PIK3CA Mutation in the ShortHER Randomized Adjuvant Trial for Patients with Early HER2+ Breast Cancer: Association with Prognosis and Integration with PAM50 Subtype.

Valentina Guarneri, Maria Vittoria Dieci, Giancarlo Bisagni, Alba A Brandes, Antonio Frassoldati, Luigi Cavanna, Antonino Musolino, Francesco Giotta, Anita Rimanti, Ornella Garrone, Elena Bertone, Katia Cagossi, Oriana Nanni, Federico Piacentini, Enrico Orvieto, Gaia Griguolo, Matteo Curtarello, Loredana Urso, Laia Paré, Nuria ChicRoberto D'Amico, Aleix Prat, Pierfranco Conte

Research output: Contribution to journalArticlepeer-review

Abstract

PURPOSE: We explored the prognostic effect of PIK3CA mutation in HER2+ patients enrolled in the ShortHER trial.

PATIENTS AND METHODS: The ShortHER trial randomized 1,253 patients with HER2+ breast cancer to 9 weeks or 1 year of adjuvant trastuzumab combined with chemotherapy. PIK3CA hotspot mutations in exon 9 and 20 were analyzed by pyrosequencing. Expression of 60 genes, including PAM50 genes was measured using the nCounter platform.

RESULTS: A mutation of the PIK3CA gene was detected in 21.7% of the 803 genotyped tumors. At a median follow-up of 7.7 years, 5-year disease-free survival (DFS) rates were 90.6% for PIK3CA mutated and 86.2% for PIK3CA wild-type tumors [HR, 0.84; 95% confidence interval (CI), 0.56-1.27; P = 0.417]. PIK3CA mutation showed a favorable prognostic impact in the PAM50 HER2-enriched subtype (n = 232): 5-year DFS 91.8% versus 76.1% (log-rank P = 0.049; HR, 0.46; 95% CI, 0.21-1.02). HER2-enriched/PIK3CA mutated versus wild-type tumors showed numerically higher tumor-infiltrating lymphocytes (TIL) and significant upregulation of immune-related genes (including CD8A, CD274, PDCD1, and MYBL2, a proliferation gene involved in immune processes). High TILs as well as the upregulation of PDCD1 and MYBL2 were associated with a significant DFS improvement within the HER2-enriched subtype (HR, 0.82; 95% CI, 0.68-0.99; P = 0.039 for 10% TILs increment; HR, 0.81; 95% CI, 0.65-0.99; P = 0.049 for PDCD1 expression; HR, 0.72; 95% CI, 0.53-0.99; P = 0.042 for MYBL2 expression).

CONCLUSIONS: PIK3CA mutation showed no prognostic impact in the ShortHER trial. Within the HER2-enriched molecular subtype, patients with PIK3CA mutated tumors showed better DFS versus PIK3CA wild-type, which may be partly explained by upregulation of immune-related genes.

Original languageEnglish
Pages (from-to)5843-5851
Number of pages9
JournalClin. Cancer Res.
Volume26
Issue number22
DOIs
Publication statusPublished - Nov 15 2020

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