A comparison between octreotide-LAR and lanreotide-SR in the chronic treatment of acromegaly

Abstract

Background: At present long-acting somatostatin analogs represent the first-line medical treatment of acromegaly. These drugs produce stable suppression of GH in most sensitive patients and IGF-I normalization in many; they also increase the compliance of acromegalic patients. The recent availability of octreotide (OC)-LAR, a somatostatin analog to be administered at 28-day intervals, has prompted us to compare, in the same group of patients, its effects and those of another somatostatin analog already available, lanreotide-SR (LSR, to be administered at 14-day intervals). Patients: Twelve somatostatin analog-sensitive acromegalic patients with active disease were enrolled in a prospective open sequential study after giving their informed consent. After chronic treatment with LSR (6-24 months), the patients were changed to treatment with OC-LAR, without wash- out. LSR had been administered at individually tailored dosages (30 mg i.m. at 7-21-day intervals, median 10 clays - every 7 days in seven patients, 10 days in two patients, 14 days in two patients and 21 days in one patient) according to GH and IGF-I responses. Disease stability was obtained, as shown by maximal GH/IGF-I suppression without any significant hormonal change between the last two control measurements. OC-LAR was administered i.m. at 28-day intervals six times at the dosage of 20 mg for the first three times and 10 or 30 mg for the last three times (according to individual GH/IGF-I responses). GH (mean of three, hourly samples) and IGF-I concentrations were evaluated on the same day as each administration of the drug, before its injection. Results: GH and IGF-I values were significantly decreased by LSR treatment. GH decreased from 41.6 ± 14.6 μg/l (mean ±S.E.) to 7.2 ± 1.5 μg/l (P<0.02), whereas IGF-I values declined from 959 ± 95 μg/l to 460 ± 61 μg/l (P<0.00001), expressed as absolute values, and from 287 ± 30% to 137 ± 19% expressed as percentage of the upper limit of normal range (%ULNR). At the end of the last cycle, OC-LAR treatment achieved a significant further suppression both in GH (to 5.1 ± 1.1 μg/l, P<0.05 compared with LSR) and in IGF-I concentrations (to 374 ± 60 μg/l, P<0.05 compared with LSR, and to 112 ± 19% as %ULNR). LSR decreased GH concentrations to less than 2.5 μg/l in one patient and normalized IGF-I concentrations in four patients. OC-LAR decreased GH concentrations to less than 2.5 μg/l in four patients and normalized or near-normalized IGF-I concentrations (i.e. to < 110%ULNR) in eight patients. Conclusions: These preliminary results show that the once-monthly OC-LAR administration schedule proved more efficacious than LSR given every 7-21 days, in a greater number of acromegalic patients.