Survival outcomes in patients with de novo metastatic Merkel cell carcinoma according to site of metastases

Merkelcell.org Summary

Merkel cell carcinoma (MCC) has a high chance of spreading to other parts of the body, which is called metastatic MCC. This study looked at 34 patients who already had metastatic MCC when they were first diagnosed (de novo metastatic MCC) to see if the location the MCC tumors spread to affected their survival. They found that, in most cases, the location of the metastatic cancer didn’t affect survival, except when the cancer had spread to the bones—those patients lived for a shorter time. Additionally, treatments such as chemotherapy and immunotherapy worked the same, no matter where the MCC had spread to.

These findings add to an earlier study of 215 patients with MCC, including 194 patients that developed metastatic MCC after they had already been treated for MCC that hadn’t yet spread, and 21 with de novo metastatic MCC. That study found that where MCC started in the body affected where it spread to later, which affected survival. Research like this helps doctors understand how both the original location and location of spread might be important for MCC treatment planning and could lead to better cancer staging guidelines for metastatic MCC that factor in the location of the cancer.

Read the previous study mentioned: Patterns of distant metastases in 215 Merkel cell carcinoma patients: Implications for prognosis and surveillance, by Lewis et. al

Abstract

Introduction
Merkel cell carcinoma (MCC) is a rare and aggressive neuroendocrine malignancy of the skin with a predilection for metastases. This study investigates the clinical outcomes in patients presenting with de novo Stage IV MCC according to the metastatic site(s) at presentation.

Materials and methods
Patients who presented with one or more sites of distant metastatic MCC at initial diagnosis between 2009 and 2023 were identified. The presence or absence of one or more metastases in each organ was categorized for each patient at the time of diagnosis. Overall survival (OS) and progression-free survival (PFS) were estimated using the Kaplan-Meier method. Competing risk analysis was used to estimate the cumulative occurrence risk of MCC-specific death. Fisher’s exact test was used for response rate analysis. Results were considered statically significant if p < 0.05. Results Thirty-four patients presented with de novo distant metastatic MCC. There was no association between the number of metastatic sites at diagnosis and OS (p= 0.58), PFS (p=0.79), or response rates (p=0.53). However, the presence of bone metastases was associated with significantly shorter OS (8.2 versus 25.2 months, HR: 2.4, 95% CI 1.01-5.7, p= 0.04). MCC-specific death in patients with lymph node metastases was significantly lower than in patients without (HR: 0.28, 95% CI: 0.09-0.87, p= 0.013). The presence of bone metastases tended to associate with an increased risk of MCC-specific death, although not statistically significant. The location of metastases was not associated with the response rate to first-line treatment. There was no significant association between site of metastases and PFS. Conclusion In this cohort of patients with de novo metastatic MCC, the presence of bone metastases, but not the number of organs involved, was associated with significantly worse OS. The presence of lymph node metastases was associated with lower MCC-specific death. Further research is warranted in larger cohorts to investigate the impact of the location of metastases on clinical outcomes. Keywords: Merkel cell cancer, metastases, de novo, survival, outcome, organ sites of metastasis, non melanoma skin cancer