Nested Case‐Control Study Utilizing MID‐NET® on Thrombocytopenia Associated With Pegfilgrastim in Patients Treated With Antineoplastic Agents

Although several spontaneous case reports on the occurrence of thrombocytopenia in patients treated with human granulocyte colony‐stimulating factor (G‐CSF) preparations have been accumulated, its actual causality is still unclear. To investigate the association between G‐CSF preparations (filgrastim, nartograstim, lenograstim, and pegfilgrastim) available in Japan and thrombocytopenia in patients treated with antineoplastic agents, a nested case‐control study was conducted using the Medical Information Database NETwork (MID‐NET®) with the cohort of the Japanese population taking antineoplastic agents between 2009 and 2018. A case of thrombocytopenia was defined as a patient who had decreased platelet counts (< 50,000/mm(3)). We identified a maximum of 10 controls for each case matched on the index date. Adjusted odds ratios (aORs) and their 95% confidence intervals (CIs) of thrombocytopenia for the use of G‐CSF preparations compared with nonuse were estimated using conditional logistic regression. From the cohort in which 33,124 patients were included, 733 cases and 5,592 controls were identified. Compared with the nonuse of G‐CSF preparations, the use of any G‐CSF preparations increased the risk of thrombocytopenia (aOR: 5.7, 95% CI: 4.3‐7.5). More detailed analysis showed that a distinctive increased risk was observed when pegfilgrastim was prescribed at 2–7 days before the index date (aOR: 7.4 95% CI: 2.0–28.1). Associations of the other G‐CSF preparations with thrombocytopenia were unclear due to the inconsistent results among different analyses. A significantly increased risk of thrombocytopenia associated with pegfilgrastim was identified, leading to a revision of precautions in the package inserts of pegfilgrastim as a regulatory safety action.