Guest Column: Q&A with a Radiologist on Prostate Cancer

How does radiation kill  prostate cancer cells—and leave healthy cells to recover? What is the difference between proton therapy and high-dose radiation? What is the future of radiotherapy in treating prostate cancer?

Radiologist Lisa Livingston

Radiologist Lisa Livingston tackles these and other questions, as our first guest columnist. Lisa has created the online site, Radiation Technician Schools, a good resource for radiation technicians on schools, career options, scholarship opportunities and more. Plus, you can find interesting articles on the history of the pharmaceutical industry in America, how mobile computing is changing health care delivery, and many other health care topics that interest everyone.  Check out her website and blog — and if you have additional questions about radiation and prostate cancer, send them to The Prostate Storm blog, and we’ll get them answered. (SV)

How does radiation kill cancer cells?

Radiation stops or slows the growth of cancer cells. It kills the genes (DNA) in cancer cells so that they can no longer grow and divide. Cancer cells tend to divide quickly and grow out of control, but radiation can impede this growth. It can also shrink a tumor and keep it from spreading to other parts of the body.

Radiation therapy does not always kill cancer cells immediately. Sometimes it can take days or weeks of treatment to kill cancer cells, and they may even continue to die after treatment ends. Tissues that grow quickly such as skin and bone marrow are generally affected right away, while nerve, breast, prostate and bone tissue will take longer to show affects.

 Why do healthy cells in the prostate recover from radiation exposure? 

Radiation therapy may kill healthy cells in the short term, but healthy cells recover if the radiation doses are short and spread out over time. Normal cells have the ability to repair themselves from damage or be replaced with new cells.

During radiation treatment, doctors try to protect healthy cells by using as low of a dosage as possible and spreading out treatment times. Newer forms of technology have found better ways to target cancer cells with higher doses of radiation, while reducing radiation to nearby healthy cells.

 What are the different types of high-dose radiation therapy?

External beam radiation therapy directs one or multiple beams of x-ray radiation through the skin at the cancer and main tumor area. Treatments are typically given once a day on weekdays. This allows enough radiation into the body to kill the cancer cells while allowing normal cells to recover over the weekend. There are several specific types of external beam therapy. For example, 3D conformal radiation therapy (3D-CRT) uses computer imaging to tailor the beams to the shape of the tumor. Another type, called image-guided radiation therapy, uses conformal techniques guided by imaging taken just before the treatment. This accounts for tumors or organs that may move between treatments, including the prostate and rectum.

Internal beam radiation therapy, or brachytherapy, implants radioactive “seeds” into the cancerous area. The seeds are smaller than a grain of rice. They are placed in the prostate while the patient is under anesthesia, and ultrasound techniques are used to ensure accuracy. The seeds emit radiation that destroys the cancer cells. This technique is less likely to affect normal cells because the seeds are already inside the body, so the radiation doesn’t have to pass through other healthy cells.

What is proton therapy, and how does it differ from high-dose radiation therapy?

Proton beam therapy is similar to external beam therapy, except it uses protons rather than electron x-rays. Compared to electron beams, proton beams cause less side scatter in the tissue, thus affecting fewer healthy cells near the cancer cells. However, the equipment used in this type of therapy is expensive and so it is only available at a few centers around the country. While proton therapy has been more successful with certain types of cancer, its advantages for treating prostate cancer remain uncertain.

What is the Cyberknife?

The Cyberknife is a non-invasive alternative to surgery for cancer treatment, including in the prostate. Similar to other radiation treatments, it delivers high doses of radiation beams to the cancerous area, but with much more accuracy than other treatments. One of the difficulties of treating prostate tumors with radiation is the fact that the prostate moves in unpredictable ways. However, the Cyberknife can continuously identify the exact location of the prostate as it performs radiosurgery. This provides a more accurate treatment and reduces the risk of harming healthy cells.

What is the future of radiotherapy in prostate cancer treatment?

The future lies in new technologies like the Cyberknife that can better detect the location of cancer cells and minimize damage to healthy cells with precise radiation doses. As proton beam therapy becomes less expensive, new tests will hopefully determine whether it is more effective than electron beam treatments. With more accurate treatment options, the amount of time needed for treatment may also be reduced in the future. 

Ed.: As always, discuss these treatment options with your doctor.