Long-term effects of depot long-acting somatostatin analog octreotide on hormone levels and tumor mass in acromegaly

The effects of a 12- to 24-month treatment with depot long-acting octreotid e (OCT-LAR) on hormone profile, tumor mass, and clinical symptoms were repo rted in 36 patients with active acromegaly [GH, 34.2 +/- 5.6 mug/L; insulin -like growth factor I(IGF-I), 784.5 +/- 40.4 mug/L]. Fifteen patients were de novo whereas 21 had previously undergone unsuccessful surgery. Serum GH (P < 0.0001) and IGF-I levels (P < 0.0001) significantly decreased as early as after the first injection of OCT-LAR and progressively decline d during the 12-24 months of treatment both in de novo and in operated pati ents. At the last follow-up, GH hypersecretion was controlled (less than or equal to2.5 mug/L) in 69.4% whereas normal IGF-I levels were achieved in 6 1.1% of patients. GH and IGF-I suppression during OCT-LAR treatment was sim ilar in de novo and operated patients as shown by nadir GH (2.3 +/- 0.6 vs. 2.2 +/- 0.6 mug/L) and IGF-I (323.1 +/- 34.9 vs. 275.5 +/- 33.0 mug/L), pe rcent suppression of GH (92.7 +/- 2.0 vs. 85.9 +/- 3.3%) and IGF-I (57.4 +/ -: 4.9 vs. 61.5 +/- 4.6%), and prevalence of GH (73.3 us. 76.2%) and IGF-I (53.3 us. 71.4%) control. A decrease in tumor volume was observed in 12 of 15 de novo patients, whereas no shrinkage was detected in 4 of 9 operated p atients. No patient had tumor reexpansion during OCT-LAR treatment. Signifi cant clinical improvement was obtained in all patients; heart rate, systoli c blood pressure, and diastolic blood pressure significantly decreased in t he entire population. A mild but significant increase of blood glucose leve ls, followed by a decrease of serum insulin levels, was observed after 3 mo nths of treatment: this effect subsided with treatment continuation. OCT-LA R treatment was well tolerated by most patients. In conclusion, long-term treatment with OCT-LAR was effective in controllin g GH and IGF-I hypersecretion in most patients with acromegaly, when applie d either as primary therapy or as adjunctive therapy after surgery. Tumor s hrinkage was observed in de novo patients during OCT-LAR treatment, suggest ing that it can be successfully applied as primary therapy in patients bear ing invasive tumors, who are less likely to be cured after surgery.