IS CHROMOSOME-9 LOSS A MARKER OF DISEASE RECURRENCE IN TRANSITIONAL CELL CARCINOMA OF THE URINARY-BLADDER

Investigation of transitional cell carcinoma of the urinary bladder (T CC) patients classified by recurrence and/or progression has demonstra ted that loss of chromosome 9, as detected by FISH analysis of the per icentromeric classical satellite marker at 9q12, occurs early. A total of 105 TCCs from 53 patients were analysed in situ by two independent observers for loss of chromosome 9 using quantitative fluorescence in situ hybridization (FISH). All 53 primary tumours were evaluated for chromosomes 9, 7 and 17. Normal ranges for chromosomal copy number wer e defined for normal skin epidermis and bladder epithelium. Values for chromosome 9 copy number outwith the range 1.51-2.10 (mean +/- 3 x s. d. of normal values) were significantly abnormal. Twenty-five TCCs wer e detected with consistent monosomic scores. Of 89 TCCs, in which mult iple tumour areas were analysed, 85 tumours (96%) demonstrated the sam e chromosome 9 copy number in all areas (2-6) analysed; only three tum ours demonstrated heterogeneity for this locus. A total of 36% (12 out of 33) of patients with subsequent disease recurrence demonstrated lo ss of chromosome 9 in their primary and all subsequent TCCs analysed. Only a single patient (n = 20) with non-recurrent TCC showed loss of c hromosome 9 (P = 0.0085). Of 53 primary tumours, eight showed signific ant elevation of chromosome 17. Of these patients, six demonstrated el evation in chromosome 7 copy number. No abnormalities were observed in non-recurrent patients. This study describes rapid quantitation of ch romosomal copy number by FISH using a pericentromeric probe for chromo some 9 in TCC of the urinary bladder. Routinely fixed and processed ma terial was evaluated without disaggregation. Strict quality control of FISH demonstrated that this technique was reproducible in a clinical environment and could be used to detect genetic changes relevant to pa tient outcome. It is proposed that loss of chromosome 9 from primary T CC of the urinary bladder identified patients at high risk of recurren ce and possible progression.