Improving Hematology Clinic Access for Patients with Cancer-Associated Thrombosis
Authors: Martin Karlyn A. , Laub Caroline , Kalhagen Lindsey , Boska Iwona , Attilio Mark , Zakarija Anaadriana , Stein Brady L. 
Published: November 2021

Abstract
Background :
Venous thromboembolism (VTE) is a common consequence for patients with malignancy, and adversely impacts quality of life, morbidity and mortality. While historically low-molecular weight heparin (LMWH) was considered standard of care for treatment of cancer-associated thrombosis (CAT), more recent data support the safety and efficacy of direct oral anticoagulants (DOACs). However, management of CAT remains complex, and a national shortage of non-malignant hematologists limits access to thrombosis experts. Our non-malignant hematology group developed a pilot program to expedite referrals for oncology patients with CAT to aid in management and selection of appropriate therapies.
Methods:
With guidance from the Process Improvement team at Northwestern Medicine, the Cancer-Associated Thrombosis clinic was established in April 2020. Information about the clinic was disseminated via administrative meetings and e-mails from the clinical practice director. Patients were referred from the Robert H. Lurie Comprehensive Cancer Center for either: (1) newly diagnosed ("acute") venous thromboembolic event (VTE) that could be managed in an outpatient setting, or (2) "ongoing management" of an established VTE diagnosis. We aimed to see acute referrals within 24 business hours and ongoing management referrals within 2 weeks. Patients were seen initially by an advanced practice provider, with case discussion with an attending non-malignant hematologist and pharmacist review for anticoagulant eligibility and teaching. Patients were to be scheduled for follow-up with an attending hematologist within 3 months. Decision-making regarding anticoagulant choice was based on perceived bleeding risk, tumor type, drug interactions, and patient preferences. Herein we report our experience during the first year (April 2020-April 2021) of the CAT clinic.
Results
Sixty-three patients were seen in the first year, of whom 59% were women, with a median age of 63 years (range 30-90 years). 20.6% of patients had a prior history of VTE, and 6.3% had a prior history of bleeding. Tumor types from nine oncology sites were represented, of which gastrointestinal (33.3%); gynecological (22.2%); hematological malignancies (14.2%), and breast (7.9%) were the most common. Among 18 patients (28.5%) referred for acute VTE, the median time to appointment was 0 days, and among 45 patients (71.4%) referred for ongoing VTE management, the median time to appointment was 10 days. The most common VTE was pulmonary embolism (PE) (25.4%), followed by proximal deep vein thrombosis (DVT) (20.6%), concurrent PE and DVT (14.3%) and upper extremity DVT (11.1%). Additionally, 7.9% of thrombotic events involved splanchnic vein and 4.8% cerebral veins (1 isolated, 2 together with DVT and/or PE).
DOACs were recommended in 29 (46%) of patients (19 apixaban, 9 rivaroxaban, 1 edoxaban), whereas enoxaparin was advised in 28 patients (44.4%). Four patients were advised to discontinue anticoagulation and 1 was advised to continue warfarin given prior DOAC failure and preference for an oral anticoagulant. Of 28 patients advised to use enoxaparin over a DOAC, the most common reasons included perceived bleeding risk/tumor type (50%), DOAC failure (21.4%), and drug-drug interactions (17.8%). Thirteen patients (21%) switched to a different anticoagulant (7 to a DOAC) in follow-up after the initial recommendation.
Thirty-seven patients (59.7%) had a follow-up visit in the CAT clinic. During follow-up, 5 patients (7.9%) experienced recurrent or progressive VTE, and 7 (11.1%) patients had bleeding events. Fifteen patients (24.2%) died during follow-up.
Conclusions
The aim of this process improvement project was to improve access and assist with anticoagulant choice and management of CAT. Compared to a historical 3 month wait time for non-malignant hematology appointments at our institution, most acute CAT patients were scheduled within 24 hours, and patients requiring ongoing management were seen within 10 days. While DOACs are increasingly prescribed for treatment of CAT, we found that DOACs were not our recommended anticoagulant in over half of patients referred to our clinic, largely due to perceived risk of bleeding/tumor type. This highlights the complexity of management of CAT, and demonstrates the benefit of dedicated thrombosis expertise to aid in management of CAT.

Disclosures
Martin: Janssen: Research Funding; Penumbra: Other: Scientific Advisory Board. Kalhagen: Harborside: Other: Consulting; Incyte: Speakers Bureau. Zakarija: Bayer: Other: Consultancy Advisory Board. Stein: Pharmassentia: Other: Advisory Board and Steering Committee; Constellation Pharmaceuticals: Other: Advisory Board x 1.