[A Case of Severe Hematological Toxicity in Response to Pazopanib]

The patient(woman, approximately 46 years old)began pazopanib (PAZ) treatment (800 mg/day)f ollowing the recurrence of retroperitoneal leiomyosarcoma. Prior to treatment, the patient's platelet count was 18.6×10(4)/µl and her neutrophil count was 1.61×10(3)/µl . The platelet count decreased to 9.2×10(4)/µl on day 7 and to 5.4×10(4)/µl on day 21 after commencement of treatment. The neutrophil count was 0.97×10(3)/µl on day 28 and 0.68×10(3)/µl on day 35 after commencement of treatment. Thus, PAZ treatment was stopped on day 35. The blood sampling results on day 42 after commencement of treatment showed that the platelet count was 13.0×10(4)/µl and that the neutrophil count had recovered to 1.28×10(3)/µl . At that time, PAZ treatment was resumed at a reduced dose of 600 mg/day. By day 84 after commencement of treatment, the platelet count had increased from 12.7 to 13.8×10(4)/µl and the neutrophil count had increased from 1.02 to 1.34×10(3)/µl ; treatment was subsequently continued. The main adverse effects that have been reported for PAZ are hypertension and frequent liver dysfunction; these reports also indicate that the incidence of severe cytopenia(thrombocytopenia, neutropenia)is quite low. However, our patient exhibited cytopenia after commencement of PAZ treatment and her blood cell counts recovered once treatment was ceased, independent of other possible medications. Our findings suggest that cytopenia should be considered as an adverse effect of PAZ.