Mitomycin belongs to the group of cancer-fighting medications known as antineoplastics, and specifically to the group of antineoplastics called actinomycins. Another actinomycin is dactinomycin. Mitomycin kills cancer cells by interfering with their growth and reproduction. It is used alone or in combination with other antineoplastic medications, radiation, or surgery to treat certain types of stomach and colon cancer. It is also used to treat a certain type of cancer of the bladder.