Other than surgery there are basically two other therapies for cancer, namely radiotherapy, done by the radiation oncologists and chemotherapy done by the medical oncologists. Recently biologic therapies or immunotherapies have come into vogue but those are also done by the medical oncologists.
Theoretically radiotherapy, if it had not its limitations, would have been the most perfect therapy for cancer. Unlike surgery it does not need to invade the body to reach the tumor and unlike chemotherapy it does not affect all the cells of the body. It kills cancer cells with ionizing radiation delivered directly to the tumor by targeting beams of radioactive rays from a machine. The rays deposit energy within the cells and that damage the genetic material of the cancer cells and make them cease to grow. The damage to the cancer cells are said to be irreversible while the collateral damage done to the surrounding normal cells is reversible.
To increase effectiveness and to minimize collateral damage various techniques are used. Radiotherapy given from a distant source located inside a machine is called teleradiotherapy, e.g. the cobalt machines and the linear accelerators and radiotherapy given from a radioactive source placed inside the body is called brachytherapy, which is generally used to supplement teletherapy in uterine cervix cancers, breast and soft tissue sarcomas, and a few cancers of the eyelid and esophagus. Between the cobalt and the linear accelerators, the later can do the job more effectively because the Linacs can target the tumor more effectively and precisely and transfer more energy inside the cancer cells thereby achieving more cancer cell kill and less damage to the normal cells.
To increase effectiveness, radiotherapists at times use drugs that make the cells more radiosensitive (radiosentisisers ) or drugs that protect the normal cells (radioprotectors). Current advances soon will make available particle beam radiation, which use fast moving subatomic particles that can deposit still higher energy and cause more damage and also innovations like radioimmonotherapy that use injections of radiolabeled antibodies, which carry radioactive molecules on their back, seek out the cancer cells specifically, and deliver doses of radiation directly to the individual cells.
In current therapeutic practice radiotherapy is often the chosen modality when the primary tumor is small and has occurred in an organ which is cosmetically and functionally important like tongue, larynx, breast, brain, and uterine cervix. But it is mostly used after surgical treatment with a view to kill any residual cancer cells in the surgical field and nodal drainage area in head and neck cancers, breast cancer, lung cancer, rectal cancer, genitourinary cancers, and sarcomas and in combination with chemotherapy for cancers of lung, testicular tumors, lymphomas and some other locally advanced cancers not in a suitable stage for surgery. It is also used for pain palliation. (See side effects at the bottom).
Chemotherapy simply means treatment with drugs or chemical agents, Treatment of infection with antibiotics is also chemotherapy. All living cells, normal or cancer, pass through a cycle of different stages of activity while dividing to grow into more cells and require various nutrients and other stimuli in each stage. The drugs used for chemotherapy take advantage of those requirements and try to stop cell division by cutting off the supply or use of those nutrients.
Consequently the drugs affect more the cells which are dividing more actively and at a faster rate. Since cancer cells divide at a much greater speed, the drugs affect those most and can achieve ‘Cell Kill’ against a growing cancer though they also kill some normal dividing cells and hence produce side affects or toxicity. Based on this fundamental fact, and from experiments and clinical observations, it has been concluded that 1) bigger growths (i.e. more cells) need greater doses of the drugs 2) growths which divide more rapidly get most affected 3) since different drugs affect different stages of the cycle a cell passes through during division, a combination of drugs is more useful than a single drug. 4) Since all cells even in a very rapidly growing tumor are not in active division at any given point of time, the drugs have to be given periodically and repeatedly. 5) But, because every drug also kills some normal cells and thereby causes toxicity, there is a limit to its dose after which body cannot tolerate it.
That is why the dose is calculated according to the body surface area of the patient not the size of the tumor and the body must be given sufficient time and rest to recover before the next dose is given.
Take for example the common protocol of a combination of adriamycin, flurauracil, and cyclophosphamide for breast cancer, each drug acting in different stage of the cell cycle. The drugs are used in dosage appropriate to an individual patient and are repeated every three weeks. But because flurauracil and adriamycin both have cardiotoxicity, many prefer to replace adriamycin with epirubicin which has less cardiotoxicity but same antitumor action or use only adriamycin and cyclophophamide.
Chemotherapeutic drugs are mostly given through intravenous injections, only a few are oral. The drugs are very toxic to the local tissues; therefore a very secure intravenous route needs to be established. Patients usually have a ‘channel’ made in one of their arm veins with the help of a short soft intravenous catheter and it is securely maintained during the administration of drugs. After a few courses this can be a painful procedure because the veins generally get damaged and it becomes difficult to establish a channel. For this, patients who receive intense chemotherapy, particularly the children, get inserted in their body an indwelling catheter or a port, which can be maintained for many months, during the course of the entire therapy, in order to avoid the repeated painful procedure of pricking to establish channel and to have a secure line all through the treatment.
Chemotherapy is the mainstay of treatment for blood and lymph gland cancers. Amongst the common solid tumors some are sensitive to chemotherapy, some are not. While oral cancers are to some extent chemosensitive, tumors of the parotid gland and thyroid are not. Whether one patient will receive chemotherapy along with surgical treatment will depend on the stage of the tumor and its sensitivity to chemotherapy. For example a young lady with breast cancer that has spread to the lymph glands in axilla will need intense chemotherapy, while an elderly lady with early breast cancer may not need it. A stage II tongue cancer will receive radiotherapy but for all stages of ovarian cancer chemotherapy is a must. Most abdominal cancers except the kidneys are candidates for chemotherapy particularly in their late stages. At times chemotherapy is given before the surgical treatment when the disease is too advanced already or in order to better the the results of surgery. Often radiotherapy and chemotherapy are combined together along with surgical treatment.
Both radiotherapy and chemotherapy have dose limiting side effects which prevent them being used to their fullest potential. Both act on dividing cells and consequently affect the normal dividing cells of the body. The cells that grow most are worst affected, like the hair follicles, cells of the lining of the mouth and the gastrointestinal tracts, and the blood cells. While chemotherapy affects all the cells of the body, radiotherapy in general affects the cells of the local part where radiotherapy is given. In that respect chemotherapy is more toxic than radiotherapy. Conversely some of the damages done by radiotherapy are permanent, like damage to the thyroid and spinal cord during radiation to neck and damage to heart or lungs during radiation to chest. Chemotherapy toxicities, except in a few cases, are reversible. The common side effects in case of radiation are change in skin color, loss of hair, sores in the treated area, and lowering of blood count, and a general sense of weakness, the most serious effect being the collateral damage to the nearby organs. The common side effects of chemotherapy are nausea and vomiting, hair loss, lowering of blood count, and mouth sores, diarrhea. Some drugs might cause neuropathy, which is at times permanent.
Many believe that the ultimate solution to the problem of cancer treatment lies in the field of immunotherapy because ultimately the body’s ability to develop an immune reaction to tumors decide if a person will be cured of his cancer, whatever the modality of treatment has been, be it surgery, radiotherapy or chemotherapy. So if methods are found to boost or develop body’s immunity reaction in general or against the specific tumor in particular, cancer can be cured. Researchers have come out with certain agents that have shown initial promise in certain tumors. Most are in preclinical testing but a few are already in clinical use. Examples are ,
BCG or Bacillus Calmette-Guérin treats bladder tumors or bladder cancer.
IL-2 or Interleukin-2 treats certain types of cancer.
Interferon alpha treats certain types of cancer.
Biologic therapy also include Targeted Cancer Therapy that use drugs that block the growth and spread of cancer. Scientists have identified specific molecules that take part in the growth of cancer or in its sustenance by drawing nutrition. These molecules now have become targets for cancer therapy with substances and because these substances interfere with specific molecular targets involved in the process of development of a cancerous growth, this kind of therapy is called molecularly targeted therapies. By acting directly on molecular and cellular changes that are specific to cancer, targeted cancer therapies may be more effective and less harmful to normal cells. Rituxan or Rituximab which treats non-Hodgkin's lymphoma or Herceptin or Trastuzumab which treats breast cancer are two examples already in clinical use. There are other agents available in the market, which act against the factors that help a cancer grow and against the blood supply of a growing tumor. Every day some new drugs are being developed for these types of therapies and it is expected that within a couple of years these drugs will make cancer therapy more effective and safe.
Alternative therapy: One would be surprised to find the number of alternative therapies available for cancer treatment, from common herbal drugs to special diets, exotic preparations made by secret societies, innovative contraptions of magnetic and electrical gadgets, and sudden discoveries of a magic elixir. The list is almost endless. While considering these products, consider two undisputable facts. One is that, cancer being a disease produced by multiple causes and having many types and forms, there will never be a one particular drug that will cure all cancers. Secondly, to date, inspite of repeated attempts by the scientific community in the whole world, no claim for such cure has either been scientifically established or documented. So look before you leap to waste your valuable money and more importantly time, which is the essence of a successful cancer treatment.
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