Chemotherapy

The first patients treated with chemotherapy in the 1940’s were given a nitrogen mustard chemical developed by the U.S. Army. Now, there are several different types of chemotherapeutic agents. These drugs are injected into the patient and travel through the bloodstream, so they work best on cancers of the blood, like leukemia. Cancers of the brain are one of the most difficult to cure with chemotherapy because there is a barrier insulating the brain from many foreign materials (like chemotherapeutic chemicals) within the blood.

Chemotherapeutic agents destroy cells by many different methods. Some directly damage the DNA and others keep the cell from making the compounds necessary for it to survive (like proteins, DNA, etc...). Other chemotherapeutic agents prevent cells from dividing and yet others seem to work and the exact mechanism isn’t even known. Chemotherapeutic agents usually act on cells at a certain stage during cell division.

The basic theory behind chemotherapy is that tumor cells divide at a much faster rate than normal cells. Therefore, tumor cells are more likely to be destroyed by chemotherapy than normal cells. There are a few exeptions. Certain normal cells divide faster than others. The faster dividing normal cells are also destroyed during chemotherapy. These include the cells of the intestinal tract, bone marrow and hair follicles. This is why patients receiving chemotherapy exhibit certain trademark side effects like nausea, vomiting and hair loss. Changes in a patient’s blood may also occur due to damage in the bone marrow. Fortunately, tumor cells cannot repair cell damage as well as normal cells do. Therefore, even the rapidly dividing tissues are not damaged to the extent of the tumor cells.

Since chemotherapeutic agents used by physicians today do not only kill tumor cells, a patient can experience a whole host of side effects. Within just hours of treatment, a patient may experience nausea, vomiting, inflammation of a vein, increased concentration of uric acid in the blood and even kidney failure. Within a few days to weeks, a decrease in the number of white blood cells and hair loss may occur. Worse of all, months to years later, a patient may become sterile or a second primary cancer may form.

These are all reasons why researchers need to develop better, more targeted chemotherapeutic agents. Ideally, a chemical should target only tumor cells, leaving normal cells unharmed.

As previously stated, chemotherapeutic agents target tumor cells due to their higher rate of cell division. Researchers are currently developing chemicals targeting other aspects of tumor cells; such as halting the tumor’s ability to induce blood vessel growth (angiogenesis). Or inducing tumor cells to differentiate so they lose their ability to divide out of control. Another area currently focused on by many scientists is on stopping metastasis. Researchers want to learn how to block metastatic tumor cells from degrading the tissue lining or block metastatic cells from “homing” to sites like the lung.