Received: 17 February 2021
Accepted: 27 May 2021
First Online: 7 June 2021
: The study was approved by the Ethical Committee of Jinan Central Hospital Affiliated to Shandong University (Jinan, China). All enrolled patients had signed an informed consent to refuse surgery because of comorbidities or unwillingness to undergo surgery. This study was conducted in accordance with the Declaration of Helsinki.
: The authors declared that they have no conflicts of interest to this work.