Key clinical point: Extended intermittent and continuous letrozole yield similar disease-free survival in postmenopausal women with hormone receptor (HR)-positive breast cancer. Circulating estrogen levels were restored after letrozole interruption.
Major finding: There was no difference in 7-year disease-free survival between intermittent and continuous letrozole groups ( P = 0.64). The median change in estradiol levels after letrozole interruption was 141% vs. 2.2% with continuous letrozole during the same duration.
Study details: The Study of Letrozole Extension ( SOLE) trial was an open-label, phase 3 study of 4,884 postmenopausal women with HR-positive, lymph node-positive, operable breast cancer, randomly assigned to extended intermittent or continuous letrozole. The SOLE-EST sub study (n=104) evaluated changes in circulating estrogen levels.
Disclosures: SOLE study was supported by Novartis and the International Breast Cancer Study Group. SOLE-EST was partially funded by the Belgian Foundation Against Cancer, Breast Cancer Trials Australia and New Zealand, and Susan G. Komen for the Cure. The authors received research support, honoraria, nonfinancial support, advisory/consulting/travel fees, and/or salary from various sources.
Source: Jerusalem G et al. Ann Oncol. 2021 Aug 9 (in press). doi: 10.1016/j.annonc.2021.07.017 .