Feasibility of myelosuppressive chemotherapy in psychiatric patients on clozapine: A systematic review of the literature.

OBJECTIVE: Clozapine is the favoured antipsychotic for treatment-refractory schizophrenia, but has a 1%-2% incidence of agranulocytosis. Patients who require chemotherapy therefore pose a unique management dilemma for haematologists, oncologists and psychiatrists. METHODS: The Ovid MEDLINE and EMBASE databases were searched to identify reports describing use of clozapine concurrent with chemotherapy until 31 March 2019. The following terms (with variations) were used: neoplasm, cancer, tumour, malignancy, chemotherapy, antineoplastic and clozapine. RESULTS: Twenty-seven cases were included after reviewing titles and abstracts for relevance. Fifteen patients had solid organ tumours, and 12 had haematological malignancies, including three who underwent autologous haematopoietic stem cell transplantation (AutoHSCT). Clozapine was continued in 14 cases (albeit dose reduced in 2), with a reported median neutropaenic nadir of 0.29 × 109 /L (range 2.2 to <0.0 × 109 /L). Clozapine was discontinued or substituted for another antipsychotic in the remaining 13 cases, all except one of whom experienced marked psychiatric deterioration. The only neutropenia-related complication was one case of bacteraemia with high-dose melphalan conditioning for AutoHSCT. CONCLUSIONS: These findings argue in favour of clozapine continuation during chemotherapy. Further research is needed to develop guidance to minimise the risk of neutropenia-related complications from concurrent treatment.