**7. Central venous catheters**

Central venous catheters (CVC) are commonly inserted in cancer patient and are utilized to deliver chemotherapy, blood and blood component transfusion and occasionally for blood sampling. Central catheter per se is a risk factor for VTE, this risk is even higher when such catheters are placed in cancer patients especially so when used for active chemotherapy (Bona, 1999; Rooden et al., 2005; Rosovsky & Kuter, 2005).

Fig. 1. Extended out-of-hospital VTE prophylaxis for cancer patients undergoing major surgery

Venous Thromboembolism Prophylaxis in Cancer Patients 119

as compared with 21 (11.6%) patients assigned to the no-filter group, had recurrent DVT (odds ratio, 1.87; 95% CI, 1.10 to 3.20) ( Decousus et al., 1998). This study was updated 8 years later; patients with IVC filters experienced a greater cumulative incidence of symptomatic DVT (35.7%versus 27.5%; HR 1.52, CI 1.02 to 2.27; *P* = 0.042), but significantly fewer symptomatic pulmonary emboli (6.2%versus 15.1%; HR 0.37, CI 0.17 to 0.79; *P* = 0.008) (The PREPIC Study Group, 2005). The conclusion from this long-term follow-up was similar to the original report; that is, with an IVC filter there is an equivalent trade-off of fewer PE at the cost of more DVTs. There was no difference in long-term morbidity or mortality in both groups.

Failure of anticoagulation: Recurrent VTE despite anticoagulation Contraindications and/or severe complications of anticoagulation:

Thrombocytopenia (Depends on count and etiology)

**Main Indications:** 

**Other indications:** 

High risk for bleeding

Real bleeding (GI,GU,GYN, CNS)

Large CNS Tumor: Primary or metastatic

Limited cardiopulmonary reserve (Cor Pulmonale)

Patients at risk for falls while on anticoagulation therapy

IVC: Inferior Vena Cava, GI: Gastrointestinal, GU: Genitourinary, GYN: Gynecological, CNS: Central

Given the lack of long term benefits of IVC filters; temporary, retrievable filters had gained increasing interest. Many different retrievable filters had recently received approval for temporary insertion. Recent data suggest that the use of these filters may be associated with low rates of PE and insertion complications (Imberti & Prisco, 2008). Nevertheless; no randomized clinical trials have been performed. In one large retrospective study that included 252 evaluable patients who had retrievable filter placed for different indications; only 47 filters were successfully retrieved yielding a retrieval rate of 18.7% ( Dabbagh et al.,

2010). Similar or higher retrieval rates were reported by others (Mismetti et al., 2007).

Regardless of the type of the filter placed, the most recent American Colleague of Chest Physicians (ACCP) guidelines recommend systemic anticoagulation, when possible, even

Cancer itself, or its treatment, might result in certain clinical complications that make systemic anticoagulation very risky (Abdel-Razeq et al., 2011). Venous thromboembolic disease is a frequent complication in patients with intracranial malignancies. Many of the primary brain tumors like gliomas or secondary metastatic tumors to the brain are either bulky or very vascular thus increasing the risk of bleeding with or without systemic anticoagulation (Ruff & Posner, 1983). Brain metastases from melanoma, choriocarcinoma, thyroid carcinoma, and renal cell carcinoma have particularly high propensities for

Immediate post-operative VTE

Large, free-floating iliocaval thrombus

Poor compliance with medications

Nervous System, VTE: Venous Thromboembolism Table 2. Indications for IVC filter placement

with the filter in place (Kearon et al., 2008).

Several clinical trials have addressed the issue of VTE prophylaxis in such patients. One study showed a benefit in reducing VTE events when low fixed-dose warfarin (1mg/day) was used for prophylaxis (Bern et al., 1990). However, two subsequent clinical trials failed to show any benefit [Heaton et al., 2002: Couban et al., 2005).

Low molecular weight heparin was also tried in two large, double-blind clinical trials (Verso et al., 2005; Karthaus et al., 2006). The first trial failed to show beneficial effect of enoxaparin when used at a dose of 40 mg once daily versus placebo in a group of 385 cancer patients with CVC (Verso et al., 2005). In the second trial, dalteparin at 5,000 units once daily was tested against placebo in 439 cancer patients who were receiving chemotherapy through such catheters; clinically relevant VTE occurred in 3.7% and 3.4% in the dalteparin and placebo recipients, respectively (Karthaus et al., 2006). Nadroparin, another LMWH, showed no advantage when tested against low fixed dose of warfarin (1 mg/day) in a small randomized trial that involved 45 evaluable patients (Mismetti et al., 2003).

Given the results of these studies, thromboprophylaxis with anticoagulants for patients with central venous catheters is not recommended.
