Introduction to Cancer Therapy (Radiation Oncology)

Radiation therapy is the use of high-energy radiation to damage cancer cells’ DNA and destroy their ability to divide and grow.  It may be delivered using machines called linear accelerators or via radioactive sources placed inside the patient on a temporary or permanent basis.  Radiation therapy may be used to cure cancer, to relieve a cancer patient’s pain or alleviate other symptoms.

Preparation for radiation therapy is focused on targeting the radiation dose to the cancer as precisely as possible to minimize side effects and avoid damaging normal cells.  Imaging tests may be used to help determine the exact shape and location of your tumor and define its boundaries.  Your doctor will give you specific instructions based on the type of exam being performed.

What is Radiation Therapy?

More than half of cancer patients are treated with radiation at some point during their course of treatment.  Radiation therapy is the use of high-energy radiation to treat cancer.  A radiation oncologist may use radiation to cure cancer or to relieve a cancer patient’s pain or alleviate other symptoms due to cancer.

Radiation therapy works because the radiation destroys the cancer cells’ ability to reproduce, and the body naturally gets ride of these cells.  Radiation affects cancer cells by damaging their DNA, so that the cancer cells can no longer divide and grow.  Radiation is most effective at killing cells that are actively dividing.  Cancer cells are more vulnerable to radiation for two reasons:

  • They divide more rapidly than normal cells
  • They do not repair this damage as effectively as normal cells.

How is Radiation Therapy Used in Cancer Care?

A radiation oncologist may use external beam radiation therapy or brachytherapy to treat cancer.  External beam radiation therapy can be generated by a linear accelerator (a machine that accelerates electrons to produce x-rays or gamma rays).  Radiation therapy given by radioactive sources that are put inside the patient is called brachytherapy.  The radioactive sources are sealed in needles, seeds, wires, or catheters, and implanted directly into or near a tumor on a temporary or permanent basis.  Brachytherapy is a common treatment for cancers of the prostate, uterus, cervix or breast.

Some cancer patients may be treated with radiation as their primary treatment.  In some cases, radiation therapy is given at the same time as chemotherapy.  Chemotherapy used with radiation therapy can improve the local response and reduce metastatic disease.

In other cases, radiation therapy is given before (neoadjuvant treatment) or after (adjuvant treatment) surgery.

Radiation Therapy Process

After radiation therapy has been ordered, a planing stage occurs.  The patient will first undergo a simulation scan on a special CT scanner.  IV or oral contrast may be used.  If a device is needed to keep the patient still (such as a mask) this is made at the simulation scan appointment.

The radiation oncologist then outlines the area to be treated, the tumor, and the areas to be avoided (such as normal organs).  The radiation plan is developed and checked by dosimetrists, medical physicists and radiation oncologists.  The radiation plan then undergoes quality and safety checks.

Radiation therapy is delivered on the treatment units by radiation therapists.  The radiation oncologist along with other healthcare team members, including nurses and dietitians, will see the patient during radiation treatment to manage side effects.

At CSNF, we offer external beam radiation in a variety of ways:

Three-Dimensional Radiation Therapy (3D)

3D Therapy allows the treatment to be delivered more precisely by better targeting the treatment area and reducing the dose to the surrounding structures.

Image-Guided Radiation Therapy (IGRT)

Most treatments are typically given by utilizing a daily CT scan of the treatment area to ensure the target volume is positioned in the correct location prior to delivering treatment.

Intensity Modulated Radiation Therapy (IMRT)

IMRT allows the intensity of the radiation to be modulated across the treatment area by adjusting the dose, size, and shape of the treatment field, so the maximum dose is delivered to the tumor, sparing surrounding structures.

Stereotactic Radiosurgery (SRS)

SRS is a nonsurgical radiation therapy used to treat functional abnormalities and small tumors of the brain. It can deliver precisely targeted radiation in fewer high-dose treatments than traditional therapy, which can help preserve healthy tissue.

Volumetric Modulated Arc Therapy (VMAT)

VMAT is a technique that allows for increased treatment speeds and dose reduction.

High-Dose Rate Brachytherapy (HDR)

Brachytherapy treatments are given internally by utilizing a radioactive source. These treatments are generally used on small breast tumors. A device is implanted into the cavity where the tumor was removed. The device remains in place over five days. Treatments are given twice a day for five days.

Download our Radiation Oncology brochure.

To make an appointment, please call one of our convenient locations below or email a staff member at


2370 Market Drive
Fleming Island, FL 32003
(904) 541-5613

7015 AC Skinner Parkway, Building 100
Jacksonville, FL 32256
(904) 516-3725

Flagler Health+ Radiation Oncology
Partner Location
97 Health Park Blvd.
St. Augustine, FL 32086
Phone: (904) 819-8200