Dose and frequency titration of somatostatin analogues in the treatment of acromegaly - an injection of expediency?

Clinical efficacy and safety results for dose escalation of somatostatin receptor ligands in patients with acromegaly: a literature review

Acromegaly is a rare disease with a multifaceted clinical presentation. In 90-95% of patients with acromegaly, the disease is caused by a growth hormone (GH)-secreting pituitary adenoma with elevated GH levels that ultimately induce excessive hepatic secretion of insulin-like growth factor-1 (IGF-1). Somatostatin receptor ligands (SRLs) are considered the standard medical choice for the treatment of acromegaly, and normalization of GH and IGF-1 is attainable with effective therapy. This review aims to summarize the literature relative to SRL dose escalation therapy in patients with acromegaly. A United States National Library of Medicine PubMed search of SRL's was conducted using the following search terms: ((((LAR) OR ATG) OR octreotide) OR lanreotide Autogel) AND acromegaly. Related articles in non peer-reviewed journals were excluded. The rationale and benefits of SRL dose optimization therapy were investigated with emphasis on describing the clinical recognition, treatment, and management of patients with acromegaly. We found that dose escalation could provide additional biochemical control of acromegaly in patients who are inadequately controlled with conventional starting doses of octreotide LAR and lanreotide Autogel(®). Furthermore, patients should routinely have their GH and IGF-1 levels closely monitored and their SRL dose increased or decreased thereafter according to individual response.

Control of IGF-I levels with titrated dosing of lanreotide Autogel over 48 weeks in patients with acromegaly

BACKGROUND

An essential criterion for control of acromegaly is normalization of IGF-I levels. Somatostatin analogues act to suppress IGF-I and GH levels.

OBJECTIVE

To assess the efficacy and safety of 48 weeks titrated dosing of lanreotide Autogel.

DESIGN

Open-label, multicentre, phase III, 48-week trial.

METHODS

Patients with active acromegaly (IGF-I levels > 1.3 times upper limit of age-adjusted normal range) were recruited. Twelve injections of lanreotide Autogel were given at 28-day intervals: during the 16-week fixed-dose phase, patients received 90 mg; in the 32-week dose-titration phase, patients received 60, 90 or 120 mg according to GH and IGF-I levels. Intention-to-treat analysis was performed to determine the proportion of patients with normalized age-adjusted IGF-I levels at study end. Secondary evaluations included GH levels, clinical acromegaly signs and safety.

RESULTS

Fifty-seven of 63 patients completed the study. Lanreotide Autogel resulted in normalized age-adjusted IGF-I levels in 27 patients (43%, 95% CI 31-55). Mean GH levels decreased from 6.2 to 1.5 microg/l at study end, with 53 of 62 patients (85%) having GH levels < or = 2.5 microg/l (95% CI 76.7-94.3) and 28 of 62 patients (45%) with levels < 1 microg/l (95% CI 32.8-57.6). Twenty-four (38%) had both normal IGF-I levels and GH levels < or = 2.5 microg/l. Acromegaly symptoms reduced significantly in most patients throughout the study. The most common adverse events were gastrointestinal, as expected for somatostatin analogues.

CONCLUSIONS

Using IGF-I as primary end-point, 48 weeks lanreotide Autogel treatment, titrated for optimal hormonal control, controlled IGF-I and GH levels effectively, reduced acromegaly symptoms and was well tolerated.

Systematic dose-extension of octreotide LAR: the importance of individual tailoring of treatment in patients with acromegaly

OBJECTIVE

The depot long-acting somatostatin analogue octreotide LAR (LAR) provides effective and well-tolerated treatment for acromegaly. Despite a 4-weekly recommended injection frequency, prolonged duration of GH suppression has been observed in some patients following treatment with long-acting somatostatin analogues. The aim of our study was to perform a prospective systematic study to determine whether extending the interval between doses of LAR allows maintenance of 'safe' GH in selected patients with acromegaly.

PATIENTS AND METHODS

Twenty-two patients (15 men, seven women), mean age 58.9 years (35-81 years) with active acromegaly (mGH > 5 mU/l), requiring treatment were selected to receive treatment with LAR. Eleven patients had received previous treatment with both transsphenoidal surgery and radiotherapy, while six had received surgery alone. All patients were commenced on treatment with 20 mg LAR intramuscularly (i.m.) every 4 weeks. Mean GH (mGH) was measured after three consecutive injections immediately prior to the fourth injection. The dose frequency was systematically reduced after every four injections if mGH < 5 mU/l. Once mGH > 5 mU/l, the dose frequency was increased and mGH reassessed.

RESULTS

The dosing interval was successfully increased to greater than 4 weeks in 20/22 patients (90.9%). Six of 22 (27.3%) were receiving injections every 8 weeks and 3/22 (13.6%) every 12 weeks. GH and IGF-I were lower on treatment compared with baseline (P < 0.01). There was no difference in individual mGH and IGF-I between the values on 4-weekly dosing and those at final dose frequency. There was no relationship between final dose frequency and either mean GH or IGF-I prior to LAR, patient age, or previous treatment. The percentage suppression following 100 micro g octreotide subcutaneously did not predict subsequent dose frequency of LAR. The drug cost if patients had continued at 4-weekly intervals would be UK pound 187 850, compared with UK pound 101 065 for the individually titrated dose frequency (P < 0.01). This represents a final cost of 53.8% of the 4-weekly injection price.

CONCLUSION

Individual tailoring of LAR administration maintains control of acromegaly, with reduced injection frequency and improved cost-effectiveness.