Radiotherapy or radiation therapy is a cancer treatment that uses high doses of radiation to kill cancer cells and shrink tumors. It works by damaging the DNA of cells, which prevents them from multiplying. When the radiation affects the cancer cell's DNA, it stops the cell from reproducing and the cell eventually dies. Since cancer cells generally grow and divide faster than normal cells, they are more susceptible to the effects of radiation.
Types of Radiation therapyThere are different types of radiation therapy used to treat cancer depending on the location and size of the tumor.
External Beam Radiation therapy: This is the most common type where a machine called a linear accelerator is used to aim high-energy rays such as X-rays, gamma rays or electron beams at the tumor. This allows doctors to deliver precise radiation doses to the tumor while avoiding nearby normal tissues as much as possible.
Internal/Implant Radiation therapy: It involves placing radioactive material inside or very close to the tumor. This technique is commonly used to treat cancers of the cervix, breast, or prostate. Some examples are brachytherapy, intracavitary radiation therapy, and interstitial radiation therapy.
Intensity-Modulated Radiation therapy (IMRT): Advanced form of external beam radiation therapy which involves shaping the radiation beams and varying the intensity over the treatment area using a computer-controlled linear accelerator. This allows a higher radiation dose to be delivered to the tumor while reducing exposure of nearby normal tissues.
Stereotactic Radiosurgery: Very focused, high dose of radiation directed at a small tumor area from different angles in one or a few sessions. It is commonly used to treat brain tumors and certain other cancers.
Proton Beam Therapy: A type of external beam radiation therapy where protons, instead of X-rays, are used to treat tumors. Protons have some properties which allow more localized radiation dosage. It is used for tumors close to critical structures.
Benefits of Radiation therapy
Some key benefits of using radiation therapy for cancer treatment are:
- It can eliminate cancer cells directly through cell death or damage the DNA of surviving cancer cells so they cannot multiply or grow.
- When combined with other treatments like chemotherapy or surgery, it can destroy remaining cancer cells and reduce recurrence risks after surgery.
- Unlike surgery, it does not involve cutting into the body and can reach tumors located in hard to access areas.
- Modern techniques allow the radiation beam to be precisely directed only at the tumor location, sparing surrounding normal tissues from exposure.
- Depending on the cancer type and stage, it may be used as the sole treatment or in combination with other treatments as part of a comprehensive care plan.
- For some cancers, radiation therapy may offer cure or long-term local control of the disease.
Planning the Treatment
Careful planning and preparation goes into radiation therapy. The radiation oncologist will first evaluate the patient's medical history, type and stage of cancer, and treatment goals. Imaging tests like CT, MRI or PET scans are done to delineate the tumor margins accurately.
Software is then used to plan the optimal radiation dose and beam angles to target the tumor while avoiding sensitive structures nearby. Tattoos or positioning aids may be put on the skin to ensure consistent treatment positioning. A treatment schedule is made balancing benefits versus side effects.
During each session, the patient lies on the table in exactly the same position so the radiation hits the tumor precisely. The actual treatment takes just a few minutes but planning and delivery require advanced technology and expertise to make it effective.
Side Effects and Risks
While well-tolerated by most patients, side effects may occur depending on the treatment area and person. Common short term side effects include fatigue, skin irritation in treated areas and nausea/vomiting. Long term effects are usually mild for modern radiation therapy except for rare cases.
Risks involve potential damage to healthy cells in the treatment area that can manifest later as another cancer. Strict quality controls, newer techniques and developing research aims to maximize cancer cell killing while reducing normal tissue damage to a minimum.
Future Directions
Advances in medical imaging, computing power and radiation therapy delivery has resulted in improved dose distributions and ability to target tumors close to vital structures. However, future areas of research include:
- Image-guided radiation therapy using technologies like MRI-linacs for real-time tumor tracking and adaptive treatments.
- Proton beam therapy with better dose distributions for pediatric tumors and sites close to serial organs.
- Hypofractionated regimens using larger doses per fraction to shorten treatment durations while maintaining efficacy and safety.
- Biomarker-guided approaches to select patients most likely to respond and tailor treatment based on individual tumor characteristics.
- Combining radiation with immunotherapy agents to trigger anti-tumor immune responses.
- Research to better understand the molecular basis for normal tissue toxicity and improve therapeutic gain through approaches like targeted radiation therapy.
In summary, as technology evolves radiotherapy remains a crucial pillar in cancer management, either alone or combined with other modalities. Ongoing research is refining techniques to boost effectiveness and increase the cure and control rates even for advanced disease presentations.
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