Transitional explant reduction assay--a new in vitro testing system for intravesical chemotherapy.

Eighty-five tumors from 49 patients with transitional cell carcinoma were examined in a model for in vitro sensitivity using tumor explant reduction assay. Individual sensitivity patterns were obtained for each tumor tested. Explants were most frequently found to be sensitive to cis-platinum (49 per cent) and least frequently sensitive to thiotepa (20 per cent). Thirteen patients were studied on multiple sequential intervals, with resistance to specific agents noted to develop in 53 per cent of the patients. To date, a prospective cross-over study has been conducted on seven patients with 15 correlates. Overall, clinical correlation of this assay for both resistance and sensitivity is 93 per cent. We report a new assay for transitional cell carcinoma of the bladder that is adaptable to small specimen samples and provides adequate material for testing 73 per cent of the time.