Validation of the Ottawa Score in Cancer Patients with Venous Thromboembolism. the Predicare Cohort Study

Introduction

Venous thromboembolism (VTE) is a difficult to treat condition in patients with cancer with a persisting risk of recurrent VTE during anticoagulant treatment with low-molecular weight heparin (LMWH). Recent data suggest that direct oral anticoagulants (DOACS) are associated with a lower risk of recurrence but a higher risk of bleeding in these patients. Predicting the risk of recurrent VTE with LMWH may help to select the best treatment option.

We conducted a prospective multicenter observational cohort study in cancer patients with VTE treated with tinzaparin for 6 months in order to validate the Ottawa score (NCT03099031) and search for additional risk of recurrent VTE. The Ottawa score is composed of 5 variables, female sex (+1), lung cancer (+1), breast cancer (-1) cancer stage 1 (-2) and previous DVT (+1). A score ≤0 is associated with a low risk of recurrent VTE.

Methods

Adult cancer patients with recent diagnosis of documented symptomatic or incidental VTE (deep vein thrombosis (DVT) or pulmonary embolism (PE) treated with tinzaparin for 6 months were included in the study. The primary endpoint was the recurrence of symptomatic or asymptomatic VTE within the first 6 months of treatment with tinzaparin. Other endpoints were symptomatic recurrent VTE, major bleeding, heparin induced thrombocytopenia (HIT), all-cause mortality within 3 and 6 months. All events were adjudicated by a Central Adjudication Committee. Time-to-event outcomes were estimated by the Kalbfleisch and Prentice method to take into account the competing risk of death. Cumulative incidences were presented with corresponding 95% confidence interval (95% CI). To validate the Ottawa score, the area under the curve (AUC) and its 95% CI were calculated on receiver operating characteristic (ROC) curve analysis; the most discriminant cut-off was then determined by calculating the Youden index. Univariate and multivariate analyses were performed to identify additional predictive factors of recurrent VTE to those included in the Ottawa score using the Fine and Gray method and adjusted on factors included in the Ottawa score. Hazard ratio and their 95% CI were calculated.

Results

A total of 409 patients were included and analyzed on an intention-to-treat basis; the median age was 68 years and 51% of patients were males. 60.4% of patients had a PE (with or without DVT) .64% received chemotherapy at inclusion or in the month before inclusion. Lung (31.3%) and digestive track (18.3%) cancers were the most common cancer types and 67.0% had stage IV cancers. According to Ottawa score, 58% of patients were classified at high clinical probability of recurrence (score ≥ 1).

During the 6 months treatment period, 23 patients had a recurrent VTE, yielding a cumulative incidence of 6.1% (95% CI 4.0-9.3) with a median time for recurrent VTE of 33 days. The recurrence rate of VTE was estimated to 7.8% (95% CI 4.9-12.5) for patients classified at high risk of recurrence according to the Ottawa score (score ≥ 1) compared to 3.8% (95%CI 1.6-8.9) for other patients (Ottawa score < 1). AUC of the Ottawa score was 0.60 (95% CI 0.55-0.65). In multivariable analysis, none of the potential risk factors for recurrent VTE was significantly associated with recurrent VTE at 6 months.

During the 6 months treatment period, 15 patients had a major bleeding and 2 patients experienced a HIT. At 3 and 6 months, 104 and 144 patients had died yielding a cumulative incidence of 26.1%, (95% CI 21.8-30.4) and 37.8% (95% CI 32.8-42.9), respectively. The main cause of death was underlying cancer.

Conclusion

In this prospective cohort of patients with cancer receiving LMWH for VTE, the Ottawa score did not accurately predict recurrent VTE. No other clinical predictor of recurrent VTE was identified in this study.