439P - Testing HR+ / HER2- patients with advanced or metastatic breast cancer for identification of tissue mutations in the PIK3CA gene: Results of a national program by the Hellenic Society of Medical Oncology (HeSMO)

Background

PIK3CA mutations have been identified in approximately up to 40% of breast cancer cases and PIK3CA targeting has already been incorporated in treatment algorithms, especially in the second line of ER+/HER2- patients. HeSMO launched a national program to provide PIK3CA mutation testing, which is officially not reimbursed, with the aim to identify mutations in the PIK3CA gene, and, therefore, lead to more therapeutic options.

Methods

All HR+/HER2- patients with a diagnosis of metastatic breast cancer were eligible to participate in this program. The result of the test was obtained using the COBAS® PIK3CA method, a diagnostic test specifically designed to detect mutations in the PIK3CA gene in tumor tissue samples (FFPE) attained by biopsy or surgically, which detects 17 different mutations in the PIK3CA gene, including the most commonly occurring in Exons 9 and 20.

Results

From June 2022 to March 2023, 149 patients from across the country were tested within this program. Sixty one (61) patients (40.94%) were detected with mutation in PIK3CA gene and 88 (59.06%) without mutation (Table). 23 patients had Exon 9 mutations (37.70%), 33 in Exon 20 (54.10%), and 8 had mutations in the remaining Exons 1, 4 and 7 (13.11%). In 1 sample 4 mutations were detected: (Exon 7/9/20), and 2 mutations in another 2 samples (Exon 9: E545X, Q546X and Exons 1/20), while in all other samples just 1 mutation was detected in each.

Table: 439P

PIK3CA mutation results of HeSMO’s program

Conclusions

In our series, 40.94% of the patients tested, were detected with mutations in PIK3CA gene, in accordance with published data. Apart from the significant implications for treatment possibilities in a substantial patients’ population, these results provide valuable epidemiological data and strengthen our efforts for reimbursement of PIK3CA mutation testing in Greece.

Clinical trial identification

Editorial acknowledgement

Legal entity responsible for the study

Hellenic Society of Medical Oncology (HeSMO).

Funding

Has not received any funding.

Disclosure

A. Koumarianou: Financial Interests, Institutional, Research Grant: Merck. G. Kesisis: Financial Interests, Personal, Invited Speaker: Bristol, MSD, Amgen, AZ, Galenica, Pfizer, Ipsen, Sanofi; Financial Interests, Personal, Advisory Board: Gilead, Novartis, Roche, Boehringer. E.A. Sogka: Financial Interests, Institutional, Invited Speaker, Invited speaker in a Greek conference: Merck. N.G. Tsoukalas: Financial Interests, Personal, Invited Speaker: Servier, Leo, Janssen, Ipsen, BMS, Gilead; Financial Interests, Personal, Advisory Board: Pfizer, Merck, Roche. N. Chatzifoti: Financial Interests, Personal, Full or part-time Employment: Hellenic Society of Medical Oncology (HeSMO). All other authors have declared no conflicts of interest.