ObjectivesThis analysis was conducted to clarify risk factors for severe adverse effects and treatment-related deaths reported during a postmarketing survey of irinotecan.MethodsThe survey covered all patients treated with irinotecan in Japan between April 1995 and January 2000. The patient background data and adverse drug reactions were collected through case report forms. Univariate and multivariate logistic regression analyses including 14 explanatory variables were performed to determine the risk factors for grade 3–4 leukopenia, thrombocytopenia and diarrhea for all patients and subgroups with five major cancers. Treatment-related deaths were also analyzed.ResultsCase report forms of 13 935 patients (94.1% of 14 802 patients registered) treated with irinotecan-based chemotherapy were collected. Major grade 3–4 adverse drug reactions were leukopenia (34.8%), thrombocytopenia (12.4%) and diarrhea (10.1%). Multivariate analysis revealed that the risk factors (odds ratio ≥1.5) common for all these three adverse drug reactions were performance status (≥3), infection and renal dysfunction before starting irinotecan therapy. Additionally, the risk factors for leukopenia were being female and prior radiotherapy, those for thrombocytopenia were age (≥65 years), while those for diarrhea were pleural effusion and watery stool. The risk factors in each cancer were also identified. The incidence of treatment-related death was 1.3% (176). Myelosuppression-related deaths accounted for 70% and interstitial lung disease for 11% of all treatment-related deaths. Being male, age, performance status ≥3, massive ascites and infection and renal dysfunction were identified as risk factors for treatment-related death.ConclusionsTo ensure the safety of irinotecan therapy, it is important to select appropriate patients by considering the risk factors.