McCune-Albright syndrome and acromegaly: Effects of hypothalamopituitary radiotherapy and/or pegvisomant in somatostatin analog-resistant patients

Background: Acromegaly, which may be present in patients with McCune-Albright syndrome (MCAS), in association with cafe-au-lait spots, precocious puberty, and fibrous dysplasia, is often difficult to treat surgically because skull base bone dysplasia prevents the removal of the pituitary adenoma. Somatostatin analogs (SAs) generally give only partial responses. The use of radiotherapy (RT) is controversial because of a possible risk of bone sarcomatous transformation. Aim: This study was a retrospective analysis of the efficacy and adverse effects of different treatment modalities in six patients with both MCAS and acromegaly. Patients and Methods: Because surgery was impossible and SA failed to normalize GH/IGF-I hypersecretion, five of the six patients received fractionated RT (45-55 Grays). Three patients (two with previous RT) were also prescribed pegvisomant. We analyzed the clinical features of acromegaly, GH, and IGF-I concentrations and bone radiological features. Results: GH and IGF-I concentrations fell after RT (median followup, 5 yr; range, 0.5-9 yr). Symptoms of acromegaly improved in parallel. Bone sarcomatous transformation was only noted in one patient in a region (the mandible) outside the radiation field. RT alone and/or combined with SA failed to normalize GH/IGF-I levels in the five patients concerned. In contrast, IGF-I levels normalized very rapidly (5-9 months) in the three patients receiving pegvisomant (10-20 mg/d). Conclusion: RT may be an option for the treatment of acromegaly in patients with MCAS when surgery is impossible and SA therapy is ineffective. However, although no bone sarcomatous transformation was observed within the radiation field in this series, this risk cannot be ruled out. As shown in this small series of severely affected patients, pegvisomant therapy may thus be useful to normalize IGF-I levels rapidly.