Pre-surgical treatment with somatostatin analogues in patients with acromegaly: the case for

Physiological bio-distribution of 68Ga-DOTA-TATE in pediatric patients

OBJECTIVE

Somatostatin receptors (SSTRs) are G protein-coupled transmembrane receptors that serve as a specific molecular target for a number of radiopharmaceuticals utilized for the imaging of neuroendocrine tumors (NETs). 68Ga-DOTA-TATE is a somatostatin analog that demonstrates a high affinity for SSTR2. Pediatric malignancies, such as neuroblastoma, pheochromocytoma, and paraganglioma, have been shown to express SSTR2, and 68Ga-DOTA-TATE is currently being used to evaluate these pediatric neoplasms. We aimed to analyze the distribution pattern of 68Ga-DOTA-TATE based on age and location in pediatric patients.

METHODS

We retrospectively analyzed 247 consecutive 68Ga-DOTA-TATE whole-body PET/CT scans performed in our department from May 2015 to April 2024 in pediatric patients with known or suspected neuroblastoma, neuroendocrine malignancy, pheochromocytoma, and paraganglioma. 93 subjects were included in this study who were disease-free at the time of imaging and had no tracer-avid lesion on 68Ga-DOTA-TATE PET/CT. The patients were divided into four groups according to age: infant (0-2 years), pre-school (3-6 years), school (7-12 years), and adolescent (13-18 years). A comparison of the SUV values of each organ across age groups was performed.

RESULTS

The highest levels of physiological uptake were observed in the spleen across all age groups, except for infants, who demonstrated the highest SUV values in the kidneys. 68Ga-DOTA-TATE uptake in the parotid glands, submandibular glands, thyroid gland, thymus, liver, spleen, adrenal glands, stomach, intestines, uterus, prostate, and testes demonstrated a statistically significant increase in the adolescent age group. In contrast to all internal organs, the lowest SUV max values were observed for all growth plates within the adolescent age group.

CONCLUSION

This study presents the bio-distribution pattern of 68Ga-DOTA-TATE in pediatric patients, according to age and location. The ranges of the SUVmax and SUVmean values of 68Ga-DOTA-TATE obtained in the various organs are of paramount importance for accurately diagnosing malignancy in 68Ga-DOTA-TATE PET/CT studies.

The Dose of Somatostatin Analogues during Pre-Surgical Treatment Is a Key Factor to Achieve Surgical Remission in Acromegaly

Purpose: to determine whether pre-surgical treatment using long-acting somatostatin analogues (SSAs) may improve surgical outcomes in acromegaly. Methods: retrospective study of 48 patients with acromegaly operated by endoscopic transsphenoidal approach and for first time. Surgical remission was evaluated based on the 2010 criteria. Results: most patients, 83.3% (n = 40), harbored macroadenomas and 31.3% (n = 15) invasive pituitary adenomas. In this case, 14 patients were treated with lanreotide LAR and 6 with octreotide LAR, median monthly doses of 97.5 [range 60–120] and 20 [range 20–30] mg, respectively, for at least 3 months preoperatively. Presurgical variables were comparable between pre-treated and untreated patients (p > 0.05). Surgical remission was more frequent in those pre-treated with monthly doses ≥90 mg of lanreotide or ≥30 mg of octreotide than in untreated or pre-treated with lower doses (OR = 4.64, p = 0.025). However, no differences were found between pre-treated and untreated patients when lower doses were included or between those treated for longer than 6 months compared to those untreated or pre-treated for shorter than 6 months. Similarly, no differences were found either in terms of surgical or endocrine complications (OR = 0.65, p = 0.570), independently of the doses and the duration of SSA treatment (p > 0.05). Conclusions: the dose of SSAs is a key factor during pre-surgical treatment, since the beneficial effects in surgical remission were observed with monthly doses equal or higher than 90 mg of lanreotide and 30 mg of octreotide, but not with lower doses.

Clinical and Radiological Predictors of Biochemical Response to First-Line Treatment With Somatostatin Receptor Ligands in Acromegaly: A Real-Life Perspective

BACKGROUND

First-generation somatostatin receptor ligands (fg-SRLs) represent the first-line medical treatment for acromegaly, recommended in patients with persistent disease after neurosurgery, or when surgical approach is not feasible. Despite the lack of strong recommendations from guidelines and consensus statements, data from national Registries report an increasing use of medical therapy as first-line treatment in acromegaly.

OBJECTIVE

We retrospectively evaluated the potential role of a large number of clinical and radiological parameters in predicting the biochemical response to 6-month treatment with fg-SRLs, in a cohort of naïve acromegaly patients referred to a single tertiary center for pituitary diseases.

METHODS

Univariable and multivariable logistic regression and linear regression analyses were performed. Biochemical response was defined based on IGF-1 levels, represented as both categorical (tight control, control, >50% reduction) and continuous (linear % reduction) variables.

RESULTS

Fifty-one patients (33 females, median age 57 years) were included in the study. At univariable logistic regression analysis, we found that younger age (≤ 40 years; OR 0.04, p=0.045) and higher BMI (OR 0.866, p=0.034) were associated with a lower chance of achieving >50% IGF-1 reduction. On the contrary, higher IGF-1 xULN values at diagnosis (OR 2.304, p=0.007) and a T2-hypointense tumor (OR 18, p=0.017) were associated with a significantly higher likelihood of achieving >50% IGF-1 reduction after SRL therapy. Of note, dichotomized age, IGF1 xULN at diagnosis, and T2-hypointense signal of the tumor were retained as significant predictors by our multivariable logistic regression model. Furthermore, investigating the presence of predictors to the linear % IGF-1 reduction, we found a negative association with younger age (≤ 40 years; β -0.533, p<0.0001), while a positive association was observed with both IGF-1 xULN levels at diagnosis (β 0.330, p=0.018) and the presence of a T2-hypointense pituitary tumor (β 0.466, p=0.019). All these variables were still significant predictors at multivariable analysis.

CONCLUSIONS

Dichotomized age, IGF-1 levels at diagnosis, and tumor T2-weighted signal are reliable predictors of both >50% IGF-1 reduction and linear % IGF-1 reduction after 6 month fg-SRL treatment in naïve acromegaly patients. These parameters should be considered in the light of an individualized treatment for acromegaly patients.

Dosimetric analysis of patients with gastro entero pancreatic neuroendocrine tumors (NETs) treated with PRCRT (peptide receptor chemo radionuclide therapy) using Lu-177 DOTATATE and capecitabine/temozolomide (CAP/TEM)

OBJECTIVE:

Two radiosensitizing chemotherapeutic drugs, capecitabine (CAP) and temozolomide (TEM), are administered concurrently to enhance the therapeutic efficacy of peptide receptor radionuclide therapy (PRRT). This study aims to assess the biodistribution and normal-organ and tumor radiation dosimetry for Lu-177 DOTATATE administered concurrently with CAP/TEM.

METHODS:

20 patients with non-resectable histologically confirmed gastroenteropancreatic neuroendocrine tumors with normal kidney function, a normal haematological profile and somatostatin receptor expression of the tumor lesions, as scintigraphically assessed by a Ga-68 DOTANOC scan, were included in two groups-case group (n = 10) and control group (n = 10). Patients included in case group were those who were advised concomitant CAPTEM therapy by the treating medical oncologist. Patients were administered CAP orally at a dose of 600mg m-2 bovine serum albumin twice a day for 14 days starting 9 days prior to PRRT and oral TEM as a single dose at a dose of 75 mg m-2 was given concurrently for the last 5 days commencing on the day of PRRT (days 9-14). In the control group, patients were treated with Lu-177 DOTATATE only. For PRRT, 6.4 GBq-7.6 GBq (173-207 mCi) of Lu-177 DOTATATE was administered as infusion into each patient over 10-15 min in a solution with positively charged amino acids for renal protection. Dosimetric calculations were done using the HERMES software.

RESULTS:

Physiological uptake of Lu-177 DOTATATE was seen in all patients in liver, spleen kidneys, and bone marrow. Radiation absorbed doses (mean ± standard deviation) were obtained as 0.29 ± 0.12 mGy/MBq for kidneys, 0.30 ± 0.18 mGy/MBq for liver, 0.63 ± 0.37 mGy/MBq for spleen, 0.019 ± 0.001 mGy/MBq for bone marrow and 3.85 ± 1.74 mGy/MBq for tumours in the case group and they were 0.31± 0.26, 0.24 ± 0.14, 0.64 ± 0.42, 0.017 ± 0.016, 5.6 ± 11.27 mGy/MBq in kidneys, liver, spleen, bone marrow and neuroendocrine tumour, respectively, in the control group. Mann-Whitney U test between the variables of two groups showed an insignificant difference (p > 0.05).

CONCLUSIONS:

The authors demonstrated no significant difference between the tumor and organ doses with Lu-177 DOTATATE in the patients treated with and without concomitant chemotherapy.

ADVANCES IN KNOWLEDGE:

To our knowledge, this is the first dedicated study exhibiting dosimetric analysis in patients undergoing PRRT in combination with chemotherapy.

Dynamic 68Ga-DOTATOC PET/CT and static image in NET patients

Purpose: To investigate the relationship between the dynamic parameters (Ki) and static image-derived parameters of 68Ga-DOTATOC-PET, to determine which static parameter best reflects underlying somatostatin-receptor-expression (SSR) levels on neuroendocrine tumours (NETs). Patients, methods: 20 patients with metastasized NETs underwent a dynamic and static 68Ga-DOTATOC-PET before PRRT and at 7 and 40 weeks after the first administration of 90Y-DOTATOC (in total 4 cycles were planned); 175 lesions were defined and analyzed on the dynamic as well as static scans. Quantitative analysis was performed using the software PMOD. One to five target lesions per patient were chosen and delineated manually on the baseline dynamic scan and further, on the corresponding static 68Ga-DOTATOC-PET and the dynamic and static 68Ga-DOTATOC-PET at the other time-points; SUVmax and SUVmean of the lesions was assessed on the other six scans. The input function was retrieved from the abdominal aorta on the images. Further on, Ki was calculated using the Patlak-Plot. At last, 5 reference regions for normalization of SUVtumour were delineated on the static scans resulting in 5 ratios (SUVratio). Results: SUVmax and SUVmean of the tumoural lesions on the dynamic 68Ga-DO-TATOC-PET had a very strong correlation with the corresponding parameters in the static scan (R²: 0.94 and 0.95 respectively). SUVmax, SUVmean and Ki of the lesions showed a good linear correlation; the SUVratios correlated poorly with Ki. A significantly better correlation was noticed between Ki and SUVtumour(max and mean) (p < 0.0001). Conclusions: As the dynamic para meter Ki correlates best with the absolute SUVtumour, SUVtumour best reflects underlying SSR-levels in NETs.

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.

Impact of pre-treatment with somatostatin analogs on surgical management of acromegalic patients referred to a single center

First-line treatment of patients with growth hormone secreting adenomas is surgical resection. Disease control can be obtained by surgery (one or multiple steps), in case followed by medical treatment or adjuvant radiation therapy (radiosurgery or radiotherapy). The impact of pre-surgical treatment with somatostatin analogs (SSAs) on surgical outcome is still controversial. The aim of this study is to retrospectively evaluate the impact of SSA pre-treatment on biochemical outcome and post-surgical hypopituitarism in a consecutive surgical series from a single referral centre, with data covering 17 years' experience and to investigate the possible predictive value of early postoperative insulin-like factor 1 (IGF-I) on long-term biochemical control. Data from 68 acromegalic patients were revised. Endocrinological long-term follow-up (minimum 6 months) was available for 57 patients. Eighty-eight percent of patients received a single-step surgical treatment (single surgery, with or without adjuvant medical therapy). The remaining 12% underwent a multi-step strategy: redo-surgery (three macroadenomas) and/or radiation (four macro- and two microadenomas). Pre-surgical SSA treatment was performed in 77.9% and resulted in a significant lowering of basal IGF-I values (p = 0.0001). Early post-surgical IGF-I was significantly lower in patients biochemically controlled with single surgery alone (p = 0.016) and after overall treatment strategies (p = 0.005). Normalization of GH and IGF-I was obtained in 56.1%, and normalization of either one of them in 27.8% of patients. No major surgery-related complications occurred. Post-treatment hypopituitarism occurred in 11.9% and was lower in SSA pre-treated patients. Our results well compare with other recently published series. Very early post-surgical IGF-I improvement might be a useful predictor for biochemical disease control. Moreover, our results suggest that pre-surgical treatment with somatostatin analogs seems to prevent hypopituitarism.

The role of primary pharmacological therapy in acromegaly

BACKGROUND AND OBJECTIVES

Primary pharmacological therapy may be the only viable treatment option for many patients with acromegaly, especially those presenting with advanced disease with large inoperable tumors. Long-acting somatostatin analogs are currently the first-line treatment of choice in this setting, where they provide biochemical control and reduce tumor size in a significant proportion of patients. We herein present a brief overview of the role of primary pharmacological therapy in the treatment of acromegaly within the context of Latin America and support this with a representative case study.

CASE DESCRIPTION

A 20 year old male presented with clinical and biochemical evidence of acromegaly. The glucose-suppressed growth hormone (GH) was 5.3 μg/L, his insulin-like growth factor-1(IGF-1) was 3.5 times the ULN and serum prolactin greater than 4,000 μg/L. Pituitary MRI revealed a large and invasive mass, extending superiorly into the optic chiasm and laterally into the left cavernous sinus. He was treated with a combination of octreotide and cabergoline with remarkable clinical improvement, normalization of GH and IGF-1 values and striking shrinkage of the adenoma.

CONCLUSION

This case illustrates how effective the pharmacological therapy of acromegaly can be and yet at the same time, raises several important issues such as the need for life-long treatment with costly medications such as the somatostatin analogs. Access to these agents may be limited in regions where resources are restricted and clinicians face challenges in order to make the most efficient use of available options.