Weekly Trastuzumab Therapy Cannot Prevent Severe Trastuzumab-induced Thrombocytopenia: A Case Report

Abstract Background: Trastuzumab can significantly prolong the survival of patients with positive human epidermal growth factor receptor-2 breast cancer. Until now, trastuzumab has been used by millions of people, and trastuzumab-induced thrombocytopenia is rare. There is no report of acute grade 4 thrombocytopenia after weekly trastuzumab therapy. We report a breast cancer patient with severe thrombocytopenia due to trastuzumab (8mg/Kg) who experienced a recurrence of severe thrombocytopenia after attempting weekly trastuzumab therapy (4mg/Kg). Case presentation：A 52-year-old woman with positive human epidermal growth factor receptor-2 breast cancer developed acicular rash with dense skin all over the body and gingival bleeding within 24 hours of trastuzumab infusion (8mg/Kg) and was confirmed to have severe thrombocytopenia, which was quickly recovered after high-dose corticosteroid pulse therapy. When the platelet count recovered, we tried weekly trastuzumab therapy (4mg/kg), Unfortunately, thrombocytopenia recurred within 24 hours. No third trastuzumab treatment was attempted. Conclusion: We are the first report to try weekly trastuzumab therapy after thrombocytopenia induced by first trastuzumab. The patient showed that reducing the dose of trastuzumab was ineffective in preventing trastuzumab-induced thrombocytopenia.