Endocrine Abstracts

Introduction: Primary SMSa treatment can be associated with hormonal remission and tumor shrinkage in patients with GH-secreting pituitary adenomas. In the 2014 Endocrine Society guideline for Acromegaly, there is no specific mention of MRI follow-up during long-term SMSa treatment. The aim of this study was to evaluate any change of GH-secreting adenoma size during primary SMSa treatment and whether regular MRI follow-up was necessary in acromegalic patients treated with first generation long-acting SMSa.

Patients and Methods: In this retrospective and monocentric study we included patients with GH/IGF-1 hypersecretion and GH-secreting pituitary adenomas with normal visual field, primarily treated with first generation long-acting SMSa between 1995 and 2015, and regularly followed (clinical evaluation, GH/IGF-1 levels, pituitary MRI) during at least 3 years. To assess meaningful adenoma change during SMSa therapy, maximal height of the adenoma under the optic chiasm, on coronal T2-weighted MRI, was manually measured by the same radiologist blinded to clinical history, at baseline and at last pituitary MRI of each patient.

Results: We included 83 patients (32 men and 51 women, mean age at diagnosis 50±12 years) with mean GH=19.3±25.6 ng/ml, IGF-1=284±110% ULN and pituitary adenoma height =12.9±4.7 mm. Patients were primarily treated with long-acting lanreotide Autogel (n=67) or octreotide LAR (n=16), and mean follow-up was 8.9±4.9 years in 36 controlled patients (GH<2.5 ng/ml, normalized IGF-1 for age and sex) and 2.0±1.6 years in 47 partially responders (decrease of IGF-1 >10%) to SMSa alone, before association with dopamine agonists/pegvisomant or pituitary surgery. During primary SMSa treatment, no increase of pituitary adenoma height was observed. Pituitary adenoma height decreased significantly in controlled patients (diagnosis: 11.9±4.8 mm, SMSa: 9.6±3.3 mm, P < 0.001), and in partially responders (diagnosis: 13.6±4.5 mm, SMSa: 11.5±4.5 mm, P < 0.001). Controlled patients were older (P < 0.05), had lower mean GH (P < 0.05) or IGF-1 (P=0.05) concentrations, and smaller pituitary adenoma (P < 0.05) at diagnosis.

Conclusion: During long-term treatment with first generation SMSa, no increase of GH-secreting adenoma size was observed. Primary SMSa treatment was associated with a significantly decrease of adenoma height in controlled and in partially responder patients. Therefore MRI follow-up does not seem useful in acromegalic patients responsive to SMSa treatment.