Despite the superior clinical efficacy of clozapine in patients with treatment-resistant schizophrenia, patients must be informed about the untoward effects, including agranulocytosis, weight gain, diabetes, myocarditis, seizures, and the newly-described hematologic malignancies.
A nationwide case-control study involving patients with schizophrenia (18-85 years of age) was conducted using data obtained from the Finnish national registers.
The study cohort consisted of 375 patients with schizophrenia diagnosed with a hematologic malignancy who were age-, gender-, and time since diagnosis of schizophrenia-matched with approximately 10 patients with schizophrenia without a hematologic malignancy (n=3734).
During a mean follow-up of 12.3 years, the incidence of hematologic malignancies among patients with schizophrenia who were prescribed clozapine was 0.7% (event rate = 61/100,000 person-years). The types of malignancies were as follows: lymphomas (n=305); leukemia (n=42); myelomas (n=22); and other (n=6).
During a mean follow-up of 12.9 years, the incidence of hematologic malignancies among patients with schizophrenia who were prescribed anti-psychotics other than clozapine was 0.5% (event rate = 41/100,000 person-years).
The adjusted odds ratio for a hematologic malignancy in clozapine-users compared to users of other anti-psychotics was 3.35.