New Cancer-Related VTE Risk Prediction Model Validated

Megan Brooks

February 28, 2023

Researchers have validated the ONKOTEV score to predict cancer-associated thrombosis among outpatients with cancer.

Based on the results of their recent analysis, the authors think the model could be useful in routine clinical practice and clinical trials for selecting patients at high risk for venous thromboembolism (VTE) who may benefit from primary prophylaxis.

The ONKOTEV score provides "good stratification" of the risk of VTE in this setting and coupled with the ease of use could represent a "breakthrough in cancer-associated thrombosis and a rationale for choosing the ONKOTEV score for risk assessment in the future," said the study authors, led by Chiara Cella, MD, PhD, with the European Institute of Oncology, Milan, Italy.

The study was published online earlier this month in JAMA Network Open.

VTE remains a common complication among patients with cancer, yet assessment of cancer-associated thrombosis risk remains "an evolving topic," the researchers explained.

Current international guidelines recommend primary prophylaxis for patients at intermediate to high risk for VTE, indicated by a Khorana score of 2 or higher.

The ONKOTEV score consists of four variables — a Khorana score of >2, metastatic disease, vascular or lymphatic compression, and a previous VTE event — with 1 point assigned to each and a total score of 2 or higher defined as high risk for VTE.

The ONKOTEV-2 validation study was conducted at three centers in Italy, Germany, and the United Kingdom among a prospective cohort of 425 outpatients (57% women; median age, 61 years) with solid tumors who were receiving active treatments. 

The most represented tumors were breast, gastroesophageal adenocarcinoma, colon, lung, rectum, and pancreatic cancers, and chemotherapy was the most common therapy.

The ONKOTEV score was calculated for each patient at baseline before starting any anti-cancer treatment and then patients were monitored for at least 8 months, and an overall follow-up period of 24 months, to detect any thromboembolic event. No patient was on anticoagulation therapy.

When a clinical suspicion of VTE emerged, patients immediately underwent an objective imaging assessment to confirm or rule out the event. VTE events were decided by a team of expert radiologists.

Most patients had an ONKOTEV score of 0 (27%) or 1 (55%), whereas 15% had an ONKOTEV score of 2, and 2.4% had a score of 3. Only one patient (0.2%) had a score of 4.

During the study period, the cumulative incidence of VTE was 12.7% (54 events).

At 6 months, the cumulative incidence of VTE was 2.6% in patients with an ONKOTEV score of 0 vs 9.1% for those with a score of 1, 32.3% for a score of 2, and 19.3% for a score greater than 2. The time-dependent area under the curve at 3, 6, and 12 months was 70.1%, 72.9%, and 72.2%, respectively.

The researchers noted that, among the individual variables in the ONKOTEV risk prediction model, metastatic disease and macroscopic vascular or lymphatic compression were highly associated with VTE (hazard ratio [HR], 4.22 and 3.25, respectively).

Patients with a Khorana score >2 appeared to have a higher risk for VTE, although the difference was not statistically significant (HR, 1.81; P =.14). Previous VTE did not appear to be independently associated with future risk for VTE (HR, 0.84; P =.76).

Ready for Prime Time?

Reached for comment, Alok Khorana, MD, a medical oncologist at the Cleveland Clinic who developed the Khorana score, noted that "the literature around VTE prediction in cancer patients is growing" with publication of two recent risk assessment models — ONKOTEV, which adds more clinical variables to the existing Khorana score, and ONCOTHROMB, which uses genetic variables in addition to clinical risk factors.

These models join a "host of existing risk scores," Khorana said, including the Vienna Cancer and Thrombosis Score, the PROTECHT score, the CONKO score and, more recently, the COMPASS-CAT model.

The current validation study focused on whether the ONKOTEV tool could successfully predict risk for VTE. The study is "well done and the results show a substantial improvement in positive predictive value, which is important in order to find the highest-risk patients," Khorana told Medscape Medical News.

The chief limitations of the study include "imbalances between the derivation and validation cohorts, as the authors point out, and external validation is needed," noted Khorana, who wasn't involved with this research.

Khorana did find it surprising that prior history of VTE was not a significant risk factor, as that has previously been shown to be associated with new VTE risk. It's also unclear how ONCOTHROMB and ONKOTEV compare with each other, he said.

But overall, Khorana agrees that the ONKOTEV score can be used in routine clinical practice to identify high-risk patients.

Cella reported receiving personal fees from Bristol-Myers Squibb and Leo Pharma, and a research grant from Ipsen (institutional). A complete list of author disclosures is available with the original article. Khorana has received consulting honoraria from Janssen, Bayer, Pfizer, Sanofi, BMS, Anthos, Medscape/WebMD.

JAMA Netw Open. Published online February 16, 2023. Full text

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