Objectives: Anaplastic thyroid cancer (ATC) is an aggressive cancer with high mortality. Immune cells are highly abundant in the ATC tumor microenvironment and increased infiltration with tumor-associated macrophages is associated with decreased survival. We hypothesize that systemic inflammatory markers are also associated with worse survival in patients with ATC and are more elevated in ATC compared to poorly differentiated thyroid cancer (PDTC).

Methods: Clinical and biochemical data were retrospectively collected from patients with ATC or PDTC that were treated at our hospital between 1999 and February 2023. Inflammatory markers at diagnosis were compared between ATC and PDTC patients and survival was compared between patients with and without systemic inflammation.

Results: Seventy-seven ATC patients and 27 PDTC patients were included. C-reactive protein (CRP), erythrocyte sedimentation rate (ESR) and absolute white blood cell count (WBC) were all significantly higher in ATC patients when compared to PDTC patients. Albumin concentrations and neutrophil-to-lymphocyte ratio (NLR) were not significantly different between both patient groups. Within ATC patients, CRP, WBC, distant metastases and NLR at diagnosis were significantly correlated with worse survival, while sex, albumin and ESR were not. Within ATC patients, those with elevated CRP at diagnosis had a significantly worse survival than patients without elevated CRP (median survival 1 and 10 months respectively). The same was true for ATC patients with leukocytosis at diagnosis (median survival 1 and 5 months respectively). Conversely, median survival of ATC subgroups with and without elevated ESR were not significantly different. In a Cox regression model with the variables absolute CRP value, WBC and distant metastases at diagnosis, both CRP and distant metastases at diagnosis significantly correlated with survival.

Conclusion: Systemic inflammation is more prevalent in ATC when compared to PDTC. Elevated CRP and leukocytosis at diagnosis are prognostic markers in ATC patients.