Assessment of efficacy and validity of Khorana risk assessment model in cancer outpatients at a regional cancer center.
Authors: Khan Noman Ahmed Jang , Yasin Hassaan , Gress Todd W. , Tirona Maria R.B. Tria 
Published: June 2022

e18689

Background: Malignancy is a known risk factor for venous thromboembolism (VTE). Several risk assessment models have been proposed in the literature. Khorana score (KS) is by far the most favored VTE risk assessment tool in cancer outpatients. The KS incorporates the site of primary cancer, baseline hemoglobin, platelets, white blood cell count, and body mass index into the risk score. Patients are classified into low (KS = 0), intermediate (KS = 1-2) and high (KS≥ 3) risk groups. Low dose prophylactic anticoagulation for up to 6 months is recommended in patients with a KS of 2 or higher. In this study we attempted to validate the efficacy of Khorana risk model in our cancer population. Methods: We identified 270 patients (18 years and older) in 2018 and 2019 from our cancer registry with a new cancer diagnosis who received chemotherapy. All the components of KS including patient’s white blood cell count (WBC), hemoglobin, platelet count, baseline body mass index (BMI), and site of the primary were collected. We reviewed medical records to assess for development of VTE over time following initial cancer diagnosis. To assess the performance of Khorana score in our population, we utilized logistic regression and receiver operating characteristic curve (ROC) analysis. We further evaluated VTE free survival by Khorana score using Cox regression analysis. Results: Among 270 patients, the mean age was 60.4 (SD 14.0). 50.6 % were males (n = 136) and 49.6 % were females (n = 134). The most common cancer site was breast (n = 57) followed by prostate (n = 55), pancreas (n = 24), lymphoma (n = 22), bladder (n = 17), lung (n = 13), colon (n = 11), and acute myeloid leukemia (n = 6). The mean Khorana score was 1.2 (SD 1.1). Prophylactic anticoagulation was indicated in 84 patients (KS ≥ 2) but only 4 patients received prophylactic anticoagulation (1.4%). Using a KS cutoff score of 2 or more, the sensitivity was 55.6% (95% CI 0.31 to 0.78), specificity was 70.6% (95% CI 0.64 to 0.76) with a positive predictive value of 11.9% (95% CI 0.06 to 0.21) and negative predictive value of 95.7% (95% CI 0.91 to 0.98). The area under the ROC curve was 0.66, indicating poor performance of the KS. Using Cox regression, those with a KS of 3 or more were 6.3 times (95% CI 1.7 to 23.5) more likely to develop a VTE compared to those with a KS of zero. However, those with KS of 1 (RH 0.96; 95% CI 0.23 to 3.9) or KS of 2 (RH 1.3; 95% CI 0.28 to 6.1) were no more likely to develop a VTE compared to those with a KS of zero. Conclusions: In our patient population, patients were unlikely to receive prophylactic anticoagulation for VTE despite many meeting KS criteria. Using a KS of 2 or higher did not perform well in predicting the risk of a symptomatic VTE. Some VTE diagnoses may have been missed since only those with suspicion of VTE underwent diagnostic testing, which could influence KS performance. However, routine testing for VTE without symptoms or signs is not considered stand or care.