PIK3CA Mutation Predicts Worse Outcomes in HER2+ Breast Cancer

The study covered in this summary was published as a preprint on ssrn.com and has not yet been peer reviewed.

Key Takeaway

Researchers observed that PIK3CA mutation was significantly associated with a lower pathologic complete response rate in patients with HER2-positive breast cancer who had received neoadjuvant therapy.
In the metastatic setting, PIK3CA mutation also predicted a worse objective response rate, progression-free survival, and time-to-progression.

Why This Matters

PIK3CA mutation occurs frequently in HER2-positive disease (20%–25% of patients), yet the evidence surrounding its significance on cancer or treatment outcomes remains unclear.
This meta-analysis suggests PIK3CA mutation does, in fact, affect patient outcomes.

Study Design

The researchers searched PubMed, Embase, and the Cochrane Library Central Register of Controlled Trials databases for studies with data on patients with a PIK3CA mutation and various outcome measures in those with HER2-positive breast cancer who had received anti-HER2 therapy.
Overall, the researchers identified 43 studies that included 11,099 patients with known PIK3CA mutation status.

Key Results

PIK3CA mutation was associated with a lower pathologic complete response rate in the neoadjuvant setting (odds ratio [OR], 0.23; P < .001); the significant association held whether patients received single- or dual-agent anti-HER2 therapy and regardless of hormone receptor status.
However, regarding disease-free survival, the authors found no significant association in the adjuvant or neoadjuvant setting.
In the metastatic setting, PIK3CA mutation predicted significantly worse objective response rate (OR, 0.26; P < .001), progression-free survival (hazard ratio [HR], 1.28; P = .024) and time-to-progression (HR, 2.27; P < .001); but the authors did not find a significant association between PIK3CA mutation and overall survival.

Limitations

The anti-HER2 agents administered in each study and methods of assessment of PIK3CA mutation were not uniform.
The number of studies included in several pooled analyses was small.

Disclosures

The study was supported by grants from the National Natural Science Foundation of China, the Sun Yat-Sen University Clinical Research Program, the Guangdong Medical Science and Technology Program, and the Tencent Charity Foundation.
The authors declared no conflicts of interest.

This is a summary of a preprint research study, “Clinical Significance of PIK3CA Mutation in Primary HER2-Positive Breast Cancer Treated with Anti-HER2 Therapy: A Systematic Review and Meta-Analysis.” The study was published as a preprint and has not been peer reviewed. The full text can be found at ssrn.com.

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