PHOENIX — Low-dose unfractionated heparin for thromboprophylaxis following abdominopelvic cancer surgery gives the most protection for the lowest overall cost, a cost analysis showed.
With good patient compliance, low-dose unfractionated heparin after discharge was a better bargain than even daily aspirin at preventing venous thromboembolism (VTE), Dr. Ciaran Bradley reported at a symposium sponsored by the Society of Surgical Oncology.
“Low-dose unfractionated heparin in fact saves money over the currently commonplace practice of doing nothing,” Dr. Bradley said. “It would be cost effective even if compliance with medication were low,” he noted. “Only if the cost of low-molecular-weight heparin were less than $100 would it start to compete for dominance in the model, and currently, it's seven times more expensive than that.”
Aspirin also appears to be an attractive alternative in this clinical situation because of its low cost, oral administration, and absence of heparin-induced thrombocytopenia.
“Even though aspirin has been relatively discounted as a primary agent for thromboprophylaxis for inpatients in the perioperative setting, it may have some utility after the discharge period, and further clinical studies using aspirin for this very scenario may be warranted,” said Dr. Bradley of the Medical College of Wisconsin, Milwaukee.
Patients who undergo abdominopelvic cancer resection are at high risk for VTE, with a postdischarge rate up to 25% reported in one study (BMJ 1988;297:28). Up to 4 weeks of VTE prophylaxis is recommended in guidelines published by the American College of Chest Physicians, National Comprehensive Cancer Network, and American Society of Clinical Oncology, he noted.
“However, we postulate that these guidelines are rarely followed, likely because of concerns over the costs of the agents as a result of bleeding complications and heparin-induced thrombocytopenia, as well as concern that patients may not be compliant with medications because those currently used are injectable formulations,” he said.
Dr. Bradley and his colleagues created a model using a reference case of a patient more than 40 years old who has undergone an open or laparoscopic procedure for abdominopelvic malignancy under general anesthesia and lasting at least 45 minutes. The hypothetical patient received in-hospital chemical prophylaxis for VTE, and was discharged on the seventh postoperative day.
The authors compared the relative costs of four postdischarge thromboprophylaxis strategies: 40 mg of low-molecular-weight heparin given subcutaneously once daily, 5,000 U of low-dose unfractionated heparin given subcutaneously three times daily, 325 mg of aspirin given orally daily, and no prophylaxis. The model assumed a constant risk of VTE and bleeding complications over the 3 weeks after discharge.
The model also assumed that the patient would not always be compliant with dosing. For example, the model assumes that daily compliance with injectable low-molecular-weight heparin would be 79% with once-daily dosing, and that compliance would drop to 65% with injectable low-dose unfractionated heparin dosed three times daily.
Using Medicare and Red Book 2006 data, the authors determined that the cost of VTE would be $4,715, which includes hospitalization plus 6 months of subsequent warfarin therapy and monitoring. Heparin-induced thrombocytopenia would cost $5,184, which includes 5 days of treatment with the thrombin inhibitor lepirudin followed by warfarin for 6 months. Bleeding complications, primarily minor bleeds not requiring treatment but some requiring transfusion, would cost $388.
The cost to patients would be $623 for low-molecular-weight heparin, $72 for low-dose unfractionated heparin, and $2 for aspirin.
But when the researchers factored in the VTE rates associated with each medication in the baseline analysis, they found that low-dose unfractionated heparin was the low-cost leader. The differences would translate into annual population savings relative to no prophylaxis of $50.1 million for low-dose unfractionated heparin and $28.8 million for aspirin, compared with excess costs of $81.3 million for low-molecular-weight heparin.
“This is a great paper,” Dr. Edward A. Levine commented in a postpresentation discussion. “This is something we all wrestle with, since we all work with oncology patients who have more than one risk factor for DVT or VTE,” he said. However, “there are a number of papers that I've seen showing that aspirin doesn't do anything in terms of preventing thromboembolism at all,” noted Dr. Levine, who is chief of surgical oncology at Wake Forest University Baptist Medical Center in Winston-Salem, N.C.
Dr. Bradley agreed that in the inpatient setting, aspirin does not appear to protect against immediate VTEs. “However, some studies have looked at aspirin after the point of discharge, and they do show a benefit, particularly in patients who have an increased VTE risk,” he said.
Dr. Bradley said that he has no relevant financial disclosures.