Significance of a Single-Time-Point Somatostatin Receptor SPECT/Multiphase CT Protocol in the Diagnostic Work-up of Gastroenteropancreatic Neuroendocrine Neoplasms

Abstract

This prospective study compared a 1-d SPECT/CT protocol with the commonly used 3-d protocol for somatostatin receptor scintigraphy in patients with gastroenteropancreatic neuroendocrine neoplasms. Additionally, the influence of SPECT/CT on patient management was evaluated. Methods: From October 2011 to October 2012, all gastroenteropancreatic neuroendocrine neoplasm patients undergoing restaging with somatostatin receptor scintigraphy on a modern SPECT/CT device were enrolled in this study. The protocol consisted of planar imaging at 4, 24, and 48 h; low-dose SPECT/CT at 24 and 48 h; diagnostic CT at 24 h using a triple-phase delay after administration of contrast; and diagnostic SPECT/CT at 24 h. All components of the imaging data were reassessed by 3 masked interpreters. The results were compared with a reference standard based on all clinical, imaging, and histopathology follow-up data available (follow-up range, 24-36 mo; mean, 29.9 mo). The reference standard was defined by a study-specific interdisciplinary tumor board that also reassessed treatment decisions. Results: Thirty-one patients were eligible for analysis (18 men and 13 women; mean age, 60.4 y). Ten had no imaging signs of disease and remained disease-free during follow-up. Twenty-one had persistent or recurrent disease (82 lesions: 24 in the liver, 21 in the lymph nodes, 16 in bone, 12 in the pancreas, and 9 in other locations). The respective lesion detection rates for interpreters 1, 2, and 3 were 51.9%, 49.4%, and 71.6% for low-dose SPECT/CT at 24 h; 51.9%, 55.6%, and 67.9% for low-dose SPECT/CT at 48 h; 63.0%, 70.4%, and 85.2% for diagnostic CT; and 77.8%, 84.0%, and 88.9% for diagnostic SPECT/CT. Interobserver agreement was moderate for diagnostic SPECT/CT (κ 5 0.44), diagnostic CT (κ 5 0.43), low-dose SPECT/CT at 48 h (κ 5 0.61), and low-dose SPECT/CT at 24 h (κ 5 0.55). For planar imaging, interobserver agreement was fair after 48 h (κ 5 0.36) and 24 h (κ 5 0.38) and moderate after 4 h (κ 5 0.42). Every lesion detectable on planar imaging or lowdose SPECT/CT was also detectable on diagnostic SPECT/CT. The CT and SPECT components of diagnostic SPECT/CT strongly complemented each other, as 34 of 82 lesions (41.4%) were detected on only the CT component or only the SPECT component. Therapeutic management was influenced by the diagnostic SPECT/CT interpretation in 8 of 31 patients (25.8%). Conclusion: The highest detection rates were achieved by diagnostic SPECT/CT. Thus, a more patient-friendly 1-d protocol is feasible. Furthermore, multiphase SPECT/CT affected management in about a quarter of patients.

The crucial role of age and site in incidence and prognosis of female neuroendocrine neoplasms in the United States: a population-based study from 2000 to 2018

“…Consistent with previous reports, the age-adjusted annual incidence of fNENs has gradually risen over the past decade, in which Grade 1 and localized fNENs rose markedly [ 14 , 15 ]. This is possibly attributed to the detection of asymptomatic early-stage disease after the extensive use of endoscopy and computed tomography [ 20 ]. Notably, the morbidity of different sites presented obvious discriminations.…”

“…Although fNENs of the lung, rectum and intestine occupy the majority, the appendiceal fNENs showed an unexpectedly tremendous increase (11-fold). Interestingly, the phenomenon was observed in recent years, partly attributed to a better understanding of the pathophysiologic presentation of NENs, improved classification system, as well as availability of advanced imaging modalities [20][21][22]. Another reason may be that pelvic surgery increased the probability of finding appendiceal fNEN [23].…”

Feasibility of a streamlined imaging protocol in technetium-99m-Tektrotyd somatostatin receptor SPECT/CT

“…Tc99m-HYNIC-Tyr3-Octreotide (Tektrotyd) has the advantage of ready availability of radio-isotope from departmental Technetium-99m generators, a single day imaging protocol and superior image resolution [7]. In addition the mean effective dose from Tc99m-Tektrotyd, reported to be 4.6 +/-1.1mSv [8], is significantly less than that for In-111-Octreotide at 8-16 mSv [9] Prior studies of In-111 SRS have shown that integration of SPECT/CT facilitates streamlining of imaging protocols with reduction in imaging time-points needed as it permits more reliable differentiation of pathological uptake from physiological activity [5,10]. Widely adopted In-111 SRS protocols recommend image acquisition at 24 (+/-48) hours' post-injection allowing 'wash-out' of accumulated bowel uptake of excreted tracer.…”

“…This study aimed to determine the feasibility of a streamlined imaging protocol in Tc99m-Tektrotyd SRS SPECT/CT with omission of 2-hour planar imaging, which, to the best of our knowledge has not been previously reported. Two prior studies have reported that use of SPECT/CT in In-111-labelled SRS allows rationalisation of dual time-point imaging to a single time-point protocol without impairment of diagnostic ability [5,10]. Our rationale for switching from In-111 SRS to Tc99m-Tektrotyd imaging of NETs included the superior image resolution afforded by the physical characteristics of Tc99m which make it better suited to gamma camera imaging, lower patient radiation exposure and increased availability of tracer from departmental generators permitting more flexibility in departmental workflow [7].…”