Provided is a composition that contains a mixture of brocolli seed and mustard seed. Before mixning the brocolli seed with the mustard seed, the broccoli seed is subjected to baking and a pressurized heat treatment. The broccolli seed is baked at a temperature of at least 200 degrees Fahrenheit for at least 60 minutes, and is subjected to a pressurized heat treatment of at least 200 degrees Fahrenheit at a pressure of at least 10 pounds/square inch for at least 5 minutes. Also provided is a method for therapy and/or prophylaxis of bladder cancer in an individual The method entails administering orally to the individual a composition that contains an isothiocyanate (ITC) such that the administration inhibits the growth and/or recurrence of bladder cancer.