Introduction
Radiation therapy or radiotherapy, is defined as various forms of radiation used to treat cancer and other diseases [1]. Main focus of radiotherapy is to cure cancer, to control the growth of the cancer and to relieve symptoms, such as pain. Radiation therapy works by damaging the DNA within cancer cells and destroying the ability of the cancer cells to reproduce [2]. When these damaged cancer cells die, the body naturally eliminates them. The radiation will affect the normal cells will also affected by radiation, however they are able to repair themselves from the radiation in a way that cancer cells cannot [6]. Sometimes radiation therapy is the only treatment a patient needs, and in other way, it is only one part of a patient’s treatment. For instance, some patients may be treated with surgery, radiation therapy and chemotherapy.
Goals of radiation therapy are to destroy tumours, decrease the risk of the cancer from return after the surgery or chemotherapy by killing tiny cancer cells that may remain and shrink tumours that are interfering with your quality of life. For example, tumours that are causing difficulty swallowing or are causing bleeding. Another goal is to alleviate pain by reducing the size of the tumour. If the patient is pregnant, radiation can be extremely harmful to the unborn child and some measures must be taken.
Two methods to deliver the radiation to the tumour, which are External Beam Radiation Therapy and Brachytherapy [1]. The radiation type will be determined based on the location of the disease. The patient need to lie still on a table and breathe normally, while the machine rotates around the patient. There is no feeling to the radiation treatments. External beam radiation therapy is a method of delivering radiation (high energy x-rays or electrons) from outside the patient and is targeted at the tumour site and surrounding area [3]. The radiation comes from a treatment machine called a linear accelerator.
TYPES OF RADIATION THERAPY
1. External beam radiation therapy (EBRT)
With EBRT, the patient is lying on a treatment table (black structure in the figure). An external source of radiation delivers the treatment to the volume created during planning, while minimizing the dose of radiation delivered to surrounding structures. The patient is awake during treatment; cannot feel or sense the radiation; and can resume all activities immediately following delivery of the treatment. The common types of external radiation are intensity modulated radiation therapy (IMRT); and three dimensional conformal radiation therapy (3D-CRT
2. Brachytherapy
BT is a form of radiation therapy where a radiation source is placed inside or next to the area requiring treatment. Depending on the cancer, BT is typically given as either high-dose rate (HDR) or low-dose rate (LDR). The patient is usually under general anesthesia during any type of BT procedure. The patient can usually resume all normal activities a few days following BT.
ADVANTAGES AND DISADVANTAGES OF RADIATION THERAPY
The advantages of radiation therapy include death of a large proportion of cancer cells within the entire tumor, and also the death of microscopic disease at the periphery of the tumor that would not be visible the naked eye at the time of surgery. Moreover, it has the ability to shrink tumors which may help to relieve mass effect and increase relative safety for the patient.
In addition, this therapy is painless, and does not require anesthesia and also it will preserve the organ, whereas removing a breast, larynx, or part of the gastrointestinal tract are not necessary which may have huge impact on a patient’s quality of life.
Radiation therapy also gives several disadvantages, such as damage to surrounding tissues like heart and lung, where it depends on how close the area is located to the tumor. Furthermore, radiotherapy is unable to kill tumor cells if it is not seen on imaging scans. Therefore the unseen area will not include in radiation planning. This therapy cannot kill totally all cancer cells in tumors especially in large size of tumor. Cancer cells in areas that do not have a good supply of oxygen may have poor killing rates by radiotherapy [8]. There is increased incidence in wound complication after the therapy.
SIDE EFFECTS OF RADIATION THERAPY
Radiation treatments use high energy waves to damage and kill cancer cells. Because the radiation can affect cells other than cancer cells, side effects may occur. The side effects that any given patient has depends on the type and amount of radiation used and the area being treated.
Generally, most common side effect is fatigue due to energy is being used in order to replace the normal cells killed in the process. The skin at the site of radiation may get red and/or sore. Besides, the patient may face development of a secondary cancer, caused by the radiation therapy, however is it uncommon effect. The side effect is depends on the several factors including the treatment site and the patient age [8].
For all types of radiotherapy, the treatment is painless where the patient will not feel the radiation, there will be no hair loss in an untreated and the patient will not having any nausea or vomiting, unless the radiotherapy involved certain organs such as esophagus, stomach and gastrointestinal tract.
OTHER THERAPEUTIC STRATEGY IN TREATMENT OF TUMOR
1. Chemotherapy
Chemotherapy can also be combined with surgery or radiation, in conjunction to increase the effectiveness of these treatment modalities. Like radiation, most chemotherapeutic agents target malignant cells that are actively replicating. Many chemotherapy drugs directly damage DNA – interfering with cell division and activating programmed cell death (apoptosis). Other antineoplastic agents act indirectly by interfering with mitosis or by blocking the utilization of nucleotides required for DNA synthesis by replicating tumor cells. Even in cancer patients of ≥ 80 years old selected for chemotherapy, both single and multi-agent therapy appeared to be feasible [6].
2. Combined Modality Treatment:
a. Surgery plus Chemotherapy
(1) Adjuvant chemotherapy
For many solid tumors, surgery followed by chemotherapy will produces a better long-term survival rate than surgery alone. This type of chemotherapy is suitable to use, when cancers are diagnosed, small numbers of malignant cells have already spread to distant sites. This makes it unlikely that surgery alone will achieve a cure [2].
(2) Neoadjuvant chemotherapy
It is used for advanced cancers that have extensively invaded surrounding tissues, where chemotherapy is given before surgery or gene therapy in order to reduce tumor size.
b. Combination of Surgery and Radiation
In early stage breast cancer, a “lumpectomy” (excision of the tumor without mastectomy) followed by irradiation of the operation site may be as effective as radical mastectomy and give long-term patient survival [4].
c. Combination of Chemotherapy and Radiation
In acute leukemia, after the chemotherapy is done, it is occasionally followed by radiation to the spine and skull to prevent the recurrence of disease in the CNS [5]. Some chemotherapy drugs can sensitize head and neck tumors to radiation therapy. But chemotherapy and radiation somehow make these tumors stronger since solid tumors adapt the body’s machinery to bring themselves more oxygen.
3. Hormonal therapy
This therapy is usually applied for cancer that is hormone dependent. Antiestrogen drugs Tamoxifen, Arimidex, and Letrozole can be used to treat some breast cancers. Corticosteroids such as Prednisolone or Dexamethasone are useful for controlling some forms of leukemia and lymphoma [5].
4. Stem Cell transplantation
Several studies have shown that a higher than normal doses of chemotherapy drugs can be given in order to achieve a higher rate of cancer cell killing. Mathematical arguments should be used more consistently, because they can serve as a guide for interpreting studies into cancer stem cells of solid tumors [6].
5. Anti-cancer-stem cell therapy
To develop drugs that target cancer Stem cells, investigation about changes in cellular mechanisms and kinetics that occur in SC populations during colorectal cancer development have been studied. Computer modelling is applied to determine which changes could give rise to exponential increases in both SC and non-SC populations in CRC. Results show that the only mechanism that can explain how these subpopulations.
6. Monoclonal antibody
Monoclonal antibodies therapy have shown clinically efficacy and even commercially benefits which have made them the most rapidly expanding class of therapeutics being adopted in many diseases indications, including cancer [7]
7. Application of Electric Field
The transmission of electric fields using insulated electrodes has demonstrated that very low-intensity, properly tuned, intermediate-frequency electric fields, termed tumor-treating fields (TTFields), selectively stunts tumor cell growth and is accompanied by a decrease in tumor angiogenesis [4].
8. Ultrasonication
Ultrasound can be used to remove solid tumors, which has been used in some of cancers treatment through ultrasound exposures.
References
[1] http://www.ijpsr.info/docs/IJPSR11-02-01-01.pdf
[2] Gavhane Y. N. et al. / International Journal of Pharma Sciences and Research (IJPSR) Vol.2 (1), 2011, 1-12 ISSN : 0975-9492
[3] H. Mohan, Textbook of Pathology 4th ed. Jaypee Publications, New Delhi. 2002, 177-180.
[4]Physician Assistant Program, Introduction to Medicine I Hematology-Oncology: Handout #9: Treatment Strategies for Cancer, University of Florida (Fall, 2006).
[5]http://radiationoncologyservicespc.com/treatment/treatment_info.htm
[6]https://www2.tulane.edu/som/cancer/clinic/cancer-and-treatment/radiation-oncology/how-does-radiation-therapy-work.cfm
[7] www.ncbi.nlm.nih.gov
[8] http://www.cancerlinkusa.com/cancer/young/tips.html