Since fatigue and dizziness have been observed with the use of letrozole and somnolence was uncommonly reported, caution is advised when driving or using machinery.
Laboratory tests: No dose-related effect of letrozole on any hematological or clinical chemistry parameter was evident. Moderate decreases in lymphocyte counts, of uncertain clinical significance, were observed in some patients receiving letrozole 2.5 mg. This depression was transient in about half of those affected. Two patients on letrozole developed thrombocytopenia; relationship to the study drug was unclear. Patient withdrawal due to laboratory abnormalities, whether related to study treatment or not, was infrequent.
Increases in SGOT, SGPT, and gamma GT ≥5 times the upper limit of normal (ULN) and of bilirubin ≥1.5 times the ULN were most often associated with metastatic disease in the liver.
About 3% of study participants receiving letrozole had abnormalities in liver chemistries not associated with documented metastases; these abnormalities may have been related to study drug therapy. In the megestrol acetate comparative study about 8% of patients treated with megestrol acetate had abnormalities in liver chemistries that were not associated with documented liver metastases; in the aminoglutethimide study about 10% of aminoglutethimide-treated patients had abnormalities in liver chemistries not associated with hepatic metastases.
Bone effects: In the extended adjuvant setting, preliminary results (median duration of follow-up was 20 months) from the bone sub-study (calcium 500 mg and vitamin D 400 IU per day mandatory; bisphosphonates not allowed) demonstrated that at 2 years the mean decrease compared to baseline in hip BMD in letrozole patients was 3% vs. 0.4% for placebo (P=0.048). The mean decrease from baseline BMD results for the lumbar spine at 2 years was letrozole 4.6% decrease and placebo 2.2% (P=0.069).
Consideration should be given to monitoring BMD.
Use in Children: The safety and effectiveness in pediatric patients have not been established.
Use in the Elderly: The median age of patients in all studies of first-line and second-line treatment of metastatic breast cancer was 64-65 years.
About 1/3 of the patients were ≥70 years old. In the first-line study, patients ≥70 years of age experienced longer time to tumor progression and higher response rates than patients <70.
For the extended adjuvant setting, more than 5,100 postmenopausal women were enrolled in the clinical study. In total, 41% of patients were aged 65 years or older at enrollment, while 12% were 75 or older. In the extended adjuvant setting, no overall differences in safety or efficacy were observed between these groups, but greater sensitivity of some older individuals cannot be ruled out.
In the adjuvant setting, more than 8,000 postmenopausal women were enrolled in the clinical study. In total, 36% of patients were aged 65 years or older at enrollment, while 12% were 75 or older. More adverse reactions were generally reported in elderly patients irrespective of study treatment allocation.
However, in comparison to tamoxifen, no overall differences with regards to the safety and efficacy profiles were observed between elderly patients and younger patients.