Summary— In a case-control investigation of 154 women with cancer of the bladder and 440 female population controls spanning the same age range, the relative risk for this cancer was 2.6 in consumers of phenacetin-containing analgesics and 2.7 in tobacco smokers. The relative risks for cancer of the renal pelvis, determined for 31 cases, were 5.4 with phenacetin and 4.7 with tobacco. Increasing consumption of either agent increased the risk for cancer at each of the two sites, while a synergistic rather than purely additive effect was apparent when both phenacetin-containing analgesics and tobacco had been taken. Consumption of analgesic preparations which contained no phenacetin did not increase the risk of developing cancer at either site.
The evidence indicates that phenacetin is a clinically important carcinogen for the lower as well as for the upper urinary tract.