GH and IGF-I levels and tumor shrinkage in response to first generation somatostatin receptor ligands in acromegaly: a comparative study between two reference centers for pituitary diseases in Brazil

Purpose To compare biochemical and tumor response rates between two reference centers for pituitary diseases in Brazil after primary and adjuvant therapy with somatostatin receptor ligands (SRL) in acromegaly. Methods Patients were classified as non-responders (NR), partial responders (PR), and full responders (FR) to 12-month SRL therapy according to: [criteria A] normal IGF-I and random GH (rGH) < 1 ng/mL (FR); >= 50% decrease of IGF-I and/or rGH (PR); < 50% decrease of IGF-I and rGH (NR); [criteria B] normal IGF-I (FR); >= 50% decrease of IGF-I (PR); < 50% decrease of IGF-I (NR). Tumor shrinkage <20% defined poor responders (tPR) and >= 20% good responders (tGR). Results We studied 219 acromegaly patients (59% women, age 43.1 +/- 13.9 years; 73 from Center I and 146 from Center II). After SRL therapy, the proportion of FR, PR, and NR by criteria A and B was 30.2 vs 49.1%, 52.8 vs 21.2% and 17 vs 29.7%, respectively (p < 0.001). Considering criteria A or B separately, there was no difference in the proportion of FR, PR and NR between two centers. However, when comparing criteria A and B, the Center I showed a difference of 30.9% in classification of FR in relation to 13.2% observed in Center II (p = 0.006). tGR were 51.4% of patients, with no differences between the centers. Conclusions IGF-I alone significantly increased positive response rates to SRLs, whereas the inclusion of rGH levels into therapeutic decision might lead to a significant increment on the costs of acromegaly management.

Automated summary

This study aimed to compare biochemical and tumor response rates between two reference centers for pituitary diseases in Brazil after primary and adjuvant therapy with somatostatin receptor ligands (SRL) in acromegaly. The results showed that there was no difference in the proportion of good responders in tumor shrinkage between the two centers when considering only IGF-I levels, but significant difference was found in the classification of full responders when both IGF-I and rGH levels were taken into account, with Center I showing a higher discrepancy.