Background: Chromogranin A (CgA) is considered the most accurate marker in the diagnosis of gastro-entero-pancreatic (GEP) endocrine tumors. Pancreatic polypeptide (PP) has also been proposed to play this role, but then not used due to its low sensitivity. The aim of the present study was to determine whether the assessment of PP would improve the diagnostic reliability of CgA in patients with GEP tumors.
Patients and methods: Both markers were assessed in 68 patients [28 functioning (F), 40 non functioning (NF)]. Twenty-seven patients disease-free (DF) after surgery, and 24 with non-endocrine tumors (non-ETs) were used as control groups.
Results: CgA sensitivity was: 96% in F, 75% in NF, 74% in pancreatic, and 91% in gastrointestinal (GI) tumors. Specificity was 89% vs DF, and 63% vs non-ETs. PP sensitivity was: 54% in F, 57% in NF, 63% in pancreatic, and 53% in GI tumors. Specificity was 81% vs DF, and 67% vs non-ETs. By combining the two markers a significant gain in sensitivity vs CgA alone was obtained: overall in GEP tumors (96% vs 84%, p = 0.04), in NF (95% vs 75%, p = 0.02), and in pancreatic (94% vs 74%, p = 0.04). More specifically, a 25% gain of sensitivity was obtained in the subgroup of NF pancreatic tumors (93% vs 68%, p = 0.04).
Conclusion: The combined assessment of PP and CgA leads to a significant increase in sensitivity in the diagnosis of GEP tumors, particularly in pancreatic NF.