By Dr Ananya Mandal, MD
Cancers are often considered incurable. With advances in diagnostic methods that allow early diagnosis and detection of cancer and advances in therapeutic modalities there are innumerable patients living fruitful lives with cancer.
People who have been successful in keeping their cancer away with treatment are said to be in remission. However, even after successful therapy and years of remission there remains a risk of relapse and return of cancer. Cancer patients thus need appropriate therapy and follow up to detect the reappearance of the cancer.
Therapy of cancers depends on many factors. Some of these are:
- Type of cancer
- Stage of cancer
- Grade or aggressive nature of the cancer
- Patient’s general health
- Patient’s acceptability of the treatment
Modalities of treatment
Cancer therapies include surgery, radiation therapy and chemotherapy.
The primary and oldest treatment for cancer is surgery, and several special surgical techniques can be used. Surgery is used also in diagnosis and staging to determine the extent and amount of disease.
Surgical therapy may be of two types - prophylactic surgery and therapeutic or curative surgery. The patient may elect for prophylactic surgery that involves removal of tissue that is not malignant but which may become malignant. A common example is prophylactic or precautionary removal of the breasts in women with a mutation in the BRCA gene that raises their risk of getting breast cancer.
Curative surgery involves removal of the tumor and is often done in conjunction with chemotherapy or radiotherapy to achieve a cure.
There is another type of surgery called palliative surgery. Palliative surgery is not done to cure cancer but is used to treat complications of advanced disease. This type of surgery may also be used to remove the bulk of the tumor.
For example, palliative surgery can debulk tumors that are blocking the function of organs. Palliative surgery is also used to treat pain that is difficult to control in other ways like medications.
Radiotherapy uses radiation to kill cells. All cells of the body have a cell cycle. The cell grows from G0, G1, S, G2, and M.
Radiation is most effective on cells in the dividing stages and less effective on cells in the “resting” phase of G0. Radiation therapy aims to stop cancer cells from dividing, thus killing them and destroying the tumor.
Radiation therapy, however, is not selective and may affect the rapidly dividing surrounding healthy cells as well. This includes cells that line the mouth and hair cells, are often destroyed also, leading to mucositis (sores in the mouth or mouth ulcers) and alopecia (loss of hair), respectively.
Other dividing cells such as blood cells are also destroyed in the process of radiation leading to low White blood cell counts and a susceptibility to infections and a low Red blood cell count leading to anemia. There may also be a low platelet count leading to bleeding tendencies.
Radiotherapy is a gradual process, with the total dose measured in grays given over an extended period of time. Very often, patients receive radiotherapy every week day for 6 weeks. The weekend is allowed for normal cells to recover. This time also allows the dead cancer cells to be removed from the body. Radiotherapy often incorporates drugs or medications such as radioprotectors or radiosensitizers to lessen damage to healthy tissue and improve the outcomes.
Radiation may be given using external beam radiation that involves visits to the doctor’s office each day of the week for the radiation dose. Hyperfractionated radiotherapy delivers radiation in smaller doses administered every 4 to 6 hours, 2 or 3 times a day. This is useful for rapidly dividing tumors.
Another form of radiotherapy is internal radiation, in which an implanted radioactive material is used to deliver a continuous dose of radiation over several days. Internal radiation is also termed brachytherapy.
Chemotherapy is the administration of drugs to kill cancer cells. Chemotherapeutic drugs can be administered as a pill, as an injection, or as an intravenous infusion. There are several hundreds of chemotherapeutic drugs that are being used alone or in combination, to treat cancer.
Like radiotherapy, chemotherapy targets rapidly dividing cells, usually aiming to disrupt cell division. Chemotherapy may be used after surgery or radiation to kill off the remaining cancer cells that have been missed by the other modalities of therapy.
Various forms of chemotherapy exist and most are categorized as antineoplastic or anticancer therapy. Many types of drugs are used as antineoplastic therapy, including alkylating agents, antimetabolites, and enzyme inhibitors.
Chemotherapy is generally given as 3 stages:
- Induction – this is the initial intensive phase of chemotherapy
- Consolidation - this stabilizes the therapy
- Maintenance – this stage may be continued for longer durations
The number of cycles in each course can vary. Chemotherapy is given in cycles, with a rest period between cycles, and cycles can last from 3 months to 3 years, depending on a number of factors. Cancer chemotherapy duration depends on type of cancer, type of drugs and responses like tumor shrinkage or progression. Chemotherapy is further classified as adjuvant or neoadjuvant, if given after or before surgery, respectively.
There are several new approaches in chemotherapy as well:
- Hormonal therapy is used for several hormone dependent cancers like breast cancer, prostate cancer etc.
- Anti-angiogenesis therapies are also used to stop the formation of new blood vessels in the tumors and starve them off literally
- Photodynamic therapy combines light and a photosensitizing agent. The drug accumulates in the diseased organ. When exposed to laser light the chemicals produced from the drug kill the cancer cells.
- Gene therapy aims to alter the genetic makeup of the tumor or of the body by inserting a desirable gene into the DNA of cells that have been removed from the patient. These removed cells are reprogrammed and reinserted into the patient’s body. In some cases, the reprogrammed cells fortify the patient’s immune system. In some cases the reprogrammed cells help in action of other chemotherapy drugs.
- Bone marrow transplantation and stem cell transplantation are other new modalities. They are often the primary therapy for blood cancers like leukemias and lymphomas and are being used as experimental treatments for other cancers as well.
Reviewed by April Cashin-Garbutt, BA Hons (Cantab)