Factors associated with advanced-stage Merkel cell carcinoma at initial diagnosis and the use of radiation therapy: Results from the National Cancer Database.

Background: The stage of disease at initial diagnosis and the use of radiation therapy (RT) are important determinants of survival in patients with Merkel cell carcinoma (MCC).

Objective: To define factors that are associated with advanced-stage MCC at the time of initial diagnosis and the use of RT.

Methods: Cross-sectional, retrospective analysis of patients with MCC registered in the National Cancer Database during the period from 2004 to 2013.

Results: A total of 11,917 patients were identified; 3152 and 4586 patients were excluded from the staging and RT analyses, respectively, because of lack of available data. African American ethnicity (odds ratio [OR], 1.49; 95% confidence interval [CI], 1.06-2.10; P = .023), lack of medical insurance (OR, 2.15; 95% CI, 1.40-3.30; P < .001), Charlson-Deyo comorbidity score of at least 1 (OR, 1.21; 95% CI, 1.09-1.34; P < .001), residence more than 26 miles from a treatment facility (OR, 1.18; 95% CI, 1.03-1.35; P = .015), tumor located on the lower limb/hip (OR, 1.59; 95% CI, 1.42-1.78; P < .001) or trunk (OR, 2.05; 95% CI, 1.81-2.33; P < .001), and poorly (OR, 2.57; 95% CI, 1.13-5.82; P = .024) or undifferentiated (OR, 3.11; 95% CI, 1.36-7.15; P = .007) tumor histology predicted advanced-stage MCC at the time of initial diagnosis. The use of RT was associated with Native American ethnicity (OR, 5.04; 95% CI, 1.10-22.99; P = .037), tumor size between 1.5 and 2.7 cm (OR, 1.27; 95% CI, 1.10-1.47; P = .001), electing not to have surgery (OR, 2.77; 95% CI, 1.90-4.03; P < .001), positive postsurgical margins (OR, 1.39; 95% CI, 1.18-1.63; P < .001), and receiving treatment at a comprehensive cancer program (OR, 1.25; 95% CI, 1.03-1.50; P = .020).

Limitations: Retrospective design limits generalizability of the results, and precise details of RT regimens utilized were not available.

Conclusions: A number of factors are associated with advanced-stage MCC at initial diagnosis and the use of RT. Health care models should account for these factors, and efforts should be directed toward improving those that are modifiable.