There is conflicting lierature on the association between SU and cancer. While meta-analysis found no evidence that SU was associated with raised cancer risk another review of 18 studies showed that SU use is associated with an increase in all-cancer risk in cohort studies (rr=1.55 [95 % cl=1.48-1.63]) ,but not in RCTs (rr=1.17 [95 % cl=0.95-1.45]) and case-cotrol studies (or=1.02 [95 % cl=0.93-1.13])