Panitumumab and irinotecan versus irinotecan alone for patients with KRAS wild-type, fluorouracil-resistant advanced colorectal cancer (PICCOLO): A prospectively stratified randomised trial - Seymour, M; Brown, SR; Middleton, G; Maughan, T; Richman, S; Gwyther, S; Lowe, C; Seligmann, J; Wadsley, J; Maisey, N; Chau, I; Hill, M; et al. (Lancet Oncology, 2013)