The 81 most important genes. A heatmap of 81 genes (rows) and 100 patients (columns) with patients ordered according to their leave-one-out support vector machine classification value: estrogen receptor-positive patients within LR+RT+ (red, n = 20) and LR-RT+/LR-RT- (blue, n = 80) groups. The gene selection and ordering are described in the text. Expression values are logarithmically transformed, centered around zero, and normalized to unit standard deviation. LR-RT- = no local recurrence, no radiotherapy given; LR-RT+ = no local recurrence after radiotherapy; LR+RT+ = local recurrence developed after radiotherapy.