Nearly one in three patients will experience venous thromboembolism (VTE) within the first year of a multiple myeloma (MM) diagnosis, but new research presented at the 2016 American Society of Clinical Oncology Annual Meeting found that VTE risk persists and changes throughout the disease process.
Results from the study, led by Brea Lipe, MD, from the University of Rochester Medical Center in New York, also suggest that thromboprophylaxis guidelines from the International Myeloma Working Group (IMWG) may need to be adjusted to include VTE risk assessment and prevention later in the disease course.
The IMWG VTE prevention guidelines categorize patients as low- or high-risk for VTE, and recommend aspirin for low-risk patients and low-molecular-weight heparin (LMWH) or warfarin for high-risk patients for the first four to six months of myeloma treatment, Dr. Lipe and study authors explained.
"Because we understand that there is a risk of clotting, there are guidelines to help try to minimize this risk. These guidelines are derived from anecdotal evidence, [and] from sub-studies of larger therapeutic trials that look at subsets of populations pre-selected for [being] very healthy patients," Dr. Lipe said in an interview with ASH Clinical News. "So, the question is, â€˜Does this work in the real world, and are we doing enough?'"
The authors identified 297 patients with MM and VTE (n=89) and 211 matched controls (patients with MM who had not experienced VTE, matched based on gender, age, and time of diagnosis) from the Healthcare Enterprise Repository for Ontological Narration (HERON) database. Patient charts were analyzed for treatment history, disease history, and risk factors for VTE.
The median time from MM diagnosis to VTE was 952 days – years after the IMWG guidelines recommend thromboprophylaxis. "Twenty-five percent of our patients clotted within the first year, but then about 45 percent developed their clot after the two-year mark," Dr. Lipe added.
Patients with a higher risk of VTE were more likely to be prescribed LMWH or warfarin versus aspirin or no prophylaxis (p<0.001). However, thromboprophylaxis guidelines "are not really followed very well," Dr. Lipe said. "About 60 percent of patients – both in the case and control groups – were what we would consider to be high risk, meaning they had multiple risk factors for developing a clot. But, of those 60 percent, only about 16 percent ever received the recommended prophylactic for that condition." The researchers did not identify an association between either patients' risk category or use of prophylactic medications and the rate of VTE, even after adjusting for differences in baseline risk factors.
When looking at the changes in patients' risk categories from diagnosis to the time of VTE, though, Dr. Lipe and authors found that case patients moved to a higher risk category over time. Changes in risk category also were associated with a higher VTE risk (p=0.06).
"Our data suggest that VTE in MM may occur later in the disease process than has historically been reported," Dr. Lipe and authors concluded. "We might not be identifying the true risk factors for clotting [in myeloma patients] – there may be some disease biology at play or other factors that are important that we're underappreciating. We need to develop better prospective studies to understand exactly who's clotting and why."
Lipe B, Baker H, Weckbaugh B, et al. Validation of a thrombosis risk assessment model in patients with newly diagnosed multiple myeloma. Abstract #8055. Presented at the 2016 American Society of Clinical Oncology Annual Meeting, Chicago, IL, June 6, 2016.