1. Department of PathologyKey Laboratory of Cancer Prevention and TherapyTianjin's Clinical Research Center for CancerNational Clinical Research Center for CancerTianjin Cancer Institute and HospitalTianjin Medical University Tianjin 300060 P. R. China
2. Department Epidemiology and BiostatisticsKey Laboratory of Cancer Prevention and TherapyTianjin's Clinical Research Center for CancerNational Clinical Research Center for CancerTianjin Cancer Institute and HospitalTianjin Medical University Tianjin 300060 P.R. China
3. Institute for Interdisciplinary Information SciencesTsinghua University Beijing 100084 P. R. China