The Natural History of Heparin Induced Thrombocytopenia (HIT) in Cancer Patients

Objective Natural history of heparin-induced thrombocytopenia (HIT), along with its treatment and outcomes, is not well established in cancer patients. In this study we sought to describe the clinical features of HIT in cancer patients.

Materials and Methods We performed a retrospective analysis of 47 patients with cancer and suspicion of HIT, based on clinical presentation and 4T-score. Only patients with a serotonin releasing assay (SRA), the gold standard confirmatory test, were included. We assessed patients for baseline characteristics, subsequently comparing SRA-positive patients with SRA-negative patients, according to demographics, type and dose level of heparin, screening/diagnostic tools (such as 4T score and IgG for platelet-factor 4 [PF4]), tumor characteristics (solid, liquid-plasma cell, liquid-non plasma cell), thrombotic events at the time of HIT along with clinical outcomes, including hemorrhagic complications from alternative anticoagulation. Continuous variables were compared between SRA-status groups by non-parametric methods. Logistic regression models were built for 30-day mortality and overall survival.

Results We found a median 4T-score of 6 (range from 4 to 7). Patients had a 61% positive SRA rate. 78.9% of patients had thrombosis at presentation. The clinically relevant bleeding rate was 18.4% (2.6% major bleeding). When stratifying by SRA results, there were no statistically significant differences between median 4T score, nor between median IgG-PF4 optical density. No deaths were attributed to bleeding complications and one death was attributed to coronary artery thrombosis related to HIT. At 4 months, ECOG greater than 1 (HR 3.39, CI95% 1.17-9.83) and solid malignancy (HR 4.08, CI95% 1.21, 13.79) were associated with a worse survival. Plasma cell malignancy was associated with a better overall survival, compared to solid tumors (Figure). Overall survival was higher for liquid malignancies (median of 48.1 months) than solid tumors (median of 1.6 months).

Conclusions There is a high frequency of thrombosis in cancer patients with HIT, compared to other populations, making it a notable debut presentation. Patients are thrombocytopenic, but the incidence of both any bleeding and major bleeding are comparable to most groups of anticoagulated cancer patients. Regardless of stage, HIT in solid malignancies was associated to worse prognosis when compared with hematologic neoplasms.

Oo:Thein Hlaing Oo served on the advisory board of Bristol-Myers Squibb.: Other: Thein Hlaing Oo served on the advisory board of Bristol-Myers Squibb. Rojas Hernandez:ANTHOS Therapeutics: Research Funding; ASPEN Pharmaceuticals: Research Funding; Daichii Sankyo: Research Funding.