Effects of Letrozole on Precocious Puberty Due to McCune Albright Syndrome
Status:
Completed
Trial end date:
2009-05-18
Target enrollment:
Participant gender:
Summary
This study will test the safety and effectiveness of letrozole in treating precocious (early)
puberty in girls with McCune-Albright syndrome (MAS). The physical changes of puberty, such
as breast enlargement, menstruation and growth spurt, as well as the emotional changes of
this developmental stage, usually begin in girls between the ages of 8 and 14. Girls with
MAS, however, often begin puberty before age 7. In MAS, large ovarian cysts produce high
levels of estrogens (female hormones) that cause the changes of puberty. Children with MAS
also have polyostotic fibrous dysplasia (PFD), a disease of bones that, depending on what
parts of the skeleton are affected, can lead to broken bones or disfigurement of the head,
face, arms and legs, or can cause pressure on nerves and blood vessels. Many children with
MAS have cafe-au-lait spots (increased pigmentation) on areas of their skin as well.
Letrozole is an estrogen-lowering drug that has been approved for treating women with breast
and other cancers. Although the drug has not been tested or approved for use in children,
some pediatric specialists have given it to girls with precocious puberty and MAS and found
that it improves their condition without harmful side effects. This study will examine
whether letrozole can lower estrogen in girls with MAS and arrest puberty. It will also study
the drug's effects on substances involved in bone growth, including calcium, phosphate and
amino acids.
Girls 1 to 8 years old with MAS may be eligible for this study. Patients who were enrolled in
NIH protocol 98-D-0145 (Screening and Natural History of Patients with Polyostotic Fibrous
Dysplasia and the McCune-Albright syndrome) are also eligible. Participants will be admitted
to the hospital for 2 to 3 days every 3 months for 15 months, for a total of 6 visits. They
will undergo a complete history and physical examination and routine blood and urine tests
every visit, as well as evaluations of their general health, growth and bone development,
endocrine system (hormone-secreting glands) status and PFD status. A hand X-ray will be taken
at the first visit and every 6 months to measure bone age advance. The children will begin
taking letrozole at the second visit and continue the drug for 6 months. They will be
evaluated after 3 months and 6 months on the drug (visits 3 and 4), and again after 3 months
and 6 months after stopping treatment (visits 5 and 6).
Parents of children who weigh more than 18 kilograms (about 40 pounds) may be asked if extra
blood may be drawn after 3 months (visit 3) and 6 months (visit 4) of treatment to measure
letrozole levels. The blood will be drawn before the morning dose and at 0.5, 1, 1.5, 2, 3,
4, 6, 8, and 24 hours after the dose through an indwelling needle placed in the vein for 8 to
24 hours.
Parents will keep a record of all episodes of menstrual bleeding and any other symptoms or
complaints. Children who respond well to therapy (decreased menses, slowed breast
development, slowed growth and bone age advance) will be offered another 12 months of
letrozole treatment.
Phase:
Phase 1
Details
Lead Sponsor:
National Institute of Dental and Craniofacial Research (NIDCR)