T2-weighted MRI signal predicts hormone and tumor responses to somatostatin analogs in acromegaly

Abstract

GH-secreting pituitary adenomas can be hypo-, iso-or hyper-intense on T2-weighted MRI sequences. We conducted the current multicenter study in a large population of patients with acromegaly to analyze the relationship between T2-weighted signal intensity on diagnostic MRI and hormonal and tumoral responses to somatostatin analogs (SSA) as primary monotherapy. Acromegaly patients receiving primary SSA for at least 23:113 months were included in the study. Hormonal, clinical and general MRI assessments were performed and assessed centrally. We included 120 patients with acromegaly. At diagnosis, 84, 17 and 19 tumors were T2-hypo-, iso-and hyper-intense, respectively. SSA treatment duration, cumulative and mean monthly doses were similar in the three groups. Patients with T2-hypo-intense adenomas had median SSA-induced decreases in GH and IGF-1 of 88% and 59% respectively, which were significantly greater than the decreases observed in the T2-iso-and hyper-intense groups (P < 0.001). Tumor shrinkage on SSA was also significantly greater in the T2-hypo-intense group (38%) compared with the T2-iso-and hyper-intense groups (8% and 3%, respectively; P < 0.0001). The response to SSA correlated with the calculated T2 intensity: the lower the T2-weighted intensity, the greater the decrease in random GH (P < 0.0001, r = 0.22), IGF-1 (P < 0.0001, r = 0.14) and adenoma volume (P < 0.0001, r = 0.33). The T2-weighted signal intensity of GH-secreting adenomas at diagnosis correlates with hormone reduction and tumor shrinkage in response to primary SSA treatment in acromegaly. This study supports its use as a generally available predictive tool at diagnosis that could help to guide subsequent treatment choices in acromegaly.

Preoperative treatment of growth hormone (GH) producing macroadenomas with somatostatin receptor ligands (SRLs) to improve surgical outcome: a critical analysis

“…Thus, these data may suggest that selective inclusion of patients with T2-hypointense tumors into a study of pre-operative tumor shrinkage (thus, weeding out the likely nonresponders) might increase the tumor shrinking rate of SRLs. However, more careful reading of the study by Potorac et al [19] does not support this hypothesis. Among 84 T2-hypointense tumors, 82% achieved tumor shrinkage by >20%, but in the total sample of 120 tumors the same effect was achieved in 63%, a modest difference.…”

“…Recently, the correlation between the responsiveness of somatotropinomas to the SRLs and their radiological appearance was studied [19][20][21]. All studies have reached the same conclusion: tumors with T2-weighted hypointense signal were dramatically more sensitive to both hormonal and morphological effects of the SRLs.…”

“…All studies have reached the same conclusion: tumors with T2-weighted hypointense signal were dramatically more sensitive to both hormonal and morphological effects of the SRLs. As an example, Potorac et al [19] have shown that the T2-hypointense tumors had an average of 88% reduction of random GH (vs. 24% in isointense and 36% in hyperintense ones), 59% reduction in IGF-1 (vs. 20% in isointense and 33% in the hyperintense ones), and their percent volume reduction was 38% (vs. 8% in isointense and 3% in hyperintense ones). T2-weighted signal correlated negatively with tumor granularity and T2 hyperintense tumors tend to have sparse granularity [21], which in turn is known to confer poor responsiveness to somatostatin [22,23].…”

Recent Progress in the Medical Therapy of Pituitary Tumors

“…Predictors of good response to first generation SRLs include densely granulated tumors [2829] (typically older patients and MRI T2-hypointensity signal [30]), lower Ki-67 expression and SSTR2A positive immunostaining [31]. Patients with familial acromegaly and aryl hydrocarbon receptor interacting protein (AIP) mutations tend to be resistant to first generation SRLs [32].…”

Pituitary acromegaly: not one disease

“…We read with interest the recent article 'T2-weighted MRI signal predicts hormone and tumor responses to somatostatin analogs in acromegaly', published in the November 2016 issue of Endocrine-Related Cancer (Potorac et al 2016). The authors concluded that 'The T2-weighted signal intensity of GH-secreting adenomas at diagnosis correlates with hormone reduction and tumor shrinkage in response to primary SSA treatment in acromegaly'.…”