Effects of urine and continued exposure to carcinogen on progression of early neoplastic urinary bladder lesions.

Based on reports of regression of superficial bladder tumors after urinary diversion, a study was designed to measure the effects of urine and continued exposure to carcinogen on the incidence of progression of N-[4-(5-nitro-2-furyl)-2-thiazolyl]-formamide-induced early urinary bladder lesions to invasive tumor. After being fed 0.2% N-[4-(5-nitro-2-furyl)-2-thiazolyl]formamide diet for 14 weeks, one-half of the male Fischer rats had urinary diversion by ureterosigmoidostomy, and the remainder were sham operated. One-half of each of these two groups was continued on the N-[4-(5-nitro-2-furyl)-2-thiazolyl]formamide diet while the remaining animals were fed regular chow postoperatively. One-half of each of the four groups was sacrificed at 3 months, and the remainder were sacrificed at 6 months after ureterosigmoidostomy or sham-operation. The incidence and mean number of tumors as well as the incidence of invasive tumor were tabulated. The combined 3- and 6-month data indicate that excreted carcinogen in the urine influences progression of the preinvasive lesions more than urine alone or systemic carcinogen alone. However, urine alone had a significant effect (p < 0.025) on tumor incidence (8 of 19 sham-operated animals with tumor versus 1 of 18 diverted animals with tumor). Urine acts as a promoter in this experimental system. These findings may have clinical applications in the treatment of early transitional cell carcinoma.