Article History
Received: 4 October 2017
Accepted: 20 February 2018
First Online: 16 April 2018
Compliance with ethical standards
: Approval was obtained from the ethics committee of the Hunan Cancer Hospital. Before data collection, all participants were informed of the purposes and potential benefits/risks of the research. Participation was completely voluntary. Informed consent forms were signed after consent was obtained.
: The authors declare that they have no conflicts of interest.