PB1357 - Pharmacological thromboprophylaxis to prevent venous thromboembolism in ambulatory patients with cancer undergoing antineoplastic drugs in real world clinical practice: a cohort study

Background: Venous thromboembolism (VTE) is the second leading cause of death in cancer patients. Clinical prediction models can identify ambulatory patients undergoing antineoplastic drugs who may benefit from primary pharmacological thromboprophylaxis. Evidence is scant on determinants of thromboprophylaxis and outcomes in clinical practice.

Aims: To estimate the incidence of VTE in a cohort of cancer ambulatory patients undergoing antineoplastic drugs, who were systematically assessed for VTE pharmacological thromboprophylaxis

Methods: In a retrospective, observational cohort study, based on a standardized protocol being active at the Humanitas Research Hospital from 2012, consecutive adult ambulatory patients starting antineoplastic drugs were evaluated for VTE thromboprophylaxis (low molecular weight heparin 80 UI/Kg) based on Khorana score and clinical judgment. The primary outcome was symptomatic VTE and asymptomatic deep vein thrombosis at ultrasound performed at 6 months. The study was approved by the local institutional review board.

Results: 443 patients were enrolled up to November 2019. Baseline characteristics are described in Table 1. Among 206 patients (46.5%) who were given thromboprophylaxis, 112 (54.4%) had Khorana score ≥ 2, as compared to 30/227 (13.2%) who did not receive thromboprophylaxis (p < 0.01). Indications for thromboprophylaxis in the remaining 94 patients who had Khorana score < 2 were: previous VTE (6 patients), other VTE risk factors (31), cancer-related risk factors (34), thrombophilia (5), multiple indications (18). Patients receiving thromboprophylaxis had a worse performance status (p 0.03).
At 6 months, VTE occurred in 32/443 (7.2%) patients, of whom 12/206 (5.9%) on thromboprophylaxis and 20/227 (8.9%) not receiving thromboprophylaxis (p 0.27). The same comparison for major bleeding was 3.9% and 2.6% (p 0.45) and for death 4.4% and 0.4% (p 0.01).

Conclusion(s): In real-world clinical practice setting, pharmacological thromboprophylaxis choice was based on Khorana score or other clinical determinants. This strategy was associated with similar VTE incidence as compared to clinical trials.