A systematic review including 3 RCTs (n=695), 4 retrospective cohort analyses (n=1 435), and one unified study of 2 prospective non-randomised trials (n=53) was abstracted in DARE.
One RCT (n=277) of a therapeutic dose of unfractionated heparin in small cell lung cancer, versus chemotherapy, showed a trend towards improved survival at 3 years that did not reach statistical significance (OR 0.64, 95% confidence interval, CI: 0.25 to 1.62). The median survival and complete response rates were significantly better in the unfractionated heparin group: 37 versus 23% (P=0.004) and 317 versus 261 days, respectively. Prophylactic doses of unfractionated heparin following surgery for colorectal cancer were tested against no further treatment in 2 RCTs (n=418). These showed a significant detrimental effect of unfractionated heparin on 3-year mortality (OR 1.66, 95% CI: 1.02 to 2.71).
A small level 2 study (n=53) that investigated pre-operative chemotherapy with and without a therapeutic dose of unfractionated heparin in colon cancer showed no difference in 3-year mortality (OR 0.52, 95% CI: 0.10 to 2.75). Four retrospective cohort studies (n=1 435) of prophylactic doses of unfractionated heparin, versus placebo or no treatment, in patients undergoing major abdominal surgery for malignant disease, showed an overall benefit on mortality after 3 years (OR 0.65, 95% CI: 0.51 to 0.84).
Comment: The quality of evidence is downgraded by inconsistency (variability in results across studies).