CANCER CURE & PREVENTION SERIES: Principles of Cancer Treatment: Radiation Oncology

Cancer 1

Dr. Vivek Karadi

When a patient is told that they have a diagnosis of cancer, they can be overwhelmed with many emotions. In the midst of these emotions, they have to now learn about the many complexities of the treatments that may be recommended for them. We have made tremendous progress over the last quarter century in the three main modalities of treatment – surgery, radiation therapy, and chemotherapy. We have learned more about how best to use these treatments together to achieve better results. In the next series of three articles, we will describe the principles of each cancer treatment modality. In this first article, I will give an overview of all three, and then provide greater detail about radiation oncology.

Cancer treatment is based on the type of cancer, where it is located, where it could be that physicians cannot see, and where it could spread. Hence we use terms such as primary tumor (where the tumor is, localized cancer), regional disease (neighboring lymph nodes), and metastatic disease (distant spread of cancer to other parts of the body).

The type and stage of the cancer gives us an idea of the level of risk associated with it, and therefore, which treatments to use. Surgery and radiation therapy are both designed to address the local-regional extent of cancer. For example, in breast cancer that would mean the breast and the regional lymph nodes. Chemotherapy is a form of systemic treatment, which means that it covers the whole body. Other forms of systemic treatment include biological or immunotherapy. Most patients currently are treated with some combination of these three modalities in order to maximize the chance for cure.

The field of radiation oncology has been around for nearly a century. The doctors who practice this specialty are known as radiation oncologists. Just as a surgeon would remove a tumor in an operation, we use radiation to destroy the tumor without surgically removing it. High doses of radiation kill cancer cells. The core principle in radiation oncology is to deliver the maximum dose of radiation to the tumor and the least amount of radiation dose to the normal tissues in the area being targeted. Over the past decade, several critical advances have been made in our field. These include our ability to see and then adequately localize the target area with better imaging. We then have very sophisticated technology to design a treatment plan for each unique patient. Finally, the greatest advancements have come in our ability to fine-tune the treatment in a way that delivers a more accurate, targeted course of therapy with less damage to surrounding healthy tissue.

The treatment process begins with a consultation with a radiation oncologist. The doctor will gather the patient’s history, perform a physical examination, review all the records, and review all the imaging. If necessary, additional laboratory or imaging tests may be ordered to further clarify the cancer stage. Once this process is complete, the doctor will determine a treatment plan for the patient. Often this plan must be coordinated with a surgical oncologist or medical oncologist. Some treatments are given sequentially, while others may be delivered concurrently.

The radiation treatment starts with a simulation. During this procedure, the position of the patient, the construction of any devices to help secure the patient in that position, and a CT scan are obtained. The patient then leaves the department and the radiation oncologist works with members of the team, including a physicist and dosimetrist, to design and calculate an optimal treatment plan. This process can take a few days.

Most radiation treatment is given externally using machines known as linear accelerators that generate high energy x-rays or electrons. No radioactivity is used with external treatment, and it is perfectly safe for the patient to be around others. External radiation is usually given over multiple sessions. Traditionally this has ranged over two to nine weeks. The accuracy of the treatment needs to be on the order of two to three millimeters, and as such, great care is taken in the delivery.

Another form of radiation is delivered internally with radioactive sources. This is called brachytherapy. Brachytherapy is routinely used for gynecological cancers and sometimes for other cancers as well.

Radiation oncology continues to evolve with the development of new technologies, improved equipment, and other medical breakthroughs discovered through clinical trials. Techniques such as intensity modulated radiation therapy (IMRT), image guided radiation therapy (IGRT), and proton therapy allow us to advance our never-ending goal of focusing our treatment on the cancer and sparing healthy tissue. Other advances include stereotactic radiosurgery (SRS) and stereotactic body radiation therapy (SBRT). These techniques allow us to safely target tumors in the brain, lung, spine, and liver with high doses of radiation in a fewer number of treatments. All of these rapid technological developments and increased clinical knowledge have not only kept our specialty exciting, but primarily have enabled radiation oncologists to more effectively treat our patients.

© 2003 Rocky Kneten for U. S. Oncology

Dr. Vivek Kavadi is a radiation oncologist at Texas Oncology–Sugar Land, 1350 First Colony Blvd., Sugar Land, Texas; and Texas Oncology–Radiation Oncology Center at Memorial Hermann Memorial City, 925 Gessner Road, Suite 100, Houston, Texas.