Competing risks analysis of Merkel cell carcinoma with concurrent chronic lymphocytic leukemia and non-Hodgkin lymphoma.

Background: Although hematogenous malignancy is a risk factor for poorer prognosis in Merkel cell carcinoma (MCC), current guidelines make no specific recommendations for surveillance.
Objective: We aim to characterize MCC-specific mortality compared to other causes of death for patients with hematologic malignancy in MCC, which will guide workup and surveillance strategies.
Methods: The Surveillance, Epidemiology, and End Results-18 registry was queried for MCC patients with chronic lymphocytic leukemia (CLL) or non-Hodgkin lymphoma (NHL).
Results: Of 8519 patients with MCC, 146 (1.7%) had CLL and 234 (2.8%) had NHL. Chronic lymphocytic leukemia patients had 5-year cumulative incidence of MCC-specific mortality of 38.4% versus 28.4% in patients without CLL/NHL. For both cohorts, oncologic risk was highest within the first three years of diagnosis with competing risks favored thereafter. On competing risk regression, a history of CLL trended toward statistical significance with poorer MCC-specific mortality (subdistribution hazard ratio: 1.33, 95% CI: 0.963-1.834, P=0.084), while NHL was not prognostic.
Conclusions: Merkel cell carcinoma patients with CLL may benefit from more aggressive initial management. Surveillance for similar length in CLL patients with MCC may be appropriate; this co-morbidity did not affect the timeframe by which the risk of competing causes of death exceeded oncologic risks.