Quantitative analyses of T2-weighted MRI as a potential marker for response to somatostatin analogs in newly diagnosed acromegaly

MRI texture analysis in acromegaly and its role in predicting response to somatostatin receptor ligands

PURPOSE

Given the paucity of reliable predictors of tumor recurrence, progression, or response to somatostatin receptor ligand (SRL) therapy in acromegaly, we attempted to determine whether preoperative MR image texture was predictive of these clinical outcomes. We also determined whether image texture could differentiate somatotroph adenomas from non-functioning pituitary adenomas (NFPAs).

METHODS

We performed a retrospective study of patients with acromegaly due to a macroadenoma who underwent transsphenoidal surgery at our institution between 2007 and 2015. Clinical data were extracted from electronic medical records. MRI texture analysis was performed on preoperative non-enhanced T1-weighted images using ImageJ (NIH). Logistic and Cox models were used to determine if image texture parameters predicted outcomes.

RESULTS

Eighty-nine patients had texture parameters measured, which were compared to that of NFPAs, while 64 of these patients had follow-up and were included in the remainder of analyses. Minimum pixel intensity, skewness, and kurtosis were significantly different in somatotroph adenomas versus NFPAs (area under the receiver operating characteristic curve, 0.7771, for kurtosis). Furthermore, those with a maximum pixel intensity above the median had an increased odds of IGF-I normalization on SRL therapy (OR 5.96, 95% CI 1.33-26.66), which persisted after adjusting for several potential predictors of response. Image texture did not predict tumor recurrence or progression.

CONCLUSION

Our data suggest that MRI texture analysis can distinguish NFPAs from somatotroph macroadenomas with good diagnostic accuracy and can predict normalization of IGF-I with SRL therapy.

Predictive factors for responses to primary medical treatment with lanreotide autogel 120 mg in acromegaly: post hoc analyses from the PRIMARYS study

PURPOSE

PRIMARYS (NCT00690898) was a 48-week, open-label, phase 3b study, evaluating treatment with the somatostatin receptor ligand lanreotide autogel (stable dose: 120 mg/28 days) in treatment-naïve patients with growth hormone (GH)-secreting pituitary macroadenoma. This post hoc analysis aimed to evaluate factors predictive of long-term responses.

METHODS

Potential predictive factors evaluated were: sex, age, and body mass index at baseline; and GH, insulin-like growth factor-1 (IGF-1), and tumor volume (TV) at baseline and week 12, using univariate regression analyses. Treatment responses were defined as hormonal control (GH ≤ 2.5 µg/L and age- and sex-normalized IGF-1), tight hormonal control (GH < 1.0 µg/L and normalized IGF-1), or ≥ 20% TV reduction (TVR). Receiver-operating-characteristic (ROC) curves were constructed using predictive factors significant in univariate analyses. Cut-off values for predicting treatment responses at 12 months were derived by maximizing the Youden index (J).

RESULTS

At baseline, older age, female sex, and lower IGF-1 levels were associated with an increased probability of achieving long-term hormonal control. ROC area-under-the curve (AUC) values for hormonal control were high for week-12 GH and IGF-1 levels (0.87 and 0.93, respectively); associated cut-off values were 1.19 μg/L and 110% of the upper limit of normal (ULN), respectively. Results were similar for tight hormonal control (AUC values: 0.92 [GH] and 0.87 [IGF-1]; cut-off values: 1.11 μg/L and 125% ULN, respectively). AUC and J values associated with TVR were low.

CONCLUSIONS

The use of predictive factors at baseline and week 12 of treatment could inform clinical expectations of the long-term efficacy of lanreotide autogel.

Magnetic resonance imaging in the management of prolactinomas; a review of the evidence

PURPOSE

This review aimed to evaluate data on the use of magnetic resonance imaging in the management of prolactinomas.

METHODS

Recent literature about prolactinoma behavior and magnetic resonance imaging in the management of prolactinomas is reviewed.

RESULTS

A review of evidence regarding prolactinoma pituitary MRI follow-up; techniques and sequences, recent data on possible gadolinium retention, the role and a review of T2-weighted images in the identification of prolactinomas and frequently encountered clinical scenarios, as well as MRI correlation with prolactin secretion, tumor growth and prediction of response to medical therapy are presented.

CONCLUSION

The underlying decision to perform serial imaging in prolactinoma patients should be individualized on a case-by-case basis. Future studies should focus on alternative imaging methods and/or contract agents.

Tumor T2 signal intensity and stalk angulation correlates with endocrine status in pituitary adenoma patients: a quantitative 7 tesla MRI study

PURPOSE

Pituitary adenomas are common CNS tumors that can cause endocrine dysfunction due to hormone oversecretion and by mass effect on the normal gland. The study of pituitary adenomas and adjacent sellar anatomy with high-resolution 7 T MRI may further characterize endocrine dysfunction. The purpose of this study was to determine the efficacy of 7 T MRI in identifying radiological markers for endocrine function.

METHODS

MR images obtained in 23 patients with pituitary adenomas were reviewed by consensus between three neuroradiologists. Landmarks and criteria were devised to measure radiological features of stalk, tumor, and normal gland. Fischer's exact tests and nominal logistic regression were performed.

RESULTS

Mean cross-sectional area of the stalk just below the infundibular recess was 6.3 ± 3.7 mm². Mean curvature and deviation angles were 34.2° ± 23.2° and 29.7° ± 17.3°, respectively. Knosp scores obtained differed between 7 T and lower field strength scans (P < 0.0001 [right] and P = 0.0006 [left]). Ability to characterize tumor was rated higher at 7 T compared with lower field MRI, P = 0.05. Confidence in visualizing normal gland was also higher using 7 T MRI, P = 0.036. The six hormone-secreting tumors had higher corrected T2 mean SI than non-secreting tumors (2.54 vs. - 0.38, P = 0.0196). Seven patients had preoperative hypopituitarism and had significantly greater stalk curvature angles than patients without hypopituitarism (71.7° vs. 36.55°, P = 0.027).

CONCLUSION

Radiological characterization of pituitary adenomas and adjacent native pituitary tissue may benefit with the use of 7 T MRI. Corrected T2 SI of tumor may be a sensitive predictor of hormonal secretion and may be useful in the diagnostic work-up for pituitary adenoma. 7 T MRI may be valuable in identifying markers of endocrine function in patients with pituitary adenomas. Our results indicate that hormone-secreting tumors have higher T2-weighted SI and tumors associated with preoperative hypopituitarism have greater stalk curvature angles.

The Clinicopathological Spectrum of Acromegaly

BACKGROUND

Acromegaly results from a persistent excess in growth hormone with clinical features that may be subtle or severe. The most common cause of acromegaly is a pituitary tumor that causes excessive production of growth hormone (GH), and rare cases are due to an excess of the GH-releasing hormone (GHRH) or the ectopic production of GH.

OBJECTIVE

Discuss the different diseases that present with manifestations of GH excess and clinical acromegaly, emphasizing the distinct clinical and radiological characteristics of the different pathological entities.

METHODS

We performed a narrative review of the published clinicopathological information about acromegaly. An English-language search for relevant studies was conducted on PubMed from inception to 1 August 2019. The reference lists of relevant studies were also reviewed.

RESULTS

Pituitary tumors that cause GH excess have several variants, including pure somatotroph tumors that can be densely or sparsely granulated, or plurihormonal tumors that include mammosomatotroph, mixed somatotroph-lactotroph tumors and mature plurihomonal Pit1-lineage tumors, acidophil stem cell tumors and poorly-differentiated Pit1-lineage tumors. Each tumor type has a distinct pathophysiology, resulting in variations in clinical manifestations, imaging and responses to therapies.

CONCLUSION

Detailed clinicopathological information will be useful in the era of precision medicine, in which physicians tailor the correct treatment modality to each patient.

Pituitary magnetic resonance imaging predictive role in the therapeutic response of growth hormone-secreting pituitary adenomas

Background

Growth hormone (GH)-secreting pituitary adenomas, responsible for the development of acromegaly, are the second most frequent type of secreting pituitary adenomas and are characterized by very variable T2-weighted signal intensity on pituitary magnetic resonance imaging (MRI). Previous data have demonstrated a correlation between T2-weighted tumor signal intensity and response to therapy with conventional somatostatin analogs (SSA) in patients with acromegaly. The aim of the current retrospective study was to investigate the correlation between the T2-weighted tumor signal on pituitary MRI and both biochemical and radiological response to first-line SSA therapy.

Methods

Twenty-two naive patients with acromegaly were eligible for the study (14 females and 8 males, mean age ± SD: 58.8±15.74). A biochemical evaluation (GH and IGF-I levels) and an MRI assessment (volume and signal intensity analysis of adenoma) were conducted in each patient at diagnosis and after 12 months of SSA therapy.

Results

On diagnostic pituitary MRI, 16 (72.7%) adenomas were T2- hypointense and 6 (27.2%) T2-hyperintense. After 12 months of SSA therapy, IGF-I levels decreased by more than 50% from baseline in 62.5% of patients with T2-hypointense and 33.3% of patients with T2- hyperintense tumor signal, respectively (P=0.03). Moreover, GH levels decreased by more than 80% from baseline in 81.3% and 33.3% of patients with T2-hypointense and T2-hyperintense tumor signal (P=0.02). A significant tumor volume reduction (≥20%) was observed in 75% of the T2-hypointense and 33.3% of the T2-hyperintense adenomas (P=0.001).

Conclusions

In naive patients with acromegaly, first-line SSA therapy is associated with a better biochemical response and greater tumor shrinkage in T2-hypointense compared to T2-hyperintense adenomas. Therefore, T2-weighted sequences of pituitary MRI can help to classify GH-secreting pituitary adenomas into a T2-hypointense and T2-hyperintense type and, therefore, to identify patients who can better respond to first-line SSA therapy.

Prediction of high proliferative index in pituitary macroadenomas using MRI-based radiomics and machine learning

PURPOSE

Pituitary adenomas are among the most frequent intracranial tumors. They may exhibit clinically aggressive behavior, with recurrent disease and resistance to multimodal therapy. The ki-67 labeling index represents a proliferative marker which correlates with pituitary adenoma aggressiveness. Aim of our study was to assess the accuracy of machine learning analysis of texture-derived parameters from pituitary adenomas preoperative MRI for the prediction of ki-67 proliferation index class.

METHODS

A total of 89 patients who underwent an endoscopic endonasal procedure for pituitary adenoma removal with available ki-67 labeling index were included. From T2w MR images, 1128 quantitative imaging features were extracted. To select the most informative features, different supervised feature selection methods were employed. Subsequently, a k-nearest neighbors (k-NN) classifier was employed to predict macroadenoma high or low proliferation index. Algorithm validation was performed with a train-test approach.

RESULTS

Of the 12 subsets derived from feature selection, the best performing one was constituted by the 4 highest correlating parameters at Pearson's test. These all showed very good (ICC ≥ 0.85) inter-observer reproducibility. The overall accuracy of the k-NN in the test group was of 91.67% (33/36) of correctly classified patients.

CONCLUSIONS

Machine learning analysis of texture-derived parameters from preoperative T2 MRI has proven to be effective for the prediction of pituitary macroadenomas ki-67 proliferation index class. This might aid the surgical strategy making a more accurate preoperative lesion classification and allow for a more focused and cost-effective follow-up and long-term management.

Invited Review: Pathology of pituitary neuroendocrine tumours: present status, modern diagnostic approach, controversies and future perspectives from a neuropathological and clinical standpoint

Neuroendocrine tumours of the adenohypophysis have traditionally been designated as pituitary adenomas to underline their usually indolent growth and lack of metastatic potential. However, they may demonstrate a huge spectrum of growth patterns and endocrine disturbances, some of them significantly affecting health and quality of life. To predict tumour growth, risk of postoperative recurrence and response to medical therapy in patients with pituitary neuroendocrine tumours is challenging. A thorough histopathological and immunohistochemical diagnostic work-up is an obligatory part of a multidisciplinary effort to precisely define the tumour type and assess prognostic and predictive factors on an individual basis. In this review, we have summarized the current status in the pathology in pituitary neuroendocrine tumours based on the selection of references from the PubMed database. We have presented possible diagnostic approaches according to the current pituitary cell lineage-based classification. The importance of recognizing histological subtypes with potentially aggressive behaviour and identification of prognostic and predictive tissue biomarkers have been highlighted. Controversies related to particular subtypes of pituitary tumours and a still limited prognostic impact of the current classification indicate the need for further refinement. Multidisciplinary approach including clinical, pathological and molecular genetic characterization will be essential for improved personalized therapy and the search for novel therapeutic targets in patients with pituitary neuroendocrine tumours.

The effect of somatostatin analogues on Ki-67 levels in GH-secreting adenomas

PURPOSE

Somatostatin analogues (SSAs) can slow down the growth of neuroendocrine tumors. However, the mechanism remains unclear. Recent studies on patients with acromegaly suggest that SSAs may induce apoptosis, increase autophagy, and decrease cell proliferation of pituitary adenoma. Ki-67-labeling index is a marker of cellular proliferation; therefore, decreased levels are associated with inhibition of proliferation. The aim of this study was to evaluate and compare the Ki-67-labeling index of GH-secreting pituitary adenoma tissues in patients who had undergone pituitary surgery twice due to residual or recurrent tumors and had received SSA treatment between the two surgeries.

METHOD

Thirty acromegaly patients who met the above criteria were identified and evaluated for the demographic, clinical and radiological features retrospectively. Surgical pathology samples of each operation were stained for Ki-67 and evaluated blindly by a staff pathologist specialized in pituitary diseases.

RESULTS

Among patients who received SSA treatment between the first and second operations, the Ki-67 index of the adenoma at the second operation was significantly lower than the Ki-67 index at the first operation. There were no differences in clinical and radiological prognostic markers between the groups with decreased and unchanged Ki-67 index.

CONCLUSION

We concluded that SSA treatment appears to decrease Ki-67 proliferation index independent of tumor features, SSA type, dose and treatment duration. This result suggests that SSA treatment may decrease cellular proliferation, supporting the previous studies.

Magnetic resonance spectroscopy may serve as a presurgical predictor of somatostatin analog therapy response in patients with growth hormone-secreting pituitary macroadenomas

PURPOSE

Somatostatin analogs (SSAs) are considered one of the most effective medical treatments for patients with growth hormone-secreting pituitary adenomas (GH-PAs). The postoperative electron microscopy (EM) pathological subtype and SSTR2 expression in the tumor are the most established predictors of patient response to SSA therapy. The aim of this study was to evaluate how will magnetic resonance spectroscopy (MRS) measurements before surgery predict the EM pathological subtypes and SSTR2 expression of tumors, and thereby serve as an indicator for the therapeutic sensitivity to SSAs of patients with GH-PAs.

METHODS

Eighteen patients with GH pituitary macroadenomas who underwent transsphenoidal surgery were included in this retrospective study. The preoperative MRS data and T2 signal intensity were obtained from patients by 1.5 T MR spectroscopy of the sellar mass. The EM pathological subtypes of tumors were determined after surgery through examination of cell granulations. The expressions of somatostatin receptor 2 (SSTR2), SSTR5, P21, P27, and Ki-67 were evaluated by immunohistochemistry.

RESULTS

The MRS parameters that were found to significantly predict the EM pathological subtypes of tumors, as calculated by the receiver operating characteristic curve, were the choline (Ch) value at 3140.5 MR units (sensitivity 69.2%, specificity 100%) and the choline/creatine (Ch/Cr) ratio at 1.27 (sensitivity 92.3%, specificity 100%). Further, the Ch/Cr ratio, but not other MRS data, was shown to negatively correlate with the expression of SSTR2 (P = 0.02). The Ch/Cr ratio was also found to positively correlate with the Ki-67 value (P < 0.05) and T2 signal (P < 0.05), but not with other factors that were examined in this study. Moreover, the Ch/Cr ratio could predict the EM pathological subtypes of tumors with an accuracy of 83.3% (5/6) for patients with an isointense T2 signal.

CONCLUSION

The Ch/Cr ratio by MRS could effectively predict the tumor subtype and was significantly correlated with the expression of SSTR2, which was consistent with other predictors. It was also able to distinguish the patients with isointense T2 signals. Our results provide a potentially new and non-invasive method to predict the response to SSAs in patients with GH pituitary macroadenomas.

Modern imaging of pituitary adenomas

Decision-making in pituitary disease is critically dependent on high quality imaging of the sella and parasellar region. Magnetic resonance imaging (MRI) is the investigation of choice and, for the majority of patients, combined T1 and T2 weighted sequences provide the information required to allow surgery, radiotherapy (RT) and/or medical therapy to be planned and long-term outcomes to be monitored. However, in some cases standard clinical MR sequences are indeterminate and additional information is needed to help inform the choice of therapy for a pituitary adenoma (PA). This article reviews current recommendations for imaging of PA, examines the potential added value that alternative MR sequences and/or CT can offer, and considers how the use of functional/molecular imaging might allow definitive treatment to be recommended for a subset of patients who would otherwise be deemed unsuitable for (further) surgery and/or RT.

T2-weighted magnetic resonance imaging characterization of prolactinomas and association with their response to dopamine agonists

PURPOSE

Recent work supports the use of T2-weighted MRI intensity as a tool for treatment stratification in acromegaly. Our study aimed to establish if the pattern of T2 intensity could be a predictor of hormonal and/or tumoral response to dopamine agonists (DAs) in prolactinomas.

METHODS

This was a retrospective study performed in two academic centers. We characterized the magnetic resonance T2-weighted aspect of prolactinomas (signal intensity and homogeneity in the whole tumors) before DA therapy and correlated this pattern to the prolactin (PRL) concentration at diagnosis and to hormonal and tumoral responses after 1 year of medical treatment. We separately analyzed a subgroup of prolactinomas visually very bright in more than 50% of the surface ("cystic" tumors).

RESULTS

Out of 70 prolactinomas, 80% were T2 hyperintense and 40% were heterogeneous. At diagnosis, heterogeneous prolactinomas were more frequent in men (68% vs. 28.9%, p ≤ 0.011), larger (median area 304.5 mm² vs. 56.5 mm², p ≤ 0.021), taller (mean height 18.6 mm vs. 9.9 mm, p < 0.001), more secreting (median PRL ULN_area 23 µg/L/cm² vs. 12.6 µg/L/cm², p ≤ 0.032) and had poorer hormonal response to DA as compared with homogeneous prolactinomas. "Cystic" tumors were diagnosed almost exclusively in women and secreted less prolactin, but showed similar hormonal and tumoral response as "non-cystic" tumors. In homogeneous prolactinomas, the T2-weighted intensity ratio was correlated to prolactin secretion, although not significantly, and did not predict hormonal and tumoral response to DA.

CONCLUSIONS

Our study confirms that hypo/isointense prolactinoma is a rare finding and suggests for the first time that the heterogeneity of prolactinoma T2 signal at diagnosis might be correlated with a different clinical behavior and could be used as a negative predictor factor of hormonal response to DA.

PREDICTIVE MARKERS FOR POSTSURGICAL MEDICAL MANAGEMENT OF ACROMEGALY: A SYSTEMATIC REVIEW AND CONSENSUS TREATMENT GUIDELINE

Objective: To clarify the selection of medical therapy following transsphenoidal surgery in patients with acromegaly, based on growth hormone (GH)/insulin-like growth factor 1 (IGF-1) response and glucometabolic control. Methods: We carried out a systematic literature review on three of the best studied and most practical predictive markers of the response to somatostatin analogues (SSAs): somatostatin receptor (SSTR) expression, tumor morphologic classification, and T2-weighted magnetic resonance imaging (MRI) signal intensity. Additional analyses focused on glucose metabolism in treated patients. Results: The literature survey confirmed significant associations of all three factors with SSA responsiveness. SSTR expression appears necessary for the SSA response; however, it is not sufficient, as approximately half of SSTR2-positive tumors failed to respond clinically to first-generation SSAs. MRI findings (T2-hypo-intensity) and a densely granulated phenotype also correlate with SSA efficacy, and are advantageous as predictive markers relative to SSTR expression alone. Glucometabolic control declines with SSA monotherapy, whereas GH receptor antagonist (GHRA) monotherapy may restore normoglycemia. Conclusion: We propose a decision tree to guide selection among SSAs, dopamine agonists (DAs), and GHRA for medical treatment of acromegaly in the postsurgical setting. This decision tree employs three validated predictive markers and other clinical considerations, to determine whether SSAs are appropriate first-line medical therapy in the postsurgical setting. DA treatment is favored in patients with modest IGF-1 elevation. GHRA treatment should be considered for patients with T2-hyperintense tumors with a sparsely granulated phenotype and/or low SSTR2 staining, and may also be favored for individuals with diabetes. Prospective analyses are required to test the utility of this therapeutic paradigm. Abbreviations: DA = dopamine agonist; DG = densely granulated; GH = growth hormone; GHRA = growth hormone receptor antagonist; HbA1c = glycated hemoglobin; IGF-1 = insulin-like growth factor-1; MRI = magnetic resonance imaging; SG = sparsely granulated; SSA = somatostatin analogue; SSTR = somatostatin receptor.

Precision medicine in the treatment of acromegaly

Acromegaly is a chronic disorder usually diagnosed late in the disease evolution, leading to substantial morbidity and mortality related to this long period of undiagnosed state as well as the difficulty in achieving normalization of GH hypersecretion and controlling tumor mass. First generation somatostatin analogues (SSA) are accepted as the first-line medical therapy or as second-line therapy in patients undergoing unsuccessful surgery. However, because a high percentage of patients experience SSA treatment failure, the inclusion of biomarkers associated with a successful or non-successful response to these drug (as well as to all classes of medical therapy) is necessary to better guide the choice of treatment, potentially allowing for a quicker achievement of disease control. The current treatment algorithms for acromegaly are based upon a "trial and error" approach with additional treatment options provided when disease is not controlled. In many other diseases, their therapeutic algorithms have been evolving towards personalizing treatment with medication that best matches individual disease characteristics, using biomarkers that identify therapeutic response, thus allowing the personalization of the therapy. It is time to introduce this approach to acromegaly treatment algorithms. This paper reviews the potential tools for doing so.

Predicting response to somatostatin analogues in acromegaly: machine learning-based high-dimensional quantitative texture analysis on T2-weighted MRI

OBJECTIVE

To investigate the value of machine learning (ML)-based high-dimensional quantitative texture analysis (qTA) on T2-weighted magnetic resonance imaging (MRI) in predicting response to somatostatin analogues (SA) in acromegaly patients with growth hormone (GH)-secreting pituitary macroadenoma, and to compare the qTA with quantitative and qualitative T2-weighted relative signal intensity (rSI) and immunohistochemical evaluation.

METHODS

Forty-seven patients (24 responsive; 23 resistant patients to SA) were eligible for this retrospective study. Coronal T2-weighted images were used for qTA and rSI evaluation. The immunohistochemical evaluation was based on the granulation pattern of the adenomas. Dimension reduction was carried out by reproducibility analysis and wrapper-based algorithm. ML classifiers were k-nearest neighbours (k-NN) and C4.5 algorithm. The reference standard was the biochemical response status. Predictive performance of qTA was compared with those of the quantitative and qualitative rSI and immunohistochemical evaluation.

RESULTS

Five hundred thirty-five out of 828 texture features had excellent reproducibility. For the qTA, k-NN correctly classified 85.1% of the macroadenomas regarding response to SAs with an area under the receiver operating characteristic curve (AUC-ROC) of 0.847. The accuracy and AUC-ROC ranges of the other methods were 57.4-70.2% and 0.575-0.704, respectively. Differences in predictive performance between qTA-based classification and the other methods were significant (p < 0.05).

CONCLUSIONS

The ML-based qTA of T2-weighted MRI is a potential non-invasive tool in predicting response to SAs in patients with acromegaly and GH-secreting pituitary macroadenoma. The method performed better than the qualitative and quantitative rSI and immunohistochemical evaluation.

KEY POINTS

• Machine learning-based texture analysis of T2-weighted MRI can correctly classify response to somatostatin analogues in more than four fifths of the patients. • Machine learning-based texture analysis performs better than qualitative and quantitative evaluation of relative T2 signal intensity and immunohistochemical evaluation. • About one third of the texture features may not be excellently reproducible, indicating that a reliability analysis is necessary before model development.

International Union of Basic and Clinical Pharmacology. CV. Somatostatin Receptors: Structure, Function, Ligands, and New Nomenclature

Somatostatin, also known as somatotropin-release inhibitory factor, is a cyclopeptide that exerts potent inhibitory actions on hormone secretion and neuronal excitability. Its physiologic functions are mediated by five G protein-coupled receptors (GPCRs) called somatostatin receptor (SST)1-5. These five receptors share common structural features and signaling mechanisms but differ in their cellular and subcellular localization and mode of regulation. SST2 and SST5 receptors have evolved as primary targets for pharmacological treatment of pituitary adenomas and neuroendocrine tumors. In addition, SST2 is a prototypical GPCR for the development of peptide-based radiopharmaceuticals for diagnostic and therapeutic interventions. This review article summarizes findings published in the last 25 years on the physiology, pharmacology, and clinical applications related to SSTs. We also discuss potential future developments and propose a new nomenclature.

Updates in Diagnosis and Treatment of Acromegaly

Acromegaly is a rare disease, caused largely by a growth hormone (GH) pituitary adenoma. Incidence is higher than previously thought. Due to increased morbidity and mortality, if not appropriately treated, early diagnosis efforts are essential. Screening is recommended for all patients with clinical features of GH excess. There is increased knowledge that classical diagnostic criteria no longer apply to all, and some patients can have GH excess with normal GH response to glucose. Treatment is multifactorial and personalised therapy is advised.

Clinicopathological significance of baseline T2-weighted signal intensity in functional pituitary adenomas

PURPOSE

To assess baseline T2-weighted signal intensity (T2-WSI) of functional pituitary adenomas (FPA), and to investigate the relationship of baseline T2-WSI with clinical features, histopathological granulation patterns, and response to treatment in patients with acromegaly, prolactinoma and Cushing's disease (CD).

METHODS

Somatotroph adenomas (n = 87), prolactinomas (n = 78) and corticotroph adenomas (n = 29) were included in the study. Baseline T2-WSI findings (grouped as hypo-, iso- and hyperintense) were compared with hormone levels, tumor diameter, granulation patterns and response to treatment.

RESULTS

Somatotroph adenomas were mostly hypointense (53%), prolactinomas were dominantly hyperintense (55%), and corticotroph adenomas were generally hyperintense (45%). Hyperintense somatotroph adenomas were larger in size with sparsely granulated pattern and tumor shrinkage rate was lower after somatostatin analogues (SSA) (p = 0.007, p = 0.035, p = 0.029, respectively). T2 hypointensity was related with higher baseline IGF-1% ULN (upper limit of normal) levels and a better response to SSA treatment (p = 0.02, p = 0.045, respectively). In female prolactinomas, hyperintensity was correlated with a smaller adenoma diameter (p = 0.001). Hypointense female prolactinomas were related to younger age at diagnosis, higher baseline PRL levels and dopamine agonist (DA) resistance (p = 0.009, p = 0.022, p < 0.001, respectively). Hyperintense corticotroph adenomas were related to larger adenoma size and sparsely granulated pattern (p = 0.04, p = 0.017, respectively). There was no significant difference in the recurrence with T2WSI in CD.

CONCLUSION

Baseline hypointense somatotroph adenomas show a better response to SSA, whereas hypointensity was related to DA resistance in female prolactinomas.

Predictors of surgical outcome and early criteria of remission in acromegaly

BACKGROUND

Transsphenoidal surgery (TSS) is the cornerstone of acromegaly treatment, however there are no robust predictors of surgical outcome and remission can only be defined three months after surgery.

PURPOSE

To analyze if biochemical, demographical, radiological, and immunohistochemical characteristics are predictors of surgical remission and investigate if immediate postoperative GH and IGF-I levels can help defining remission earlier.

METHODS

Consecutive acromegaly patients submitted to TSS between 2013-2016 were evaluated. Remission criteria was defined as normal IGF-I and GH <1 mcg/L three months after surgery. Data of age, sex, GH and IGF-I levels, tumor volume, cavernous sinus invasion, T2-weighted signal, Ki-67, and granulation pattern were correlated with remission status. GH and IGF-I levels at 24, 48 h, and one week postoperative were evaluated as early criteria of remission.

RESULTS

Sixty-nine patients were included (84% macroadenomas) and surgical remission was achieved in 45%. No difference between cured and not cured patients concerning age, gender, preoperative GH or IGF-I levels, tumor volume, T2-weighted signal, Ki-67 and tumor granularity was observed. Remission was obtained in 20 of 36 (56%) of the non-invasive tumors, and in 3 of 16 (19%) of the invasive tumors (p = 0.017). A GH <1.57 mcg/L 48 h after surgery was able to predict remission with 93% sensitivity and 86% specificity and an IGF-I < 231% ULNR one week after surgery predicted remission with 86% sensitivity and 93% specificity.

CONCLUSION

Cavernous sinus invasion is the only preoperative predictor of surgical remission. GH at 48 h and IGF-I one week after surgery can define earlier not cured patients.

The Predictive Value of Suprasellar Extension for Visual Function Evaluation in Chinese Patients with Nonfunctioning Pituitary Adenoma with Optic Chiasm Compression

OBJECTIVE

To analyze the quantitative relationship between suprasellar extension (SSE) and visual function impairment in Chinese patients with nonfunctioning pituitary adenoma (NFPA) with optic chiasm compression.

METHODS

We retrospectively reviewed 117 patients with NFPA and optic chiasm compression treated at our hospital between January 2013 and December 2016. The quantitative relationships between SSE detected on sagittal and coronal magnetic resonance imaging (MRI) sections and visual function, including visual acuity (VA) and visual fields (VFs), were analyzed. The cutoff value of SSE to predict a VF defect (VFD) was calculated using a receiver operating characteristic curve. The mean deviation (MD) value was used to quantitatively analyze the VFs, and multiple linear regression analysis was performed to investigate risk factors of VFD.

RESULTS

Among 117 patients with NFPA, 77 (65.8%) had VFD, and the mean VA was 0.42 ± 0.38 logMAR. The cutoff value of the sagittal SSE was 14.0 mm, with 77.9% sensitivity and 80.0% specificity, and the cutoff value of the coronal SSE was 15.8 mm, with 81.8% sensitivity and 85.0% specificity. The values of SSE on 2 MRI sections were correlated with VA (P < 0.001) and the MD (P < 0.001). Multiple linear regression analysis demonstrated that SSE on sagittal views (P < 0.001), SSE on coronal views (P < 0.001), duration of the disease (P = 0.027), and apoplexy (P = 0.036) were related to the degree of VF damage.

CONCLUSIONS

VFD in patients with NFPA with chiasm compression can be predicted by SSE on MRI. There is a linear correlation between SSE and the MD value.

Association between radiological parameters and clinical and molecular characteristics in human somatotropinomas

Acromegaly is a rare but severe disease, originated in 95% of cases by a growth hormone-secreting adenoma (somatotropinoma) in the pituitary. Magnetic resonance imaging (MRI) is a non-invasive technique used for the diagnosis and prognosis of pituitary tumours. The aim of this study was to determine whether the use of T2-weighted signal intensity at MRI could help to improve the characterisation of somatotropinomas, by analysing its relationship with clinical/molecular features. An observational study was implemented in a cohort of 22 patients (mean age = 42.1 ± 17.2 years; 59% women; 95% size>10 mm). Suprasellar-extended somatotropinomas presented larger diameters vs. non-extended tumours. T2-imaging revealed that 59% of tumours were hyperintense and 41% isointense adenomas, wherein hyperintense were more invasive (according to Knosp-score) than isointense adenomas. A higher proportion of hyperintense somatotropinomas presented extrasellar-growth, suprasellar-growth and invasion of the cavernous sinus compared to isointense adenomas. Interestingly, somatostatin receptor-3 and dopamine receptor-5 (DRD5) expression levels were associated with extrasellar and/or suprasellar extension. Additionally, DRD5 was also higher in hyperintense adenomas and its expression was directly correlated with Knosp-score and with tumour diameter. Hence, T2-weighted MRI on somatotropinomas represents a potential tool to refine their diagnosis and prognosis, and could support the election of preoperative treatment, when required.

MANAGEMENT OF ENDOCRINE DISEASE: Personalized medicine in the treatment of acromegaly

Acromegaly is associated with high morbidity and elevated mortality when not adequately treated. Surgery is the first-line treatment for most patients as it is the only one that can lead to immediate cure. In patients who are not cured by surgery, treatment is currently based on a trial-and-error approach. First-generation somatostatin receptor ligands (fg-SRL) are initiated for most patients, although approximately 25% of patients present resistance to this drug class. Some biomarkers of treatment outcome are described in the literature, with the aim of categorizing patients into different groups to individualize their treatments using a personalized approach. In this review, we will discuss the current status of precision medicine for the treatment of acromegaly and future perspectives on the use of personalized medicine for this purpose.

AIP and the somatostatin system in pituitary tumours

Classic somatostatin analogues aimed at somatostatin receptor type 2, such as octreotide and lanreotide, represent the mainstay of medical treatment for acromegaly. These agents have the potential to decrease hormone secretion and reduce tumour size. Patients with a germline mutation in the aryl hydrocarbon receptor-interacting protein gene, AIP, develop young-onset acromegaly, poorly responsive to pharmacological therapy. In this review, we summarise the most recent studies on AIP-related pituitary adenomas, paying special attention to the causes of somatostatin resistance; the somatostatin receptor profile including type 2, type 5 and truncated variants; the role of G proteins in this pathology; the use of first and second generation somatostatin analogues; and the role of ZAC1, a zinc-finger protein with expression linked to AIP in somatotrophinoma models and acting as a key mediator of octreotide response.

T2-weighted MRI signal intensity as a predictor of hormonal and tumoral responses to somatostatin receptor ligands in acromegaly: a perspective

T2-weighted MRI signal intensity of GH-secreting pituitary adenomas is gaining recognition as a marker of disease characteristics and may be a predictor of response to treatment of acromegaly. Adenomas that are T2-hypointense are more common, are smaller and are less likely to invade the cavernous sinus compared to the T2-iso and hyperintense tumors. T2-hypointense tumors are also accompanied by higher IGF1 values at baseline. When presurgical somatostatin receptor ligand (SRL) therapy is administered, T2-hypointense adenomas have better hormonal responses and have greater tumor shrinkage. Adjuvant SRL therapy of patients with T2-hypointense tumors that are uncured by surgery is also associated with a better hormonal response. We review the studies that have dealt with the T2-weighted signal intensity of GH-secreting pituitary tumors and elaborate on the details and nuances of this promising avenue of research.

Expression of Somatostatin Receptor 2 in Somatotropinoma Correlated with the Short-Term Efficacy of Somatostatin Analogues

The expression of somatostatin receptor subtypes (SSTRs) in pituitary growth hormone- (GH-) secreting adenomas may predict the response to somatostatin analogues (SSA). Our aim was to evaluate the value of the immunohistochemical (IHC) scores of 2 subtypes, SSTR2 and SSTR5, in predicting the short-term efficacy of SSA therapy in patients with active acromegaly. Ninety-three newly diagnosed acromegalic patients were included in our study. These patients were categorized into either a SSA-pretreated group (SA, n = 63) or a direct-surgery group (DS, n = 30), depending on whether or not presurgical SSA treatment was received. IHC analysis, using a 12-grade scoring system, with rabbit monoclonal antibodies against SSTR2 and SSTR5, was performed on all adenoma tissues. The reduction of GH, IGF-1, and tumor size after treatment with SSA for 3 months was measured. Compared with that in the DS group, SSTR2 expression was lower in the SA group. Additionally, in the SA group, SSTR2 expression was positively correlated with the reduction of IGF-1 and tumor volume. However, there was no correlation between the SSTR5 score and the efficacy of SSA. In conclusion, the protein expression of SSTR2, but not of SSTR5, is a valuable indicator in predicting biochemical and tumor size response to short-term SSA treatment in acromegalic patients.

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

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 3 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.

The value of an acute octreotide suppression test in predicting short-term efficacy of somatostatin analogues in acromegaly

Predicting the efficacy of long-acting somatostatin analogues (SSA) remains a challenge. We aim to quantitatively evaluate the predictive value of the octreotide suppression test (OST) in short-term efficacy of SSA in active acromegaly. Sixty-seven newly diagnosed acromegaly patients were assessed with OST. Subsequently, all patients were treated with long-acting SSA for 3 months, followed by reassessment. Nine parameters were tested, including GH_n (the nadir GH during OST), ΔGH1 (= [GH_0h-GH_n]/GH_0h, GH_0h was the baseline GH during OST), ΔGH2 (= [GH_m-GH_n]/GH_m, GH_m was the mean GH on day curve), AUC_(0-6h) (the GH area under the curve during OST) , ΔAUC1 (= [GH_0h-AUC_(0-6h)]/GH_0h), ΔAUC2 (=[GH_m-AUC_(0-6h)]/GH_m), AUC_(m-6h) (the GH AUC during OST where GH_m was used instead of GH_0h), ΔAUC1' (=[GH_0h-AUC_(m-6h)]/GH_0h) and ΔAUC2' (=[GH_m-AUC_(m-6h)]/GH_m). The Youden indices were calculated to determine the optimal cutoffs to predict the short-term efficacy of SSA. ΔGH2 more than 86.83%, ΔAUC2 more than -57.48% and ΔAUC2' more than -57.98% provided the best predictors of a good GH response (sensitivity 93.8%, specificity 85.7%). ΔGH2 more than 90.51% provided the best predictor of a good tumor size response (sensitivity 84.8%, specificity 87.5%). The percentage fall of GH_n (ΔGH) was a better predictive parameter than GH_n. OST showed higher efficiency in predicting the efficacy of octreotide LAR than lanreotide SR. In conclusion, OST is a valid tool to predict both GH and tumor size response to short-term efficacy of SSA in acromegaly, especially for octreotide LAR. GH_m is better to be used as basal GH than GH₀ during OST.

Predictive value of T2 relative signal intensity for response to somatostatin analogs in newly diagnosed acromegaly

INTRODUCTION

The difficulty of predicting the efficacy of somatostatin analogs (SSA) is not fully resolved. Here, we quantitatively evaluated the predictive value of relative signal intensity (rSI) on T1- and T2-weighted magnetic resonance imaging (MRI) for the short-term efficacy (3 months) of SSA therapy in patients with active acromegaly and assessed the correlation between MRI rSI and expression of somatostatin receptors (SSTR).

METHODS

This was a retrospective review of prospectively recorded data. Ninety-two newly diagnosed patients (37 males and 55 females) with active acromegaly were recruited. All patients were treated with pre-surgical SSA, followed by reassessment and transspenoidal surgery. rSI values were generated by calculating the ratio of SI in the tumor to the SI of normal frontal white matter. The Youden indices were calculated to determine the optimal cutoff of rSI to determine the efficacy of SSA. The correlation between rSI and expression of SSTR2/5 was analyzed by the Spearman rank correlation coefficient.

RESULTS

T2 rSI was strongly correlated with biochemical sensitivity to SSA. The cutoff value of T2 rSI to distinguish biochemical sensitivity was 1.205, with a positive predictive value (PPV) of 81.5 % and a negative predictive value (NPV) of 77.3 %. No correlation was found between MRI and tumor size sensitivity. Moreover, T2 rSI was negatively correlated with the expression of SSTR5.

CONCLUSION

T2 rSI correlates with the expression of SSTR5 and quantitatively predicts the biochemical efficacy of SSA in acromegaly.

Pros and cons in endocrine practice: pre-surgical treatment with somatostatin analogues in acromegaly

The aim of this commentary is to balance the pros and cons for pre-surgical SSA treatment in a modern perspective ending up with a pragmatic recommendation for treatment based on the current evidence and expertise of the authors. Even though prospective and randomized studies in this particular area are hampered by obvious limitations, the interpretation of the four published trials has in general been in favor of pre-treatment with SSA, showing a better outcome following surgery. However, major drawbacks of these studies, such as non-optimal diagnostic criteria for cure, potential selection bias, and timing of the postoperative evaluation in SSA pre-treated patients, limit their overall interpretation. Three matched-controlled studies showed remarkably similar results with no apparent beneficial effect of SSA pre-treatment on surgical outcome. Both prospective, randomized studies and retrospective studies did not find any significant difference in the rate of endocrine and non-endocrine complications related to surgery, despite the beneficial clinical effects of SSA treatment in most acromegalic patients. The newly diagnosed patient with acromegaly should be carefully evaluated in the trans-disciplinary neuroendocrine team and treatment individualized accordingly. The issue of SSA pre-treatment to improve surgical outcome is yet to be settled and further methodologically sound studies are probably necessary to clarify this point.