Gene expression patterns as marker for 5-year postoperative prognosis of primary breast cancers

To establish the novel prognostic markers for breast cancer, gene expression profile was examined genome-wide. We used cDNA microarray consisting of 18,432 human genes to compare genome-wide expression profiles of eight primary breast cancers, four from patients who died of breast cancer within 5 years after surgery (5D group) and four who survived disease-free for more than 5 years (5S group). We identified 21 genes whose expression was greater in tumors from the 5D group than in 5S tumors, and 23 with higher expression in the 5S group than in the 5D group. We established a Prognostic Index (PI) for prediction of postoperative prognosis, based on the aberrant expression profiles of ten of those genes. Among 20 additional cases chosen blindly, ten presented with high prognostic scores (>7, good) according to the PI; the remaining ten cases revealed scores