Laboratory Tests: No dose-related effect of Letrozole on any hematologic or clinical chemistry parameter was evident. Moderate decreases in lymphocyte counts, of uncertain clinical significance, were observed in some patients receiving Letrozole tablets 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% 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.
Use in Children: The safety and effectiveness in pediatric patients have not been established.
Use in Elderly: The mean age of patients in the two randomized trials, that compared Letrozole tablets (0.5 mg and 2.5 mg) to megestrol acetate and to aminoglutethimide, was 64 years. Thirty percent of patients were >70 years old. The proportion of patients responding to each dose of Letrozole was similar for women >70 years old and <70 years old.