“With human bladder cancer … culture, cytotoxicity of thiotepa was increased up to 10-fold (P less than 0.01) … with pentoxifylline, with a major clinical metabolite of pentoxifylline, or with caffeine ; the pentoxifylline concentrations required (0.4-1.0 mM) … clinically achievable in the bladder after nontoxic p.o.”