Predictors of tumor shrinkage after primary therapy with somatostatin analogs in acromegaly: a prospective study in 99 patients.

CONTEXT: Primary treatment with depot octreotide and lanreotide induces tumor shrinkage in newly diagnosed patients with acromegaly.

OBJECTIVE: The objective of the study was to evaluate clinical predictors of tumor shrinkage.

DESIGN: This was an analytical, observational, open, prospective study.

SUBJECTS: The study included 99 patients: 13 with microadenoma and 86 with macroadenoma (25 enclosed, 32 extrasellar, 29 invasive).

MAIN OUTCOME MEASURES: Age, gender, estimated disease duration, body mass index, GH and IGF-I levels, and tumor volume at diagnosis and after 12 months of treatment were measured. Percentage of GH, IGF-I, and tumor size changes from baseline were also analyzed. Tumor changes were scored as absent (+/- 0-25%), mild (+/- 25.1-50%), moderate (+/- 50.1-75%), or notable (75%).

INTERVENTIONS: Sixty patients (60.6%) received depot octreotide im (20-30 mg every 28 d), and 39 patients (39.4%) received lanreotide im (60-90 mg every 28 d).

RESULTS: Basal tumor volume and maximal tumor diameter correlated with age, disease duration, and GH levels. After 12 months, GH levels were controlled (
CONCLUSIONS: Most patients with acromegaly (75.5%) had 25% or greater tumor shrinkage after 12 months of primary somatostatin analog therapy: significant increase of tumor mass occurred in only 2.1% of patients (uncontrolled during treatment). Best predictor of tumor shrinkage was posttreatment IGF-I.