Incidence of cancer after a first episode of idiopathic venous thromboembolism treated with 3 months or 1 year of oral anticoagulation

Low-Molecular-Weight Heparin Versus Warfarin in Adult Cancer Patients as a Precision Medicine for Thrombosis: A Systematic Review and Meta-Analysis

Venous thromboembolism (VTE) is a condition often seen in patients diagnosed with cancer and is recognized as a predictor of poor outcomes in these patients. The probability of VTE recurring is generally higher in people with cancer than in those without; hence, addressing this issue is essential when making healthcare decisions. Therefore, our systematic review was primarily designed to compare low-weight- molecular heparin (LMWH) to warfarin in reducing recurrent VTE among cancer patients. However, other outcomes were also evaluated, such as mortality and bleeding events observed more in cancer patients. The selection of relevant articles was carried out using a database search and a manual search, which involved reviewing reference lists of articles eligible for inclusion in the current review. The methodological quality of each included study was then assessed using Cochrane's risk of bias tool in the Review Manager software (RevMan 5.4.1). Additionally, pooled results were examined using the Review Manager software and presented as forest plots. Our search of electronic databases elicited a total of 2163 articles, of which only six were deemed eligible for inclusion and analysis. Data pooled from the six studies demonstrated the effectiveness of LMWH in minimizing the reoccurrence of VTE over warfarin [risk ratio (RR): 0.67; 95% CI: 0.47 - 0.95; p = 0.03]. However, LMWH had a similar effect statistically as warfarin on the major bleeding events (RR: 1.05; 95% CI: 0.62 - 1.77; p = 0.85), minor bleeding events (RR: 0.80; 95% CI: 0.54 - 1.20; p = 0.28), and all-cause mortality (RR: 1.00; 95% CI: 0.88 - 1.13; p = 0.99). While LMWH demonstrated its effectiveness in minimizing the incidence of VTE recurrence over warfarin in cancer patients, it had no statistical difference in terms of mortality or bleeding events when compared to warfarin. Based on our findings, we recommend that LMWH continues to be used as a first-line treatment regimen to mitigate recurrent VTE in cancer patients.

The impact of warfarin on overall survival in cancer patients

Venous thromboembolism (VTE) is a common complication in patients with cancer. Warfarin has largely been replaced by low-molecular-weight heparin (LMWHs) and direct oral anticoagulants (DOACs) as the standard of care in cancer-associated VTE. The survival benefit of these anticoagulants over warfarin in the cancer population was not demonstrated in clinical trials, possibly due to insufficient sample size and limited follow-up duration. There are emerging population-based studies suggesting that warfarin may be associated with improved overall survival in cancers and may have a protective effect against certain types of cancers. Warfarin may exert its anti-neoplastic properties through both coagulation pathway -dependent and -independent mechanisms, the latter of which are mediated by inhibition of the Gas6-AXL signaling pathway. Further research should emphasize on identifying clinical and laboratory predictors of beneficial effects of warfarin. In this review article, we summarize and update the current evidence regarding the potential impact of warfarin on the overall survival of cancer patients and incidence of cancer, as well as review the potential mechanism of such effect and future perspectives.

Association of Vitamin K and Non-Vitamin K Oral Anticoagulant Use and Cancer Incidence in Atrial Fibrillation Patients

The association between the use of vitamin K antagonists (VKAs) and cancer risk reduction remains unclear. We aimed to assess the association between the use of VKAs or direct oral anticoagulants (DOACs) and the incidence of cancer in a large cohort of patients with atrial fibrillation (AF) by means of a population‐based, propensity‐weighted cohort study using population‐wide databases including patients diagnosed with nonvalvular AF (NVAF) followed for up of 5 years (median 2.94 years). We created two cohorts based on the initiation therapy (VKA or DOAC). Initiation with VKA or DOAC was defined as filling a prescription with no previous exposure in the preceding 12 months. Cancer diagnoses of any type and for specific tumors (lung, colon, prostate, bladder, and breast). We included 39,989 patients, 31,200 (78.0%) in the VKA cohort. Incidence rate for any cancer was 12.45 per 1,000 person‐year in the DOAC cohort vs. 14.55 in the VKA cohort (adjusted hazard ratio (HR): 1.16, 95% confidence interval (CI): 1.02–1.32). In secondary outcomes, no differences were found for specific types of cancer, such as lung (HR: 1.28, CI: 0.89–1.83), colon (HR: 0.84, CI: 0.62–1.13), prostate (HR: 1.40, CI: 0.94–2.10), bladder (HR: 1.07, CI: 0.76–1.52), and breast (HR: 1.05, CI: 0.66–1.69). Sensitivity analyses yielded similar results. Subgroup analyses also produced consistent findings, except for men, for whom VKA was associated with a lower risk of colon cancer (HR: 0.68, 95% CI: 0.48–0.96). Our results do not confirm a chemoprotective effect of VKA when compared with DOAC in a large, real‐world cohort of patients with NVAF followed for up to 5 years.

Anticoagulation for the long-term treatment of venous thromboembolism in people with cancer

BACKGROUND

Cancer increases the risk of thromboembolic events, especially in people receiving anticoagulation treatments.

OBJECTIVES

To compare the efficacy and safety of low molecular weight heparins (LMWHs), direct oral anticoagulants (DOACs) and vitamin K antagonists (VKAs) for the long-term treatment of venous thromboembolism (VTE) in people with cancer.

SEARCH METHODS

We conducted a literature search including a major electronic search of the Cochrane Central Register of Controlled Trials (CENTRAL; 2016, Issue 1), MEDLINE (Ovid), and Embase (Ovid); handsearching conference proceedings; checking references of included studies; use of the 'related citation' feature in PubMed and a search for ongoing studies in trial registries. As part of the living systematic review approach, we run searches continually, incorporating new evidence after it is identified. Last search date 14 May 2018.

SELECTION CRITERIA

Randomized controlled trials (RCTs) assessing the benefits and harms of long-term treatment with LMWHs, DOACs or VKAs in people with cancer and symptomatic VTE.

DATA COLLECTION AND ANALYSIS

We extracted data in duplicate on study characteristics and risk of bias. Outcomes included: all-cause mortality, recurrent VTE, major bleeding, minor bleeding, thrombocytopenia, and health-related quality of life (QoL). We assessed the certainty of the evidence at the outcome level following the GRADE approach (GRADE handbook).

MAIN RESULTS

Of 15,785 citations, including 7602 unique citations, 16 RCTs fulfilled the eligibility criteria. These trials enrolled 5167 people with cancer and VTE.Low molecular weight heparins versus vitamin K antagonistsEight studies enrolling 2327 participants compared LMWHs with VKAs. Meta-analysis of five studies probably did not rule out a beneficial or harmful effect of LMWHs compared to VKAs on mortality up to 12 months of follow-up (risk ratio (RR) 1.00, 95% confidence interval (CI) 0.88 to 1.13; risk difference (RD) 0 fewer per 1000, 95% CI 45 fewer to 48 more; moderate-certainty evidence). Meta-analysis of four studies did not rule out a beneficial or harmful effect of LMWHs compared to VKAs on major bleeding (RR 1.09, 95% CI 0.55 to 2.12; RD 4 more per 1000, 95% CI 19 fewer to 48 more, moderate-certainty evidence) or minor bleeding (RR 0.78, 95% CI 0.47 to 1.27; RD 38 fewer per 1000, 95% CI 92 fewer to 47 more; low-certainty evidence), or thrombocytopenia (RR 0.94, 95% CI 0.52 to 1.69). Meta-analysis of five studies showed that LMWHs probably reduced the recurrence of VTE compared to VKAs (RR 0.58, 95% CI 0.43 to 0.77; RD 53 fewer per 1000, 95% CI 29 fewer to 72 fewer, moderate-certainty evidence).Direct oral anticoagulants versus vitamin K antagonistsFive studies enrolling 982 participants compared DOACs with VKAs. Meta-analysis of four studies may not rule out a beneficial or harmful effect of DOACs compared to VKAs on mortality (RR 0.93, 95% CI 0.71 to 1.21; RD 12 fewer per 1000, 95% CI 51 fewer to 37 more; low-certainty evidence), recurrent VTE (RR 0.66, 95% CI 0.33 to 1.31; RD 14 fewer per 1000, 95% CI 27 fewer to 12 more; low-certainty evidence), major bleeding (RR 0.77, 95% CI 0.38 to 1.57, RD 8 fewer per 1000, 95% CI 22 fewer to 20 more; low-certainty evidence), or minor bleeding (RR 0.84, 95% CI 0.58 to 1.22; RD 21 fewer per 1000, 95% CI 54 fewer to 28 more; low-certainty evidence). One study reporting on DOAC versus VKA was published as abstract so is not included in the main analysis.Direct oral anticoagulants versus low molecular weight heparinsTwo studies enrolling 1455 participants compared DOAC with LMWH. The study by Raskob did not rule out a beneficial or harmful effect of DOACs compared to LMWH on mortality up to 12 months of follow-up (RR 1.07, 95% CI 0.92 to 1.25; RD 27 more per 1000, 95% CI 30 fewer to 95 more; low-certainty evidence). The data also showed that DOACs may have shown a likely reduction in VTE recurrence up to 12 months of follow-up compared to LMWH (RR 0.69, 95% CI 0.47 to 1.01; RD 36 fewer per 1000, 95% CI 62 fewer to 1 more; low-certainty evidence). DOAC may have increased major bleeding at 12 months of follow-up compared to LMWH (RR 1.71, 95% CI 1.01 to 2.88; RD 29 more per 1000, 95% CI 0 fewer to 78 more; low-certainty evidence) and likely increased minor bleeding up to 12 months of follow-up compared to LMWH (RR 1.31, 95% CI 0.95 to 1.80; RD 35 more per 1000, 95% CI 6 fewer to 92 more; low-certainty evidence). The second study on DOAC versus LMWH was published as an abstract and is not included in the main analysis.Idraparinux versus vitamin K antagonistsOne RCT with 284 participants compared once-weekly subcutaneous injection of idraparinux versus standard treatment (parenteral anticoagulation followed by warfarin or acenocoumarol) for three or six months. The data probably did not rule out a beneficial or harmful effect of idraparinux compared to VKAs on mortality at six months (RR 1.11, 95% CI 0.78 to 1.59; RD 31 more per 1000, 95% CI 62 fewer to 167 more; moderate-certainty evidence), VTE recurrence at six months (RR 0.46, 95% CI 0.16 to 1.32; RD 42 fewer per 1000, 95% CI 65 fewer to 25 more; low-certainty evidence) or major bleeding (RR 1.11, 95% CI 0.35 to 3.56; RD 4 more per 1000, 95% CI 25 fewer to 98 more; low-certainty evidence).

AUTHORS' CONCLUSIONS

For the long-term treatment of VTE in people with cancer, evidence shows that LMWHs compared to VKAs probably produces an important reduction in VTE and DOACs compared to LMWH, may likely reduce VTE but may increase risk of major bleeding. Decisions for a person with cancer and VTE to start long-term LMWHs versus oral anticoagulation should balance benefits and harms and integrate the person's values and preferences for the important outcomes and alternative management strategies.Editorial note: this is a living systematic review (LSR). LSRs offer new approaches to review updating in which the review is continually updated, incorporating relevant new evidence as it becomes available. Please refer to the Cochrane Database of Systematic Reviews for the current status of this review.

Effects of warfarin on biological processes other than haemostasis: A review

Warfarin is the world's most widely used anticoagulant drug. Its anticoagulant activity is based on the inhibition of the vitamin K-dependent (VKD) step in the complete synthesis of a number of blood coagulation factors that are required for normal blood coagulation. Warfarin also affects synthesis of VKD proteins not related to haemostasis including those involved in bone growth and vascular calcification. Antithrombotic activity of warfarin is considered responsible for some aspects of its anti-tumour activity of warfarin. Some aspects of activities against tumours seem not to be related to haemostasis and included effects of warfarin on non-haemostatic VKD proteins as well as those not related to VKD proteins. Inflammatory/immunomodulatory effects of warfarin indicate much broader potential of action of this drug both in physiological and pathological processes. This review provides an overview of the published data dealing with the effects of warfarin on biological processes other than haemostasis.

Oral anticoagulation in people with cancer who have no therapeutic or prophylactic indication for anticoagulation

BACKGROUND

Oral anticoagulants may improve the survival of people with cancer through both an antitumor effect and antithrombotic effect, yet increase the risk of bleeding.

OBJECTIVES

To evaluate the efficacy and safety of oral anticoagulants in ambulatory people with cancer undergoing chemotherapy, hormonal therapy, immunotherapy or radiotherapy, but otherwise have no standard therapeutic or prophylactic indication for anticoagulation.

SEARCH METHODS

We conducted a comprehensive literature search in February 2016 that included a major electronic search of Cochrane Central Register of Controlled Trials (CENTRAL) (2016, Issue 1), MEDLINE (Ovid) and Embase (Ovid); handsearching of conference proceedings; checking of references of included studies; a search for ongoing studies; and using the 'related citation' feature in PubMed. As part of the living systematic review approach, we are running continual searches and will incorporate new evidence rapidly after it is identified. This update of the systematic review is based on the findings of a literature search conducted on 14 December 2017.

SELECTION CRITERIA

Randomized controlled trials (RCTs) assessing the benefits and harms of vitamin K antagonist (VKA) or direct oral anticoagulants (DOAC) in ambulatory people with cancer. These participants are typically undergoing systemic anticancer therapy, possibly including chemotherapy, target therapy, immunotherapy or radiotherapy, but otherwise have no standard therapeutic or prophylactic indication for anticoagulation.

DATA COLLECTION AND ANALYSIS

Using a standardized form, we extracted data in duplicate on study design, participants, intervention outcomes of interest and risk of bias. Outcomes of interest included all-cause mortality, symptomatic venous thromboembolism (VTE), symptomatic deep vein thrombosis (DVT), pulmonary embolism (PE), major bleeding, minor bleeding and health-related quality of life (HRQoL). We assessed the certainty of evidence for each outcome using the GRADE approach (GRADE Handbook).

MAIN RESULTS

Of 8545 identified citations, including 7668 unique citations, 16 papers reporting on 7 RCTs fulfilled the inclusion criteria. These trials enrolled 1486 participants. The oral anticoagulant was warfarin in six of these RCTs and apixaban in the seventh RCT. The comparator was either placebo or no intervention. The meta-analysis of the studies comparing VKA to no VKA did not rule out a clinically significant increase or decrease in mortality at one year (risk ratio (RR) 0.95, 95% confidence interval (CI) 0.87 to 1.03; risk difference (RD) 29 fewer per 1000, 95% CI 75 fewer to 17 more; moderate certainty evidence). One study assessed the effect of VKA on thrombotic outcomes. The study did not rule out a clinically significant increase or decrease in PE when comparing VKA to no VKA (RR 1.05, 95% CI 0.07 to 16.58; RD 0 fewer per 1000, 95% CI 6 fewer to 98 more; very low certainty evidence), but found that VKA compared to no VKA likely decreases the incidence of DVT (RR 0.08, 95% CI 0.00 to 1.42; RD 35 fewer per 1000, 95% CI 38 fewer to 16 more; low certainty evidence). VKA increased both major bleeding (RR 2.93, 95% CI 1.86 to 4.62; RD 107 more per 1000, 95% CI 48 more to 201 more; moderate certainty evidence) and minor bleeding (RR 3.14, 95% CI 1.85 to 5.32; RD 167 more per 1000, 95% CI 66 more to 337 more; moderate certainty evidence).The study assessing the effect of DOAC compared to no DOAC did not rule out a clinically significant increase or decrease in mortality at three months (RR 0.24, 95% CI 0.02 to 2.56; RD 51 fewer per 1000, 95% CI 65 fewer to 104 more; low certainty evidence), PE (RR 0.16, 95% CI 0.01 to 3.91; RD 28 fewer per 1000, 95% CI 33 fewer to 97 more; low certainty evidence), symptomatic DVT (RR 0.07, 95% CI 0.00 to 1.32; RD 93 fewer per 1000, 95% CI 100 fewer to 32 more; low certainty evidence), major bleeding (RR 0.16, 95% CI 0.01 to 3.91; RD 28 fewer per 1000, 95% CI 33 fewer to 97 more; low certainty evidence); and minor bleeding (RR 4.43, 95% CI 0.25 to 79.68; RD 0 fewer per 1000, 95% CI 0 fewer to 8 more; low certainty evidence).

AUTHORS' CONCLUSIONS

The existing evidence does not show a mortality benefit from oral anticoagulation in people with cancer but suggests an increased risk for bleeding.Editorial note: this is a living systematic review. Living systematic reviews offer a new approach to review updating in which the review is continually updated, incorporating relevant new evidence, as it becomes available. Please refer to the Cochrane Database of Systematic Reviews for the current status of this review.

Association of Warfarin Use With Lower Overall Cancer Incidence Among Patients Older Than 50 Years

IMPORTANCE

In cancer models, warfarin inhibits AXL receptor tyrosine kinase-dependent tumorigenesis and enhances antitumor immune responses at doses not reaching anticoagulation levels. This study investigates the association between warfarin use and cancer incidence in a large, unselected population-based cohort.

OBJECTIVE

To examine the association between warfarin use and cancer incidence.

DESIGN, SETTING, AND PARTICIPANTS

This population-based cohort study with subgroup analysis used the Norwegian National Registry coupled with the Norwegian Prescription Database and the Cancer Registry of Norway. The cohort comprised all persons (N = 1 256 725) born between January 1, 1924, and December 31, 1954, who were residing in Norway from January 1, 2006, through December 31, 2012. The cohort was divided into 2 groups-warfarin users and nonusers; persons taking warfarin for atrial fibrillation or atrial flutter were the subgroup. Data were collected from January 1, 2004, to December 31, 2012. Data analysis was conducted from October 15, 2016, to January 31, 2017.

EXPOSURES

Warfarin use was defined as taking at least 6 months of a prescription and at least 2 years from first prescription to any cancer diagnosis. If warfarin treatment started after January 1, 2006, each person contributed person-time in the nonuser group until the warfarin user criteria were fulfilled.

MAIN OUTCOMES AND MEASURES

Cancer diagnosis of any type during the 7-year observation period (January 1, 2006, through December 31, 2012).

RESULTS

Of the 1 256 725 persons in the cohort, 607 350 (48.3%) were male, 649 375 (51.7%) were female, 132 687 (10.6%) had cancer, 92 942 (7.4%) were classified as warfarin users, and 1 163 783 (92.6%) were classified as nonusers. Warfarin users were older, with a mean (SD) age of 70.2 (8.2) years, and were predominantly men (57 370 [61.7%]) as compared with nonusers, who had a mean (SD) age of 63.9 (8.6) years and were mostly women (613 803 [52.7%]). Among warfarin users and compared with nonusers, there was a significantly lower age- and sex-adjusted incidence rate ratio (IRR) in all cancer sites (IRR, 0.84; 95% CI, 0.82-0.86) and in prevalent organ-specific sites (lung, 0.80 [95% CI, 0.75-0.86]; prostate, 0.69 [95% CI, 0.65-0.72]; and breast, 0.90 [95% CI, 0.82-1.00]). There was no observed significant effect in colon cancer (IRR, 0.99; 95% CI, 0.93-1.06). In a subgroup analysis of patients with atrial fibrillation or atrial flutter, the IRR was lower in all cancer sites (IRR, 0.62; 95% CI, 0.59-0.65) and in prevalent sites (lung, 0.39 [95% CI, 0.33-0.46]; prostate, 0.60 [95% CI, 0.55-0.66]; breast, 0.72 [95% CI, 0.59-0.87]; and colon, 0.71 [95% CI, 0.63-0.81]).

CONCLUSIONS AND RELEVANCE

Warfarin use may have broad anticancer potential in a large, population-based cohort of persons older than 50 years. This finding could have important implications for the selection of medications for patients needing anticoagulation.

Associated Risk of Malignancy in Patients with Cardiovascular Disease: Evidence and Possible Mechanism

Cardiovascular disease and malignancy are leading causes of morbidity and mortality. Increased risk of malignancy was identified in patients with cardiovascular disease, including patients with heart failure, heart failure after myocardial infarction, patients undergoing cardiac intervention, and patients after a thrombotic event. Common risk factors and biological pathways can explain this association and are explored in this review. Further research is needed to establish the causes of malignancy in this population and direct possible intervention.

Risk of cancer after anticoagulation in patients with unprovoked venous thromboembolism: an observational cohort study

Essentials Data on long-term cancer risk are controversial in patients with venous thromboembolism (VTE). We assessed long-term rates and risk factors of cancer in patients with VTE. Cancer risk after anticoagulation is not higher in VTE patients than in the general population. VTE recurrence is not predictive of a future cancer diagnosis.

SUMMARY

Background Patients with venous thromboembolism (VTE) are at risk of having a subsequent cancer diagnosis. The risk is highest during the first 6 months. Reports on cancer rates thereafter are controversial. We aimed to assess long-term rates and risk factors of cancer in patients with VTE. Methods and Results We followed patients with a first unprovoked VTE after discontinuation of anticoagulation, and excluded those receiving long-term antithrombotic therapy or with major thrombophilia. The study endpoint was the occurrence of cancer. Sixty-two (5.2%) of 1188 patients developed cancer during a median follow-up of 98 months. The cumulative incidence rates of cancer were 0.7% (95% confidence interval [CI] 0.2-1.2%), 3.1% (95% CI 2.0-4.1%) and 9% (95% CI 6.5-11.5) after 1, 5 and 15 years; these were not significantly different from those in the matched general population (0.6%, 3.4%, and 12.2%, respectively). The corresponding standardized incidence ratios (ratio of the observed cancer cases and the number of cases based on national cancer incidence rates) of 1.1 (95% CI 0.5-2.5), 1.0 (95% CI 0.6-1.4) and 0.9 (95% CI 0.7-1.2) did not indicate a difference in cancer incidence between our cohort and the general population. Advancing age (hazard ratio [HR] per decade 1.5, 95% CI 1.2-2.0) and shorter duration of anticoagulation (HR per 1-month decrease 1.3, 95% CI 1.1-1.6) were associated with an increased cancer risk, whereas VTE recurrence was not (HR 1.17, 95% CI 0.66-2.07). Conclusions Asymptomatic patients with unprovoked VTE who have completed anticoagulation therapy do not have a higher cancer risk. The inverse association between the duration of anticoagulation and the incidence of cancer warrants further investigation.

Vitamin K and its analogs: Potential avenues for prostate cancer management

Epidemiological studies have demonstrated a relationship between cancer incidence and dietary habits. Especially intake of certain essential nutrients like vitamins has been shown to be beneficial in experimental studies and some clinical trials. Vitamin K (VK) is an essential nutrient involved in the blood clotting cascade, and there are considerable experimental data demonstrating its potential anticancer activity in several cancer types including prostate cancer. Previous in vitro and in vivo studies have focused mainly on anti-oxidative effects as the underlying anticancer mechanism of VK. However, recent studies reveal that VK inhibits the growth of cancer cells through other mechanisms, including apoptosis, cell cycle arrest, autophagy, and modulation of various transcription factors such as Myc and Fos. In the present review, we focus on the anticancer effect of dietary VK and its analogs on prostate cancer, with an emphasis on the signaling pathways that are activated following exposure to these compounds. This review also highlights the potential of VK and its derivatives as an adjuvant treatment in combination with other vitamins or with chemotherapeutic drugs. Based on our recent results and a review of the existing literature, we present evidence that VK and its derivatives can potentially be explored as cancer therapy, especially for prostate cancer.

Warfarin use and prostate cancer risk in the Finnish Randomized Study of Screening for Prostate Cancer

OBJECTIVE

Anticoagulants, especially vitamin K antagonists (VKAs) such as warfarin, have been hypothesized to have antitumor properties, and use of VKAs has been associated with a lower prostate cancer (PCa) risk. This study estimated PCa risk among users of warfarin and other anticoagulants.

MATERIALS AND METHODS

All anticoagulant use among 78,615 men during 1995-2009 was analyzed. Cox regression, adjusted for age, screening trial arm and use of other medications, with medication use as a time-dependent variable, was used to estimate PCa risk overall, and by tumor grade and stage.

RESULTS

In total, 6537 men were diagnosed with PCa during 1995-2009 (1210 among warfarin users). Compared to non-users, warfarin use was associated with an increased risk of PCa [multivariable-adjusted hazard ratio (HR) = 1.11, 95% confidence interval (CI) 1.01-1.22]. This was limited to short-term, low-dose use, and was not observed in long-term use. A similar overall risk increase was observed for Gleason grade 7-10 PCa. Low-dose, short-term use of warfarin was associated with an increased risk of metastatic PCa. However, the increase in risk vanished with continued use. Compared to other anticoagulants, low-dose use of warfarin was associated with a slightly elevated overall PCa risk (HR = 1.19, 95% CI 1.00-1.43). The increase in risk disappeared in long-term, high-dose use.

CONCLUSIONS

This study, which included a larger number of PCa cases with warfarin exposure than previous studies, does not support previous notions of decreased risk of PCa among warfarin users. A similar risk of PCa was found among warfarin users and the general population, and no difference in risk was found between warfarin and other anticoagulants.

Risk of breast cancer among patients with bioprosthetic or mechanical valve replacement: a population-based study in Sweden

The association between breast cancer and warfarin is inconclusive as most previous studies examined their association using patients with thromboembolism, whereas thromboembolism itself is a risk factor for cancer. We explored this issue using patients received mechanical heart valves replacement as a proxy for warfarin exposure as these patients need a lifelong warfarin treatment, and compared them with patients received bioprosthesis valves replacement (short-term warfarin treatment) in Sweden between 1987 and 2010. Patients who were operated on for valve replacement were identified from the Swedish Hospital Discharge Registry and linked to the Swedish Cancer Registry to examine the hazard ratios of subsequent breast cancer. A total of 12,242 women were operated on for valve replacement (5481 with mechanical valve and 6401 with bioprosthetic valve). For the entire cohort, the HR of breast cancer was 1.49 (95 % CI 1.09-2.02) among patients with mechanical valve replacement compared to those with bioprosthetic valve replacement. After controlling for a number of confounding factors using propensity score weighting, the HR was 1.69 (95 % CI 1.15-2.47). Our study found that patients with mechanical valve replacement have an increased risk of breast cancer compared to those with bioprosthetic valve replacement. If confirmed, this increased risk should be considered when recommending breast cancer screening for women with mechanical valve replacement. Long-term use of warfarin may explain the observed increase. If so, patients who have used warfarin long-term for other reasons should be studied for a possible increased risk of breast cancer.

Anticoagulation for the long-term treatment of venous thromboembolism in patients with cancer

BACKGROUND

Cancer increases the risk of thromboembolic events in patients including those receiving anticoagulation treatments.

OBJECTIVES

To compare the efficacy and safety of low molecular weight heparin (LMWH) and oral anticoagulants for the long-term treatment of venous thromboembolism (VTE) in patients with cancer.

SEARCH METHODS

We conducted a comprehensive search for studies of anticoagulation in cancer patients including 1. a February 2013 electronic search of: the Cochrane Central Register of Controlled Trials (CENTRAL Issue 12, 2012), MEDLINE, and EMBASE; 2. a handsearch of conference proceedings; 3. checking of references of included studies; 4. use of the 'related citation' feature in PubMed; and 5. a search of clinicaltrials.gov for ongoing studies.

SELECTION CRITERIA

We included randomized controlled trials (RCTs) comparing long-term treatment with LMWH versus oral anticoagulants (vitamin K antagonist (VKA) or ximelagatran) in patients with cancer and symptomatic objectively confirmed VTE.

DATA COLLECTION AND ANALYSIS

Using a standardized data form, we extracted data on methodological quality, participants, interventions and outcomes of interest: survival, recurrent VTE, major bleeding, minor bleeding, thrombocytopenia, and postphlebitic syndrome. We assessed the quality of evidence at the outcome level following the GRADE approach.

MAIN RESULTS

Of 9559 identified citations, 10 RCTs (11 reports) were eligible and reported data for 1981 patients with cancer. We excluded 14 studies in which patients with cancer constituted study subgroups, but did not report outcome data for them. Meta-analysis of seven RCTs comparing LMWH with VKA found no statistically significant survival benefit (hazard ratio (HR) 0.96; 95% confidence interval (CI) 0.81 to 1.14) but a statistically significant reduction in VTE (HR 0.47; 95% CI 0.32 to 0.71). The remaining findings did not exclude a beneficial or harmful effect of LMWH compared with VKA for the outcomes of major bleeding (RR 1.07; 95% CI 0.52 to 2.19), minor bleeding (RR 0.89; 95% CI 0.51 to 1.55), or thrombocytopenia (RR 0.98; 95% CI 0.57 to 1.66). We judged the quality of evidence as low for mortality, major bleeding, and minor bleeding, and as moderate for recurrent VTE.One RCT comparing dabigatran with VKA did not exclude beneficial or harmful effects of one agent over the other. One RCT comparing six months' extension of anticoagulation with 18 months of ximelagatran 24 mg twice daily versus no extended ximelagatran did not exclude beneficial or harmful effects for the outcomes of reduction in VTE, mortality, and minor bleeding. One RCT comparing once-weekly subcutaneous injection of idraparinux for three or six months versus standard treatment (parenteral anticoagulation followed by warfarin or acenocoumarol) suggested a reduction in recurrent VTE (HR 0.39; 95% CI 0.14 to 1.11) at six months, but did not exclude beneficial or harmful effects for the outcomes of mortality (HR 0.99; 95% CI 0.66 to 1.48) and major bleeding (RR 1.04; 95% CI 0.39 to 2.83).

AUTHORS' CONCLUSIONS

For the long-term treatment of VTE in patients with cancer, LMWH compared with VKA reduces venous thromboembolic events but not mortality. The decision for a patient with cancer and VTE to start long-term LMWH versus oral anticoagulation should balance the benefits and harms and integrate the patient's values and preferences for the important outcomes and alternative management strategies.

Oral anticoagulation in patients with cancer who have no therapeutic or prophylactic indication for anticoagulation

BACKGROUND

Several basic research and clinical studies have led to the hypothesis that oral anticoagulants may improve the survival of patients with cancer through an antitumor effect in addition to their antithrombotic effect.

OBJECTIVES

To evaluate the efficacy and safety of oral anticoagulants in patients with cancer with no therapeutic or prophylactic indication for anticoagulation.

SEARCH METHODS

We performed a comprehensive search for studies of anticoagulation in patients with cancer including 1. a February 2013 electronic search of the following databases: Cochrane Central Register of Controlled Trials (CENTRAL), MEDLINE, and EMBASE; 2. a handsearch of the American Society of Clinical Oncology (starting with its first volume, 1982) and of the American Society of Hematology (starting with the 2003 issue); 3. checking of references of included studies; 4. use of the 'related citation' feature in PubMed; and 5. searching clinical trials.gov for ongoing studies.

SELECTION CRITERIA

Randomized controlled trials (RCTs) comparing vitamin K antagonist or other oral anticoagulants with no intervention or placebo in patients with cancer without clinical evidence of venous thromboembolism.

DATA COLLECTION AND ANALYSIS

Using a standardized data form, we extracted data on risk of bias, participants, interventions and outcomes of interest that included all-cause mortality, venous thromboembolism, major bleeding, and minor bleeding.

MAIN RESULTS

Of 9559 identified citations, seven RCTs (eight reports) fulfilled the inclusion criteria. The oral anticoagulant was warfarin in six of these RCTs and apixaban in the seventh RCT. The comparator was either placebo or no intervention. The use of warfarin had no effect on mortality at six months (risk ratio (RR) 0.98; 95% confidence interval (CI) 0.82 to 1.22), one year (RR 0.97; 95% CI 0.89 to 1.04), two years (RR 0.98; 95% CI 0.81 to 1.18), or five years (RR 0.92; 95% CI 0.83 to 1.01). One study assessed the effect of warfarin on venous thromboembolism and did not show or exclude a beneficial or detrimental of effect (RR 0.15; 95% CI 0.02 to 1.20). Warfarin increased both major bleeding (RR 4.24; 95% CI 1.86 to 9.65) and minor bleeding (RR 3.19; 95% CI 1.83 to 5.55). We judged the quality of evidence as moderate for all outcomes.The study assessing the effect of apixaban did not show or exclude a beneficial effect or detrimental of apixaban on mortality at six months (RR 0.16; 95% CI 0.01 to 1.66); major bleeding (RR 0.62; 95% CI 0.06 to 6.63); and minor bleeding (RR 2.87; 95% CI 0.16 to 51.82). We judged the quality of evidence as low for all outcomes.

AUTHORS' CONCLUSIONS

Existing evidence does not suggest a mortality benefit from oral anticoagulation in patients with cancer while the risk for bleeding is increased.

Use of oral anticoagulants and risk of prostate cancer: a population-based case-control study in Montreal, Canada

PURPOSE

A few recent epidemiological observations suggest that anticoagulant medications may protect against prostate cancer development. Most studies have been small or subjected to methodological issues, including potential confounding. We provide here new evidence on this association in the context of a population-based case-control study of prostate cancer conducted in Montreal, Canada.

METHODS

Cases were 1,588 men with incident prostate cancer, aged ≤75 years, diagnosed across French hospitals in the Montreal area between 2005 and 2009. Concurrently, 1,618 population controls from the same residential area and age distribution (±5 years) were randomly selected from the electoral list of French-speaking men. In-person interviews elicited information on socio-demographic, lifestyle and environmental factors, along with a detailed medical history. Unconditional logistic regression was used to assess the association between lifetime use of anticoagulants and prostate cancer risk.

RESULTS

102 subjects (2.6 % of cases and 3.7 % of controls) reported a history of oral anticoagulant therapy. After controlling for age, ancestry, education, family history of prostate cancer, prostate cancer screening frequency, diabetes, body mass index and statin use, ever use of oral anticoagulants showed a weak inverse, non-statistically significant association with prostate cancer (odds ratio 0.76, 95% confidence interval 0.50-1.16). Similar results were observed in analyses considering duration of use or indication for use, restricted to subjects recently screened or stratified by cancer aggressiveness.

CONCLUSIONS

Our findings provide weak support for a protective effect of oral anticoagulant therapy against prostate cancer. Further confirmation is required, especially in light of potential bleeding complications associated with anticoagulants.

Oral anticoagulation in patients with cancer who have no therapeutic or prophylactic indication for anticoagulation

BACKGROUND

Several basic research and clinical studies have led to the hypothesis that oral anticoagulants may improve the survival of patients with cancer through an antitumor effect in addition to their antithrombotic effect.

OBJECTIVES

To evaluate the efficacy and safety of oral anticoagulants in patients with cancer with no therapeutic or prophylactic indication for anticoagulation.

SEARCH METHODS

We performed a comprehensive search for studies of anticoagulation in patients with cancer including 1. a February 2013 electronic search of the following databases: Cochrane Central Register of Controlled Trials (CENTRAL), MEDLINE, and EMBASE; 2. a handsearch of the American Society of Clinical Oncology (starting with its first volume, 1982) and of the American Society of Hematology (starting with the 2003 issue); 3. checking of references of included studies; 4. use of the 'related citation' feature in PubMed; and 5. searching clinical trials.gov for ongoing studies.

SELECTION CRITERIA

Randomized controlled trials (RCTs) comparing vitamin K antagonist or other oral anticoagulants with no intervention or placebo in patients with cancer without clinical evidence of venous thromboembolism.

DATA COLLECTION AND ANALYSIS

Using a standardized data form, we extracted data on risk of bias, participants, interventions and outcomes of interest that included all-cause mortality, venous thromboembolism, major bleeding, and minor bleeding.

MAIN RESULTS

Of 9559 identified citations, seven RCTs (eight reports) fulfilled the inclusion criteria. The oral anticoagulant was warfarin in six of these RCTs and apixaban in the seventh RCT. The comparator was either placebo or no intervention. The use of warfarin had no effect on mortality at six months (risk ratio (RR) 0.98; 95% confidence interval (CI) 0.82 to 1.22), one year (RR 0.97; 95% CI 0.89 to 1.04), two years (RR 0.98; 95% CI 0.81 to 1.18), or five years (RR 0.92; 95% CI 0.83 to 1.01). One study assessed the effect of warfarin on venous thromboembolism and did not show or exclude a beneficial or detrimental of effect (RR 0.15; 95% CI 0.02 to 1.20). Warfarin increased both major bleeding (RR 4.24; 95% CI 1.86 to 9.65) and minor bleeding (RR 3.19; 95% CI 1.83 to 5.55). We judged the quality of evidence as moderate for all outcomes.The study assessing the effect of apixaban did not show or exclude a beneficial effect or detrimental of apixaban on mortality at six months (RR 0.16; 95% CI 0.01 to 1.66); major bleeding (RR 0.62; 95% CI 0.06 to 6.63); and minor bleeding (RR 2.87; 95% CI 0.16 to 51.82). We judged the quality of evidence as low for all outcomes.

AUTHORS' CONCLUSIONS

Existing evidence does not suggest a mortality benefit from oral anticoagulation in patients with cancer while the risk for bleeding is increased.

Cancer risk in long-term users of vitamin K antagonists: a population-based case-control study

Some evidence suggests that long-term use of vitamin K antagonists (VKAs) has a cancer chemopreventive effect. Such an effect would have considerable implications in terms of understanding tumor biology. To evaluate if long-term VKA treatment influences the risk of developing cancer, we performed a matched case-control analysis. We used data from four Danish nationwide registers. Cases were all Danish individuals with a first-time cancer diagnosis (except nonmelanoma skin cancer) between 2000 and 2009. For each case, eight controls, matched by birth year and gender, were selected from the source population by risk-set sampling. Long-term VKA use was defined as exposure to VKA for a period of 3 or more years. Conditional logistic regression was used to compute odds ratios (ORs) for cancer associated with long-term VKA exposure, adjusting for potential confounders. Prespecified subanalyses were performed for selected cancer sites, subgroups and measures of exposure. A total of 238,196 cases and 1,713,176 controls were included. The adjusted OR for cancer associated with long-term VKA exposure was 0.99 (95% CI: 0.95-1.02). Long-term VKA use was associated with increased ORs for alcohol- or obesity-related cancer sites, whereas we observed a decreased risk of prostate cancer (OR: 0.86; 95% CI: 0.78-0.95). Our study does not support a general chemopreventive effect of VKA drugs. However, in accordance with findings from previous studies, we found an inverse association between use of VKA and prostate cancer.

The association between vitamin K antagonist therapy and site-specific cancer incidence estimated by using heart valve replacement as an instrumental variable

Earlier studies suggest a protective association between vitamin K antagonist (VKA) anticoagulants and the incidence of cancer. The authors examined the associations between VKA therapy and incidence of 24 site-specific cancers with a Danish population-based cohort study, using heart valve replacement as an instrumental variable. The authors enrolled 9,727 Danish residents who received a replacement heart valve between 1989 and 2006. The heart valve recipients were matched with 95,481 unexposed individuals on age and sex. The authors used the heart valve replacement instrument to estimate rate ratios associating VKA therapy with incidence of the 24 site-specific cancers using Poisson regression models. Direct associations between VKA therapy and incidence of the 24 cancers were estimated in a prescription validation subset. The instrumental variable associations were plotted according to the inverse normal of rank percentile and subjected to semi-Bayes shrinkage adjustment for multiple comparisons. The pattern of associations was consistent with a null-centered Gaussian distribution. No individual cancer site showed a substantial positive or negative association with VKA therapy in the prescription validation subset, the instrumental variable analysis, or the analysis with semi-Bayes adjustment. These results do not support the existing hypothesis that VKA therapy is associated with reduced cancer risk.

Oral anticoagulation in patients with cancer who have no therapeutic or prophylactic indication for anticoagulation

BACKGROUND

A number of basic research and clinical studies have led to the hypothesis that oral anticoagulants may improve the survival of patients with cancer through an antitumor effect in addition to their antithrombotic effect.

OBJECTIVES

To evaluate the efficacy and safety of oral anticoagulants in patients with cancer with no therapeutic or prophylactic indication for anticoagulation.

SEARCH STRATEGY

A comprehensive search for studies of anticoagulation in cancer patients including (1) a February 2010 electronic search of the following databases: Cochrane Central Register of Controlled Trials (CENTRAL, The Cochrane Library), MEDLINE, EMBASE, ISI the Web of Science; (2) hand search of the American Society of Clinical Oncology (starting with its first volume, 1982) and of the American Society of Hematology (starting with its 2003 issue); (3) checking of references of included studies; and (4) use of "related article" feature in PubMed.

SELECTION CRITERIA

Randomized controlled trials (RCTs) comparing vitamin K antagonist or other oral anticoagulants to no intervention or placebo in cancer patients without clinical evidence of venous thromboembolism.

DATA COLLECTION AND ANALYSIS

Using a standardized data form we extracted data on risk of bias, participants, interventions and outcomes of interest that included all cause mortality, venous thromboembolism, major bleeding and minor bleeding.

MAIN RESULTS

Of 8187 identified citations, five RCTs fulfilled the inclusion criteria. Warfarin was the oral anticoagulant in all of these RCTs and it was compared to either placebo or no intervention. The quality of evidence was moderate for all outcomes. The effect of warfarin on reduction in mortality was not statistically significant at six months (Relative risk (RR) = 0.96; 95% CI 0.80 to 1.16), at one year (RR = 0.94; 95% CI 0.8 to 1.03) at two years (RR = 0.97; 95% CI 0.87 to 1.08) or at five years (RR 0.91; 95% CI 0.83 to 1.01). One study assessed the effect of warfarin on venous thromboembolism and showed a RR reduction of 85% (P = 0.031). Warfarin increased both major bleeding (RR = 4.24; 95% CI 1.85 to 9.68) and minor bleeding (RR = 3.34; 95% CI 1.66 to 6.74).

AUTHORS' CONCLUSIONS

Existing evidence does not suggest a mortality benefit from oral anticoagulation in patients with cancer while increasing the risk for bleeding.

Anticoagulation for the long-term treatment of venous thromboembolism in patients with cancer

BACKGROUND

Cancer increases the risk of thromboembolic events even while on anticoagulation.

OBJECTIVES

To compare the efficacy and safety of low molecular weight heparin (LMWH) and oral anticoagulants for the long-term treatment of venous thromboembolism (VTE) in patients with cancer.

SEARCH STRATEGY

A comprehensive search for studies of anticoagulation in cancer patients including a February 2010 electronic search of: the Cochrane Central Register of Controlled Trials (CENTRAL), MEDLINE, EMBASE and ISI Web of Science.

SELECTION CRITERIA

Randomized controlled trials (RCTs) comparing long-term treatment with LMWH versus oral anticoagulants (vitamin K antagonist (VKA) or ximelagatran) in patients with cancer and symptomatic objectively-confirmed VTE.

DATA COLLECTION AND ANALYSIS

Using a standardized data form we extracted data on methodological quality, participants, interventions and outcomes of interest: survival, recurrent VTE, major bleeding, minor bleeding, thrombocytopenia and postphlebitic syndrome. We assessed the quality of evidence at the outcome level following the GRADE approach.

MAIN RESULTS

Of 8187 identified citations, nine RCTs were eligible and reported data for 1908 patients with cancer. Meta-analysis of seven RCTs showed that LMWH, compared to VKA provided no statistically significant survival benefit (hazard ratio (HR) 0.96; 95% confidence interval (CI) 0.81 to 1.14) but a statistically significant reduction in VTE (HR 0.47; 95% CI 0.32 to 0.71). Other results did not exclude a beneficial or harmful effect of LMWH compared to VKA for the outcomes of major bleeding (RR 1.05; 95% CI 0.53 to 2.10) or thrombocytopenia (RR 1.02; 95% CI 0.60 to 1.74). The quality of evidence was low for mortality, major bleeding and minor bleeding and moderate for recurrent VTE. One RCT comparing six months extension of anticoagulation with 18 months ximelagatran 24 mg twice daily versus placebo found a reduction in VTE (HR 0.16; 95% CI 0.09 to 0.30) but did not exclude beneficial or harmful effects for the outcomes of mortality and bleeding. One RCT, comparing dabigatran to VKA, did not exclude beneficial or harmful effect of one agent over the other.

AUTHORS' CONCLUSIONS

For the long-term treatment of VTE in patients with cancer, LMWH compared to VKA reduces venous thromboembolic events but not death. The decision for a patient with cancer and VTE to start long-term LMWH versus oral anticoagulation should balance the benefits and downsides and integrate the patient's values and preferences for the important outcomes and alternative management strategies.

Oral anticoagulation in patients with cancer who have no therapeutic or prophylactic indication for anticoagulation

BACKGROUND

A number of basic research and clinical studies have led to the hypothesis that oral anticoagulants may improve the survival of patients with cancer through an antitumor effect in addition to their antithrombotic effect.

OBJECTIVES

To evaluate the efficacy and safety of oral anticoagulants in patients with cancer with no therapeutic or prophylactic indication for anticoagulation.

SEARCH STRATEGY

A comprehensive search for studies of anticoagulation in cancer patients including (1) a February 2010 electronic search of the following databases: Cochrane Central Register of Controlled Trials (CENTRAL, The Cochrane Library), MEDLINE, EMBASE, ISI the Web of Science; (2) hand search of the American Society of Clinical Oncology (starting with its first volume, 1982) and of the American Society of Hematology (starting with its 2003 issue); (3) checking of references of included studies; and (4) use of "related article" feature in PubMed.

SELECTION CRITERIA

Randomized controlled trials (RCTs) comparing vitamin K antagonist or other oral anticoagulants to no intervention or placebo in cancer patients without clinical evidence of venous thromboembolism.

DATA COLLECTION AND ANALYSIS

Using a standardized data form we extracted data on risk of bias, participants, interventions and outcomes of interest that included all cause mortality, venous thromboembolism, major bleeding and minor bleeding.

MAIN RESULTS

Of 8187 identified citations, five RCTs fulfilled the inclusion criteria. Warfarin was the oral anticoagulant in all of these RCTs and it was compared to either placebo or no intervention. The quality of evidence was moderate for all outcomes. The effect of warfarin on reduction in mortality was not statistically significant at six months (Relative risk (RR) = 0.96; 95% CI 0.80 to 1.16), at one year (RR = 0.94; 95% CI 0.8 to 1.03) at two years (RR = 0.97; 95% CI 0.87 to 1.08) or at five years (RR 0.91; 95% CI 0.83 to 1.01). One study assessed the effect of warfarin on venous thromboembolism and showed a RR reduction of 85% (P = 0.031). Warfarin increased both major bleeding (RR = 4.24; 95% CI 1.85 to 9.68) and minor bleeding (RR = 3.34; 95% CI 1.66 to 6.74).

AUTHORS' CONCLUSIONS

Existing evidence does not suggest a mortality benefit from oral anticoagulation in patients with cancer while increasing the risk for bleeding.

Long-term use of vitamin K antagonists and incidence of cancer: a population-based study

Whether long-term use of vitamin K antagonists (VKAs) might affect the incidence of cancer is a longstanding hypothesis. We conducted a population-based study including all cancer- and thromboembolism-free patients of our health area; study groups were defined according to chronic anticoagulant use to VKA-exposed and control groups. Cancer incidence and cancer-related and overall mortality was assessed in both groups. 76 008 patients (3231 VKA-exposed and 72 777 control subjects) were followed-up for 8.2 (± 3.2) years. After adjusting for age, sex, and time-to-event, the hazard ratio of newly diagnosed cancer in the exposed group was 0.88 (95% confidence interval [95% CI] 0.80-0.98; P < .015). VKA-exposed patients were less likely to develop prostate cancer, 0.69 (95% CI 0.50-0.97; P = .008). The adjusted hazard ratio for cancer-related and overall mortality was 1.07 (95% CI 0.92-1.24) and 1.12 (95% CI 1.05-1.19), respectively. These results support the hypothesis that anticoagulation might have a protective effect on cancer development, especially prostate cancer.

Cancer prevention and vitamin K antagonists: an overview

The relation of cancer to thromboembolism has been described since the mid 1800s. Different studies in animal and in vitro models have confirmed the link between the haemostatic system and both tumor stroma formation and metastasis. Although the mechanisms of warfarin effects on cancer are not elucidated, but are based on hypothesis, various studies have reported interesting results in this setting. But does warfarin added to recommended anti-tumour therapy improve survival of cancer patients? For the time being it is difficult to answer this question. Data from the literature are few and sometimes contradictory. Trials are characterized by important differences in studied cohorts, histological types of cancers evaluated, and in the treatment protocols. Most studies show that there is benefit from the addition of warfarin to chemotherapy in the tumour development, expansion and on the patient survival, especially in particular types of cancers. These data, although fascinating, do not rationalize the use of anticoagulation in the routine prophylaxis of cancer, however, they call for efforts in preparing large scale randomized trials to elucidate the effect of anticoagulation in the setting of neoplastic disease.

The long-term risk of cancer in patients with a first episode of venous thromboembolism

BACKGROUND

In patients with venous thromboembolism (VTE), 15-20% will have prevalent cancer when VTE is diagnosed but little is known about such patients' long-term risk, time course and predictors of new cancer.

PATIENTS AND METHODS

We studied an inception cohort of patients with a first VTE who were not diagnosed with cancer within 3 months after VTE and who had follow-up for up to 120 months. We determined the annual risk for a new cancer [number of events and 95% confidence interval (CI)] per 100 person-years in all patients and in those with unprovoked VTE and identified predictors for new cancer.

RESULTS

We studied 1852 patients with VTE who received anticoagulant therapy for 12 months (mean) and were followed for 4.2 years (mean). During follow-up, there were 105 (5.7%) patients diagnosed with new cancer during the period after the initial 3 months from diagnosis, for an annual risk of 1.32 (CI, 1.09-1.60) per 100 person-years. The risk for new cancer appeared uniform over time. The annual risk for new cancer was more than 2-fold higher in patients presenting with unprovoked compared with those with provoked VTE [1.76 (CI, 1.39-2.20) vs. 0.83 (CI, 0.58-1.16) per 100 person-years; P<0.001]. Clinical predictors for new cancer were increasing age [hazard ratio (HR), 1.23; CI, 1.05-1.44] and unprovoked VTE (HR, 1.86; CI, 1.21-2.87).

CONCLUSION

In patients with a first VTE and without prevalent cancer, the risk for new cancer is about 1-2% per year, appears to be uniform over time, and is higher in patients with unprovoked VTE and those with advanced age.

Does antithrombotic therapy improve survival in cancer patients?

Venous thromboembolism (VTE) is a common complication of malignancy, and is associated with significant morbidity and mortality. Anticoagulant therapy, in the form of heparin and warfarin, plays an important role in the prevention of recurrent VTE. Recent studies have demonstrated that long-term therapy with low molecular weight heparin (LMWH) is more effective than warfarin in patients with cancer. In addition, accumulating clinical evidence suggests that LMWH significantly improves overall survival in cancer patients without VTE. Intriguingly, however, this improved survival cannot simply be explained by a reduction in fatal pulmonary embolism. Furthermore, the beneficial effects persist long after the LMWH has been discontinued, suggesting that LMWH can directly influence tumour cell biology. This hypothesis is entirely plausible, given the complex feedback mechanisms that exist between tumour cells, coagulation proteases, and vascular endothelial cells. Furthermore, an accumulating body of in vitro experimental evidence suggests that both heparin and warfarin have direct antineoplastic effects. Further large randomized controlled trials will be required in order to validate these exciting preliminary data, and to define whether anticoagulant therapy may constitute a useful adjunctive therapy in the management of cancer patients without VTE.

Coagulation, anticoagulation and pancreatic carcinoma

An increase in coagulation in patients with pancreatic carcinoma has long been documented. In this Review, we present what is known about the pathophysiology of increased coagulation in cancer and how it applies to pancreatic carcinoma. The relationship between the activation of coagulation or symptomatic thromboembolic disease and the development of pancreatic carcinoma is explored. Data on the relationship between thromboembolic disease and the behavior of pancreatic cancer before, during or after a diagnosis is made are also reviewed. Finally, the rationale and evidence for the use of oral anticoagulants or heparin in patients with pancreatic carcinoma is presented. This Review is a critical appraisal of what is known, and when the evidence is acceptable, on the subject of thromboembolism, anticoagulation, and treatment with anticoagulants in patients with pancreatic carcinoma.

The Risk of Cancer Progression in Women With Gynecological Malignancies and Thrombophilic Polymorphisms: A Pilot Case-Control Study

Cancer produces a hypercoagulable state, which might lead to thrombosis, and on contrary, unprovoked venous thromboembolism might be the manifestation of an occult cancer. In this pilot case-control study, we assessed the risk of gynecological malignant diseases related to the presence of the factor V Leiden and prothrombin G20210A polymorphisms. Fifty-two women underwent an operation for gynecological malignancy and were enrolled in the study. Women who underwent an operation for gynecological nonmalignant disease in the same days of cases were considered as controls. The presence of factor V Leiden and prothrombin G20210A was assessed in case and control groups. In all, 7 out of 52 cases were carriers of the 2 polymorphisms compared with 20 out of 198 controls (odds ratio = 1.3; 95% confidence interval, 0.6-3.0). The results were also similar when the risk was considered separately for the site of cancer. As for advanced and metastatic malignancies, the odds ratios were 2.3 (95% confidence interval, 0.9-6.0) and 3.3 (95% confidence interval, 1.0-11), respectively, compared to noncancer patients. When these 2 groups were compared to nonadvanced cancer group, the odds ratios for carriers of polymorphisms were 2.7 (95%confidence interval, 0.7-11.0) and 3.9 (95%confidence interval, 0.8-18.6) for advanced cancer and metastatic malignancies, respectively. Women with factor V Leiden or prothrombin G20210A polymorphisms who developed gynecological malignancy might present with a higher stage of cancer at the time of surgery. Larger case-control studies in similar cohort of patients are needed to confirm these findings.

Venous thromboembolic events and organ-specific occult cancers: a review and meta-analysis

BACKGROUND

Despite a recognized association between venous thromboembolic events (VTE) and cancer, little is known about the strength and the features of this association. We performed a meta-analysis in order to clarify this issue.

METHODS

We retrieved data from 40 reports published between 1982 and 2007: 12 contained cancer risk estimates for patients with either idiopathic or secondary VTE vs. subjects without VTE and 17 for patients with idiopathic vs. secondary VTE. We also pooled risk estimates from four cohort studies to assess the association between VTE and specific forms of cancer and conducted a proportional incidence study, based on the remaining 28 reports, which did not provide risk estimates.

RESULTS

The pooled relative risk (RR) of cancer was 3.2 [95% confidence interval (95% CI) 2.4-4.5] for patients with any form of VTE vs. no VTE, 2.7 (95% CI 1.9-3.9) for patients with idiopathic vs. no VTE and 3.8 (95% CI 2.6-5.4) for patients with idiopathic vs. secondary VTE. In the pooled cohort studies, RRs for VTE vs. no VTE were significantly elevated for cancers of the ovary (RR 7.0), pancreas (RR 6.1), liver (RR 5.6), blood (4.2), brain (RR 3.8), kidney (RR 3.4), lung (3.1), colon (2.9), and esophagus (2.1). In the proportional incidence study, cancers of the pancreas, colon, and blood were significantly more frequently observed than in the general population.

CONCLUSIONS

Overall we found a 3-fold excess risk of occult cancer in patients with VTE. The risk varies according to tumor site and is highest for cancers of the ovary, pancreas, and liver.

Anticoagulation for the long term treatment of venous thromboembolism in patients with cancer

BACKGROUND

Cancer increases the risk of thromboembolic events and the risk of recurrent thromboembolic events while on anticoagulation.

OBJECTIVES

To compare the efficacy and safety of low molecular weight heparin (LMWH) and oral anticoagulants (vitamin K antagonist (VKA) and ximelagatran) for the long term treatment of venous thromboembolism (VTE) in patients with cancer.

SEARCH STRATEGY

A comprehensive search was undertaken including a January 2007 search of electronic databases; Cochrane Central Register of Controlled Trials (CENTRAL), (The Cochrane Library 2007, Issue 1). MEDLINE (1966 onwards; accessed via OVID), EMBASE (1980 onwards; accessed via OVID) and ISI the Web of Science. Hand search of the proceedings of the American Society of Clinical Oncology and of the American Society of Hematology. Checking of references of included studies, relevant papers and related systematic reviews. Use of "related article" feature in PubMed; and (5) search of ISI the Web of Science for papers citing landmark studies.

SELECTION CRITERIA

Randomized controlled trials (RCTs) comparing long term treatment with LMWH versus oral anticoagulants (VKA or ximelagatran) in patients with cancer and symptomatic objectively confirmed VTE.

DATA COLLECTION AND ANALYSIS

Using a standardized data form we extracted data on methodological quality, participants, interventions and outcomes of interest: survival, recurrent VTE, major bleeding, minor bleeding, thrombocytopenia and postphlebitic syndrome.

MAIN RESULTS

Of 3986 identified citations, eight RCTs were eligible and reported data for patients with cancer. Their overall methodological quality was moderate. Meta-analysis of six RCTs showed that LMWH, compared to VKA provided no statistically significant survival benefit (Hazard ratio (HR) = 0.96; 95% CI 0.81 to 1.14) but a statistically significant reduction in VTE (HR = 0.47; 95% (Confidence Interval (CI) = 0.32 to 0.71). There was no statistically significant difference between LMWH and VKA in bleeding outcomes (RR = 0.91; 95% CI = 0.64 to 1.31) or thrombocytopenia (RR = 1.02; 95% CI = 0.60 to 1.74). One RCT compared tinzaparin and dalteparin and showed no differences in the outcomes of interest. One RCT compared a six months extension of anticoagulation with 18 months Ximelagatran 24mg twice daily versus placebo. It showed a reduction in VTE (HR = 0.16; 95% CI 0.09 to 0.30) with no apparent effect on survival or bleeding.

AUTHORS' CONCLUSIONS

For the long term treatment of VTE in patients with cancer, LMWH compared to VKA reduces venous thromboembolic events but not death. The decision for a patient with cancer and VTE to start long term LMWH versus oral anticoagulation should balance the benefits and downsides and integrate the patient's values and preferences for the important outcomes and alternative management strategies.

Use of warfarin and risk of urogenital cancer: a population-based, nested case-control study

BACKGROUND

Indirect evidence suggests that prolonged treatment with warfarin might be associated with a decreased incidence of urogenital cancer. We aimed to assess this association in a large population-based study.

METHODS

Beneficiaries of Saskatchewan Health who were eligible for prescription drug benefits and aged 50 years or over with no history of cancer since 1967 were enrolled into a nested, matched case-control study. 19 412 new cases of urogenital cancer diagnosed between Jan 1, 1981, and Dec 31, 2002, were identified by use of information from the Saskatchewan Cancer Agency registry. For each case, six controls, totalling 116 470, who were matched for age, sex, and time of diagnosis were selected randomly. Conditional logistic regression analysis was used to calculate adjusted incidence rates of urogenital cancer in relation to warfarin use.

FINDINGS

Compared with men who never used warfarin, men with 4 years of warfarin use had an adjusted incidence rate of 0.80 (95% CI [0.65-0.99]). For warfarin use 76-100% of the time, the adjusted rate ratios were 0.80 (0.66-0.96) during year 2 preceding diagnosis of prostate cancer, 0.76 (0.62-0.94) during year 3, and 0.67 (0.53-0.86) during year 4. No significant association was found between warfarin and risk of other urogenital cancers.

INTERPRETATION

Our results suggest that warfarin has an antitumour effect that is specific to prostate cancer. Further investigation, with more complete assessment of confounders and that addresses the effect of warfarin on mortality of prostate cancer, is warranted.

Oral anticoagulation for prolonging survival in patients with cancer

BACKGROUND

A number of basic research and clinical studies have led to the hypothesis that oral anticoagulants may improve the survival of patients with cancer through an antitumour effect in addition to their antithrombotic effect.

OBJECTIVES

To evaluate the effectiveness and safety of oral anticoagulation (including vitamin K antagonists and ximelagatran) as an intervention to improve survival of patients with cancer.

SEARCH STRATEGY

A comprehensive search for studies of anticoagulation in cancer patients including (1) a January 2007 electronic search of the following databases: Cochrane Central Register of Controlled Trials (CENTRAL), MEDLINE, EMBASE, ISI the Web of Science; (2) hand search of the American Society of Clinical Oncology (starting with its first volume, 1982) and of the American Society of Hematology (starting with its 2003 issue); (3) checking of references of included studies; and (4) use of "related article" feature in PubMed.

SELECTION CRITERIA

Randomized clinical trials (RCTs) comparing vitamin K antagonist or ximelagatran to no intervention or placebo in cancer patients without clinical evidence of venous thromboembolism.

DATA COLLECTION AND ANALYSIS

Using a standardized data form we extracted data on methodological quality, participants, interventions and outcome of interest that included all cause mortality, symptomatic deep venous thrombosis, symptomatic pulmonary embolism, major bleeding and minor bleeding.

MAIN RESULTS

Of 3986 identified citations five RCTs fulfilled the inclusion criteria. Warfarin was the oral anticoagulant in all of these RCTs and it was compared to either placebo or no intervention. The overall methodological quality of these RCTs was acceptable. The effect of warfarin on reduction in mortality was not statistically significant at six months (Relative risk (RR) = 0.96; 95% CI 0.80 to 1.16), at one year (RR = 0.95; 95% CI 0.86 to 1.05) at 2 years (RR = 0.97; 95% CI 0.87 to 1.08) or at five years (RR 0.91; 95% CI 0.83 to 1.01). In the subgroup of patients with small cell lung cancer (SCLC), warfarin reduced mortality at six months (RR = 0.69; 95% CI 0.50 to 0.96) but not at one year (RR = 0.88; 95% CI 0.77 to 1.01). This six month mortality benefit was statistically significant in the subgroup of extensive SCLC (RR = 0.65; 95% CI 0.45 to 0.93) but not in the subgroup of limited SCLC (RR = 0.68; 95% CI 0.36 to 1.28). One study assessed the effect of warfarin on venous thromboembolism and showed a RR reduction of 85% (p = 0.031). Warfarin increased both major bleeding (RR = 4.24; 95% CI 1.85 to 9.68) and minor bleeding (RR = 3.34; 95% CI 1.66 to 6.74). Warfarin increased the risk of major bleeding (RR 5.46; 95% CI 3.04 to 9.81) and minor bleeding (RR 4.01; 95% CI 1.30 to 12.42) also in patients with SCLC. There was no evidence for a significant reduction in mortality in any other cancer subtype.

AUTHORS' CONCLUSIONS

Existing evidence does not suggest a mortality benefit from oral anticoagulation in patients with cancer. In patients with SCLC, the evidence suggests a survival benefit at six months from warfarin particularly when the disease is extensive. The decision for a patient with extensive SCLC to start warfarin for survival benefit should balance that benefit with the downsides of increased bleeding risk in light of patient values for these outcomes.

The effect of anticoagulants on cancer risk and survival: systematic review

OBJECTIVES

Several in vitro and in vivo studies have shown that low molecular weight heparin and warfarin may directly inhibit tumour cell growth and prevent metastatic spread. However, the clinical evidence in support of an anti-cancer effect is less conclusive. We summarize the evidence from clinical studies that examine the effect of these anticoagulants on cancer development and briefly describe the current understanding of the potential mechanisms by which anticoagulants may exert an anti-cancer effect.

METHODS

English-language articles reporting on warfarin, coumarin or low molecular weight heparin for the treatment or prevention of cancer were selected from PUBMED. All randomized clinical trials, case-control studies, cohort studies, and meta-analyses were retrieved. Detailed data review and abstraction was performed according to pre-specified criteria.

RESULTS

Of ninety-nine articles retrieved, 12 warfarin and 17 low molecular weight heparin articles were included in the review. We found no consistent evidence that warfarin may improve cancer survival, though there is indirect evidence that prolonged warfarin use may decrease the risk of urogenital cancer. Low molecular weight heparin may improve survival of patients with small cell lung cancer and those with advanced malignancy who have more favorable prognoses.

CONCLUSION

Clinical evidence exists in support of an anti-neoplastic effect of anticoagulants. However, more research is needed to further define which cancer type and stage would most benefit from low molecular weight heparin, as well as to explore the role of warfarin in urogenital tumour development.

Venous Thromboembolism in Patients With Cancer Part I: Survey of Oncology Nurses' Attitudes and Treatment Practices for Ambulatory Settings

Patients with cancer have a higher incidence of venous thromboembolism (VTE). Little information currently exists on VTE and the understanding and beliefs of oncology nurses. Therefore, the attitudes and treatment practices of ambulatory oncology nurses were surveyed to determine the current knowledge base of VTE in patients with cancer. Survey results are presented along with a thorough literature review of thromboembolism and the unique risk factors for this frequent complication in patients with cancer. The causes of VTE in this patient population often are multifactorial and include hypercoagulability, stasis, and vascular endothelial damage from procedures or the neoplastic process itself. In particular, chemotherapy administration can increase the risk of thrombosis considerably. New therapies, including thalidomide, require oncology nurses caring for these patients to have heightened awareness of the potential for thrombogenic complications. This is the first of two articles that address the problem of thromboembolism in patients with cancer, including the survey results. (See part II on page 465.) Oncology nurses are essential in the care of VTE in patients with cancer and can help with patient identification, treatment, and compliance for improved patient outcomes.

Thrombosis-related complications and mortality in cancer patients with central venous devices: an observational study on the effect of antithrombotic prophylaxis

BACKGROUND

Recent guidelines do not recommend antithrombotic prophylaxis (AP) to prevent catheter-related thrombosis in cancer patients with a central line.

PATIENTS AND METHODS

This study assessed the management of central lines in cancer patients, current attitude towards AP, catheter-related and systemic venous thromboses, and survival.

RESULTS

Of 1410 patients enrolled, 1390 were seen at least once in the 6-month median follow-up. Continuous AP, mainly low-dose warfarin, was given to 451 (32.4%); they were older, with a more frequent history of venous thromboembolism (VTE), and more advanced cancer. There was no difference in catheter-related thrombosis in patients given AP or not (2.8% and 2.2%, odds ratio 1.29, 95% confidence interval 0.64-2.6). The median time to first catheter-related complication was 120 days. Systemic VTE including deep and superficial thromboses and pulmonary embolism, were less frequent with AP (4% versus 8.2%, P = 0.005). Mortality was also lower (25% versus 44%, P = 0.0001). Multiple logistic regression analysis found only advanced cancer and no AP significantly associated with mortality. No major bleeding was recorded with AP.

CONCLUSIONS

Current AP schedules do not appear to prevent catheter-related thrombosis. Systemic VTE and mortality, however, appeared lower after prophylaxis.

Tromboembolia venosa en pacientes con cáncer

The association between neoplastic diseases and venous thromboembolism (VTE) is known since long time ago. The nature of this association is bidirectional. On one hand, cancer increases the incidence of venous thrombosis and, on the other hand, the hemostatic system does play a key role in the tumorigenesis process. However, despite recent advances in the field, prophylaxis and treatment of VTE in cancer patients is still a challenge, due to the complexity of this type of patients. This review is focused on some important points regarding management of VTE in cancer patients such as physiopathology, epidemiology, search for hidden malignancy, prognostic impact, prophylaxis in the medical and surgical setting, or initial and long-term treatment.

Cancer and venous thromboembolism

Venous thromboembolism occurs commonly in patients with cancer. The pathogenetic mechanisms of thrombosis involve a complex interaction between tumour cells, the haemostatic system, and characteristics of the patient. Among risk factors for thromboembolism are long-term immobilisation, especially in hospital, surgery, and chemotherapy with or without adjuvant hormone therapy. Although prophylaxis and treatment of thromboembolism in patients with cancer draw on the agents that are commonly used in those without cancer, there are many special features of patients with cancer that make use of these drugs more challenging. Low-molecular-weight heparins are the cornerstone of prophylaxis and treatment of venous thromboembolism in patients with cancer. These drugs have the potential to increase survival, at least in patients with more favourable outlook. About 10% of patients with idiopathic venous thromboembolism have an underlying malignant disorder that can be detected by extensive diagnostic investigation. However, the issue of whether screening for occult malignant disease ultimately improves prognosis and survival remains to be resolved.

Warfarin versus low-molecular-weight heparin therapy in cancer patients

The association between cancer and venous thromboembolism (VTE) is well established. Importantly, VTE is a significant cause of mortality in cancer patients. Although long-term warfarin (Coumadin(trade mark); Bristol-Myers Squibb; New York, NY) therapy is the mainstay of treatment for cancer patients with VTE, there are many practical problems with its use in this population. In particular, achieving therapeutic drug levels is difficult in cancer patients due to the increased risk of drug interactions, malnutrition, vomiting, and liver dysfunction in these patients. Moreover, cancer patients are at an increased risk of adverse effects of warfarin therapy. In contrast, low-molecular-weight heparins (LMWHs) are associated with a lower risk of adverse events compared with warfarin in patients with cancer. These agents also offer practical advantages compared with warfarin, including more predictable anticoagulant effects and ease of administration in addition to possible antineoplastic effects. Several LMWHs have demonstrated superior efficacy to warfarin in the secondary prevention of VTE. In particular, the LMWH, dalteparin (Fragmin; Pfizer; New York, NY), has recently been shown to have superior efficacy to warfarin in a large trial of patients with cancer and VTE without increasing the risk of bleeding. A randomized trial of dalteparin has also shown improved response rates and survival in patients with small cell lung cancer. In view of the availability of more effective and reliable alternatives to warfarin therapy in cancer patients, it is appropriate to reassess the role of warfarin therapy in patients with cancer and VTE. Further evaluation of the LMWHs for effects on cancer outcome is indicated.