Evaluation of HER2 expression in prostate cancer among Mexican patients.

e17059 Background: Prostate cancer is one of the main types of cancer in men, specifically in Mexico there is an increasing trend in incidence in the last two decades. The lack of targeted therapy in this neoplasm compels us to find new biomarkers that could work as possible drug targets. HER2 is a protein in cell membrane that has been targeted with different types of antibodies in multiple neoplasms, such as breast or gastric cancer. In prostate cancer, there are few reports of HER2 expression; in one study the incidence of HER2 in prostatic tissue was 15%, mainly with low expression of the protein; in another report that included a total of 2,525 patients, they reported up to 22.5% of HER2 expression being HER2 1+ and 2+ the most common report. There are no reports of HER2 expression in Mexican population. Methods: We identified patients diagnosed with prostate cancer through prostatectomy or Transurethral resection of the prostate, between January 2017 and December 2021 in a private hospital in Mexico City, and then performed immunohistochemistry utilizing clone HER2 (4B5). Results: A total of 277 patients with prostate cancer, and finally analyzed a total of 194 patients, reporting an expression of 21.1% of patients, with expression of HER2 1+ in 20.1%, HER2+ 0.5% and HER2 3+ in 0.5% of patients. We found an association between the presence of HER2 and the prognostic group according to Gleason score that the patients were allocated to. Conclusions: Our study shows that expression of HER2 in prostate cancer in Mexican population is more similar than the reported in other countries, and that this biomarker could be used as a prognostic factor. As well, the overexpression of this protein might be used as a targeted therapy, since there is evidence of the use of drugs as fam-Trastuzumab deruxtecan in different types of tumors that have a low expression of HER2, adding a new possible therapeutic weapon in a tumor with limited therapeutic options. Characteristics of patients at baseline. Characteristic n (%) Age at diagnosis (median) - yr 66 (61 – 72) Prostate cancer family history 36 (18.5%) Smoking history 81 (41.75%) BMI Normal 76 (39.18%) Overweight 91 (46.91%) Obesity 25 (12.89%) Previous cancer 10 (5.15%>) Metastasis at diagnosis 8 (4.12%) Grade Group (ISUP) 1 47 (24.23%) 2 51 (26.29%) 3 30 (15.46%) 4 11 (5.67%) 5 53 (27.32%) HER2 Expression No expression 153 (78.9%) 1+ 39 (20.1%) 2+ 1 (0.5%) 3+ 1 (0.5%)