Case Report Safe neoadjuvant trastuzumab-based treatment in HER2 + inflammatory early breast cancer in a glucose 6-phosphate dehydrogenase-deficient postmenopausal woman: A case report and review of the literature Alberto J Cunquero-Toma´s 1 , Claudio D A ´ vila-Andrade 1 , Javier Milara 2 , Karla Javier 3 , Vega Iranzo 1 and Carlos Camps 1,4,5 Abstract Introduction: Glucose 6-phosphate dehydrogenase (G6PD) is a basic antioxidant pathway for erythrocytes, being its deficiency the most common gene mutation worldwide. As breast cancer is one of the most frequent tumors, many of these patients may present with G6PD deficiency prior treatment without notice. Case report: We present the case of a woman deficient for G6PD with the diagnosis of Stage IIIB (cT4d cN1cM0) HER2-enriched early breast cancer. Management and outcome: The patient underwent neoadjuvance with trastuzumab and anthracycline-free chemo- therapy, based on docetaxel (75mg/m 2 , 120 mg) and carboplatin (AUC 5, 560 mg). She did not present hemolytic crisis and no blood transfusions were needed. She achieved a good pathologic response and completed one-year adjuvant trastuzumab without incidences. Discussion: Although the role of HER2 and trastuzumab in oxidative stress is not yet completely understood, we suggest that trastuzumab may be a suitable agent for treatment in patients with HER2-enriched breast cancer in a non-oxidative chemotherapy scheme, with acceptable responses and no triggering hemolytic crisis. Keywords Breast cancer, G6PD deficiency, trastuzumab, neoadjuvance Date received: 22 January 2019; revised: 26 May 2019; accepted: 28 May 2019 Introduction Glucose 6-phosphate dehydrogenase (G6PD) located at the Xq28 region 1 is a crucial enzyme in most human cells, including erythrocytes, where it is almost the only antioxidant pathway remaining after all its development during the hematopoiesis. Accounting for almost 400 million people affected, G6PD deficiency is the most common gene mutation worldwide. 2 As a consequence, it should not be rare that women with diagnosed breast cancer may carry this deficiency, adding some more difficulties to their anticancer treatment choice, considering the little information in this field. 1 Medical Oncology Department, Hospital General Universitario Valencia, Valencia, Spain 2 Pharmacology Department, Hospital General Universitario Valencia, Valencia, Spain 3 Hemathology Department, Hospital General Universitario Valencia, Valencia, Spain 4 Faculty of Medicine, Universidad de Valencia, Valencia, Spain 5 CIBERONC, Madrid, Spain Corresponding author: Alberto J Cunquero-Toma´s, Tres Cruces, 2, Valencia 46014, Spain. Email: albertojacobocunquerotomas@gmail.com J Oncol Pharm Practice 0(0) 1–4 ! The Author(s) 2019 Article reuse guidelines: sagepub.com/journals-permissions DOI: 10.1177/1078155219858173 journals.sagepub.com/home/opp