Long-acting
somatostatin analogs (SSA) are widely used for the treatment of
acromegaly achieving biochemical control of the disease in 50-75% of the patients. One of the goals of the treatment of
acromegaly is the control of
tumor growth, especially in patients in whom SSAs are used as first-line
therapy. Over the recent years, there has been growing evidence that SSAs are able to induce
tumor shrinkage in patients with
acromegaly. However, most of the data are from patients under treatment with
octreotide, either subcutaneously or intramuscularly with long-acting formulation, whereas the data on
lanreotide SR or Autogel are very few. Indeed,
octreotide and
lanreotide, i.e. the two commercially available SSAs, show slight differences in pharmacokinetics and patterns of receptor affinities with potentially different
therapeutic effects. We aimed to perform a systematic review of literature data concerning the shrinkage effects of long-acting
lanreotide in patients with
acromegaly. The analysis was focused on the following issues: differences in shrinkage effects between primary and secondary medical treatment, predictive value of baseline
tumor volume and correlation between biochemical control and shrinkage effects. The peer-reviewed medical literature was searched to identify clinical trials studying the effects of
lanreotide SR or Autogel on
adenoma size in
acromegaly. To be included in this analysis, studies had one of the following designs: randomized controlled trial; prospective, nonrandomized trial; retrospective study. Twenty-two studies were found to be eligible for the final analysis, in which
tumor size was measured as an end-point for
lanreotide treatment. Overall a total of 32.8% of patients experienced a variable degree (from 10 to 77%) of
tumor shrinkage during
lanreotide SR or Autogel treatment. The analysis showed that
tumor shrinkage was more frequent in naïve patients as compared with those previously treated by
radiotherapy, surgery or drugs other than
lanreotide. The data on the correlation between
tumor shrinkage and baseline
tumor size were discordant, but when baseline
tumor size was specified, more than 80% of patients undergoing shrinkage under
lanreotide Autogel had macroadenomas. Finally, with
lanreotide Autogel there was no evident correlation between biochemical response and
tumor shrinkage. Our systematic review of the literature shows that
lanreotide particularly when used as first-line
therapy is able to quite frequently induce
tumor shrinkage in patients with
acromegaly. This finding suggests that this
drug may have a role in the primary treatment of
acromegaly.