Efficacy of Sandostatin LAR (long-acting somatostatin analogue) is similar in patients with untreated acromegaly and in those previously treated with surgery and/or radiotherapy.

Abstract

Somatostatin analogues have been used as an adjunct to surgery and radiotherapy in the treatment of acromegaly for over 15 years, but debate surrounds their use as primary therapy. Newman suggested that octreotide was equally effective as primary or adjuvant therapy, but the effects of previous surgery/radiotherapy may have led to a preselection bias. In an attempt to eliminate this bias, the efficacy of the depot somatostatin analogue Sandostatin LAR as primary and adjuvant therapy has been assessed using GH and IGF-I levels at diagnosis as baseline values. We retrospectively analysed the GH and IGF-I data from a large multicentre study in which patients' biochemical response to treatment with the depot somatostatin analogue Sandostatin LAR as primary and adjuvant therapy was assessed. We used GH and IGF-I levels at diagnosis as baseline values to eliminate any preselection bias. In 91 patients (42 male) studied, mean serum GH fell from 36.2 +/- 3.3 micro g/l (SEM) at diagnosis to 2.2 +/- 0.2 micro g/l after 48 weeks of treatment (P < 0.0001). In the primary (n = 34) and adjuvant (n = 57) therapy groups, mean GH fell from 30.7 +/- 5.7 to 2.6 +/- 0.4 micro g/l (P < 0.0001) and from 39.5 +/- 4.1 to 2.0 +/- 0.2 micro g/l (P < 0.0001), respectively. Sixty-two percent of patients in the primary therapy group and 70% in the adjuvant therapy group achieved GH < 2 micro g/l. Serum IGF-I levels were available in 67 patients (34 male). In the primary therapy group (n = 25) mean IGF-I fell from 764 +/- 68 to 414 +/- 31 micro g/l (P < 0.0001) at 48 weeks. In the adjuvant therapy group (n = 42) mean IGF-I was 666 +/- 50 micro g/l, falling to 384 +/- 30 micro g/l (P < 0.0001) at 48 weeks. 72% of patients achieved normal age-related IGF-I-values. There were no statistically significant differences in GH or IGF-I levels between the primary and adjuvant therapy groups at diagnosis, pre Sandostatin LAR or after 48 weeks of treatment. This retrospective study demonstrates that in a group of patients with similar diagnostic GH and IGF-I levels, Sandostatin LAR was equally effective as primary therapy in acromegalic patients as in patients previously treated with surgery and/or radiotherapy.