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

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 internals, 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 days - 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 mu g/l (mean +/- S.E.) to 7.2 +/- 1.5 mu g/l (P < 0.02), whereas IGF-I values declined from 959 +/- 95 mu g/l to 460 +/- 61 mu g/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 mu g/l, P < 0.05 compared with LSR) and in IGF-I concentrations (to 374 +/- 60 mu g/l, P < 0.05 compared with LSR, and to 112 +/- 19% as %ULNR), LSR decreased GH concentrations to less than 2.5 mu g/l in one patient and normalized LGF-I concentrations in four patients. OC-LAR decreased GH concentrations to less than 2.5 pg/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-WR administration schedule proved more efficacious than LSR given every 7-21 days, in a greater number of acromegalic patients.