Description of Medical ServiceThe phosphatidylinositol 3-kinase (PI3K)/protein kinase B (AKT)/mammalian target of rapamycin (mTOR) pathway is postulated to be a central oncogenic pathway that regulates cell proliferation, cell metabolism, growth, survival, and apoptosis. Changes in PI3K activity are associated with resistance to endocrine, chemo-, radio-, and anti-HER2 therapies. Phosphatidylinositol-4,5-bisphosphate 3-kinase catalytic subunit alpha (PIK3CA) mutations are reported in up to 45% of hormone receptor-positive (HR+)/human epidermal growth factor receptor 2-negative (HER2-) brea st cancers.
Testing for PIK3CA mutations can be performed on either tissue or plasma samples. Testing for PIK3CA mutation would be preferentially performed using fresh tissue, biopsied at the site of local recurrence or metastasis, but archival tissue could be used instead. The biopsy would typically be performed, and testing requested, by a surgeon or oncologist.
Description of Medical ConditionApproximately 60-70% of breast tumours are HR+/HER2-. While endocrine therapy is the treatment of choice for subjects with HR+ advanced breast cancer, progressive disease ultimately develops in all subjects, either due to primary resistance or relapse/progression following an initial response. Two new classes of targeted compounds (mTOR inhibitors, and cyclin-dependent kinase 4/6 inhibitors) are believed to be effective when combined with endocrine therapy. However, to date no predictive biomarkers have been identified to select patients that would benefit the most from these therapies.
Reason for ApplicationNew MBS item
Medical Service TypeCo-dependent therapeutic
Previous Application Number/sNot Applicable
Consultation SurveyConsultation Survey (PDF 489 KB)
Consultation Survey (Word 70 KB)