Breast Cancer: PIK3CA Mutation to Predict Chemotherapy Resistance Interview with:
Prof. Dr. med. Sibylle Loibl MD
Unit Head of Medicine & Research
Member of Management Board
Associate Professor University Frankfurt
GBG Forschungs GmbH
 Neu-Isenburg What are the main findings of the study?

Dr. Loibl: We could demonstrate that patients with a HER2+ primary breast cancer harbouring a PIK3CA mutation are less likely to achieve a pathological complete response after treatment with an anthracycline/taxane containing therapy in combination with trastuzumab and lapatinib, than patients whose tumours does not harbour the mutation (so called wild type). This difference was largest in the group with HER2+, HR + tumours. The pCR rate in this cohort was as low as 6.3%.

Looking at the differences in another study with either trastuzumab or lapatinib anti-HER2 treatment is seems as patients with a PIK3CA mutated tumour have a low pCR rate irrespective of the antiHER2 treatment, whereas the patients with a wild type tumour benefit from trastuzumab and the double blockade. Were any of the findings unexpected?

Dr. Loibl: Other investigations from the Neo-Altto study, the Neosphere study and the TRBRC 006 study showed basically similar results and report on pCR rates below 10% for the HER2+, HR+, PIK3CA mutated tumours. What should clinicians and patients take away from your report?

Dr. Loibl: I would not yet recommend to test all HER2+ tumours for PIK3CA mutation status as the data need to be confirmed and alternative treatment options for these patients have not yet been investigated. But I am confident that this will be implemented into clinical practice soon. Current running clinical trials are already stratifying for the PIK3CA mutation status. What recommendations do you have for future research as a result of this study?

Dr. Loibl: We need to further look into the PIK3CA mutation and need to address this issue in prospective clinical trials, trying to optimize the systemic treatment for patients whose tumour harbour a PIK3CA mutation.


PIK3CA mutation predicts resistance to anti-HER2/chemotherapy in primary HER2-positive/hormone receptor-positive breast cancer

Prospective analysis of 737 participants of the GeparSixto and GeparQuinto studies

San Antonio Breast Symposium 2013


Last Updated on December 20, 2013 by Marie Benz MD FAAD