Plasma Progastrin-Releasing Peptide and Chromogranin A Assays for Diagnosing and Monitoring Lung Well-Differentiated Neuroendocrine Tumors: A Brief Report

Progastrin-Releasing Peptide As a Diagnostic Biomarker of Pulmonary and Non-Pulmonary Neuroendocrine Neoplasms

BACKGROUND

Progastrin-releasing peptide (ProGRP) is the precursor of the gastrin-releasing peptide, a neuropeptide secreted by cells of neural and endocrine origin. Recently, ProGRP has emerged as a circulating biomarker for small cell lung cancer (SCLC), a subtype of aggressive and poorly differentiated neuroendocrine neoplasm (NEN). Given the ability of the neuroendocrine SCLC cells to secrete this peptide, we performed an in-depth narrative review aimed at collecting, summarizing, and critically analyzing the available literature about the possible value of ProGRP as a biomarker for pulmonary NENs other than SCLC, and for NENs of non-pulmonary origin.

METHODS

We conducted an extensive search on international databases (PubMed, Web of Science, and Scopus).

RESULTS

We selected 21 pertinent published articles (12 original studies and 9 case reports). Overall, the original studies included 1,711 patients, and the case reports described the clinical course of 10 patients.

CONCLUSION

The data analyzed suggest a potential role for ProGRP as a diagnostic biomarker for typical and atypical lung carcinoids, pulmonary large cell neuroendocrine carcinoma, medullary thyroid carcinoma, non-pulmonary neuroendocrine carcinomas, prostate cancer with neuroendocrine differentiation, and the pancreatobiliary neuroendocrine carcinoma. Despite these promising results, additional studies are needed, to clarify the role of ProGRP as the diagnostic biomarker for specific NENs.

An Overview of Circulating Biomarkers in Neuroendocrine Neoplasms: A Clinical Guide

Neuroendocrine neoplasms (NENs) are a heterogeneous group of diseases that are characterized by different behavior and clinical manifestations. The diagnosis and management of this group of tumors are challenging due to tumor complexity and lack of precise and widely validated biomarkers. Indeed, the current circulating mono-analyte biomarkers (such as chromogranin A) are ineffective in describing such complex tumors due to their poor sensitivity and specificity. In contrast, multi-analytical circulating biomarkers (including NETest) are emerging as more effective tools to determine the real-time profile of the disease, both in terms of accurate diagnosis and effective treatment. In this review, we will analyze the capabilities and limitations of different circulating biomarkers focusing on three relevant questions: (1) accurate and early diagnosis; (2) monitoring of disease progression and response to therapy; and (3) detection of early relapse.

Pro-Gastrin-Releasing Peptide as a Biomarker in Lung Neuroendocrine Neoplasm

There is a lack of effective biomarkers for diagnosing lung neuroendocrine neoplasms (LNENs). A known small cell lung cancer (SCLC) biomarker is a pro-gastrin-releasing peptide (ProGRP), but not for all LNENs, especially for bronchopulmonary carcinoids. This study aimed to evaluate the diagnostic value of ProGRP and chromogranin A (CgA) in diagnosing LNENs. The ProGRP and CgA levels in 290 cases of LNENs and 54 healthy controls (HCs) were measured. The median ProGRP concentration in the group of LNEN patients was 136.4 pg/mL, higher than that of HCs at 6.5 pg/mL. Most of the LNEN cohort was well-differentiated tumors (typical and atypical carcinoids, n = 262, 91.7% of all LNENs). The sensitivity, specificity, and area under the curve (AUC) of ProGRP when distinguishing LNENs vs. HCs were 94.8%, 100%, and 0.995. CgA (AUC = 0.375) could not determine LNENs vs. HCs. Therefore, based on these results, ProGRP may be considered as an effective marker for diagnosing LNENs.