Rudolph Virchow clearly demonstrated the association between malignancy and venous thromboembolic events. VTE – deep vein thrombosis and pulmonary embolism – affect between 15% and 38% of patients with gynecologic malignancies after surgery.
The rate of pulmonary embolism (PE) in this patient population can be as high as 6.8%, with the case fatality rate being 11%-12% (Obstet. Gynecol. 2012;119:155-67). Other factors associated with the development of VTE include prior VTE, older age, African American race, prolonged operative time, obesity, and prior radiation therapy (Obstet. Gynecol. 1987;69:146-50). The risk of VTE in women undergoing gynecologic surgery is quadrupled in the presence of malignancy(Obstet. Gynecol. 2006;107:666-71) and these patients are twice as likely to die from a VTE compared to matched controls (Gynecol. Oncol. 2007;106:439-45).
Additionally, cancer patients are typically older, have longer and more complex surgeries, and the presence of a pelvic mass further contributes to venous stasis (Obstet. Gynecol. 2012;119:155-67).
Although the treatment of VTE is fairly similar between patients with malignancy and those without cancer, treatment of a VTE in patients with cancer can be further complicated by higher VTE recurrence rates and increased risk of bleeding. Furthermore, issues related to the malignant disease process such as prognosis, presence and location of metastasis, and life expectancy should be taken into consideration when managing VTE in this patient population.
Generally, in the setting of an acute or recurrent VTE, initial therapy with a parenteral anticoagulant (heparin or low-molecular-weight heparins [LMWH]) should be immediately instituted in patients with a gynecologic malignancy, unless there is evidence of active bleeding or any other contraindication for the use of an anticoagulant.
Other factors associated with cancer such as immobilization, the presence of metastases, and impaired renal function with a creatinine clearance less than 30 mL/min, may increase the risk of bleeding complications but are not absolute contraindications to anticoagulation (Thromb. Haemost. 2008;100:435-9). The initial treatment phase, which last for 5-10 days, is then followed by a longer treatment phase lasting 3-6 months.
In the majority of cases, LMWH is the preferred agent for both the initial and prolonged treatment phase assuming adequate renal function. Based on evidence from a meta-analysis of 16 randomized controlled trials in cancer patients receiving initial anticoagulation for VTE, LMWH is associated with a 30% reduction in mortality without an increased risk of bleeding in comparison to unfractionated heparin (Cochrane Database. Syst. Rev. 2014;6:CD006649).
When compared with the vitamin K antagonist warfarin, LMWH appears to be associated with a significantly reduced rate of recurrent VTE (hazard ratio, 0.47; 95% confidence interval 0.32-0.71). However, this was not associated with a survival advantage (N. Engl. J. Med. 2003;349:146-53).
There are no trials comparing the different formulations of LMWH. In our practice, we routinely use the LMWH enoxaparin dosed at 1 mg/kg subcutaneously twice daily. Other well-studied LMWHs include dalteparin and tinzaparin.
LMWHs are primarily renally excreted, thus, in patients with compromised renal function, the biological half-life of the medication may be prolonged, leading to potential bleeding complications. The majority of LMWH trials excluded patients with creatinine clearance less than 30 mL/min, therefore, in patients with compromised renal function, one option would be to decrease the daily dose by as much as 50% and closely monitor antifactor XA levels. Alternatively, the use of unfractionated heparin in the acute setting followed by warfarin with close monitoring of the patient’s international normalized ratio could prove less cumbersome and ultimately safer for these patients. However, given the limitations of the currently available data we would not recommend the routine use of newer oral anticoagulation agents.
Patients with a malignancy are at increased risk for the development of a recurrent VTE even in the setting of anticoagulation. Some of the risks factors for this phenomenon include presence of central venous catheters, interruption of therapy for procedures, and immobilization. In cases of recurrent VTE, consideration should be given to extending the duration of treatment beyond the initial planned 3-6 months. Other patients that may benefit from extended therapy include those with continued immobility or active cancer burden.
LMWH is also the preferred agent for extended therapy based on very limited evidence from experimental studies suggesting that LMWH may have antineoplastic effects and thus a survival advantage. However, in the setting of a recurrent VTE, there is very limited data on which to base the choice of extended treatment. Options include switching the therapeutic agent, increasing the dose or frequency of administration, or placement of an inferior vena cava filter. Consultation with a hematologist may also be warranted in this and more complicated scenarios.