Although the blood thinner heparin has been used for several decades to prevent and treat blood clots, researchers are now questioning whether the drug could be effective in treating cancer.

Even though results from large studies have been promising, a study by investigators from McMaster University and the University at Buffalo, suggests that these studies still fail to provide precise answers to key questions, with regard to the benefits of low molecular weight heparin (LMWH) for cancer patients. The study is published today in the New England Journal of Medicine.

Commenting on an editorial in the same issue of the journal, the researchers explain that although the anti-clotting effect of heparin is well established, the speculated anti-tumor effect is not. Therefore, the researchers question whether cancer patients who don’t have clotting problems should be offered the drug.

In a 2011 Cochrane Review, the researchers systematically complied the available evidence of how individuals with cancer may benefit from heparin. Currently, the team was invited to comment on the SAVE-ONCO study, involving 3,200 individuals with metastatic or locally advanced solid tumors.

Participant’s of the study receiving chemotherapy also received a preventative dose of semuloparin (ultra-low-molecular weight heparin) once daily for just over 3 months.

According to results from this study, the largest to date, semuloparin had no statistically considerable effect on severe bleeding and death, despite considerably lowering the incidence of thromboembolism.

The researchers conclude that there is a small potential survival benefit in light of the evidence that earlier studies, together with another recent study, confirm and further support these findings.

The team estimated:

“If 1,000 patients with cancer were to use a prophylactic dose of LMWH, approximately 30 would avert death, 20 would avert a clotting complication and one would suffer a major bleeding episode over a 12-month period.”

According to Dr. Elie Akl, associate professor in the Department of Medicine in UB’s School of Medicine and Biomedical Sciences and in McMaster University’s Department of Clinical Epidemiology and Biostatistics, and Schünemann, professor of medicine and chair of the Department of Clinical Epidemiology and Biostatistics, McMaster University, the findings have meaning for patients as well as other healthcare decision makers.

Akl and Schünemann explain:

“Patients who are not bothered much by daily injections of LMWH can avert hospitalizations for a clotting complication and possibly achieve a prolongation of life if they accept an increased risk of bleeding and its subsequent treatment.”

The researchers note that cancer patients who remain optimistic about their chances of survival will have to face “some uncertainty”, regarding whether their stage and type of cancer are linked to the likely survival benefit of LMWH.

According to Akl and Schünemann, further research is needed to determine which cancer patients would benefit most, the extent of this survival benefit, and if this benefit is suitable for cancers that do not respond well to other treatments. Akl and Schünemann aim to conduct a sophisticated examination of the published trials (individual patient data meta-analysis), in order to investigate these questions.

Written by: Grace Rattue