Erratum: Cancer outcomes and all-cause mortality in adults allocated to metformin: Systematic review and collaborative meta-analysis of randomised clinical trials (Diabetologia DOI: 10.1007/s00125-012-2653-7) - Stevens, R; Ali, R; Bankhead, C; Bethel, M; Cairns, B; Camisasca, R; Crowe, F; Farmer, A; Harrison, S; Hirst, J; Home, P; Kahn, SE; et al. (2012)