PI3KCA mutation prevalence and outcome among patients with metastatic breast cancer in Bulgaria treated with first-line endocrine therapy.

Authors

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Radostina Gencheva

MHAT “Nadezhda”, Sofia, Bulgaria, Sofia, Bulgaria

Radostina Gencheva , Savina Hadjidekova , Mila Petrova , Dimo Krustev , Petya Kraleva , Georgi Zhbantov , Nikolay Vladimirov Conev , Dragomir Svetozarov Stoyanov , Jeliazko Iliev Arabadjiev , Eliz Tazimova , Svitlana Bachurska , Ivan Galev , Mariyana Eneva , Mariela Tsvetkova , Rada Staneva , Eleonora Dimitrova , Rossen Hadjiev , Ivan Donev

Organizations

MHAT “Nadezhda”, Sofia, Bulgaria, Sofia, Bulgaria, Genetic Laboratory MHAT “Nadezhda”, Sofia, Bulgaria, MHAT "Nadezhda", Sofia, Bulgaria, Department of Anatomy and Histology, Medical University of Sofia, Sofia, Bulgaria, Medical Oncology Dept, MHAT Nadezhda Hospital, Sofia, Bulgaria, Medical University of Varna, Varna, Bulgaria, UMHAT Sveta Marina EAD, Varna, Bulgaria, Tokuda Hospital Sofia, Sofia, Bulgaria, Acibadeu City Clinic, Sofia, Bulgaria, Department of general and clinical pathology, University Specialized Oncology Hospital, Sofia, Bulgaria, Sofia, Bulgaria, Department of clinical pathology, University Hospital Acibadem City Clinic Tokuda, Sofia, Bulgaria, Hospital Pharmacy MHAT “Nadezhda”, Sofia, Bulgaria, Novartis Oncology, Sofia, Bulgaria, Genetic Laboratory MHAT "Nadezhda", Sofia, Bulgaria, Forensic department, University Hospital Lozenetz, Sofia, Bulgaria, Department of Medical Oncology, Nadezhda Hospital, Sofia, Bulgaria

Research Funding

Pharmaceutical/Biotech Company
Novartis

Background: There are phosphatidylinositol-4,5-biphosphate 3-kinase catalytic subunit alpha (PIK3CA) mutations in 30-40% of hormone receptor-positive (HR+), human epidermal growth factor receptor 2-negative (HER2) tumor samples. Nevertheless, clinical outcomes in this group vary amongst research trials. Methods: We sought to determine the incidence of PIK3CA mutations in Bulgarian patients with metastatic HR+, HER2-negative breast cancer, as well as to evaluate and compare progression-free survival (PFS) in the real world between wild-type (WT) and mutant cohorts. In this multicentric retrospective analysis, 250 tissue samples were collected between 2016 and 2022 from three Bulgarian oncology centers. Qualitative real-time PCR was used to determine the existence of PIK3CA mutations. The median follow-up time was 28 months. Results: The mean age was 57.6±11.6 years for the mutant cohort and 56.5±12.2 for the wild-type cohort (p=0.52). The percentage of patients with visceral metastatic disease was 58.8% (n=147). Postmenopausal patients were 84.3% (n=210). PIK3CA mutation prevalence was 29.2% (n=73). The most prevalent mutation was found in exon 20: H1047R (9.2%). Among all clinicopathological features, we observed only a significant relation between the presence of a mutation and a metastatic stage at diagnosis (p = 0.002). 67.1% of the patients received endocrine therapy (ET) + CDK4/6 inhibitor as first-line therapy, while the remainder receive ET monotherapy. Patients with PIK3CA mutation did not have significantly different median PFS compared to WT patients (32 months (95%, CI: 22-40) versus 24 months ((95%, CI: 21-36) (p=0.45)); HR=0.86 (95%, CI: 0.5-1.3) (p=0.46). In propensity matching score analysis (matched for treatment utilized as a first line ET, menopausal status, and locations of metastatic disease), we confirmed our finding (36 months (95%, CI: 20-40) versus 26 months (95%, CI: 21-38), p = 0.69). Conclusions: We demonstrated that the prevalence of PIK3CA mutations in Bulgarian patients is comparable to that reported in other countries. Our findings suggest that the presence of a PIK3CA mutation has no effect on the efficacy of endocrine therapy of first-line treatment. In summary, our study provides valuable insights into the topic, but limitations including the retrospective design and small sample size suggest that the findings need to be replicated by more robust studies and larger sample sizes to draw definitive conclusions.

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Abstract Details

Meeting

2023 ASCO Annual Meeting

Session Type

Publication Only

Session Title

Publication Only: Breast Cancer—Metastatic

Track

Breast Cancer

Sub Track

Biologic Correlates

Citation

J Clin Oncol 41, 2023 (suppl 16; abstr e13005)

DOI

10.1200/JCO.2023.41.16_suppl.e13005

Abstract #

e13005

Abstract Disclosures