Chromosomal imbalances in noninvasive papillary bladder neoplasms (pTa)

Almost 70% of urinary bladder neoplasms present as low-grade papillary noni nvasive tumors (stage pTa). To determine which genomic alterations can occu r in pTa tumors of different grades and to evaluate the prognostic signific ance of chromosomal imbalances, we analyzed 113 pTa tumors (40 grade 1, 55 grade 2, 18 grade 3) by comparative genomic hybridization. pTaG1 (1.9 +/- 2 .0) and pTaG2 (3.1 +/- 2.9) tumors had only few genomic alterations with 9q - (44%), 9p- (36%), and -Y(21%) being most prevalent. Neither the total num ber of aberrations nor any individual alteration was linked to the risk of recurrence in 95 pTaG1/G2 tumors with clinical follow-up information. pTaG3 tumors were characterized by a high number of alterations (7.7 +/- 4.5; P < 0.0001 for G3 versus G2). Several chromosomal imbalances that have previo usly been reported to be typical for invasive bladder neoplasms were signif icantly more frequent in pTaG3 than in pTaG2 tumors, including 2q-, 5p+, 5q -, 6q-, 8p-,10q-, 18q-, and 20q+. A malfunction of genes at these loci may contribute to the development of high-grade urothelial neoplasias. However, there is no evidence for a direct role of these alterations for developmen t of invasive tumor growth.