Thrombopoietin receptor agonists (TPO-RAs) reduced chemotherapy delays or dose reductions (OR = 0.37; 95% CI: 0.20–0.67) and the incidence of grade 3/4 thrombocytopenia (OR = 0.50; 95% CI: 0.27–0.93). This evidence concerns the gene MPL and Thrombocytopenia.