Chemotherapy and Radiation Therapy

The blind artillery which cuts down its own men with the same pleasure as it does the enemies.
Aleksandr I. Solzhenitsyn, Cancer Ward

What makes a cancer grow is an imbalance between M, the rate at which cells are produced, and L, the rate at which cells are lost. (See chapter "Anything grows" In theory, treatment can he directed at either preventing or slowing down cell division, or increasing the rate of cell loss. Any treatment which can permanently decrease the rate of cell division (without doing the same thing to all of the other cells of the body), or can permanendy increase the rate of cell loss, would be potentially able to chemically cure a cancer. Most treatments for cancer do not alter these rates at all. What they do is to prune back the tumor (if you remember the diagram; what they do is to empty the bucket). If the surgery or therapy is successful, the entire tumor is removed so that there are no longer any tumor cells left to divide.

The ideal therapeutic agent would act like penicillin or the sulfonamides, and would selectively kill or inhibit the tumor cells, without simultaneously destroying the normal ones. The major problem in finding a drug that will do this can be seen by pointing out some of the differences between bacteria and cancer cells. It is well established that penicillin and the sulfonamides kill or inhibit the vast majority of the organisms that they are supposed to attack, but not all. There are always a few left over. The genetic variability in bacteria (and tumor cells) is such that there are inevitable variants that are resistant to the drug. In the case of bacteria, the remaining organisms are taken care of by the natural body defenses. In the case of cancer cells, the cells are identical, or sufficiently similar to the normal cells of the animal's body so that the individual does not react against them. Any cells that are resistant to the drug and are left over will grow and start the tumor growth cycle all over again. Only this time the cells that grow are resistant to the drug that was used against them. The same principle also holds true for the use of radiation.
In theory it should be possible to prune a tumor way back with one drug; prune the remnant of the tumor with another, and so on, until, like the Cheshire Cat in Alice in Wonderland, there is nothing left but the grin, and that soon disappears. The only trouble with this approach is that while you are doing this to the tumor, you are simultaneously doing the same thing to the normal cells, so that when the tumor disappears, so does the patient; a mere detail to "Alice" fans.
As I've stated, the effect of radiation and chemicals is to destroy a large number of cells. One would ordinarily suppose that this would always be a good idea. The problem is not as simple as it seems. For example: Suppose we were dealing with a tumor that had a doubling time of one week (the tumor would double its size in that time). If we could only manage to kill half of the cells, it would make a difference of one week in the life of the patient. If you could kill 99% or 99.99%, it might make a considerably greater difference in the life of the patient. If, on the other hand, we had a tumor that had a doubling time of one year and you reduced the mass of the tumor by half, it would make a difference of one year to the patient. The effect of radiation and chemotherapy is usually severe illness for a period of time. In order, therefore, to predict whether the radiation were worth using, one would have to know two things: (1) What the doubling time of the tumor is, and (2) What percentage of the cells are destroyed by the radiation. The doubling time of the tumor can be calculated by measurements of the tumor, but there is no real way of knowing what the sensitivity of the cells is to radiation. The approach used is generally empiric. There is some information about the past behavior of specific types of tumors in response to radiation or chemicals. Some types of tumors are more sensitive than others.
There is one important exception to these generalizations. The rare tumor called choriocarcinoma is a cancer usually derived from placental tissue that remained after a baby was born, or an abortion had taken place. This tissue continues to invade the uterus, and sometimes metastasizes. Since this tissue is genetically the same as the baby rather than the mother, it is "different." It therefore responds to treatment in the same way as do bacteria. The chemicals can kill it; and since it is genetically different, the individual bearing it also attacks it immunologically. This tumor can often be completely cured by chemotherapy.
A second possible exception are tumors caused by distinctive viruses. In experimental tumors in mice, when a virus causes a tumor, there is some of the individuality of the virus that is transmitted to the cell surface, such that the cells are immunologically different from the cells from which they originated. It is conceivable that this difference can be exploited, and that chemotherapy might prune back the tumor to the point where the individual's defense system can take over and destroy the rest of the cells. This may be the key to some of the apparent successes in the chemical treatment of acute leukemia, and a tumor called Burkitt's lymphoma.

Very little has been tried in the way of re-educating cancer cells back to a normal state. To do this successfully, one would have to understand the normal physiology of the cell, and what went wrong with it. Until we reach this point, we will have to resort to the usual primitive approach to an enemy -- kill! Unfortunately, in attacking the enemy, one also attacks the patient.

One thing becomes apparent from reading the literature, and talking to a variety of physicians: The chemical treatment of cancer is sufficiently complex and new that it should no more be trusted to the general medical practitioner than should heart surgery. There are relatively few physicians who have the know-how to treat cancer with chemicals, and these are almost exclusively located in either major cancer or medical centers. There is little question that an individual with a curable type of tumor would do better at one of these centers. With tumors that can only be palliated, one must weigh the relative advantages of going to a treatment center against the personal advantages of staying home. It is always a good idea for a patient with cancer to go to one of these centers to find out what they have to offer. It may be very little, or it may be a great deal. Most practitioners aren't too well informed about what is available.

The therapeutic use of x-ray works on the principle that if you can't cut it out, kill it. Many radiotherapists, having an evangelistic streak, feel that it's better to kill it where it sets rather than take it out and then kill it. A knife, however, is much more selective than a radiation beam with regard to what it kills.
I asked a surgeon whose judgment I respected how he would have his wife treated for cancer of the uterine cervix. He said that surgery would be his choice if he knew a first-rate surgeon in a good modern hospital. If there was any question, he would prefer taking his chances with radiation therapy; even with a mediocre radiotherapist. I asked the same ques tion of a radiologist, and he said that he would prefer a mediocre surgeon to a mediocre radiotherapist.
The legitimate uses of radiation are almost exclusively on tumors that cannot be reached surgically. Radiation is effective on tumors of cells of the defense system (the tumor called Hodgkin's disease) and with incurable tumors which can be reduced in size with radiation. There is no question but that radiation works, and that it has prolonged the lives of some people with cancer. It reminds me of the story of the man who was playing roulette and was asked by a friend if he didn't know that the roulette wheel was rigged. He replied, "Of course I know the game is fixed." "Then why do you play it?" asked his friend. His reply was, "Because it is the only wheel in town!"
Since x-ray also produce cancer, it's not a good idea to use it if there is another equally effective way of treatment; provided that the risks are comparable. This is particularly true with regard to its use on children and young adults.

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