CRD summary

The authors concluded that pharmacological prophylaxis in cancer patients is associated with lower rates of deep vein thrombosis, without an increase in bleeding complications. The limited search, incomplete reporting of review methods, limited validity assessment and inappropriate data synthesis mean that the results of the review may not be reliable.

Authors' objectives

To evaluate the efficacy and safety of different types of deep venous thrombosis (DVT) prophylaxis in cancer patients who are undergoing surgery.

Searching

MEDLINE (1966 to 2005) was searched using the reported search terms. Only studies reported in English were eligible for inclusion. In addition, reference lists of identified studies, previous reviews and meta-analyses were screened.

Study selection

Assessment of study quality

The authors did not explicitly state that they assessed validity. However, details of the level of blinding were tabulated. The authors did not state how blinding was assessed.

Data extraction

The authors independently reviewed the extracted data and resolved any disagreements by consensus. For each study, the number of oncology patients with each outcome of interest was extracted for each treatment group and the DVT rate was presented.

Methods of synthesis

Results of the review

Twenty-six RCTs (n=7,639) were included.

Twelve studies reported double-blinding. Two additional studies reported a blinded outcome assessment.

All studies.

Based on 24 studies (n=5,933) using FUT, venography or ultrasound DVT detection methods, the overall DVT rate was lowest among patients who received heparin prophylaxis (LDUH or LMWH high or low dose) plus mechanical prophylaxis, compared with patients who received heparin prophylaxis alone (LDUH or LMWH) or no prophylaxis: 5% versus 12.7% and 35.2%, respectively.

DVT rates using different methods of DVT detection.

For studies using FUT detection, the DVT rate was significantly lower among patients who received heparin prophylaxis (LDUH or LMWH) plus mechanical prophylaxis or heparin prophylaxis (LDUH or LMWH) alone compared with no prophylaxis: 5% and 11.1% versus 36.7% (p<0.05 for all heparin versus control), based on 17 studies (n=4,005). For studies using ultrasound detection, the rate of DVT detection among patients receiving heparin prophylaxis (LDUH or LMWH) was significantly lower than the control group: 1.8% versus 6.3% (p<0.05), based on 2 studies (n=107). Rates of DVT detection among patients receiving any type of heparin were greatest for venography (16.4%), followed by FUT (11.1%) and ultrasound (1.8%), and were lowest for clinical examination (0.2%, based on 2 studies). The difference between all different methods of DVT detection was statistically significant (p<0.05).

Type of heparin (17 studies using FUT).

There was no significant difference in DVT rates between groups receiving LDUH compared with LMWH (p>0.05). Rates of DVT were significantly lower for patients receiving high-dose LMWH compared with low-dose LMWH (7.9% versus 14.5%, p<0.0001) and for patients receiving high-dose LDUH compared with low-dose LDUH (8% versus 13.4%, p=0.0132).

DVT location (9 studies, n=284).

Proximal DVTs were significantly less common among patients receiving LDUH or LMWH compared with no prophylaxis (12.7% versus 41.4%, p=0.0001).

Bleeding complications.

There were no significant differences (p>0.05) between LDUH and LMWH groups in terms of minor complications (7 studies, n=2,114), major complications (7 studies, n=2,083) or discontinuation rates in high-dose regimens (4 studies, n=1,668).

Authors' conclusions

Pharmacological prophylaxis in cancer patients is associated with lower DVT rates, without an increase in bleeding complications. Greater reductions in DVT rates were found for higher doses compared with lower-dose regimens and where mechanical prophylaxis was used concurrently.

CRD commentary

The review addressed a clear question that was defined in terms of the participants, intervention, outcomes and study design. The search strategy was limited to English language publications listed in one electronic database and the reference lists of identified studies; this makes the review vulnerable to publication and language bias and the possibility of studies being missed. Methods were used to minimise reviewer errors and bias in the extraction of data but it was unclear whether similar steps were taken at the study selection stage. The validity assessment, being limited to blinding, was inadequate.

The studies were pooled and a subgroup analysis used to examine the effects of different types of interventions and other factors. However, the method used to combine the studies treated the results as if they had come from one large study, which ignores between-study variation and increases the probability of identifying a statistically significant effect. In addition, there was no assessment of statistical heterogeneity, so it is not possible to determine whether pooling the results was appropriate. The conclusions appear to reflect the data presented, but the limited search, incomplete reporting of review methods, limited validity assessment, inappropriate methods of pooling data, and lack of an examination of differences in DVT rates between studies, mean that the results of the review may not be reliable.

Implications of the review for practice and research

Practice: The authors stated the need for surgical patients with cancer to receive routine pharmacological prophylaxis.

Research: The authors did not state any implications for further research.

Funding

Robert Wood Johnson Clinical Scholars Program.

Bibliographic details

Leonardi M J, McGory M L, Ko C Y. A systematic review of deep venous thrombosis prophylaxis in cancer patients: implications for improving quality. Annals of Surgical Oncology 2007; 14(2): 929-936. [PubMed: 17103259]

Indexing Status

Subject indexing assigned by NLM

MeSH

Anticoagulants /adverse effects /therapeutic use; Dose-Response Relationship, Drug; Female; Heparin /adverse effects /therapeutic use; Humans; Male; Middle Aged; Neoplasms /complications /surgery; Randomized Controlled Trials as Topic; Surgical Procedures, Operative /adverse effects; Venous Thrombosis /diagnosis /epidemiology /etiology /prevention & control

AccessionNumber

12007000532

Database entry date

01/09/2008

Record Status

This is a critical abstract of a systematic review that meets the criteria for inclusion on DARE. Each critical abstract contains a brief summary of the review methods, results and conclusions followed by a detailed critical assessment on the reliability of the review and the conclusions drawn.