LETTER TO EDITOR

Year : 2020  |  Volume : 3  |  Issue : 4  |  Page : 884-885

Challenges in cancer associated thrombosis (CAT)

Anuprita Daddi
Department of Medicine, Cancer Thrombosis Clinic, Tata Memorial Hospital, Homi Bhaba National Institute, Mumbai, Maharashtra, India

Correspondence Address:
Anuprita Daddi
Department of Medicine, Cancer Thrombosis Clinic, Tata Memorial Hospital, Dr E Borges Road, Parel, Mumbai - 400 012, Maharashtra
India

Source of Support: None, Conflict of Interest: None

1. Tumor thrombosis – Many cancers such as Wilms' tumor, renal cell carcinoma, adrenal cortical carcinoma, hepatocellular carcinoma (RCC), intravenous leiomyomatosis (though rare), islet cell tumors of the pancreas, and thyroid, testicular, lung, colorectal cancers commonly show macrovascular invasion to nearby vessels along with infiltration of primary site. Cases of embolization leading to stroke, bowel infarction, and left ventricular obstruction causing sudden death have also been reported. Fluorodeoxyglucose (FDG) positron emission tomography (PET) scan helps to distinguish tumor thrombus from “bland” thrombus (free of neoplastic cells).^[2] This is a very important differentiation to make before the initiation of anticoagulation, as anticoagulation plays no role in tumor thrombosis. Also, the presence of tumor thrombus markedly worsens the prognosis and impacts the treatment approach. In such cases, surgical excision along with chemotherapy plays an important role.
2. Arterial thrombosis – There is an increased risk of arterial thrombosis in patients with cancer. The incidence of arterial thromboembolic events (ATEs) has been reported to be 4.7% at 6 months of cancer diagnosis in patients.^[3] ATEs can result from the use of certain chemotherapeutic drugs like vascular endothelial growth factor inhibitors, platinum-based agents, taxanes, and tyrosine kinase inhibitors and are predictive of worse outcomes. In patients without cardiovascular risk factors, an episode of ATE can be considered as an indication to screen for occult malignancies. Similarly, radiation therapy also predisposes patients to ATE due to accelerated atherosclerosis, oxidative stress, endothelial damage and fibrin deposition by activating the coagulation cascade.
3. Direct oral anticoagulants (DOACs) – Although DOACs are now a preferred alternative to low-molecular-weight heparin (LMWH) with no need for frequent monitoring and convenient mode of administration, the clinical effect of various drug interactions with the DOACs is not well described. DOAC's interact with other drugs primarily though the cytochrome P450 (CYP) and P-glycoprotein efflux transporter. Four inhibitors of CYP3A4 and P-glycoprotein with moderate activity have been identified, namely abiraterone, crizotinib, cyclosporine, and imatinib. The administration of these drugs concomitantly with the DOAC's can lead to an increase in the concentration of the DOACs in the plasma. Drugs such as bexarotene, paclitaxel, prednisone, and vemurafenib moderately induce the CYP3A4 activity without affecting the P-glycoprotein transporter. Bicalutamide inhibits the activity of CYP3A4 to a moderate extent and if used concomitantly, can increase the concentration of apixaban and rivaroxaban in the plasma.^{[4],[5],[6],[7],[8],[9],[10]}
4. Venous thromboembolism in the palliative setting – In the palliative setting, there are no specific guidelines for VTE prophylaxis. An informed decision along with the patients and their caregivers should be made regarding the initiation of anticoagulation. Lifelong anticoagulation may be required as there is a high risk of VTE recurrence if anticoagulation is stopped. However, most authorities recommend discontinuation of anticoagulation in actively dying patients.
5. Superficial vein thrombosis – If it is progressive or proximal to the deep veins (approximately 3 cm), anticoagulation with therapeutic dose LMWH for 6 weeks is suggested (National Comprehensive Cancer Network 2018)
6. Recurrent VTE – Along with drug compliance, and the underlying disease burden, some situations also warrant thrombophilia profile evaluation.

References

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