Résumé
BACKGROUND: Activating PIK3CA mutations occur in 20-30% of patients with metastatic breast cancer (mBC). A recent study showed that alpha selective PI3K inhibitors improve outcome in patients with PIK3CA mutation, HR+/Her2- mBC. There is a need to better understand the natural history of PIK3CA mutant mBC to optimally position of this drug family.
PATIENTS AND METHODS: 649 patients from SAFIR02 trial (NCT02299999), for which mutational profile was available and with clinical data entered in a database, were selected for this analysis. Associations between PIK3CA mutation, clinical characteristics and outcome were analyzed.
RESULTS: 143 patients (22%) harbor PIK3CA mutation in tumor sample. 10% (n=27) and 34% (n=104) of TNBC and HR+/Her2- mBC presented a PIK3CA mutation respectively (p<0.001). In patients with HR+/Her2- mBC, there is no significant association between PIK3CA mutation and site of metastases or number of metastases (p<0.01). In the same group, patients with PIK3CA mutations were less sensitive to chemotherapy (stable disease or response: 51.3% vs. 69.2% in PIK3CA wild type; p=0.005) (Odds ratio multivariate: 0.40 [95% CI: 0.22-0.71] p=0.002). The median overall survival (OS) for patients with PIK3CA mutated HR+/Her2- mBC was of 19.6 months vs. 23.5 for patients with PIK3CA wild type (p=0.048) (HR multivariate: 1.44 [95% CI: 1.02-2.03] p=0.039). HR+/Her2- mBC with PIK3CA mutations presented more frequently a MAP3K1 mutation (16% vs. 4%, p=0.0002). In the TNBC group, the median OS in patients with PIK3CA mutated cancer was of 24.2 months vs. 14 months in the wild type group (p=0.028).
CONCLUSION: Patients with PIK3CA mutated, HR+/Her2- mBC are less sensitive to chemotherapy and present a shorter survival. These data emphasize the need for new therapies in this setting, and to position these therapies earlier than chemotherapy in the treatment sequences.
Citation Format: Fernanda Mosele, Benjamin Verret, Amelie Lusque, Thomas Filleron, Thomas Bachelot, Monica Arnedos, Mario Campone, Florence Dalenc, Claudia Lefeuvre, Marie Paule Sablin, Hervé Bonnefoi, Ludovic Lacroix, Ivan Bièche, Anthony Gonçalves, William Jacot, Marta Jimenez, Amelie Jacquet, Fabrice Andre, Fabrice Andre. Natural history and outcome of patients presenting a metastatic breast cancer with PIK3CA mutation [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 4895.