The association of venous thromboembolism with survival in pediatric cancer patients: a population-based cohort study

Impact of clinically unsuspected venous thrombotic events on CVC removal and survival in pediatric cancer patients: A population-based study from the Maritimes, Canada

Venous thromboembolism (VTE) is a well-recognized complication in pediatric cancer patients. We aimed to determine the frequency of central venous catheter (CVC) removal and survival impact of children with cancer who develop VTE. After ethics approval, a retrospective population-based study of cancer patients less than 21 years between 2005 and 2020, in the Maritime Provinces Nova Scotia, New Brunswick, and Prince Edward Island was conducted. Clinical data was collected from hospital charts and online medical records. Data on demographics, cancer diagnosis and treatment, diagnosis of VTE, use of CVC, were assessed. Kaplan-Meier survival curves were computed and compared among study groups. This study included 770 patients with a male to female ratio of 1.1:1. There were 49 patients with symptomatic VTE, 49 patients with clinically unsuspected VTE, and 671 patients with no VTE. There were 15 (1.9%) non-CVC-symptomatic (ncsVTE), 34 (4.4%) CVC-symptomatic (csVTE), 40 (5.2%) non-CVC-clinically unsuspected (ncuVTE), 9 (1.2%) CVC-clinically unsuspected (cVTE), and 671 (87%) no VTE patients. The mean number of CVCs required during treatment was significantly higher among patients with VTE (p < 0.001). Both symptomatic and clinically unsuspected VTE required significantly more CVCs compared to no VTE patients (p < 0.001 and p = 0.049 respectively). Kaplan-Meier survival curves showed ncsVTE patients' survival was significantly reduced compared to all other patients (p < 0.001). This study demonstrates that pediatric oncology patients with ncsVTE have significantly lower survival. This suggests that ncsVTE may be a biomarker for increased disease burden. This study also demonstrated that clinically unsuspected VTE had significantly more CVCs placed during treatment compared to patients without a VTE, indicating the need for better screening.

Development and validation of thromboembolism diagnostic algorithms in children with cancer from real-world data

OBJECTIVE

To evaluate the accuracy of diagnostic algorithms developed using the International Classification of Diseases (ICD-9-CM and ICD-10-CA) diagnostic codes and physician billing codes for thromboembolism (TE) from health administrative data compared to chart review diagnoses of TE in children with cancer.

METHODS

Using data linkage between the Pediatric Oncology Group of Ontario Network Information System (Ontario pediatric cancer registry) and various administrative data housed at ICES, eight algorithms were developed including a single reference to one of the billing codes, multiple references with varying time intervals, and combinations of various billing codes during primary cancer therapy for the whole cohort and, for early (<04/2002) and later (≥04/2002, solely ICD-10 codes) periods. Reference standard was chart review data from prior studies (from 1990 to 2016) among children (≤19 years) with cancer and radiologically confirmed TE.

RESULTS

Records of 2056 patients diagnosed with cancer at two participating sites during study period were reviewed; 112 had radiologically confirmed TE. The algorithm with addition of anticoagulation utilization codes was the best performing algorithm (sensitivity = 0.76;specificity = 0.85). With use of ICD-10 only codes, sensitivity of the same algorithm improved to 0.84 with specificity of 0.80.

CONCLUSION

This study provides a valid approach for ascertaining pediatric TE using real-world data.

IMPACT

Research in pediatric thrombosis, especially cancer-related thrombosis, is limited mainly due to small-sized studies. Real-world data provide ready access to large and diverse populations. However, there are no validated algorithms for identifying thrombosis in real-world data for children. An algorithm based on combination of thrombosis and anticoagulation utilization codes had 76% sensitivity and 85% specificity to identify diagnosis of thrombosis in children in administrative data. This study provides a valid approach for ascertaining pediatric thrombosis using real-world data and offers a good avenue to advance pediatric thrombosis research.

Risk factors and clinical impact of thrombosis during induction chemotherapy for pediatric acute lymphoblastic leukemia: A report from CYP-C

Thromboembolism (TE) is associated with reduced survival in pediatric acute lymphoblastic leukemia (ALL). It has been hypothesized that TE might signal leukemic aggressiveness. The objective was to determine risk factors for TE during ALL induction (TEind ) therapy and whether TEind is associated with treatment refractoriness. This retrospective cohort study using the population-based Cancer in Young People Canada (CYP-C) registry included children <15 years of age diagnosed with ALL (2000-2019) and treated at one of 12 Canadian pediatric centers outside of Ontario. Univariate and multivariable logistic regression models were used to determine risk factors for TEind and whether TEind predicted induction failure and ALL treatment intensification. The impact of TEind on overall and event-free survival was estimated using Cox proportional hazard regression models. The study included 2589 children, of which 45 (1.7%) developed a TEind . Age (<1 year and ≥10 years vs. 1-<10 years), T-cell phenotype, high-risk ALL, and central nervous system involvement were all associated with TEind in univariate analysis. Age and T-cell phenotype remained independent predictors of TEind in multivariable analysis. Induction failure occurred in 53 patients (2.1%). TEind was not associated with induction failure (OR: not estimable) or treatment intensification (adjusted OR [95% CI]: 0.66 [0.26-1.69]). TEind was independently associated with overall survival (adjusted HR [95% CI]: 2.54 [1.20-5.03]) but not event-free survival (adjusted HR [95% CI] 1.86 [0.98-3.51]). In this population-based study of children treated with contemporary chemotherapy protocols, TEind was associated with age and T-cell phenotype and mortality but did not predict induction failure.

Safety and Efficacy of Direct Oral Anticoagulants for Treatment of Venous Thromboembolism in Pediatric Oncology Patients

BACKGROUND/OBJECTIVES

Children with cancer have an increased risk for developing a venous thromboembolism (VTE) during their treatment course. Direct oral anticoagulants (DOACs) represent a relatively new class of oral medications to treat VTE; however, data are limited to support use in this patient group. Given the safety and efficacy data from numerous perspective adult studies, providers now consider off-label use in select children.

METHODS

We performed a single-center, retrospective review of children 0 to 20 years of age from 2012 to 2020 with malignancy and confirmed VTE, with the objective to evaluate the hypothesis that the safety and the efficacy of DOACs are noninferior to enoxaparin in this population. The primary composite efficacy outcome comprises symptomatic recurrent VTE, death due to VTE, and thrombus progression. The principal safety outcome is a combination of major and clinically relevant nonmajor bleeding.

RESULTS

The safety and efficacy outcomes collected revealed that DOAC use was equivalent when compared with the enoxaparin group for treatment of VTE. One patient in the DOAC group had clinically relevant, nonmajor bleeding compared with 2 patients in the enoxaparin group. No treatment failures were observed.

CONCLUSIONS

This single-center study suggests that DOACs are both safe and efficacious for the treatment of VTE in children with cancer. It also highlights the need for larger studies to address this clinical question.

Venous Thromboembolic Events in Adolescent and Young Adult Patients with Acute Lymphoblastic Leukemia

Acute venous thromboembolisms (VTEs) are serious complications that occur during acute lymphoblastic leukemia (ALL) chemotherapy. The data elucidating risk factors for developing VTEs are limited in adolescent and young adult patients being treated per pediatric ALL protocols. In a cohort of 66 patients, 14 (21%) experienced VTEs. The majority of VTEs occurred during induction chemotherapy after the first dose of asparaginase, and in the upper extremities. Five-year relapse-free and overall survival were not impacted by VTEs. Contrary to VTEs in adults, hypoalbuminemia and increased body mass index were not associated with an elevated risk of VTE.

Challenges in Management of VTE in Children With Cancer: Risk Factors and Treatment Options

Venous thromboembolism (VTE) occurs in 2.1 to up to 50% of children with cancer and contributes to long term morbidity as well as early mortality in this population. Pediatric patients with malignancy are predisposed to VTE due to the prothrombotic nature of cancer and its associated coagulopathies as well as chemotherapeutic agents, use of central venous catheters, surgery, radiotherapy, and concomitant thrombophilia. Management of thrombosis in this population is challenging due to concomitant thrombocytopenia, associated bleeding risks, concurrent co-morbidities, and toxicities of therapy. The aim of this paper is to highlight clinically relevant issues and management dilemmas using clinical vignettes. We review the clinical significance of asymptomatic and symptomatic thrombosis, examine the various options for asparaginase-associated thrombosis, address the role and controversies of direct oral anticoagulants, and describe our approach to managing anticoagulation therapy in the context of chemotherapy-induced thrombocytopenia.

Venous Thromboembolism in Pediatric Cancer Patients with Central Venous Catheter-A Systematic Review and Meta-analysis

Pediatric cancer patients hold an increased risk of venous thromboembolism (VTE) due to their cancer. Central venous catheters (CVCs) further increase the VTE risk. This systematic literature review elucidates the VTE incidence in pediatric cancer patients with CVC. MEDLINE and EMBASE were searched in August 2020 without time limits. We included studies reporting original data on patients ≤18 years with any CVC type and any cancer type, who were examined for VTE with ≥7 days follow-up. In total, 682 unique records were identified, whereof 189 studies were assessed in full text. Altogether, 25 studies were included, containing 2,318 pediatric cancer patients with CVC, of which 17% suffered VTE. Fifteen studies (n = 1,551) described CVC-related VTE and reported 11% CVC-related VTE. Concerning cancer type, 991 children suffered from acute lymphoblastic leukemia (ALL) and 616 from solid tumors. Meta-analysis revealed VTE incidence (95% confidence interval) of 21% (8-37) for ALL and 7% (0.1-17) for solid tumors. Additionally, 20% of children with tunneled or nontunneled CVC and 12% of children with implantable ports suffered VTE. In conclusion, pediatric cancer patients with CVC have substantial VTE risk. Children with ALL and CVC have higher VTE incidence than children with solid tumors and CVC. Implantable port catheter should be preferred over tunneled or nontunneled CVC to reduce VTE risk. Thrombophilia investigation does not seem relevant in pediatric cancer patients with CVC and VTE. To prevent VTE, intensified catheter care is recommended, especially in children with ALL.

Thrombosis is associated with worse survival in children with acute lymphoblastic leukemia: A report from CYP-C

There are conflicting data about whether the development of cancer-associated thrombo-embolism (TE) negatively impacts survival in children. The objective was to determine whether TE during treatment was associated with overall survival (OS) and event-free survival (EFS) in children with acute lymphoblastic leukemia (ALL). We performed a population-based retrospective cohort study using the Cancer in Young People-Canada registry. Children <15 years of age were diagnosed with de novo ALL (2000-2016). The primary exposure variable was radiologically-confirmed thrombo-embolism requiring medical intervention. Multivariable Cox regression models were used to determine the impact of thrombo-embolism on survival, where TE was time-dependent. We included 2006 children (median age: 4 years, 88.5% precursor B-cell ALL). Thrombo-embolism occurred in 113 patients (5.6%), at a median time of 107 days (interquartile range: 35-184 days) after ALL diagnosis. Among standard/low-risk patients, 41/1165 (3.5%) developed TE while among high/very high-risk patients, 72/841 (8.6%) developed TE. Patients with TE had a significantly worse OS (adjusted HR [aHR] of death: 2.61, 95% CI: 1.62-4.22, p < 0.001) and EFS (aHR of an event [death, relapse, second malignancy]: 2.03, 95% CI: 1.35-3.05, p = 0.001), compared with patients without TE. No statistically significant difference was seen in standard/low risk ALL for OS and EFS, but TE was associated with a significantly lower OS and EFS in children with high/very high-risk ALL (aHR of death: 2.90, 95% CI: 1.79-4.72, p < 0.001; aHR of an event: 2.02, 95% CI: 1.30-3.12, p = 0.002). Thus, TE led to a statistically significant reduction in OS and EFS in children with high risk/very high-risk leukemia.

Use of Tissue Plasminogen Activator as a Surrogate Measure for Central Venous Catheter Dysfunction and Survival Outcome in Children with Cancer: A Population-Based Retrospective Cohort Study

Central venous catheter (CVC) dysfunction is often associated with thrombosis, which in turn has been linked with poorer survival outcomes in cancer patients. Our objective was to examine the association of tissue plasminogen activator (tPA) administration as a surrogate measure of CVC dysfunction with survival in pediatric cancer patients. The present study uses data from a population-based retrospective cohort of pediatric oncology patients from the Canadian Maritime provinces treated between 2000 and 2017 at the IWK Health Centre, Halifax, NS. Demographics, diagnosis, date of death or date of last visit, and tPA use for CVC dysfunction were obtained from clinical databases and the provincial Cancer in Young People in Canada registry. The association between tPA administration and survival was examined using a Cox regression model adjusted for sex, age at diagnosis, cancer type, thrombosis, CVC duration, diagnosis era, and treatment modalities. Out of 821 patients, 206 received one or more doses of tPA during upfront therapy. The death rate was 21% and 15% respectively in patients who did and did not receive tPA. In the adjusted regression model, after receiving one or more doses of tPA, children had significantly poorer survival as compared to those that did not receive tPA (HR: 1.496, 95% CI: 1.019, 2.197). CVC dysfunction may be associated with a poorer prognosis in pediatric cancer patients. Future studies should corroborate these findings in other populations, examine the influence of other potential confounders, and determine the role of CVC dysfunction in prognostic models of cancer survival.

Feasibility and safety of delivering full-dose anticoagulation therapy in children treated according to Dana-Farber Cancer Institute acute lymphoblastic leukemia consortium therapy protocols

BACKGROUND

The literature is void of an evidence-based anticoagulation therapy (ACT) management strategy in the context of thrombocytopenia. We examined the impact of thrombocytopenia on low-molecular-weight heparin (LMWH) dosing and incidence of bleeding in children with acute lymphoblastic leukemia (ALL) or lymphoblastic lymphoma (LL) who developed thromboembolism (TE) during therapy according to DFCI ALL protocols.

PROCEDURE

Patient records from our tertiary care center were reviewed for demographics, details of diagnoses and therapy of ALL/LL and TE diagnoses, platelet counts during ACT, LMWH dosing, and bleeding episodes.

RESULTS

Thirty-nine TEs were diagnosed in 33 patients [mean age 9 years (range, 2.5-18); 16 males and 31 with ALL] during the study period. A majority (85%) of patients were diagnosed with TE in the consolidation phase with mean time to TE 5.75 months from ALL/LL diagnosis. All patients received LMWH, and the median duration of ACT was 5.9 months (range, 1-11 months). Platelets were measured weekly. On 29 occasions, platelet nadir was <50 × 10⁹ /L, and twice it was < 20 × 10⁹ /L. One (3%) patient had major bleeding episode while on ACT. Platelet count at the time of bleeding was 222 × 10⁹ /L. Ninety-two procedures [83 lumbar punctures (LPs), 9 central venous line (CVL) insertion/revision] were completed without bleeding complications. Asparaginase was held temporarily with TE diagnosis in 48% of patients; most (88%) patients completed all scheduled doses as per protocol.

CONCLUSIONS

Ability to administer full-dose LMWH, expected bleeding rate, and completion of asparaginase doses while on ACT suggest full-dose ACT is feasible and safe in children with ALL/LL who develop TE during DFCI ALL consortium therapy protocols.