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Changes in PIK3CA mutation status are not associated with recurrence, metastatic disease or progression in

L M Arthur1, A K Turnbull, L Renshaw

  • 1Edinburgh Breast Unit, Western General Hospital, Edinburgh, EH4 2XU, UK.

Breast Cancer Research and Treatment
|August 9, 2014
PubMed

Insights

PIK3CA mutations are common in breast cancer but rarely change during recurrence. Acquisition of PIK3CA mutations is not the cause of endocrine resistance, though PTEN loss impacts progression time.

Area of Science:

  • Oncology
  • Molecular Biology
  • Genetics

Background:

  • The phosphatidylinositol-3-kinase (PI3K) pathway is crucial for breast cancer cell growth and survival.
  • PI3K pathway activation, via PIK3CA mutations or PTEN loss, is implicated in endocrine therapy resistance.
  • Understanding PIK3CA mutation dynamics in primary versus recurrent breast cancer is key to addressing treatment resistance.

Purpose of the Study:

  • To investigate changes in PIK3CA mutation status between primary and recurrent breast cancer samples.
  • To determine if PIK3CA mutation acquisition contributes to endocrine therapy resistance.
  • To correlate PIK3CA and PTEN status with recurrence patterns and treatment outcomes.

Main Methods:

  • Profiling of matched primary and recurrent breast cancer samples (n=120) using a qPCR-based assay for PIK3CA mutations.
  • Assessing PTEN protein levels via immunohistochemistry.
  • Characterizing recurrence sites, including local, metastatic, and new primary cancers.

Main Results:

  • PIK3CA mutations were present in 43% of primary and 41% of recurrent tumors.
  • PIK3CA mutation status remained stable in most patients (92%) with local recurrence or metastatic disease.
  • Significant PIK3CA status changes were observed in patients developing new primary cancers (64%).
  • PTEN loss at diagnosis correlated with a shorter time to progression.

Conclusions:

  • PIK3CA mutation status is generally stable in breast cancer, and its acquisition does not drive endocrine resistance.
  • PTEN loss is a significant prognostic marker for shorter progression time in breast cancer patients.
  • These findings provide comprehensive data on PIK3CA status, recurrence, and endocrine resistance.

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