PHOENIX – Patients with inflammatory bowel disease undergoing major abdominal surgery have a persistent elevation of the risk of blood clots postoperatively that warrants extended prophylaxis similar to that recommended for patients with colorectal cancer, new data suggest.
Investigators led by Dr. Molly Gross, a colorectal surgeon at the University of Utah in Salt Lake City, retrospectively analyzed data from the National Surgical Quality Improvement Program (NSQIP) database, assessing rates of venous thromboembolism (VTE) among nearly 46,000 patients with inflammatory bowel disease (IBD) or colorectal cancer who had major abdominal surgery.
Dr. Molly Gross
Study results, reported at the annual meeting of the American Society of Colon and Rectal Surgeons, showed that the IBD group had a 35% higher adjusted risk of VTE at 30 days relative to the colorectal cancer group. Also, the majority of the events in the IBD group occurred a week or more after surgery, by which time most patients would have been leaving the hospital or already home.
"The National Comprehensive Cancer Network (NCCN) currently recommends that colorectal cancer patients undergoing major abdominal surgery receive up to 4 weeks of postoperative out-of-hospital prophylaxis with either subcutaneous heparin or Lovenox [enoxaparin]," Dr. Gross commented. "There are currently no such recommendations for IBD patients undergoing similar operations."
Taken together, the study’s findings "lead to our conclusion that postdischarge VTE prophylaxis recommendations for IBD patients should mirror those for colorectal cancer patients," she maintained. "This would suggest a change in clinical practice to extend out-of-hospital VTE prophylaxis in IBD patients."
"You have done excellent work, and I congratulate you on the statistical rigor that’s quite evident in your study," said Dr. Justin Lee, of St. Elizabeth’s Medical Center in Brighton, Mass., who was invited to discuss the study.
However, he questioned the low absolute 30-day rates of VTE seen in the study – 2.7% in the IBD group and 2.1% in the colorectal cancer group – as compared with those reported in other studies.
The NCCN guidelines for patients with colorectal cancer "are based on large prospective studies considered to be closer to real-time data than NSQIP. If you look at those studies, they show anywhere from a 7% to 12% 30-day rate of deep vein thrombosis in colorectal cancer patients. And if you treat them with long-term prophylaxis within 30 days after surgery, it brings the rate down to 4% or 4.5%," he explained – about twice that in the presented study.
"How do you reconcile [these rates]?" Dr. Lee asked. "And should you apply your recommended 30-day postop prophylaxis to all IBD surgical patients when in fact the 2.7% is actually lower than the literature-quoted rate of deep vein thrombosis" in patients with colorectal cancer on anticoagulation?
Dr. Gross speculated that the difference in rates between the cancer studies and the current study was multifactorial in origin, stemming from differing study designs (randomized controlled trial vs. retrospective review), differing surgical populations (patients undergoing open surgery only in an older era vs. patients undergoing open or laparoscopic surgery in the current era), and uncertainty in their study about how many patients with colorectal cancer received extended prophylaxis.
Given the generally low rates of VTE events, "it would be difficult to adequately power a large randomized controlled trial," she added. "So we are kind of making a lot of assumptions that we hope we could decrease morbidity and mortality in IBD patients without significantly causing increased cost or bleeding complications" by using extended prophylaxis.
Dr. John Migaly of the Duke University Medical Center in Durham, N.C., who comoderated the session, noted that the incidence of VTE after surgery showed a sharp drop-off at approximately day 20. "That would be about 2 weeks after discharge. Is there an optimal length, in your opinion, of VTE prophylaxis, instead of just saying 4 weeks is fine?" he asked.
The investigators based that 4-week recommendation on the conclusions of a trial among oncology patients (N. Engl. J. Med. 2002;346:975-80), according to Dr. Gross. "It is probably variable based on patient condition: how much they are ambulating, how much they are back to their regular status, and how active their IBD is. So I think it would be difficult to come up with an ideal for every patient; that [4 weeks] is an arbitrary number created from that study."
For the study, Dr. Gross’ team analyzed data from the NSQIP database for the years 2005 through 2010, restricting analyses to 8,888 patients with IBD and 37,076 patients with colorectal cancer who had major abdominal surgery.
