Funding for this research was provided by:
European Regional Development Fund (18.104.22.168/VIAA/2/18/270, LZP-2018/1-0135)
Received: 3 April 2021
Accepted: 8 August 2021
First Online: 28 August 2021
: The study protocol (version 4.5, revised on 7 September 2015) of the GISTAR study was approved by the Ethics Committee of the International Agency for Research on Cancer (IEC 12–36) as well as the national Ethics Committees in Latvia; the Ethics Committee of Riga East University Support Foundation (No.14-A/13) and the Central Medical Ethics Committee (No. 01–29.1/11). The protocol is registered in the ClinicalTrials.gov database (NCT02047994).
: Not applicable.
: The authors declare that they have no competing interests.