Identification of H-ras mutations in urine sediments complements cytology in the detection of bladder tumors.

BACKGROUND

Urinary cytology has long been used as a noninvasive screen for the detection of urinary tract cancer but is limited by the generation of false positive and false negative results. More recently, molecular changes associated with urothelial neoplastic progression have been identified in DNA from urine sediments, demonstrating an alternative approach for identifying neoplastic change in the bladder.

PURPOSE

The purpose of this prospective study was to determine the value of detection of H-ras (also known as HRAS) mutations in urine sediment DNA as a clinical indicator of tumor presence, recurrence, and/or progression.

METHODS

Urine sediments were collected from 100 patients presenting with bladder tumors, with follow-up samples collected from 19 patients. DNA extracted from urine sediments was analyzed for changes in exon 1 of the H-ras gene, using single-strand conformation polymorphism (SSCP) analysis. A representative number of aberrant H-ras/SSCP migrating bands were excised and sequenced to confirm the presence of a mutation. Human bladder specimens were obtained from patients (93 of the 100 patients initially and 18 of the 19 patients studied by follow-up) and histologically evaluated for tumor content and grade.

RESULTS

Mutations in exon 1 of the H-ras gene were detected in urine sediments from 44% (44 of 100) of the patients; concordant results were obtained by cytologic analysis, where 33% (31 of 93) of the patients displayed positive cytology. Analysis of the distribution of abnormalities with tumor grade revealed greater detection of low-grade (1-2) lesions using ras analysis (47%) compared with cytology (16%). In contrast, cytology was more effective in identifying the presence of carcinoma in situ. Combined results from these two approaches substantially increased the sensitivity of tumor detection, resulting in the identification of tumors in 60% of patients.

CONCLUSIONS

Identification of H-ras mutations in DNA from urine sediments facilitates the detection of low-grade bladder tumors and, in combination with cytology, increases the overall tumor detection from 33% to 60%. Preliminary results in patient follow-up suggest that detection of H-ras mutations may have some clinical utility in detecting the presence of abnormal cells in the absence of an overt lesion following cystoscopy or positive cytology.