PIK3CA mutations may be discordant between primary and corresponding metastatic disease in breast cancer.

Abstract

PURPOSE:

PIK3CA mutations are frequent in breast cancer and activate the PI3K/Akt pathway. Unexpectedly, PIK3CA mutation appears in general to be associated with better outcome. In a cohort of patients where both primary and metastatic lesions were available, the objective was to assess changes in PIK3CA mutations. We wished to discern whether selective pressures occur and the influence of PIK3CA mutation on time to recurrence.

EXPERIMENTAL DESIGN:

Formalin-fixed paraffin-embedded tumor blocks were obtained from 104 patients with paired samples from primary tumors and corresponding asynchronous metastatic breast tumors. Samples were analyzed for PIK3CA mutations (exons 9 and 20) as well as immunohistochemical evaluation for PTEN, pAKT, Ki67, ER, and HER2.

RESULTS:

PIK3CA mutation was detected in 45% of the primary tumors. Overall, there was a net gain in mutation in metastatic disease, to 53%; nonetheless, there were instances where metastases were wild type in patients with PIK3CA mutant primary tumors. Laser capture microdissection on a subset of cases revealed microheterogeneity for PIK3CA mutational status in the primary tumor. PIK3CA mutants overall showed a significantly longer time to first recurrence than wild type cases (P = 0.03).

CONCLUSION:

PIK3CA mutations occur at high frequency in primary and metastatic breast cancer; these may not necessarily confer increased aggressiveness as mutants had a longer time to recurrence. Because PIK3CA status quite frequently changes between primary and metastatic disease, it emphasizes the necessity of assessing the PIK3CA status in the metastatic lesion for selection of PIK3CA inhibitor therapy.

• Authors: Jeanette Dupont Jensen, Anne-Vibeke Laenkholm, Ann Knoop, Marianne Ewertz, Raj Bandaru, Weihua Liu, Wolfgang Hackl, J Carl Barrett, Humphrey Gardner
• Journal: Clinical cancer research : an official journal of the American Association for Cancer Research (Clin Cancer Res) Vol. 17 Issue 4 Pg. 667-77 (Feb 15 2011) ISSN: 1557-3265 [Electronic] United States
• PMID: 20940279 (Publication Type: Comparative Study, Journal Article, Research Support, Non-U.S. Gov't)
• Copyright: ©2010 AACR.

Chemical References

• Intracellular Signaling Peptides and Proteins
• Phosphatidylinositol 3-Kinases
• Class I Phosphatidylinositol 3-Kinases
• PIK3CA protein, human
• PTEN Phosphohydrolase
• PTEN protein, human

Topics

• Breast Neoplasms (drug therapy, genetics, pathology, secondary)
• Class I Phosphatidylinositol 3-Kinases
• Female
• Genetic Association Studies
• Genetic Heterogeneity
• Humans
• Intracellular Signaling Peptides and Proteins (metabolism)
• Logistic Models
• Molecular Targeted Therapy
• Mutation, Missense
• Neoplasm Metastasis
• Neoplasm Recurrence, Local (genetics)
• PTEN Phosphohydrolase (metabolism)
• Phosphatidylinositol 3-Kinases (genetics)