Thromboprophylaxis prescribing and thrombotic event rates in multiple myeloma patients treated with lenalidomide or thalidomide at a specialist cancer hospital.

Aim: To assess thromboprophylaxis prescribing patterns against current guidelines and report thromboembolism (TE) incidence in multiple myeloma (MM) patients treated with thalidomide (thal) or lenalidomide (len) at a specialist cancer hospital over a one-year period.

Method: Dispensing records of thal and len, diagnosis of MM, patients' characteristics, disease status, co-prescribed medicines including thromboprophylaxis and incidence of TE were extracted from patients' records and a patient survey conducted to identify patients who sourced thromboprophylactic medicines outside the hospital.

Results: Enoxaparin was most the commonly prescribed thromboprophylactic agent (43%), followed by low-dose aspirin (26%) and therapeutic warfarin (6%). The thromboprophylactic strategy (including no prophylaxis) could not be determined for 22% of patients. TE incidence (with any thromboprophylaxis) was 9.3 and 9.1% in thal-based and len-based regimens, respectively.

Conclusion: Both aspirin and enoxaparin thromboprophylaxis were prescribed for patients on both low-risk and high-risk immunomodulatory drug-based regimens, deviating from current consensus guidelines. Treatment of comorbidities constituted the rationale for maintenance on therapeutic warfarin. Fixed low-dose warfarin was not prescribed. TE event rates (with any thromboprophylaxis) were consistent with those reported in the literature. Documentation of a chosen strategy was lacking for nearly a quarter of patients, resulting in uncertainty of treatment plan for other members of the multidisciplinary treating team. Centers need to work towards evidence-based institutional guidelines and improving documentation practices for thromboprophylaxis in their MM patients.