Severe thrombocytopenia induced by second exposure to trastuzumab can be alleviated by prolonging the interval between treatments

Trastuzumab Associated With Recurrent Severe Thrombocytopenia and Successful Use of Pertuzumab Monotherapy

Trastuzumab is a mainstay chemotherapeutic agent used in the treatment of human epidermal growth factor receptor 2 (HER2)/neu-positive breast cancer that, though generally well-tolerated, is classically associated with side effects like cardiotoxicity. Cytopenias can be seen but are generally secondary to other chemotherapeutic agents used in conjunction with trastuzumab. Herein, we present a case of recurrent severe thrombocytopenia following trastuzumab use that resolved following discontinuation. Our patient then finished a year of maintenance therapy with pertuzumab alone and is still in remission four years later. This is the eleventh report of this severe adverse effect described in the literature. This report contributes to the body of work describing this severe side effect by illustrating a clear temporal relationship between trastuzumab and severe thrombocytopenia, while also providing an alternate treatment option with chemotherapy and pertuzumab monotherapy. Given that pertuzumab is typically only used in addition to trastuzumab, evidence of its successful independent use is of clinical value to patients who may not be able to tolerate trastuzumab.

Drug-induced thrombocytopenia associated with trastuzumab in a patient with HER2-positive recurrent gastric cancer

Here, we report a 57-year-old female patient with HER2-positive recurrent gastric cancer who experienced drug-induced thrombocytopenia associated with trastuzumab, a humanized anti-HER2 monoclonal antibody. Shortly after the initiation of S-1, oxaliplatin, and trastuzumab chemotherapy, the patient experienced severe thrombocytopenia and did not respond to platelet transfusions. Based on the findings of increased numbers of polynuclear megakaryocytes in the bone marrow and an elevated level of platelet-associated IgG (PA-IgG), the patient was diagnosed with drug-induced thrombocytopenia (DITP). The platelet count recovered rapidly with oral prednisolone (1 mg/kg). Since we initially suspected oxaliplatin as the causal agent, S-1 was restarted as a monotherapy, followed by trastuzumab after a 3-week interval, without oxaliplatin. On the second day after the addition of trastuzumab, severe thrombocytopenia occurred again, which suggests that trastuzumab was responsible for the DITP. The patient no longer experienced severe thrombocytopenia during the subsequent S-1 and oxaliplatin chemotherapy, which supports this hypothesis.

Trastuzumab-induced thrombocytopenia after eight cycles of trastuzumab treatment

Trastuzumab, a humanized monoclonal antibody derived from recombinant DNA, is used in patients with breast cancer with HER2 gene amplification. The survival benefit from trastuzumab has been well established in patients with early and metastatic breast cancer who had over expression of HER2. We reported a case of severe thrombocytopenia after eight cycles of trastuzumab treatment for breast cancer. Before the 9th trastuzumab treatment, the patient’s platelet decreased to 48 × 10⁹/L. Recombinant human thrombopoietin was used, and the platelet level increased to normal level. Before the 10th treatment, the platelet count of the patient was 99 × 10⁹/L. However, during the 10th and 11th trastuzumab treatment, the platelet count decreased to 5 × 10⁹/L in 24 h. After treatment with TPO and corticosteroids, the platelet levels increased to the normal level in 7 days. Trastuzumab-induced thrombocytopenia is rare but still occurred even after 8 cycles of trastuzumab treatment.