CORRELATION OF PIK3CA MUTATIONS WITH CLINICOPATHOLOGICAL FEATURES IN BREAST CANCER

Konference: 2016 XL. Brněnské onkologické dny a XXX. Konference pro nelékařské zdravotnické pracovníky

Téma: XV. Nádory prsu

Číslo abstraktu: XV/187

Autoři: Mgr. Barbora Kubová; Mgr. Jarmila Šimová; RNDr. Magdalena Uvírová; Mgr. Jana Žmolíková; Mgr. Sylva Pitronová; MUDr. Zlatuše Bravencová; MUDr. Iva Tomášková; MUDr. Robert Ondruššek; MUDr. Nina Dvořáčková; Doc.MUDr. Jana Dvořáčková, Ph.D., M.I.A.C

Background:

Breast cancer is the most frequently diagnosed cancer in female. Molecular aberrations in the phosphatidylinositol 3-kinase (PI3K) pathway have been documented across cancers, especially PIK3CA mutations and loss of PTEN. But their prognostic/predictive and therapeutic implications are still controversial.

Methods:

Molecular profiling was performed on 266 breast tumour DNA samples isolated from FFPE. PIK3CA (exons 9 and 20) and AKT1 mutations were determined by primer extension method. Status of HER2 gene expression was evaluated by FISH. Progesterone receptor (PR) and estrogen receptor (ER) status was performed by immunohistochemistry. Correlations between PIK3CA mutations and clinicopathological features were estimated with the chi-squared test (95% CI). Relaps-free survival (RFS) rates, in the subgroup of HER2+ breast cancer patient treated with trastuzumab (neoadjuvant/adjuvant) were calculated, based on the Kaplan-Meier method, and the curves were compared using the log-rank test.

Results:

Frequency of PIK3CA mutations were detected in 25.9% (69/266). Mutation p.E17K in AKT1 gene was detected in 1.9% (3/160). PIK3CA mutations were significantly as­sociated with ER+ (p = 0.0004), PR+ (p = 0.004) and borderly significant with low histopathological grade (p = 0.05). Differences in distribution of PIK3CA mutations were found among breast cancer subtypes (ER+, HER2+ and triple negative, p = 0.00635). In the subgroup of 50 HER2+ patients treated with trastuzumab, better RFS was observed in PIK3CA wild-type patients compared with mutated tumours (p = 0.0001).

Conclusions:

This study confirm high prevalence of PIK3CA mutations and their significant correlation with some clinicopathological characteristics in breast cancer tumour. In the present study, focusing on HER2-positive breast cancer treated with trastuzumab, patients with activating mutations in PIK3CA had a poorer outcome than PIK3CA wild-type cases. Currently, there is no sufficient evidence to recommend routine genotyp i ng of PIK3CA in clinical practice, many studies remain still inconsistent, so further data collection is required to draw a definitive answer.

Supported by TE - The Technology Agency programme "Competence Centres", TE02000058, Center of competence for molecular diagnostics and personalized medicine

Datum přednesení příspěvku: 28. 4. 2016