Treatment with Octreotide Does Not Reduce Tumor Uptake of 68Ga-DOTATATE as Measured by PET/CT in Patients with Neuroendocrine Tumors

Hepatocellular carcinoma and gastroenteropancreatic neuroendocrine tumors: potential role of other positron emission tomography radiotracers

18F-Fluorodeoxyglucose avidity for gastroenteropancreatic neuroendocrine tumors and hepatocellular carcinoma is variable, depending on the underlying tumor biology. Experience with non-fluorodeoxyglucose (FDG) tracers (eg, 18F-labeled amine precursors l-dihydroxyphenylalanine and 68Ga-DOTA-peptides for gastroenteropancreatic neuroendocrine tumors and radiolabeled acetate or choline for hepatocellular carcinoma) is evolving and expanding rapidly. This article reviews the role of FDG and non-FDG radiotracers in the imaging evaluation of patients with gastroenteropancreatic neuroendocrine tumors or hepatocellular carcinoma.

The clinical value of scintigraphy of neuroendocrine tumors using (99m)Tc-HYNIC-TOC

PURPOSE

To assess the value of whole body scintigraphy using (99m)Tc-HYNIC-TOC (Tektrotyd) and with single photon emission computerized tomography (SPECT) in the detection of primary and metastatic neuroendocrine tumors (NETs).

METHODS

Thirty patients with different neuroendocrine tumors, mainly gastroenteropancreatic (GEP), were investigated. Whole body scintigraphy was performed 2 h (if necessary 10 min and 24h) after i.v. administration of 740 Mbq (99m)Tc-Tektrotyd, Polatom. In cases of unclear findings obtained by whole body scintigraphy, investigation was followed by SPECT.

RESULTS

From 12 patients with NETs of unknown origin, there were 10 true positive (TP), and 2 false negative (FN) findings. Diagnosis was made with SPECT in 6 patients. From 8 patients with gut carcinoids, there were 4 TP, 2 true negative (TN), one FN, and one false positive (FP) finding. Diagnosis was made with SPECT in 2 patients. From 7 patients with neuroendocrine pancreatic carcinomas there were 4 TP and 3 TN findings. Diagnosis was made with SPECT in 2 patients. From 3 patients with gastrinomas there were 2 TP findings and one TN findings. Diagnosis was made with SPECT findings in 2 patients. Sensitivity of (99m)Tc-HYNIC-TOC was 87%, specificity 86%, positive predictive value 95%, negative predictive value 67% and accuracy 87%.

CONCLUSION

We concluded that scintigraphy with (99m)Tc-Tektrotyd is an useful method for diagnosis, staging and follow up of the patients with NETs.

Neuroendocrine tumor disease: an evolving landscape

Gastroenteropancreatic neuroendocrine neoplasms (GEP-NENs) represent a heterogenous group of tumors arising from a variety of neuroendocrine cell types. The incidence and prevalence of GEP-NENs have markedly increased over the last three decades. Symptoms are often absent in early disease, or vague and nonspecific even in advanced disease. Delayed diagnosis is thus common. Chromogranin A is the most commonly used biomarker but has limitations as does the proliferative marker Ki-67%, which is often used for tumor grading and determination of therapy. The development of a multidimensional prognostic nomogram may be valuable in predicting tumor behavior and guiding therapy but requires validation. Identification of NENs that express somatostatin receptors (SSTR) allows for SSTR scintigraphy and positron emission tomography imaging using novel radiolabeled compounds. Complete surgical resection of limited disease or endoscopic ablation of small lesions localized in stomach or rectum can provide cure; however, the majority of GEP-NENs are metastatic (most frequently the liver and/or mesenteric lymph nodes) at diagnosis. Selected patients with metastatic disease may benefit from advanced surgical techniques including hepatic resection or liver transplantation. Somatostatin analogs are effective for symptomatic treatment and exhibit some degree of antiproliferative activity in small intestinal NENs. There is a place for streptozotocin, temozolomide, and capecitabine in the management of pancreatic NENs, while new agents targeting either mTOR (everolimus) or angiogenic (sunitinib) pathways have shown efficacy in these lesions.

Temozolomide and unusual indications: review of literature

Temozolomide (TMZ) was first known to be useful as a radiosensitiser in both primary brain tumours like glioblastoma multiforme and oligodendroglioma. Later, TMZ proved its efficacy in the treatment of melanoma. Multiple publications have demonstrated the benefit of TMZ in terms of efficacy and tolerance (used as mono-therapy or as adjuvant chemotherapy) compared to the "gold standard" treatment of this kind of tumours. Furthermore, several recent clinical trials have shown the particular importance of TMZ in other types of cancer. This publication deals with the use of TMZ in cancers which are not formal indications for TMZ (excluding glioblastoma multiforme, oligodendroglioma and melanoma). It also includes a necessary review of recent literature about the role of TMZ in the treatment of brain metastases, lymphomas, refractory leukaemia, neuroendocrine tumours, pituitary tumours, Ewing's sarcoma, primitive neuroectodermal tumours, lung cancer and other tumours.

[Gastroenteropancreatic neuroendocrine tumors: diagnosis and therapy in nuclear medicine]

The over expression of somatostatin receptors (SSTR) in neuroendocrine tumors (NET) enables diagnosis and targeted therapy using radio-labelled somatostatin analogues. PET with (68)Ga-DOTATATE or (68)Ga-DOTATOC, both with a high affinity to the SSTR subtype 2, enables diagnosis of NET with a very high sensitivity and has a significant influence on the therapeutic management of patients with NET. In particular, therapy with (177)Lu-DOTATATE, which offers a considerably lower nephrotoxicity as compared to (90)Y-DOTATOC, has only few side effects and is usually well tolerated. Up to 46% of patients suffering from GEP-NET show a response to this therapy, which is able to mitigate tumour-related symptoms and significantly improve quality of life.