A. Ramos-Navas (San Cristóbal de La Laguna, Spain)
Hospital Universitario de CanariasAuthor Of 1 Presentation
32P - PIK3CA exon 9 and 20 mutations in early luminal breast cancer. Case series and review of the literature.
Abstract
Background
PI3K/AKT/mTOR pathway is frequently altered in breast cancer. PIK3CA mutations have been described in up to 40% of luminal breast carcinomas. Mutations located in two hotspots in exons 9 and 20 (codons 545, 546 and 1074) account for more than 85% of all point mutations in this gene. PIK3CA alterations have been shown to be related with endocrine therapy resistance.
Methods
We have searched for mutations on PIK3CA exons 9 and 20 in a set of 166 luminal, treatment naive, breast cancer cases. DNA was extracted from paraffin embedded tissue from the primary tumor. We used a previously published pyrosequencing protocol by Nosho et al (Neoplasia, 2008). We reviewed current literature on early breast cancer and sistemic therapy resistance.
Results
26.5% (44 samples) of all the cases in our serie was mutant for either exons 9 or 20. Mutation distribution showed codon 1074, exon 20, as the most frequently mutated (16.87%). H1047R was the most common change seen. PIK3CA mutations have been commonly considered an adquired resistance mechanism to endocrine therapy. Its importance on early breast cancer development and treatment selection has not been deeply explored.
Conclusions
PIK3CA mutations are common in luminal breast cancer. These changes also occur among treatment naive patients. The role of such alterations in the natural history of the disease and its role on primary resistance to endocrine therapy remains to be determined.
Legal entity responsible for the study
The authors.
Funding
Has not received any funding.
Disclosure
All authors have declared no conflicts of interest.