Is the combination of chromogranin A and pancreatic polypeptide serum determinations of interest in the diagnosis and follow-up of gastro-entero-pancreatic neuroendocrine tumours?

INTRODUCTION: Chromogranin A (CgA) is the principal tumour marker for gastroenteropancreatic neuroendocrine tumours (GEPNET). Combining serum CgA and pancreatic polypeptide (PP) levels may increase the sensitivity of tumour markers in the diagnosis of GEPNET.
OBJECTIVES: (1) To evaluate the sensitivity of PP and CgA in GEPNET. (2) To compare changes in serum CgA and PP levels with the morphological evolution of the tumours. PATIENTS AND METHODS: Sixty-six pancreatic and 49 gastrointestinal NET, with at least one serum determination of CgA and PP at the same time were retrieved from an institutional data base. Secondly, the variations in serum CgA or PP at successive determinations were compared to Response Evaluation Criteria in Solid Tumours (RECIST) criteria in 57 patients (112 follow-up visits) with high serum CgA levels and in 21 patients (37 follow-up visits) with high serum PP levels.
RESULTS: Among the 115 patients included in the study group, an increase in serum CgA (normal <98 μg/L) or PP (normal <100 pmol/L) was found in respectively 79 (69%) and 36 (31%) cases. Seven patients had normal CgA and elevated PP levels. Both markers were significantly more elevated in metastatic disease (74% versus 51% for CgA and 37% versus 18% for PP). The concordance rates between serum markers and RECIST criteria were 51% for CgA and 54% for PP.
CONCLUSIONS: Serum PP determination identify few false-negative results of serum CgA determination in GEPNET. Our study does not validate the use of CgA or PP as surrogate markers for detecting changes in tumour burden.