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

Abstract

Purpose: Merkel Cell carcinoma is a rare and aggressive cutaneous neoplasm. We studied the incidence, challenges in management and outcomes of lesions located in the limb from an aggregated database in order to evaluate whether the prognosis of peripheral MCC behaves similarly to rest of the body.

Methods and Materials: A 949-patient aggregated database (March 1982 - February 2015) was built from records of six cancer institutions and the literature consisting of patient characteristics, treatment details and outcomes to achieve adequate statistical power since it is a rare cancer. Equivalent doses in 2-Gy fractions (EQD2) = total dose×[(dose per fraction+α/β)/(2+α/β)], assuming α/β=10, were calculated to compare different dose-fractionations.

Results: 942/949 patients in the database have available data on original site(s), with primary in the head and neck 48.1% (453/942), limb 37.7% (355/942) and trunk 10.6% (100/942). Among those with a limb primary at presentation, 273/355 (76.9%) had clinical stage I or II, i.e. localized disease, 64/355 (18.0%) with stage III/nodal disease, 9/355 (2.5%) with stage IV/distant metastases and 8/355 (2.3%) with unknown stage. Radiotherapy (RT) techniques include: no RT in 236/355 (66.5%), primary site only in 33/355 (9.3%) with a median dose of 50 (range: 28-68.7) Gy2 or local+nodal coverage in 35/355 (9.9%) with a median dose of 50 (range: 37.3-60.0) Gy2. Among 343 patients with known outcome, local recurrence occurred in 74/343 (21.6%), nodal recurrence in 175/343 (51.0%) and distant recurrence in 108/343 (31.5%). The 5-year overall survival (OS) of the limb subgroup was 45.4%, compared with those of trunk (24.5%, P=0.005, logrank test). Corresponding 5-year cause-specific survival (CSS) was 60.0% vs 34.2% (P=0.000015). Limb lesions have better 5-year OS than head and neck (45.4% vs 35.5%, P=0.0027) and CSS (60.0% vs 58.2%, P=0.37).

Conclusions: Before the era of immunotherapy, peripheral lesions in the limbs have better outcomes than truncal lesions. Enrolment in clinical trials of neoadjuvant and adjuvant immunotherapy may help to improve prognosis of these patients.