Plasma cell-free tumor DNA, PIK3CA and TP53 mutations predicted inferior endocrine-based treatment outcome in endocrine receptor-positive metastatic breast cancer

PURPOSE

How to factor both tumor burden and oncogenic genomic mutations as variables to predict the outcome of endocrine-based therapy (ET) in ER-positive/HER2-negative metastatic breast cancer patients (MBC) remains to be explored.

METHOD

Blood samples prospectively collected from 163 ER-positive/HER2-negative female MBC patients, before ET, were used for cell-free tumor DNA (cfDNA) analysis. cfDNA was subjected to next-generation sequencing (NGS) to interrogate oncogenic PIK3CA hotspot and TP53 DNA-binding domain (DBD) mutations, including single nucleotide variants (SNVs) or small insertions and deletions (InDels). The variant calling threshold was set at 0.5%. Progression-free survival (PFS) was measured from the start of the ET treatment to the time of disease progression of the same treatment regimen.

RESULTS

Overall, the median PFS was 8.3 months (95% CI 5.7-11.1 months). The median cfDNA was 38.5 ng (range 4.4-1935 ng). The proportion of patients with PIK3CA and TP53 alterations were 25.1 and 15.3%, respectively. Patients with high total cfDNA (HR 1.74, p = 0.003), PIK3CA mutation (HR 1.74, p = 0.007), and TP53 mutation (HR 1.64, p = 0.047) in liquid biopsy conferred worse outcome after ET. Even for patients with low tumor burden, the detrimental effect of PIK3CA or TP53 mutation remained significant (p < 0.001). For patients with either PIK3CA (p < 0.001) or TP53 mutation (p = 0.004), there was significant positive correlation between allele frequency (AF) and total cfDNA.

CONCLUSION

After adjustment of cfDNA level, PIK3CA and TP53 mutations observed in liquid biopsy exerted detrimental effects on the outcome of ET-based regimens. The AF of PIK3CA or TP53 may be a surrogate marker for PFS.

Neoadjuvant endocrine therapy for luminal breast tumors: State of the art, challenges and future perspectives

Neoadjuvant endocrine treatment (NET) associates to satisfactory rates of breast conservative surgery and conversions from inoperable to operable hormone receptor-positive (HR+)/HER2-negative breast cancer (BC), with less toxicities than neoadjuvant chemotherapy (NACT) and similar outcomes. Hence, it has been proposed as a logical alternative to NACT in patients with HR+/HER2- BC candidate to a neoadjuvant approach. Nevertheless, potential barriers to the widespread use of NET include the heterogeneous nature of patient response coupled with the long duration needed to achieve a clinical response. However, interest in NET has significantly increased in the last decade, owing to more in-depth investigation of several biomarkers for a more adequate patient selection and on-treatment benefit monitoring, such as PEPI score, Ki67 and genomic assays. This review is intended to describe the state-of-the-art regarding NET, its future perspectives and potential integration with molecular biomarkers for the optimal selection of patients, regimen and duration of (neo)adjuvant treatments.