Received: 27 August 2018
Accepted: 12 July 2019
First Online: 30 July 2019
Ethics approval and consent to participate
: Not applicable. Research has not pertained to individual subject data. According to the Polish legislation, cancer data were previously rendered anonymous with codes. Any additional approval from ethical committees was not required since our study did not involve direct patient contact<b>.</b>
: Not applicable.
: The authors declare that they have no competing interests.