Effects of lanreotide SR and Autogel on tumor mass in patients with acromegaly: a systematic review

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.