Discussion
pain, muscle pain, breast cancer
SECONDARY, BREAST CANCER
The aim of the present study was to analyze the effects of letrozole on serum estradiol (E2) and estrone (E1) levels in postmenopausal breast cancer patients by using a highly sensitive and specific LC–MS/MS method. Quality of life and tolerability of the treatment were secondary outcome measures.AIs suppress plasma estrogen levels in postmenopausal women. At menopause, mean plasma E2 levels vary from 10 to 60 pmol/L [As expected, mean E2 levels measured by routine chemiluminescent immunoassay were higher than levels obtained with LC–MS/MS. E2 measured by immunoassay at three or 12 months did not differ compared to baseline levels which is in line with our findings from a previous study [Baseline levels for E1 measured by a sensitive LC–MS/MS ranged from less than 5 pmol/L (LLOQ < 5 pmol/L) to 226 pmol/L with a mean of 66 pmol/L. Levels of serum E1 also decreased below the LLOQ level in 89 of 90 patients during letrozole treatment. Only in one patient, serum E1 level remained above 5 pmol/L at three months and decreased below LLOQ at 12 months.Adjuvant AI treatment is recommended for at least five years and extended treatment for up to ten years especially for patients with high-risk features [There was no change in global health status, and all functional scales scores remained stable during the first year of adjuvant letrozole treatment. The reported overall QoL was higher than 70 points and all functional scales were higher than 80 points, which is similar to the QoL of the general population [Women with higher pre-treatment E2 levels experienced more joint and muscle pain during letrozole treatment. However, we did not find any association between pre-treatment hormone levels and the other significant side-effects. The relationship between sensitivity to pain and estrogen levels is poorly understood. However, pain sensitivity decreases during high estrogen phases of the menstrual cycle [The main strength of the current study is the use of the sensitive LC–MS/MS estrogen assay for monitoring changes in the levels of postmenopausal E2 during AI treatment. Another strength is the systematic assessment of QoL and symptoms with relevant questionnaires during AI treatment. Limitations include the relatively small number of patients, the lack of a control group, and the short one- year follow-up time.