ESMO Breast 2026: Long-Term Letrozole Therapy Ensures Durable Estrogen Suppression

Lead chemist Bjørn-Erik Bertelsen from the Hormone Laboratory at Haukeland University Hospital in Bergen presented new data at ESMO Breast Cancer 2026 showing that letrozole achieves sustained and clinically complete estrogen suppression in nearly all postmenopausal patients with confirmed drug exposure. The study suggests that insufficient suppression is primarily linked to prolonged lack of exposure or premature transition to AI monotherapy — not biological variability or short treatment interruptions.