PIK3CA-mutations in breast cancer.

PURPOSE: Phosphatidylinositide-3-kinase (PI3K) regulates proliferation and apoptosis; somatic PIK3CA-mutations may activate these processes. Aim of this study was to determine the prevalence of PIK3CA-mutations in a cohort of early stage breast cancer patients and the association to the course of disease. PATIENTS AND METHODS: From an unselected cohort of 1270 breast cancer patients (PiA, Prognostic Assessment in routine application, NCT01592825) 1123 tumours were tested for the three PIK3CA hotspot-mutations H1047R, E545K, and E542K by qPCR. Primary objectives were the prevalence of somatic PIK3CA-mutations and their association to tumour characteristics. Secondary objective was the association of PIK3CA-mutations to recurrence-free interval (RFI) and overall survival. RESULTS: PIK3CA-mutation rate was 26.7% (300 of 1123). PIK3CA-mutations were significantly more frequent in steroid hormone-receptor (SHR)-positive HER2-negative (31.4%), and G1 and G2 tumours (32.8%). Overall, we did not observe a significant association of PIK3CA-mutations to RFI. In SHR-positive BCs with PIK3CA-mutations, a strong trend for impaired  RFI was observed (adjusted HR 1.64, 95% CI 0.958-2.807), whilst in SHR-negative BCs PIK3CA-mutations were insignificantly associated with improved RFI (adjusted HR 0.49; 95% CI 0.152-1.597). Of note, we observed a significantly detrimental prognostic impact of PIK3CA-mutations on RFI in SHR-positive, HER2-negative BCs if only aromatase inhibitors were administered as adjuvant therapy (adjusted HR 4.44, 95% CI 1.385-13.920), whilst no impact was observed in tamoxifen treated patients. CONCLUSION: This cohort study speficies the overall mutation rate of PIK3CA in early breast cancer. The impact of PIK3CA-mutations on RFI and OS was heterogeneous. Our results suggest that estrogen deprivation failes to be active in case of PIK3CA-mutation.

Factors influencing the agreement on histopathological assessments of breast biopsies among pathologists.

AIMS: It has been recommended that the histopathology results of core biopsies of the breast are categorized according to the B-categorization scheme. We measured the interobserver variability of the B-categorization of core biopsies of the breast. METHODS AND RESULTS: Core biopsies were taken among 765 women at the University of Halle between 2006 and 2008. All histological slides were reviewed in a blinded fashion by two experienced breast pathologists. We calculated observed and chance-corrected agreements (kappa) and 95% confidence intervals (CI). The prevalence of B3-B5 biopsies was 41.6%. The observed and weighted kappa agreement of the five-level B-categorization scheme was 0.87 (95% CI: 0.84 -0.89) and 0.89 (95% CI: 0.89-0.91), respectively. The most frequent disagreement was between B2 and B3 (47 of 103 disagreements, 45.6%). Overall, 49.5% of all disagreements were clinically relevant disagreements that would imply different therapeutic strategies. Agreement was modified by referral group, Breast Imaging Reporting and Data System (BIRADS) level, radiological breast density, imaging guidance and application of immunohistological staining. CONCLUSIONS: Interobserver agreement of the B-categorization scheme was high and was modified by referral status, level of radiological suspicion of breast cancer, breast density, imaging guidance of core biopsies and requirement of additional immunohistological staining.