[68Ga]-DOTATOC PET Imaging for Neuroendocrine Tumors

Introduction and Rationale

Non-invasive imaging and monitoring of neuroendocrine tumors has traditionally relied upon conventional scintigraphy and/or dedicated CT (¹¹¹In-octreotide scintigraphy). Imaging and monitoring of neuroendocrine tumors through the detection and tracking of tumor-based somatostatin receptors using diagnostic somatostatin analogs is still relatively new, yet current research suggests that it can be far more accurate than traditional methodologies (Hofmann et al., 2001; Buchmann et al., 2007; Gabriel et al., 2007; Poeppel et al., 2011). One study showed that the newer technique achieved a sensitivity of ninety-seven percent, a specificity of ninety-two percent, and an accuracy of ninety-six percent, with only one false positive tumor detection and two false negative results in a data pool of eighty-four patients (Gabriel et al., 2007).

Traditional tumor detection methods applied in the same study had significantly higher false negative rates and more frequent failures to diagnose tumors in many areas of the body, whereas the two false negatives resulting from [68Ga]-DOTATOC somatostatin receptor analysis were both related to tumors in the gastrointestinal tract with liver metastases (Gabriel et al., 2007). The continued study of various artificial somatostatin analogs as a means of imaging neuroendocrine tumors is called for by these preliminary findings.

Superiority of Somatostatin Receptor-Based Imaging

More specifically, the study of [68Ga]-DOTATOC as the most effective of these analogs is also warranted by the research (Hofmann et al., 2001; Buchmann et al., 2007; Gabriel et al., 2007; Poeppel et al., 2011). Much of the current literature finds that [68Ga]-DOTATOC PET applications — and other PET applications using different somatostatin analogs — are more effective than traditional methods of neuroendocrine tumor detection and monitoring, and the general recommendation of including such testing as part of best practices can already be made (Hoffmann et al., 2011; Gabriel et al., 2007).

Studies comparing the accuracy and efficacy of [68Ga]-DOTATOC relative to other somatostatin analogs used in similar or otherwise identical PET studies also suggest that [68Ga]-DOTATOC is more effective and accurate than its counterparts; however, these results are not yet conclusive and call more fervently for further research in order to establish the true accuracy level of [68Ga]-DOTATOC in relation to other neuroendocrine tumor detection and monitoring methods (Buchmann et al., 2007; Poeppel et al., 2011). Establishing and confirming best practices in this regard will lead to greater efficiency and cost-effectiveness in diagnostic testing, and to substantially better patient outcomes through increased accuracy and the earlier detection and treatment of neuroendocrine tumors.

Proposed Study Design and Participant Selection

Potential participants who have recently undergone diagnostic treatment at one of several area hospitals will be contacted by current physician and/or nursing staff to ascertain initial desire to participate, with contact by research staff made only after initial agreement. Full disclosure and privacy information will be delivered, and consent obtained, before further examinations for inclusion appropriateness are made. A cohort of approximately one hundred participants recently diagnosed and not yet treated for neuroendocrine tumors will eventually be selected for this study, providing an adequate sample size to produce significant validity, reliability, and generalizability (Gabriel et al., 2007). A control group of approximately twenty-five individuals recently given negative results on conventional scintigraphy and/or dedicated CT diagnostic measures for neuroendocrine tumors will also be included.

All study participants will undergo imaging and diagnostic testing for neuroendocrine tumors using each of the three target methodologies: [68Ga]-DOTATOC-based PET imaging, conventional scintigraphy, and dedicated CT (¹¹¹In-octreotide scintigraphy). All tests will be completed on each patient within a four-day timeframe, and all testing for the study will be completed within a three-month period. Follow-up documentation of treatments, neuroendocrine tumor diagnosis confirmation or rejection using histopathology, CT and MRI, and an ultimate determination of neuroendocrine tumor status at the time of initial testing will also be conducted in order to validate the findings of initial diagnostic outcomes. Follow-up examinations will occur at three weeks and again at six weeks after initial testing (Buchmann et al., 2007; Gabriel et al., 2007). Several local facilities have the capabilities to perform all necessary tests as described herein, and will be selected based on cost, availability, and proximity to participants in order to reduce rates of attrition.