General Cancer Information

Chemotherapy

Was first shown effective in the 1940's for Hodgkin's Disease, using a drug similar to the mustard gas from World War I (Mechlorethamine). Previously, all patients had died from Hodgkin's Disease, and this drug (in combination with some others) saved the lives of over half of these patients! This was obviously a major advance in the war against cancer. In short order, new chemotherapy agents were found effective against leukemia, testicular cancer, and childhood cancers. Hundreds of drugs have now been developed, and most cancers show some "response" to them, either alone or combined with other drugs and therapies. Chemotherapy works by interfering with the division of cancer cells, and when they can't divide, they die out. It selectively kills cells which are dividing rapidly, as cancer cells tend to do. The side-effects are from the chemother- apy killing normal cells that also divide rapidly, such as hair follicles (causing baldness), gut cells (causing nausea, vomiting, and diarrhea) and bone marrow (leads to anemia and infections). These side effects are pretty much common to all chemotherapy agents. Specific drugs have other side effects, such as heart or nerve damage, or sterility, which are described along with the particular cancers they are used for. Chemotherapy is administered by a "medical oncologist" and patients must be carefully monitored when getting it, owing to the side effects. While chemotherapy goes all over the body (called "systemic therapy") and can kill cells which have escaped from the original tumor, it is usually less effective in killing a bulky original tumor (called "local therapy"). Since getting control of the both the original tumor and any metastasis is critical for cure, chemotherapy may be combined with some local treatment like surgery, radiation therapy, or both, to increase it's effect.

Unfortunately, many cancers develop resistance to chemotherapy over time, much the same way as bacteria can develop resistance to antibiotics. This means that while the tumor may initially shrink, indicating a good response, a celebration is premature. The chemotherapy may cease to become effective and the cancer can grow and spread rapidly. It then seems to be resistant to other chemotherapy agents (called "second line" or "salvage" therapy) also. Many dose regimens, schedules , and combinations of chemotherapy have been tried to reduce this problem. It seems clear that it is important to hit the cancer very hard right away, trying to kill it before it can develop resistance.

No one "magic bullet" drug has yet been found that cures all cancer, and it seems unlikely that any one drug ever will. This is because "cancer" is a name representing many different diseases, and a drug which is effective against one cancer may be useless against another. Over- all, about 10% of all new cancers are curable using chemo- therapy alone, with childhood cancers faring better. Results are much better when it is used in combination with other treatments like surgery and radiation therapy, at the price of greater side effects.