Long-term treatment with clozapine and other antipsychotic drugs and the risk of haematological malignancies in people with schizophrenia: a nationwide case-control and cohort study in Finland

SPS commentary:

In the case-control study (n=375 matched to ≥10 controls without cancer) & cohort study (n=55,949), the cumulative incidence of haematological malignancies during mean follow-up of 12·3 years was 102 (0.7%) cases among 13 712 patients on clozapine (61 cases per 100 000 person-years), and during mean follow-up of 12·9 years was 235 (0.5%) malignancies among 44,171 patients having used other antipsychotic medication than clozapine (41 cases per 100 000 person-years). The researcher stress that acknowledging the small absolute risk compared with the previously observed absolute risk reduction in all-cause mortality is important.

According to a commentary, it is important to observe that the effect of clozapine is likely to be weak in absolute terms in comparison to people exposed to other antipsychotic medications and the general population more broadly, given the rare incidence of haematological malignancies generally. It highlights the importance of contextualising this risk by much more common adverse outcomes such as cardiovascular morbidity and mortality; and conversely the improved all-cause survival seen with clozapine treatment. It notes that although not a cause for alarm, these data are another reminder that holistic assessment of medical comorbidity is important in people prescribed clozapine. They merit further investigation but should not be interpreted as a reason to deny a marginalised group access to potentially transformative and life-saving treatment, to which there are few alternatives.