There's good reason for that. Cancer is a much more complex disease than, say, a bacterial infection. Cancer, on the other hand, has many different causes. In addition, a physician can give an antibiotic such as penicillin to a patient with bacterial pneumonia and cure the disease within weeks. But scientists doubt that anyone will ever find a treatment that is specific for cancer in the way that antibiotics are specific for bacterial infections.
Antibiotics work because the biochemistry of bacteria is far different from that of human beings.
But the biochemistry of cancer cells differs little from that of normal cells, making it impossible so far to develop a poison that kills cancer cells only. In addition, antibiotics need kill only 70 to 80 percent of the bacteria causing the infection. The patient's immune system overcomes the rest. Some evidence indicates the immune system works to some degree against cancer, but other evidence says that, in at least some cancers, every cancer cell must be destroyed to prevent recurrence. He also has data that suggest that survival of a single tumor cell may be sufficient to kill the host.