Radiotherapy is a vital treatment modality for cancer patients. It uses high-energy radiation beams to kill cancer cells or damage their DNA so they cannot grow and divide. Let us explore in detail how radiotherapy works and its applications in cancer treatment.
What is Radiotherapy?
Radiotherapy, also called radiation therapy, is a medical treatment that uses beams of intense energy, such as X-rays or protons, to kill cancer cells and shrink tumors. It is usually given as part of cancer treatment along with surgery, chemotherapy, targeted therapy or hormonal therapy. Radiotherapy was discovered in 1895 by a German scientist Wilhelm Roentgen. Since then, it has evolved as an effective cancer treatment option and saves millions of lives worldwide.
Types of Radiotherapy
There are three main types of radiotherapy used in cancer treatment:
- External Beam Radiotherapy: It involves delivering a beam of radiation from outside the body using a large machine called a linear accelerator. It is the most common type used to treat various cancers.
- Brachytherapy: It involves placing a radioactive source inside or near the area that needs treatment. Brachytherapy delivers radiation close to the tumor site with less exposure to other parts of the body. It is used to treat cervical, prostate and breast cancers.
- Systemic Radiotherapy: Radioactive material is taken orally or injected into the body to reach cancer cells anywhere in the body. It is used to treat some blood cancers like leukemia.
How does Radiotherapy Work?
Radiotherapy works by damaging the DNA inside cancer cells. When cancer cells divide, the damaged DNA cannot duplicate properly. This prevents the cells from multiplying and causes them to die. Radiotherapy can directly kill cancer cells or slow their growth and reduce tumor size. Normal cells are also affected by radiation but they can repair themselves better and are less likely to divide than cancer cells. The goal is to deliver higher radiation doses to the tumor while limiting exposure to nearby normal tissues as much as possible.
Planning the Radiotherapy Treatment
Before starting the treatment, dosimetrists and radiation oncologists carefully plan it using medical imaging scans of the patient. These images are used to determine the location and size of the tumor. Patients are immobilized using customized casts or molds to ensure accuracy. A simulator machine reproduces the treatment position and technicians mark skin with permanent ink to locate the treatment area each time.
Radiation oncologists determine the radiation dose required, its fractionation schedule and beam angles and sizes based on the tumor features. Computer treatment planning software is used to optimize the radiation dose distribution and minimize normal tissue exposure. A treatment plan report summarizing all the parameters is prepared and approved by the radiation oncologist before the first treatment session.
Delivering the Radiotherapy Treatment
On treatment days, patients lie down comfortably on the treatment couch of a linear accelerator while immobilized as per their treatment position. The machine rotates around the patient and delivers precisely targeted radiation beams of varying intensities, angles and sizes as per the treatment plan. It can rotate 360 degrees around the body to target the tumor from all angles needed. Treatment sessions usually last less than 30 minutes. Most patients receive external beam radiotherapy daily, Monday through Friday, for 3 to 8 weeks depending on their cancer type and stage. The total treatment period may last up to a few months if chemotherapy or surgery are given before or after radiotherapy. Radiotherapy side effects depend on the treatment site but are usually temporary and can be managed with medication.
Applications of Radiotherapy in Cancer Treatment
Some of the common cancers treated with radiotherapy alone or in combination with other therapies include:
- Brain and spinal cord tumors: Radiotherapy is a standard treatment along with or after surgery to destroy remaining cancer cells. It is also used to relieve symptoms in advanced cases.
- Head and neck cancers: It is widely used to treat cancers of oral cavity, lips, tongue, salivary glands, thyroid, nasopharynx etc.
- Lung cancer: Radiotherapy is an effective treatment, especially for non-small cell lung cancer in combination with chemotherapy. It is also used for palliation of symptoms in advanced lung cancer.
- Breast cancer: It is used after breast-conserving surgery or lumpectomy to destroy any remaining cancer cells and reduce the risk of recurrence. It can also be used before surgery to shrink large tumors.
- Prostate cancer: Radiotherapy alone or with hormone therapy is the main non-surgical treatment for localized prostate cancer. It is also used after prostatectomy for higher risk cases.
- Cervical cancer: It is a primary treatment along with chemotherapy for locally advanced cervical cancer. It is also used with brachytherapy to boost treatment after surgery.
- Skin cancer: Radiotherapy is very effective for treating basal cell carcinoma and squamous cell carcinoma skin cancers when surgery is not possible or preferred.
- Lymphomas: It plays a key role in treating NHL and HL lymphomas either alone or with chemotherapy depending on stage and risk factors.
Outcomes and Side Effects of Radiotherapy
When used appropriately,radiotherapy provides excellent cancer control and cure rates for several cancers. Its precision has improved tremendously over time reducing normal tissue damage. However, some common side effects may be temporary fatigue, skin irritation at the treatment site, nausea, loss of appetite and hair loss near the treatment area. With modern techniques and immunosuppressants, most side effects are mild to moderate and reversible. Radiotherapy helps eliminate tumors, extend life span and improve quality of life in millions of cancer patients worldwide.
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