[1] Georgetown Univ, Canc Genet & Epidemiol Program, Dept Oncol, Vincent T Lombardi Canc Res Ctr, Washington, DC 20057 USA
[2] Cairo Univ, Dept Publ Hlth, Cairo, Egypt
[3] Assiut Univ, S Egypt Canc Inst, Assiut, Egypt
[4] Ain Shams Univ, Dept Community Environm & Occupat Med, Cairo, Egypt
[5] Univ Maryland, Dept Epidemiol & Prevent Med, Baltimore, MD 21201 USA