specific survival was 77.6% vs 60.6% (P=0.2, logrank test) with/without NRT for these 682 new patients. We then focused on all stages of small primary tumors <1 cm, the nodal recurrence was 17.4% (4/23)/24.6% (28/114) with/without NRT (P=0.6, cstYc).

CONCLUSIONS: Overall, NRT significantly reduced nodal recurrence. Management of small primary tumors ≤1 cm warrant further investigation with multicenter participation.