RESUMO
PIK3CA mutation frequency varies among breast cancer (BC) subtypes. Recent evidence suggests combination therapy with the PI3K inhibitor (PI3Ki) alpelisib and endocrine therapy (ET) improves response rates and progression-free survival (PFS) in PIK3CA-mutant, hormone receptor positive (HR+) BC versus ET alone; thus, better understanding the clinical and epidemiologic elements of these mutations is warranted. This systematic review characterizes the PIK3CA mutation epidemiology, type of testing approaches (e.g., liquid or tissue tumor biopsy), and stability/concordance (e.g., consistency in results by liquid versus solid tumor sample, by the same method over time) in patients with HR+/HER2- advanced (locally unresectable) or metastatic disease (HR+/HER2- mBC) and explores performance (e.g., pairwise concordance, sensitivity, specificity, or predictive value) of respective mutation findings. A comprehensive search of PubMed/MEDLINE, EMBASE, Cochrane Central, and select conference abstracts (i.e., AACR, ASCO, SABCS, ECCO, and ESMO conferences between 2014 and 2017) identified 39 studies of patients with HR+, HER2- mBC. The median prevalence of PIK3CA mutation was 36% (range: 13.3% to 61.5%); identified testing approaches more commonly used tissue over liquid biopsies and primarily utilized next-generation sequencing (NGS), polymerase chain reaction (PCR), or Sanger sequencing. There was concordance and stability between tissues (range: 70.4% to 94%) based on limited data. Given the clinical benefit of the PI3Ki alpelisib in patients with PIK3CA mutant HR+/HER2- mBC, determination of tumor PIK3CA mutation status is of importance in managing patients with HR+/HER2- mBC. Prevalence of this mutation and utility of test methodologies likely warrants PIK3CA mutation testing in all patients with this breast cancer subtype via definitive assessment of PIK3CA mutational status.
RESUMO
PIK3CA mutations may have prognostic value for patients with hormone receptor-positive/human epidermal growth factor receptor 2-negative metastatic breast cancer, representing an important potential target for systemic therapy. Prognostic and predictive values associated with PIK3CA mutations are not well understood. A comprehensive search of PubMed/MEDLINE, EMBASE, Cochrane Central, and conference abstracts was performed for English-language articles published January 1993 through April 2019. Articles were categorized by treatment arms based on experimental and treatment drug classes. Information on progression-free survival (PFS), hazard ratios, overall survival, response rate, and clinical benefit rate was obtained. A total of 17 studies were included. Among those evaluating non-PI3Ki based therapies, 91% showed numerically shorter median PFS, ranging from 1.5 to 19.2 months and 1.8 to 29.6 months for the mutant versus non-mutant subgroups, respectively. Where reported (n = 13 studies), PFS was shorter between those arms offering endocrine monotherapy (range, 1.6-14.7 months) compared with a corresponding targeted therapy + endocrine monotherapy (range, 3.9-29.6 months). Of 5 PI3Ki-based arms comparing PFS, higher median PFS in PIK3CA mutant versus non-mutant cases was demonstrated. PFS was shorter for patients with PIK3CA mutant (range, 1.6-19.2 months) compared with PIK3CA wild-type (range, 1.8-29.6 months) in 10 (71%) of 14 treatment arms reporting PFS. Studies (n = 4) not reporting PFS reported response rate, but there were no clear directional trends. The presence of PIK3CA mutations may be associated with worse clinical outcomes in patients with hormone receptor-positive/human epidermal growth factor receptor 2-negative metastatic breast cancer. Clinical outcomes such as PFS may be improved using a combination of PI3Ki-based therapies and endocrine therapies among this population. However, more research is warranted to fully elucidate this association.