Treating Cancer with External Beam Radiation

There are several treatment options available when it comes to cancer treatment, one of the most common being external beam radiation therapy.  In external beam radiation a beam, or many beams, of radiation are shot through a person’s skin onto the cancerous tumor destroying the tumor and nearby cells of cancer.   To reduce the consequences of treatment it is usually given Monday through Friday, five days a week for several weeks.  This gives patients enough radiation to shrink and kill off the cancerous tumors while allowing healthy cells to restore themselves.


The beam of radiation that moves through the skin and targets the cancerous tumor is delivered through a machine known as a linear accelerator, also known as a LINAC.  A linear accelerator produces high-energy x-rays which treat the cancer.  This treatment option is done using computers and specialized software to create a treatment plan.  This plan will control the shape and size of the radiation beam as well as how it will enter your body to treat the tumor while pardoning the normal tissue.


Different types of cancer require specialized delivery of radiation using external radiation therapy.  In this installment on external beam radiation we will discuss several methods of delivery.


3-D CRT: Three-Dimensional Conformal Radiation Therapy


No two tumors are the same shape or size.  No two patients’ bodies are the same either. 3-D CRT uses advancements in technology like CT, PET, or MR scans to display the tumors size, shape, and location relevant to the surrounding organs.  This allows the radiation oncologist to tailor the beams of radiation with special shielding options to your exact tumor.  The more targeted treatment ensures that less of the surrounding healthy tissues receive the harmful radiation.


IMRT: Intensity Modulated Radiation Therapy


IMRT, is a specialized from of 3-D CRT that shapes radiation to cover only the tumor sparing healthy, normal tissue surrounding the cancerous tumor.   In IMRT, the beams of radiation are broken down into several smaller beams with each beam’s intensity being able to be adjusted individually.  This allows the beam’s closer to the healthy tissue to deliver less intense radiation without decreasing the radiation delivered to the tumor.


IGRT: Image Guided Radiation Therapy


Image guided radiation therapy uses conformal radiation treatment that is guided by images from a CT, ultrasound, or x-rays taken right before treatment.  Since tumors can move between treatments, IGRT offers more targeted treatments as the images are taken right before treatment is given.  Your team of oncologists will confer the images between treatments to adjust the treatment that is needed.  Sometimes in IGRT doctors will place a marker in or near the tumor to help localize the treatment.  IGRT is another option in radiation treatment that allows for precise targeting of cancerous cells, protecting the healthy cells.


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