Prognostic significance of PI3K pathway (PI3Kp) dysregulation in metastatic breast cancer (MBC) patients (pts).
566 Background: PI3Kp dysregulation represents a potential target for therapies that are currently being tested in clinical trials. This observational retrospective study aims to evaluate the prognostic implications of PI3Kp dysregulation in MBC. Methods: MBC pts with PI3Kp status assessment from Sep09 to Sep11 were reviewed. PIK3CA mutation status analyzed in paraffin-embedded tissue by DxS PI3K Mutation Test Kit or Sequenom MassARRAY. PTEN status determined by IHC. PI3Kp status: (a) No dysregulation: PIK3CA wt and PTEN normal; (b) PI3Kp dysregulation: PIK3CA mutation (PIK3CAmut) or PTEN low (HScore≤50). Results: 232 MBC pts screened, median age 49.8 (22.9-83.1) and median MBC lines 4 (1-15). Distribution: HR+/HER2- 99 (43%), HER2+ 52 (22%), triple negative 35 (15%), unclassified 46 (20%). Sites of metastasis: visceral 173 (75%), only skin 10 (4%), only bone 49 (21%). PIK3CA status assessed in 174 pts, 53 (22.8%) bearing a mutation (21 exon9, 32 exon20). PTEN status assessed in 229 pts, PTEN low 61 (26.6%). PI3Kp dysregulation in 103/185 pts (55.6%). Time to progression to first line MBC treatment (TTP) and overall survival after MBC diagnosis (OS) are shown. Disease free survival (DFS) and distant-disease free survival (DDFS) in pts initially diagnosed with early breast cancer (n=193) has also been calculated. Conclusions: These results suggest that PI3Kp dysregulation, either by PIK3CA mutation or PTEN low, does not seem to have impact on disease recurrence, response to first line MBC treatment or overall MBC survival.[Table: see text]