Background: At present long-acting somatostatin analogs represent the first
-line medical treatment of acromegaly, These drugs produce stable suppressi
on of GH in most sensitive patients and IGF-I normalization in many: they a
lso increase the compliance of acromegalic patients. The recent availabilit
y of octreotide (OC)-LAR, a somatostatin analog to be administered at 28-da
y internals, has prompted us to compare, in the same group of patients, its
effects and those of another somatostatin analog already available, lanreo
tide-SR (LSR, to be administered at 14-day intervals).
Patients: Twelve somatostatin analog-sensitive acromegalic patients with ac
tive disease were enrolled in a prospective open sequential study after giv
ing 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 max
imal GH/IGF-I suppression without any significant hormonal change between t
he last two control measurements. OC-LAR was administered i.m, at 28-day in
tervals six times at the dosage of 20 mg for the first three times and 10 o
r 30 mg for the last three times (according to individual GH/IGF-I response
s!, GH (mean of three, hourly samples) and IGF-I concentrations were evalua
ted on the same day as each administration of the drug, before its injectio
n.
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 ra
nge (%ULNR). At the end of the last cycle, OC-LAR treatment achieved a sign
ificant further suppression both in GH (to 5.1 +/- 1.1 mu g/l, P < 0.05 com
pared 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 concentr
ations to less than 2.5 mu g/l in one patient and normalized LGF-I concentr
ations 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 concentrati
ons (i.e, to < 110%ULNR) in eight patients.
Conclusions: These preliminary results show that the once-monthly OC-WR adm
inistration schedule proved more efficacious than LSR given every 7-21 days
, in a greater number of acromegalic patients.