Completeness of RET testing in patients with medullary thyroid carcinoma in Denmark 1997–2013: a nationwide study

Jes Sloth Mathiesen,1,2 Jens Peter Kroustrup,3 Peter Vestergaard,3,4 Kirstine Stochholm,5,6 Per Løgstrup Poulsen,6 Åse Krogh Rasmussen,7 Ulla Feldt-Rasmussen,7 Sten Schytte,8 Stefano Christian Londero,8 Henrik Baymler Pedersen,9 Christoffer Holst Hahn,10 Jens Bentzen,11 Sören Möller,2,12 Mette Gaustadnes,13 Maria Rossing,14 Finn Cilius Nielsen,14 Kim Brixen,2 Anja Lisbeth Frederiksen,2,15 Christian Godballe1 On behalf of the Danish Thyroid Cancer Group (DATHYRCA) 1Department of ORL Head & Neck Surgery and Audiology, Odense University Hospital, Odense, Denmark; 2Department of Clinical Research, University of Southern Denmark, Odense, Denmark; 3Department of Clinical Medicine and Endocrinology, Aalborg University Hospital, Aalborg, Denmark; 4Steno Diabetes Center North Jutland, Aalborg, Denmark; 5Department of Internal Medicine and Endocrinology, Aarhus University Hospital, Aarhus, Denmark; 6Center for Rare Diseases, Aarhus University Hospital, Aarhus, Denmark; 7Department of Medical Endocrinology, Copenhagen University Hospital, Copenhagen, Denmark; 8Department of ORL Head and Neck Surgery, Aarhus University Hospital, Aarhus, Denmark; 9Department of ORL Head & Neck Surgery, Aalborg University Hospital, Aalborg, Denmark; 10Department of ORL Head & Neck Surgery, Copenhagen University Hospital, Copenhagen, Denmark; 11Department of Oncology, Herlev Hospital, Herlev, Denmark; 12Odense Patient data Explorative Network (OPEN), Odense University Hospital, Odense, Denmark; 13Department of Molecular Medicine, Aarhus University Hospital, Aarhus, Denmark; 14Center for Genomic Medicine, Copenhagen University Hospital, Copenhagen, Denmark; 15Department of Clinical Genetics, Odense University Hospital, Odense, Denmark Background: The completeness of REarranged during Transfection (RET) testing in patients with medullary thyroid carcinoma (MTC) was recently reported as 60%. However, the completeness on a population level is unknown. Similarly, it is unknown if the first Danish guidelines from 2002, recommending RET testing in all MTC patients, improved completeness in Denmark. We conducted a nationwide retrospective cohort study aiming to evaluate the completeness of RET testing in the Danish MTC cohort. Additionally, we aimed to assess the completeness before and after publication of the first Danish guidelines and characterize MTC patients who had not been tested.Methods: The study included 200 patients identified from the nationwide Danish MTC cohort 1997–2013. To identify RET tested MTC patients before December 31, 2014, the MTC cohort was cross-checked with the nationwide Danish RET cohort 1994–2014. To characterize MTC patients who had not been RET tested, we reviewed their medical records and compared them with MTC patients who had been tested.Results: Completeness of RET testing in the overall MTC cohort was 87% (95% CI: 0.81–0.91; 173/200). In the adjusted MTC cohort, after excluding patients diagnosed with hereditary MTC by screening, completeness was 83% (95% CI: 0.76–0.88; 131/158). Completeness was 88% (95% CI: 0.75–0.95; 42/48) and 81% (95% CI: 0.72–0.88) (89/110) before and after publication of the first Danish guidelines, respectively. Patients not RET tested had a higher median age at diagnosis compared to those RET tested. Median time to death was shorter in those not tested relative to those tested.Conclusion: The completeness of RET testing in MTC patients in Denmark seems to be higher than reported in other cohorts. No improvement in completeness was detected after publication of the first Danish guidelines. In addition, data indicate that advanced age and low life expectancy at MTC diagnosis may serve as prognostic indicators to identify patients having a higher likelihood of missing the compulsory RET test. Keywords: RET testing, medullary thyroid carcinoma, Denmark