Department of Biostatistics, Lineberger Comprehensive Cancer Center, University of North Carolina, Chapel Hill, NC 27599, USA. pfkuan@bios.unc.edu|Department of Biostatistics, Lineberger Comprehensive Cancer Center, University of North Carolina, Chapel Hill, NC 27599, USA. pfkuan@bios.unc.edu|Department of Biostatistics, Lineberger Comprehensive Cancer Center, University of North Carolina, Chapel Hill, NC 27599, USA. pfkuan@bios.unc.edu|Department of Biostatistics, Lineberger Comprehensive Cancer Center, University of North Carolina, Chapel Hill, NC 27599, USA. pfkuan@bios.unc.edu