Introduction Parenteral anticoagulants may improve outcomes in patients with
cancer by reducing risk of venous thromboembolic disease and through a direct
antitumour effect. Study-level systematic reviews indicate a reduction in
venous thromboembolism and provide moderate confidence that a small survival
benefit exists. It remains unclear if any patient subgroups experience
potential benefits. Methods and analysis First, we will perform a
comprehensive systematic search of MEDLINE, EMBASE and The Cochrane Library,
hand search scientific conference abstracts and check clinical trials
registries for randomised control trials of participants with solid cancers
who are administered parenteral anticoagulants. We anticipate identifying at
least 15 trials, exceeding 9000 participants. Second, we will perform an
individual participant data meta-analysis to explore the magnitude of survival
benefit and address whether subgroups of patients are more likely to benefit
from parenteral anticoagulants. All analyses will follow the intention-to-
treat principle. For our primary outcome, mortality, we will use multivariable
hierarchical models with patient-level variables as fixed effects and a
categorical trial variable as a random effect. We will adjust analysis for
important prognostic characteristics. To investigate whether intervention
effects vary by predefined subgroups of patients, we will test interaction
terms in the statistical model. Furthermore, we will develop a risk-prediction
model for venous thromboembolism, with a focus on control patients of
randomised trials. Ethics and dissemination Aside from maintaining participant
anonymity, there are no major ethical concerns. This will be the first
individual participant data meta-analysis addressing heparin use among
patients with cancer and will directly influence recommendations in clinical
practice guidelines. Major cancer guideline development organisations will use
eventual results to inform their guideline recommendations. Several knowledge
users will disseminate results through presentations at clinical rounds as
well as national and international conferences. We will prepare an evidence
brief and facilitate dialogue to engage policymakers and stakeholders in
acting on findings. Trial registration number PROSPERO CRD4201300352