The Radiation Oncology Center, led by Dr. Jason Citron and Dr. Stephen Ronson, employs state-of-the-art radiotherapy equipment including:

  • SAVI Targeted Accelerated Partial Breast Irradiation (APBI)
  • Biograph 40 PET/CT
  • Intensity Modulated Radiotherapy (IMRT)
  • RapidArc Therapy
  • Image-Guided Radiotherapy (IGRT)
  • Varian Clinac iXTM Linear Accelerator
  • Varian TrueBeam™
  • High-Dose Rate (HDR) Brachytherapy for GYN and Breast Malignancies
  • Low-Dose Rate (LDR) Brachytherapy for Prostate Cancer
  • 4-D CT-Simulator with Respiratory Gating
  • Stereotactic Radiosurgery (SRS)
  • Stereotactic Body Radiotherapy (SABR)
  • 3-D Cone-Beam CT for precise pre-treatment alignment

Radiation therapy is the use of penetrating beams of high-energy waves or streams of particles called radiation to treat disease. Radiation has been used to treat cancer since the late 19th century. In fact, the first successful radiation treatment for cancer was reported in 1898.

In its earliest state, radiation was given in single, large doses, which caused many complications. By 1940, doctors had begun dividing the total dose of radiation into several smaller doses allowing normal tissues to repair the radiation damage.

In the last 50 years, technology has allowed for great advances in radiation therapy, including deeper penetration of the radiation and less scatter to healthy tissues. Currently, there exists a delicate balance between using radiation to treat cancer cells and minimizing its adverse side effects on the body's normal cells.

How Does Radiation Therapy Work?

Radiation therapy destroys the ability of cancer cells to grow and divide. When high-energy ionizing radiation is given as cancer therapy, some cells are directly damaged, but more cells are indirectly affected by the radiation. The rays or particles enter the cell's nucleus, interact with water present in the nucleus, and form a free radical called hydroxyl radical. The hydroxyl radical is unstable and causes damage to the cell's DNA. Due to this damage, some cells die immediately. Some cells will survive in the short-term, but are unable to divide and will die at the time of mitosis, or cell division.

Normal, healthy tissues are affected by radiation therapy as well, and this accounts for the adverse side effects seen with this type of treatment. To help minimize side effects, radiation is divided into doses and spread out over time. In addition, radiation is targeted as much as possible to shield normal tissues and only irradiate the cancer cells.

Unlike chemotherapy, which is a systemic treatment, radiation therapy is a localized treatment. This means it affects only the cells in the specific areas of the body where the radiation is directed. Radiation therapy is sometimes used in combination with other therapies, like chemotherapy or hormonal therapy, to help improve treatment results. Also, radiation therapy can be given before, during or after surgery.

What Is Radiation Therapy Used For?

Radiation therapy is given with the intention of completely destroying the disease. When this is not possible, controlling the growth and spread of the cancer is the goal. In addition, improving quality of life by controlling symptoms associated with cancer is an aim of radiation therapy. These symptoms include pain, uncontrolled bleeding, tumor obstruction around major blood vessels and organs, and spinal cord compression.

Determining if your cancer may be appropriately treated by radiation therapy is based on several factors, such as tumor type, location, size, and response to other modalities including surgery and chemotherapy. Your radiation oncologist is the only medical professional qualified to render an absolute opinion on the role of radiation therapy in the management of your disease.

Some factors affecting how well radiation therapy will work include the following:

  • Phase of cell - a cell goes through five phases in its cycle of division—from resting to mitosis. Cells in the resting phase are less sensitive to radiation (and therefore less likely to be damaged) than cells that are actually dividing (in mitosis).
  • Division rate of the cell - rapidly dividing cells are more sensitive than slowly dividing cells.
  • Oxygenation - because oxygen is necessary to form the hydroxyl radical (which leads to cell destruction), highly oxygenated tissues are more sensitive to radiation therapy. This has been clearly demonstrated in cervical cancers and cancers of the head and neck. In fact, the presence of oxygen is so important that patients who smoke, and therefore lower the oxygen level to their tumor, suffer from a 50% reduction in the ability of the radiation to kill the cancer.

What Are the Types of Radiation Therapy?

External Radiation Therapy

In external radiation therapy, rays are directed at the tumor from outside the body. Prior to treatment, your doctor will develop a plan to determine the best method for delivering treatment. In a process called simulation, you will be asked to lie on the examination table while the radiation therapist uses a special X-ray machine to define the area of treatment. Radiographic studies, like a CT scan, an MRI, or a barium enema, help the physician visualize the exact area that needs treatment. Using this information, the doctor can calculate the maximum radiation dose to the tumor, while minimizing the dose to the normal surrounding tissues.

A CT scan is a type of X-ray that uses a computer to produce cross-sectional images of the inside of the body. An MRI scan uses magnetic waves to produce images of the inside of the body. Using a large magnet, radio waves, and a computer, an MRI produces two-dimensional and three-dimensional pictures. A barium enema is a rectal injection of barium, a substance that coats the lining of the colon and rectum. It is done before x-rays are taken in order to create better X-ray images.

If you receive external radiation therapy, you will go to the hospital or clinic each day for treatment. Usually, treatments are given 5 days a week for 2 to 8 weeks. The total dose of radiation and the number of treatments necessary will depend on the size, location, and type of cancer you have, as well as your general health and other medical treatments you may be having. This procedure is like having an x-ray. Actual treatment time (the time you are receiving radiation) ranges from 2 to 5 minutes.

Delivery of External Radiation Therapy

Different types of machines are used to deliver the radiation. The higher the energy produced by the machine, the greater the depth of penetration. In addition, there is less radiation scatter with higher energies.

At the end of the treatment regimen, the tumor site often gets an extra dose of radiation, called a boost.

Internal Radiation Therapy

Internal radiation therapy, also called brachytherapy, places the radiation source as close as possible to the cancer cells. Radioactive material, sealed in a thin wire, catheter, or tube, is placed directly into the affected tissue. This method concentrates the radiation on the cancer cells and minimizes the radiation damage to the normal tissue nearby.

The radioactive substances used for internal radiation therapy include the following:

  • Cesium
  • Iridium
  • Iodine
  • Phosphorus
  • Palladium

The type of implant and how it is placed depends on the size and location of the tumor. Methods include the following:

  • Interstitial radiation - implant is placed directly into the tumor via catheters, seeds, or capsules. This is commonly used for prostate cancer.
  • Intracavitary radiation - implant is placed in special applicators inside a body cavity. This is commonly used for cervical cancer.
  • Intraluminal radiation - implant is placed in special applicators inside a body passage or lumen. This is commonly used for lung or esophageal cancer.
  • Surface brachytherapy - implant is placed in or against the tumor. This is commonly used for skin cancer or melanoma of the eye.

Implants may be removed after a short time or left in place permanently. When left in place, the implants become non-radioactive in a short time. For the placement of most types of implants, you will need to be in the hospital.

Indications for internal radiation therapy include cancers of the head and neck, lung, breast, uterus, thyroid, cervix, rectum, bladder and prostate. It is sometimes given in combination with external radiation therapy.

What Adverse Effects Can Occur with Radiation Therapy?

Radiation therapy affects normal, healthy cells as well as cancer cells. When radiation is targeted at a cancerous site, there is destruction of normal tissue, in addition to cancer cells, in that area. A majority of the adverse effects are due to this phenomenon. The following are general side effects that can occur with radiation therapy. Side effects specific to the treatment of certain cancers are covered in the individual cancer reports.


Fatigue, or feeling tired, can be a symptom of the cancer itself, as well as a side effect of cancer treatment. It is experienced by many people receiving radiation therapy. The exact cause is not known, but it may result from a combination of lowered red blood cell counts, lack of sleep, pain and poor appetite. Fatigue many occur after treatment each day and become chronic as treatment continues. Fatigue is not a life-threatening side effect, but it can be disruptive to daily life.

The level of fatigue varies among people, but generally, most people are able to continue work and light activities. To help combat fatigue, try not to do too much. If you start to feel tired, limit your activities. Try to get enough rest at night and take naps or short breaks throughout the day. Allow people to help you with daily responsibilities, like shopping, house cleaning and child care.

Some people have found that light exercise, such as walking, helps combat fatigue. Talk with your doctor about how much exercise is right for you both during and after radiation therapy.

Skin Reactions

Skin reactions are normal and expected with radiation therapy. Reactions can occur as soon as 2 weeks into treatment. The skin becomes red and irritated and slight swelling may appear. After a few weeks of treatment, skin may become very dry, itchy, and flaky. In some types of radiation therapy, skin may develop a moist reaction. The skin starts to shed, leaving a raw, painful area. If this occurs, it is important to let your doctor know.

Skin reactions are more common in areas receiving large doses of radiation. Also, certain areas of the skin are more sensitive, such as facial skin, skin over bony prominences, and skin with a pre-existing surgical wound. When radiation therapy is used along with chemotherapy, there is a higher risk of developing a skin reaction. Most skin reactions disappear a few weeks after treatment is completed.

The following suggestions may help you avoid skin problems:

  • Wash with lukewarm water and mild soap, and pat dry
  • Do not wear tight clothing over the area
  • Do not rub, scratch, or scrub the skin in the treated area
  • Avoid putting anything hot or cold on the treated area
  • Avoid exposing the radiated area to the sun during treatment
  • Ask your doctor to recommend a cleanser and moisturizer for your sensitive skin

Blood Abnormalities

If large areas of active bone marrow are treated with radiation therapy, a decrease in bone marrow function occurs. Such treatment areas include the pelvis, spine, sternum, ribs, long bones, and skull. This can lead to low levels of red blood cells (anemia), white blood cells (neutropenia), and platelets (thrombocytopenia). Resulting complications may include fatigue, serious infection and uncontrolled bleeding.

During radiation therapy, blood levels may be monitored, particularly if chemotherapy is also being delivered, or if a large part of the body is being irradiated. For many sites treated with radiation, there is no reason to get blood samples, unless you begin to feel poorly and the doctor wants to determine if low blood counts are to blame. If a blood test shows significant bone marrow effects, your doctor may wait until your blood counts increase before continuing treatment. Blood transfusions are sometimes necessary.

Hair Loss

Radiation therapy can cause hair loss, also known as alopecia. Hair loss occurs only in the area being treated with radiation. If you receive radiation to your head, you may lose some or all of the hair on your scalp. Hair usually grows back after treatment is finished. The amount of hair that grows back depends on how much and what kind of radiation you received. Some people find that when their hair grows back, the color or texture may be slightly different.

Although not life-threatening, hair loss can be upsetting. Many people buy a wig or hairpiece, or use hats or scarves, to cover their heads. If you buy a wig because of cancer treatment, it is a tax-deductible expense and may be covered in part by health insurance.

Loss of Appetite (Anorexia)

Anorexia, or loss of appetite, can be a symptom of the cancer itself, as well as a side effect of cancer treatment. It is not unusual to lose one or two pounds a week during radiation treatment. You will be weighed weekly to monitor your weight.

Many small meals, rather than three large ones, can help make eating seem less overwhelming. Ask your doctor for a referral to a registered dietitian (RD) to assist you in setting up a diet plan that helps you maintain weight. In addition, medications to increase your appetite are available. If it is painful to chew and swallow, you may want to try a powdered or liquid diet supplement. It is crucial that you get enough calories and protein so that your body has enough energy to fight the cancer. Studies have found that people who eat well cope better with their cancer and its treatment.


7501 Osler Drive
Suite G04
Towson, MD 21204
Ph. 410-427-2525


8:30 a.m.-5 p.m., Monday-Friday
On call for emergencies

The mission of the Radiation Oncology Center is to see patients through each stage of their disease, from diagnosis through treatment and follow-up care. Our staff strives to treat the whole person and offer guidance throughout the journey.

For more information about radiation oncology, please call 410-337-1338 for a referral.