Letrozole for Lymphangioleiomyomatosis

Lymphangioleiomyomatosis, or LAM, is an uncommon, progressive, cystic lung disease that predominantly affects young women. Pulmonary parenchymal changes consistent with LAM are found in about one third of women with tuberous sclerosis complex (TSC), an autosomal dominant tumor suppressor syndrome. LAM also occurs in a sporadic form that is not associated with germline mutations in TSC genes. Recent evidence that recurrent LAM after lung transplantation results from seeding of the graft from a remote source and suggests a metastatic mechanism for the disease. Since LAM occurs almost exclusively in women, and is exacerbated by pregnancy, menses and hormonal therapies suggest that estrogen suppression might be expected to prevent or delay progression of disease. In postmenopausal women, estrogens are mainly derived from the action of the aromatase enzyme, which converts adrenal androgens (primarily androstenedione and testosterone) to estrone and estradiol. The suppression of estrogen biosynthesis in peripheral tissues can therefore be achieved by specifically inhibiting the aromatase enzyme. Letrozole is a nonsteroidal aromatase inhibitor (inhibitor of estrogen synthesis) that has been shown to be effective in other neoplasms that affect women, such as breast cancer.