Two studies have found an association between smoking and advanced stage or poorly differentiated prostate cancer (Daniell 1995 J Urol 154: 153-7; Hussain et al 1992 Int J Radiat Oncol Biol Phys 24: 451-61) which lends further support to this theory, however another 9 studies did not (Le Marchand et al 1994, Severson et al 1989, Thune and Lund 1994, Talamini et al 1993, Giles et al 1996, Slattery and West 1993, Walker et al 1992, Hayes et al 1994, Norrish et al 1998).