Somatostatin receptor scintigraphy and chromogranin A assay in staging and follow-up of patients with well-differentiated neuroendocrine tumors

Abstract

Chromogranin A (CgA) assay and somatostatin receptor scintigraphy (SRS) are implemented in the standard workup of neuroendocrine tumors (NETs). The aim of this study was to assess the value of SRS and CgA in staging and follow-up patients with well-differentiated NETs. A total of 88 consecutive patients with histologically confirmed well-differentiated NETs were included. General data such as sex, age, site of primary tumor and metastases, medication, and follow-up results, including CgA values, were gathered. The number of lesions on SRS were scored and categorized from 0 to 3 and the uptake was scored from 0 to 4. CgA values differed significantly between patients with and without clinical symptoms (P=0.028), a positive and negative SRS (P=0.005), the different SRS scores (P=0.002), the number of lesions (P=0.001), and the presence or absence of liver metastasis (P=0.003). The sensitivity, specificity, positive predictive value, and negative predictive value were 78, 93, 98, and 47% for SRS and 62, 100, 100, and 35% for CgA; however, by combining the test, all results improved. All patients (n=11) referred for routine follow-up had stable CgA values, whereas in one patient only the SRS score increased. In the group of patients with a suspicion on tumor progression during follow-up (n=14), CgA values increased in nine patients. In this group, the SRS score increased in two patients. Despite the higher sensitivity of SRS than of CgA in staging and restaging well-differentiated NETs, both tests are required at the initial stage. Disease extent, symptoms, and liver metastasis have an impact on both SRS results and CgA values. CgA has an important value in the assessment of tumor progression during follow-up, whereas the role of SRS in the routine follow-up of well-differentiated NETs is limited.