Absolute lymphocyte count: A potential prognostic factor for Merkel cell carcinoma

Background: Absolute lymphocyte count (ALC) is a laboratory value commonly obtained during workup of patients with Merkel cell carcinoma (MCC). Objective: We report the prognostic impact of ALC as a surrogate of immune status in MCC. Methods: A complete blood cell count was available for 64 patients with MCC in the month before definitive surgery, chemotherapy, or radiation. Statistical analysis was performed with classification and regression tree analysis, log rank test, and Cox model. Results: Median overall survival (OS) for the cohort was 97 months. Median OS for patients with an ALC less than 1.1 k/mm(3) was 18.8 versus 110.1 months for those with ALC greater than or equal to 1.1 k/mm(3) (P = .002, hazard ratio 0.29). Multivariate analysis of OS controlling for ALC, sex, stage, adjuvant chemotherapy, hematologic malignancy, and immunosuppression demonstrated ALC as a prognostic factor (P = .03). Disease-free survival at 36 months for ALC less than 1.1 k/mm(3) was 26.9% versus 64.4% for those with ALC greater than or equal to 1.1 k/mm(3) (P = .01). ALC was not a significant predictor for disease-free survival on multivariate analysis (P = .12). Limitations: This is a single-institution retrospective data set. Conclusion: ALC is associated with OS but not disease-free survival in MCC using a threshold of less than 1.1 k/mm(3). This test may provide additional prognostic information for patients with MCC.