Introduction: A growth hormone-secreting pituitary adenoma (GH-PA) increases the risk of complications and death. Its management is determined by MRI data and decrease of insulin-like growth factor-1 (IGF-1) during the octreotide suppression test (OST). Currently, there is evidence that MRI-T2-hypointensive somatotropinoma and high expression of somatostatin receptors type 2 (SSTR2) according to immunohistochemical analysis (IHC) predict high efficacy of somatostatin analogues (SSA).
Objective: To study the relationship of the MR-structure, MR-signal intensity, the SSTR1-5, p53 and Ki-67 expression with the sensitivity of GH-PA to octreotide to assess their predictive value.
Materials and methods: This retrospective study included 34 patients. 15 MRI of pituitary gland, 19 IHC, 29 OST were performed. The average values of the signal intensities of the somatotropinomas areas of 23 adjacent sections on T2-, pre-contrast T1- (preT1) MRI images relative to white and gray matter were calculated. 17 patients received SSA during the last 3 months. Correlation analysis was performed in the STATISTICA 12 program.
Results: High sensitivity to octreotide is associated with a lower average intensity of T2-hypointense plots of adenomas relative to gray matter (r=−0.9) and greater intensities of preT1-hypointensive (relative to gray matter) and preT1-isointensive (relative to white matter) r=0.9 each. However, the combination of preT1-hyperintense plots with preT1-hypointense or T2-iso-intensive zones correlates with reduced suppression of IGF-1 (r=−0.88 and −0.79 respectively). Presence of T2-isointensive and preT1-hypo- and preT1-isointensive plots correlates with a higher concentration of GH before OST (r≥0.83 each), which is a predictor of lower sensitivity to octreotide. High intensity of T2-hyperintense plots relative to gray matter is associated with higher SSA doses (r=0.89), including the simultaneous presence of the T2-hypointensive area (r=0.52). The expression of SSTR2 positively correlates with suppression of IGF-1 after OST (r=0.56). The presence of SSTR2 was strongly associated with lower doses of SSA (r=−0.91). When comparing participants with suppression of IGF-1<30% and 3060%, the latter had higher SSTR2 levels (1.82±1.1 vs 3.00±0.00). p53 expression implies less suppression of IGF-1 (r=−0.57) and higher SSA doses (r=0.77). Ki-67 has a positive correlation with prolactin level (r=0.83). All results are significant (P<0.05).
Conclusion: Hypointense adenoma on T2-weighted images and high concentration of SSTR2 are positive predictors of response to SSA therapy. T2-iso- and T2-hyperintensive, as well as preT1-hypo- and preT1-isointensive sites of adenomas suggest the resistance to SSA. Further research is needed to study this results because of a small sample group of this work.
18 - 21 May 2019
European Society of Endocrinology