Patients and methods
amenorrhea, Cancer
CANCER
This study was carried out at the Helsinki University Central Hospital Comprehensive Cancer Center from October 2015 to January 2017. Eligible patients were postmenopausal women with hormone receptor-positive early-stage breast cancer for whom adjuvant letrozole treatment was planned. Prior adjuvant chemotherapy was not allowed. The patients were classified as postmenopausal if they were either ≥ 60 years of age or had a history of amenorrhea for at least 12 months with serum E2 and FSH levels within the postmenopausal range. Adjuvant treatment with letrozole 2.5 mg daily was started in all patients.The levels of E2 and FSH were analyzed by a solid-phase, enzyme-labeled chemiluminescent immunoassay in an Immulite 2000 Xpi analyzer (Siemens Healthineers, Tarrytown, NY USA) at three and 12 months during letrozole treatment. After the completion of the trial the levels of serum E2 and E1 were studied by a highly sensitive LC–MS/MS using duplicate serum samples taken at the same time as routine monitoring samples during baseline and at three and 12 months of letrozole treatment and stored in a deep freezer (− 80 C) until analysis.The patients filled structured QoL and side-effect questionnaires at the start of letrozole treatment and after 12 months. The scores at the start of treatment and after 12 months were calculated.The study was approved by the local ethics committee at the Helsinki University Hospital. Informed consent was obtained from each participant.