Management and Outcomes of Merkel Cell Carcinoma in Canada Between 2000 and 2018 from the Pan-Canadian Merkel Cell Collaborative

Merkelcell.org Summary

Merkel cell carcinoma (MCC) is a rare but aggressive skin cancer, and little has been known about how it is treated in Canada. This study followed 899 Canadian patients diagnosed with MCC between 2000 and 2018 at 10 major cancer centers. Over the 18-year period, the median age at diagnosis remained steady at 75 years, and the stage at diagnosis did not change significantly either. About 50–60% of patients were diagnosed at early stages (stage I or II), 30–40% at stage III (tumors involving skin and lymph nodes), and 10% at stage IV (cancer that had already spread to other organs). While these patterns stayed the same, treatment approaches have evolved. More patients received surgery, either alone or combined with radiation, while fewer were treated with radiation alone or monitored without being actively treated. Five years after diagnosis, about 48% of patients were still alive, and nearly half of them had no return of their cancer. Encouragingly, deaths specifically due to MCC declined between 2012 and 2018, likely because of the growing impact of newer treatments like immunotherapy. In fact, the risk of dying from MCC dropped by 43% during this later period.
These findings show that while meaningful progress has been made, especially with the introduction of immunotherapy, MCC remains a serious disease, and further advances are still needed to improve outcomes for patients.

Abstract

Background: The management and survival outcomes of patients with Merkel cell carcinoma (MCC) in Canada are currently unknown. The objective of this study was to investigate the management and outcomes of patients diagnosed with MCC in Canada from 2000 to 2018.

Patients and methods: This retrospective cohort study evaluates management and temporal survival differences among patients diagnosed with MCC in ten large urban university centers in three provinces during three periods: 2000-2005, 2006-2011, and 2012-2018.

Results: There were 899 patients included with a median follow-up of 22.8 months. There were no significant changes in patient and tumor characteristics between the three periods. There were increases in the use of radiologic staging (2000-2005, 53.4%; 2006-2011, 73.7%; 2012-2018, 78.1%; p < 0.01), surgery as the sole treatment (2000-2005, 25.7%; 2006-2011, 34.0%; 2012-2018, 31.8%; p = 0.02), and surgery with adjuvant radiation (2000-2005, 37.2%; 2006-2011, 36.2%; 2012-2018, 43.7%; p =0.02) during the study period. Between 2000 and 2018, the 5-year median overall survival (OS) was 47.9% (95% confidence interval (CI) 43.2-55.8%), disease-free survival was (DFS) 48.9% (95% CI 42.4-55.1%), and cancer-specific survival (CSS) was 49.7% (95% CI 43.2-55.8%). There were no significant differences in OS and DFS between the three periods on multivariable analysis. Compared with 2000-2005, there was no significant difference in CSS from 2006 to 2011 (hazard ratio (HR) 1.02 95% CI 0.66-1.62, p = 0.9), but there was a significant improvement in CSS from 2012 to 2018 (HR 0.57 95% CI 0.34-0.97, p = 0.04).

Conclusions: Despite changes in the utilization of staging, surgery, and radiation, the prognosis of patients with MCC in Canada remains poor, highlighting the need for improved management strategies.