Our data indicated that the pattern of allelic loss at chromosome 9p21 (p16) and 17p13 (p53) in primary bladder cancer was generally maintained during cancer progression to metastasis, and an identical pattern of allelic loss in primary cancer was conserved in paired metastatic carcinoma, suggesting that allelic loss of these chromosome regions most likely occurs prior to the
metastatic sequence. It is possible that allelic loss at these loci may be used as bladder cancer markers when the primary tumor of metastasis is unknown.