The following article features coverage from the European Society of Medical Oncology (ESMO) 2017 Congress in Madrid, Spain. Click here to read more of Cancer Therapy Advisor’s conference coverage.

Letrozole plus taselisib, a selective PI3-kinase inhibitor, improved objective response rate (ORR) among postmenopausal women with estrogen receptor–positive, HER2-negative early-stage breast cancer, according to a late-breaking abstract presented at the European Society of Medical Oncology (ESMO) 2017 Congress in Spain.

Previous studies demonstrated that single-agent taselisib and combined treatment with endocrine therapy has activity against PI3KCA-mutant breast cancer. This trial sought to determine if the letrozole and taselisib combination was effective in early-stage breast cancer.

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The phase 2 LORELEI trial ( Identifier: NCT02273973) randomly assigned 334 postmenopausal women with stage I to III, operable early breast cancer to receive letrozole plus taselisib or placebo for 16 weeks followed by surgery. The co-primary endpoints were ORR as measured by MRI and pathologic complete response (pCR) at surgery.

Neoadjuvant treatment with letrozole plus taselisib significantly improved ORR in the overall cohort at 50% compared with 39.3% with letrozole plus placebo (odds ratio [OR], 1.55; 95% CI, 1.00-2.38; P = .049). A similarly significant benefit was observed in the PI3KCA-mutated subanalysis with the taselisib combination compared with letrozole plus placebo (56.2% vs 38%, respectively; OR, 2.03; 95% CI, 1.06-3.88; P = .033).

There was no significant difference in pCR rates in the overall and PI3KCA-mutated cohorts between the combination and placebo groups.

Common grade 3 to 4 adverse events (AEs) included gastrointestinal disorders, infections, and skin/subcutaneous disorders. An AE of special interest was hyperglycemia, which occurred as grade 3 to 4 in 1.2% of patients. AEs resulted in taselisib discontinuations in 10.8% of patients and dose reductions in 11.4% of patients.

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These results suggest that neoadjuvant letrozole plus taselisib improves response rates among women with estrogen receptor–positive, HER2-negative early breast cancer. The authors indicated that comprehensive biomarker analyses are ongoing.

Read more of Cancer Therapy Advisor‘s coverage of the European Society of Medical Oncology (ESMO) 2017 Congress by visiting the conference page.


  1. Saura C, De Azambuja E, Hlauschek D, et al. Primary results of LORELEI: a phase II randomized, double-blind study of neoadjuvant letrozole (LET) plus taselisib versus LET plus placebo (PLA) in postmenopausal patients (pts) with ER+/HER2-negative early breast cancer (EBC). Presented at: European Society of Medical Oncology (ESMO) 2017 Congress; Madrid, Spain: September 8-12, 2017. Abstract LBA10_PR.