Received: 3 June 2019
Accepted: 3 October 2019
First Online: 8 November 2019
Ethics approval and consent to participate
: This study was deemed exempt from institutional review board approval by Sun Yat-sen University Cancer Center and the informed consent was waived. This study was conducted in accordance with the ethical standards of the World Medical Association Declaration of Helsinki.
: Not applicable.
: The authors declare that they have no competing interests.