Nattaya Sintawichai¹, Panisenee Lawasut², Nattaya Poovorawan¹, Napa Parinyanitikul^{1, *}

¹Division of Medical Oncology, Department of Medicine, Faculty of Medicine, King Chulalongkorn Memorial hospital and Chulalongkorn University
²Division of Hematology, Department of Medicine, Faculty of Medicine, King Chulalongkorn Memorial hospital and Chulalongkorn University

*Corresponding Author: Napa Parinyanitikul, Medical Oncologist, King Chulalongkorn Memorial Hospital and Chulalongkorn University, Bangkok, Thailand

Abstract
Immunotherapy has emerged as the new therapeutic frontier of cancer treatment including triple-negative breast cancer. In IMPassion130, combination atezolizumab with nab-paclitaxel demonstrated better survival outcomes compared to chemotherapy alone in metastatic TNBCs (mTNBCs) with PD-L1 positive subgroup [1]. Although immune-related adverse events (irAEs), which can affect multiple organ sites can commonly occur. However, hematologic adverse events especially autoimmune hemolytic anemia (AIHA) was rarely reported but often cause severe complications with immunotherapy treatment [2].
This clinical data reported AIHA was a rare adverse event of interest of atezolizumab in the treatment of metastatic TNBC. This event was be discussed with current knowledge and evidence of data associated with previous reports of immune‐related adverse events in using immune checkpoint inhibitors.

Keywords: autoimmune hemolytic anemia, immune-related adverse event, triple-negative breast cancer.

AIHA characterized by acute onset of anemia accompanying with evidence of biochemical data of hemolysis and positive direct antiglobulin test (DAT). When AIHA develop after initiation or re- initiation of immunotherapy, the possibility of immune-related adverse event was suspected [3]. AIHA infrequently occurs after treating with PD-1 or PD-L1 checkpoint inhibitors approximately 0.15-0.25 % which is higher than anti-CTLA-4 (0.06 %). In other, solid cancer settings, the incidence of AIHA from atezolizumab was reported rarely 0.24 % and could occur in early or later after this drug administration. The steroid is the mainstay of AIHA treatment. Unfortunately, around 20 % of this irAE had a fatal outcome [5].

Here, we reported clinical information of metastatic triple-negative breast cancer patient treated with atezolizumab plus paclitaxel. Rare hematological immune-related adverse event, AIHA, were observed and discussed with the current knowledge of evidence from several previous studies about immune‐related adverse events after immune checkpoint inhibitors administration.

Case report
A 50-year-old female previously was diagnosed with stage II (pT2N0M0) left triple-negative breast cancer in 1999, 20 years ago. Left breast-conserving therapy with axillary lymph node dissection and completed classical CMF were given. Postoperative radiotherapy was performed after adjuvant chemotherapy. In August 2019, she developed a new left breast mass. Mammogram and ultrasound breast showed BIRAD4c. Then USG-guides FNA was performed and showed mammary ductal carcinoma. Chest and upper abdominal CT scan for staging revealed a 3.9 cm enhancing breast mass with several small satellite nodules in the left breast, a 3.6 cm matted left internal mammary lymph node, and multiple small left subpectoral, axillary, and supraclavicular lymphadenopathies. She underwent left simple mastectomy in September 2019 and pathological findings reported invasive ductal carcinoma, grade III with wide-spread lymph vascular invasion and satellite tumor (ER: 0 %, PR: 0 %, HER2-negative, Ki67: 90 %). Even with no family history of breast cancer, genetic BRCA1/2 testing was performed and showed VUS BRCA2. Radiation at the left chest wall, internal mammary lymph node, and axilla was given after palliative surgery. However, PET/CT scan showed several bones, liver, and lymph node metastases. Her PET/CT was shown in figure 1. Serum CEA and CA 15-3 were 0.96 ng/mL (0-5) and 14.66 IU/mL (0-30), respectively. Before starting the palliative chemotherapy, PD-L1 testing was recommended and PD- L1 immunohistochemistry reported positive (>10 % of immune cells). Based on the IMPassion130 study, atezolizumab plus paclitaxel, not nab-paclitaxel was given on 16^th December 2019. Per our institution's practice, dexamethasone premedication was omitted in C1D15 because of no previous hypersensitivity reaction. Neither severe hematologic toxicity nor GI and neurological toxicity was observed during the first and second cycles of treatment. Additionally, no immune-related adverse events (IrAEs) were reported.

Figure 1: PET/CT scan showed A) multiple left cervical lymphadenopathies B) left internal mammary lymphadenopathies C) multiple bone metastases and D) liver metastases.

On cycle 3^rd, C3D1, CBC showed anemia grade II (Hb 8.1 g/dL, Hct 25.2, RDW 19.9 %) but no neutropenia or thrombocytopenia was observed. She denied a history of blood loss either GI, GU, or elsewhere. Her anemia got worse to grade III (Hb 6.5 g/dL, Hct 21.7, RDW 22.9 %) and she had symptomatic palpitation and functional class change. So, hematology consultation was introduced. Her peripheral blood smear confirmed normochromic-normocytic anemia, polychromasia 2+, various in size of spherocytes 2+ but no schistocyte and normal NRBC/white blood cell and platelet. Further investigations showed serum ferritin 1,191 ng/mL (13-150), serum iron 38 ug/dL (37-145), TIBC 176 ug/dL (228-428), reticulocyte count 2.1 % (1-2), haptoglobin 167 mg/dL (35-250), LDH 915 U/L (140-280) and negative direct and indirect antiglobulin tests were identified. Severe autoimmune hemolytic anemia (AIHA) was the final diagnosis. Since no concomitant medications related to the etiology of AIHA were demonstrated. Immune-hemolytic anemia which is a rare immune-related adverse event from atezolizumab was suspected. Therefore, the only atezolizumab was temporarily discontinued on cycle 4^th, C4D1. Due to her severe hemolysis, transfusion of leucocyte poor packed red cell and prednisolone with dose 60 mg/day (1MKD) was initiated. Summary serial CBC reports during this event was shown in table 1. Moreover, mild transaminitis,  possibly from atezolizumab and paclitaxel occurred during hemolysis. Her blood testing for IrAEs was summarized in table 2. Two weeks after prednisolone, anemia with her symptoms of dyspnea and palpitation gradually improved (CBC: Hb 8.7 g/dL, Hct 28.7 %, WBC 5,300 cell/mm3, N 70.8 %, Platelet 228,000 cell/mm3). Prednisolone was then taped with a dose of 10 mg per week. In our case of grade III hemolysis and pandemic COVID-19 infection, resuming atezolizumab was not considered. Currently, palliative paclitaxel alone was then administered without additional adverse events.

Table 1: Serial CBC testing in our case report

1. Before starting atezolizumab on 12/16/2019
2. Before starting C2D1 on 1/20/2020
3. Before starting C3D1 on 2/17/2020
4. Before starting C4D1 on 3/16/2020
5. Two weeks after prednisolone on 3/26/2020
6. Four weeks after prednisolone on 4/9/2020

Table 2: Blood testing for IrAEs monitoring

1. Before starting atezolizumab on 12/16/2019
2. Before starting C3D1 on 2/17/2020
3. Before starting C4D1 on 3/16/2020

Discussions
Here, we reported AIHA with DAT negative (Grade 3; ATCAE version 5) after atezolizumab and paclitaxel administration for 8 weeks. By excluding all possibilities of abrupt onset of anemia such as drug related AIHA, irAE from atezolizumab was the likely cause of this immune hemolysis.

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