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| 25 years ago, at about this time of year, while anxious over finishing my Ph.D, I found out that I had cancer and it would take three weeks for the specialists at Dana Farber to see me. While I had time on my hands I learned about cancer. While we are waiting for the time that I will describe the staging and treatment of my cancer, allow me to give a description of cancer and its treatment in a greatly over-simplified form. I hope you find it informative, and will help you to understand how chemotherapy works as I describe it later. Cell biology is the farthest from my training so I relied heavily on Wikipedia's entry on cell cycle. |
| CANCER IN A NUTSHELL - PART FOUR GENERAL PRINCIPLES OF CANCER CHEMOTHERAPY - - |
| Cancer is treated with three main techniques. Surgery to cut out the cancerous cells, radiation therapy to destroy a cells where the radiation is applied, and cancer chemotherapy. Chemotherapy means treating a disease with chemical agents or drugs in general, but the phrase chemotherapy in common usage refers to treatment of with anticancer agents. Cancer chemotherapy has the advantage of being systematic meaning it travels through out the entire body. In the last 20 years, biological and targeted therapies have been developed, but these are not in wide-spread use yet. I will be discussing classical chemotherapy treatments which were started after World War II and came into wide use in the late 60s and early 70s. |
| Upfront let me say cancer chemotherapy is basically a selective, selective, controlled administration of poisons. No matter how they deliver the "medicine" in IV bottles, these substances are known toxic, nasty compounds. Why would physicians administer such vile substances to their patients? It has to do with the nature of cancer that I discussed in my last few Chronicles. Cancer cells are normal cells that have gone rogue by dividing uncontrollably and dismissing tissue boundaries. They are controlled by DNA like all the rest of your cells, and go through the cell cycle like all the cells in your body. The trick with cancer chemotherapy is to attack cancer cells selectively even though they are very similar to normal cells. Anti-cancer drugs target rapidly dividing cells, and because several normals cells normally rapidly divide, there will be collateral damage. The so called side effects of cancer chemotherapy are unlike other side effects because they are expected from the toxic nature of the treatment. |
| How did chemotherapy begin? During World War II, even though there were agreements against chemical warfare, both sides kept supplies just in case. One such stockpile of sulfur mustard was aboard the US ship John Harvey that was sunk by a German air raid in Bari, Italy. A little over 600 soldiers were hospitalized with effects from the blistering gas. Of these, 68 died of their injuries. Autopsies of these victims found that there bone marrow and lymph cells were essentially destroyed. Dr. Stewart Francis Alexander, a Lieutenant Colonel and expert in chemical warfare theorized that because the mustard gas had most affected the rapidly dividing cells, it might be effective against rapidly dividing cancer cells. A related compound called nitrogen mustard suppressed tumors in mice and in a human patient with lymphoma. Researchers then searched for toxic agents that would be treatments for cancer. |
| In general chemotherapy agents most affect the rapidly dividing normal cells. Damage to each of these cells leads to a related side effect. The cells that are most rapidly diving under normal circumstances and the side effects that are associated with them in parentheses are: bone marrow (reduction of blood cells: red cells (anemia), white cells (immune suppression), and platlets (clotting problems), hair cells (loss of hair), gastrointestinal system (inflammation of GI tract, ulcers, and taste problems), and sex cells (infertility). Specific drugs may also attack specific organs. The nausea and vomiting that occur after administration of drugs is a remnant of our dinosaur brain that assumes that toxic substances in the blood means one has eaten something terrible and the body attempts to remove the offensive material from the stomach. The cumulative effects of these shocks to the body generally result in what is called a general sense of malaise or fatigue. |
| What would you say if I told you that all cancers can be eliminated today? The problem is that the dose to do this would kill the patient. Instead a chemotherapy is generally given in several doses over a time period of usually weeks of months. The goal is to balance killing cancer cells with minimization of damage to the patient. The usual procedure is to try to kill a large portion of the cancer cells, say 99.9%, allow the patent to recover during which there is some growth in the cancer cells, and repeat the process until every cancer cell is eliminated. The most susceptible cancer cells are those that are most rapidly dividing such as leukemias, lymphomas, testicular, and ovarian cancers. In contrast organ cancers such as pancreas, kidney, or lung cancers are less rapidly dividing, and respond less favorably to chemotherapy. |
| There are several possible goals of chemotherapy. In favorable cases, the goal may be to cure the cancer. In some cases management of cancer as a chronic disease may be the best choice. For some cases, it is used to reduce suffering even though cure is not possible. Preoperative administration of chemotherapy may be used to reduce a tumor, so surgery is less traumatic. One of the more common uses of chemotherapy is to treat post operative or post radiation patients even in the absence of evidence of cancer to try to mop up and destroy every last cancer cell. The latter method was used in my case. |
| Next up I will describe the mechanism of action of various classes of anti-cancer drugs. |
| CANCER IN A NUTSHELL - PART THREE THE CELL CYCLE EMPHASIZING THE ROLE OF DNA |
| Stay tuned for more of the story. |
| (Cancer Chronicles is a series of status updates that account the events of 25 years ago when I went through a bout with cancer. Its purposes are multi-fold: catharsis, education, information, celebration, etc. ) |
| This originally was posted to facebook October 15, 2012. |
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