Circulating pro-gastrin releasing peptide (ProGRP) in patients with medullary thyroid carcinoma

Serum calcitonin (CT) is pivotal in medullary thyroid cancer (MTC) management. Recently, progastrin releasing peptide (ProGRP) has been proposed as a candidate complementary tumor marker of MTC. As current data are sparse our study was undertaken to evaluate the distribution of ProGRP in patients with MTC and its relationship with the tumor burden. Additionally, serial measurement of CT, carcinoembryonic antigen (CEA) and ProGRP was evaluated in three patients undergoing tyrosine kinase inhibitors (TKI).

Seventy-eight, 125 and 62 sera from patients with MTC, non-medullary malignant and benign thyroid diseases were collected, respectively. ProGRP measurement was performed by Elecsys^® assays on Cobas e601 platform (Roche Diagnostics).

Significantly higher ProGRP levels were found in MTC compared to non-MTC patients. Among MTC patients ProGRP levels accurately discriminate patients with active from those with cured disease and, respectively, patients with loco-regional active disease from those with distant metastasis. Finally, ProGRP performed better than CT and CEA in monitoring the response to TKI therapy in three patients monitored serially.

Serum ProGRP is promising as a complementary tumor marker in MTC patients. Further studies will be required, mainly focused on monitoring ProGRP during TKI treatment for early detection of resistance and assessing its usefulness to avoid the observed false positive fluctuations that occur with CT and carcinoembryonic antigen.