Somatostatin Receptor-targeted Therapy Research Articles

Immunohistochemical assessment and clinical, histopathologic, and molecular correlates of membranous somatostatin type-2A receptor expression in high-risk pediatric central nervous system tumors.

177Lu-DOTATATE, a radionuclide therapy that binds somatostatin type-2A receptors (SST2A), has demonstrated efficacy in neuroendocrine tumors and evidence of central nervous system (CNS) penetration, supporting potential expansion within pediatric neuro-oncology. Understanding the prevalence of SST2A expression across pediatric CNS tumors is essential to identify patients who may benefit from somatostatin receptor-targeted therapy and to further elucidate the oncogenic role of SST2A. SST2A immunohistochemistry (IHC) was performed on tumor specimens and interpreted by an experienced pathologist (blinded), utilizing semi-quantitative scoring of membranous expression within viable tumor. Immunoreactive cell percentage was visually scored as 0 (none), 1 (<10%), 2 (10-50%), 3 (51-80%), or 4 (>80%). Staining intensity was scored as 0 (none), 1 (weak), 2 (moderate), or 3 (strong). Combined scores for each specimen were calculated by multiplying percent immunoreactivity and staining intensity values (Range: 0-12). A total of 120 tumor samples from 114 patients were analyzed. Significant differences in SST2A IHC scores were observed across histopathologic diagnoses, with consistently high scores in medulloblastoma (mean ± SD: 7.5 ± 3.6 [n=38]) and meningioma (5.7 ± 3.4 [n=15]), compared to minimal or absent expression in ATRT (0.3 ± 0.6 [n=3]), ETMR (1.0 ± 0 [n=3]), ependymoma (grades I-III; 0.2 ± 0.7 [n=27]), and high-grade glioma (grades III-IV; 0.4 ± 0.7 [n=23]). Pineoblastoma (3.8 ± 1.5 [n=4]) and other embryonal tumors (2.0 ± 4.0 [n=7]) exhibited intermediate, variable expression. Among medulloblastomas, SST2A IHC scores were higher in non-SHH (8.5 ± 3.1) than SHH (5.0 ± 3.3) molecular subgroups (p=0.033). In a subset of paired primary and recurrent specimens from four patients, SST2A IHC scores remained largely unchanged. High membranous SST2A expression was demonstrated in medulloblastoma, meningioma, and some rarer embryonal tumors with potential diagnostic, biologic, and therapeutic implications. Somatostatin receptor-targeted therapy such as 177Lu-DOTATATE deserves further investigation in these highly SST2A-expressing pediatric CNS tumors.

Invasive Breast Carcinoma with Neuroendocrine Differentiation: A Single-Center Analysis of Clinical Features and Prognosis.

Introduction Invasive breast cancer with neuroendocrine differentiation is a rare subtype of breast malignancy. Due to frequent changes in the definition of these lesions, the correct diagnosis, estimation of exact prevalence, and clinical behaviour of this entity may be challenging. The aim of this study was to evaluate the prevalence, clinical features, and outcomes in a large cohort of patients with breast cancer with neuroendocrine differentiation. Patients Twenty-seven cases of breast cancer with neuroendocrine differentiation have been included in this analysis. Twenty-one cases were identified by systematic immunohistochemical re-evaluation of 465 breast cancer specimens using the neuroendocrine markers chromogranin A and synaptophysin, resulting in a prevalence of 4.5%. A further six cases were identified by a review of clinical records. Results Median age at the time of diagnosis was 61 years. 70% of patients had T2 – 4 tumors and 37% were node-positive. The most common immunohistochemical subtype was HR-positive/HER2-negative (85%). 93% were positive for synaptophysin and 48% for chromogranin A. Somatostatin receptor type 2A status was positive in 12 of 24 analyzed tumors (50%). Neuroendocrine-specific treatment with somatostatin analogues was administered in two patients. The 5-year survival rate was 70%. Conclusions Breast cancer with neuroendocrine differentiation is mostly HR-positive/HER2-negative and the diagnosis is made at a higher TNM stage than in patients with conventional invasive breast carcinoma. Moreover, breast cancer with neuroendocrine differentiation was found to be associated with impaired prognosis in several retrospective trials. Due to somatostatin receptor 2A expression, somatostatin receptor-based imaging can be used and somatostatin receptor-targeted therapy can be offered in selected cases.

BIOM-42. IMMUNOHISTOCHEMICAL ASSESSMENT OF MEMBRANOUS SOMATOSTATIN TYPE 2A RECEPTOR (SST2A) EXPRESSION ACROSS HIGH-RISK PEDIATRIC CENTRAL NERVOUS SYSTEM (CNS) TUMORS

Abstract INTRODUCTION 77Lu-DOTATATE, a radionuclide therapy which binds SST2A, has demonstrated efficacy in neuroendocrine tumors and evidence of CNS penetration, supporting potential expansion within pediatric neuro-oncology. Understanding the prevalence of SST2A expression across pediatric CNS tumors is essential to identify patients who may benefit from somatostatin receptor-targeted therapy and to further elucidate the oncogenic role of SST2A. METHODS SST2A immunohistochemistry (IHC) was performed on tumor specimens and interpreted by two experienced pathologists (blinded), utilizing semi-quantitative scoring of membranous expression within viable tumor. Immunoreactive cell percentage was visually scored as 0 (none), 1 (&amp;lt; 10%), 2 (10-50%), 3 (51-80%), or 4 (&amp;gt;80%). Staining intensity was scored as 0 (none), 1 (weak), 2 (moderate), or 3 (strong). Combined scores for each specimen were calculated by multiplying percent immunoreactivity and staining intensity values (range=0-12). RESULTS A total of 117 tumor samples from 113 patients were analyzed. Significant differences in SST2A IHC scores were observed across histopathologic diagnoses, with consistently high scores in medulloblastoma (mean±SD=7.6±3.6 [n=36]) and meningioma (5.7±3.4 [n=15]), compared to minimal or absent expression in ATRT (0.3±0.6 [n=3]), ETMR (1.0±0 [n=3]), ependymoma (grades I-III; 0.2±0.7 [n=26]), and high-grade glioma (grades III-IV; 0.4±0.7 [n=22]). Pineoblastoma (3.8±1.5 [n=4]) and other embryonal tumors (2.3±3.8 [n=8]) exhibited intermediate, variable expression. Among expressors, there was no association between SST2A IHC score and patient age, sex, presence of metastases, likelihood of relapse, or prior treatment. In a subset of paired primary and recurrent specimens from 3 patients, SST2A IHC scores remained largely unchanged. Among medulloblastomas, SST2A IHC scores were higher in non-SHH (8.6±3.2) than SHH (5.0±3.3) molecular subgroups (p=0.033). CONCLUSIONS High membranous SST2A expression was demonstrated in medulloblastoma, meningioma, and some rarer embryonal tumors with potential diagnostic, biologic, and therapeutic implications. Somatostatin receptor-targeted therapy such as 177Lu-DOTATATE deserves further investigation in these highly SST2A-expressing pediatric CNS tumors.

Somatostatin Receptor–Targeted Radioligand Therapy in Head and Neck Paraganglioma

Surgical resection is the therapy of choice in head and neck paraganglioma but is associated with considerable morbidity. For treatment of inoperable or progressive disease, less aggressive adjuvant options are warranted. This study assessed effectiveness and safety of peptide receptor radionuclide therapy (PRRT) with lutetium-177-DOTATATE for head and neck paraganglioma with emphasis on response assessment. A retrospective analysis of 7 patients with head and neck paraganglioma treated with PPRT between May 2014 and October 2016 was performed. Three patients had jugulotympanic paraganglioma, 3 patients had carotid body tumors, and 1 patient had a combination of both. Patients underwent PRRT after discussion in the local tumor board regarding progressive disease, inoperability, or lack of other adjuvant options. All patients underwent 3-5 cycles of PRRT. Treatment response was evaluated by gallium-68-DOTATATE positron emission tomography/computed tomography and contrast-enhanced computed tomography or magnetic resonance imaging. Outcome measures were two-dimensional tumor diameters and total tumor volumes. Median patient age was 60 years (interquartile range: 14-84 years). All patients had stable disease at posttherapy assessment. Decreasing tumor volumes were found in 4 patients. Clinical symptoms improved in 2 patients. No progression or adverse events occurred during a median follow-up of 39 months (interquartile range: 35-47 months). Somatostatin receptor-targeted therapy using lutetium-177-DOTATATE shows promising effectiveness with a high safety profile. Patients in whom surgical morbidity outweighs oncologic benefit should be informed about PRRT as a treatment option.

One Single-Time-Point Kidney Uptake From OctreoScan Correlates With Number of Desintegrations Measured Over 72 Hours and Calculated for the 6.7 Hours Half-Life Nuclide 177Lu

In somatostatin receptor-targeted therapy, renal toxicity is an expected side effect, and therefore pretherapeutic dosimetry based on a measured kinetics is preferable. In contrast, a convenient one single-time-point scan might also reveal relevant information on expected dose to organs. However, very early time points might not reflect the true retention by the renal cortex and therefore be of limited value to predict dose for the long-lived 177Lu. Dosimetry with 111In-octreotide was performed in 24 patients, and the number of disintegrations (ND) were calculated for 177Lu. Uptake values for each time point were correlated with ND. The fitting algorithm was best with biexponential equations in 18 patients. Mean biologic half-life of the alpha component was 6 hours (+/-12 hours) and for the beta component 82 hours (+/-38 hours). For the early time points, correlation with ND was generally poor. For later time points, correlation increased markedly after 4 hours (4 hours: r = 0.83, 72 hours: r = 0.93) and were also capable of predicting dosimetry to some extent. In conclusion, thorough quantification of the 4 hours single-time-point scans seems to be enough to predict the expected renal dose for radionuclide therapies to some degree.