Tuesday, August 12, 2014

Radiation for Dummies

Radiation is one method often used in conjunction with or instead of chemotherapy to treat different types of cancer (most often solid tumors). During our cancer journey, Jim has been treated five times with radiation leading one to believe that I should know how it works. And I do—until I forget. With each course of radiotherapy, I return to my sources for a refresher on the physiology and physics involved in this complex procedure.

With Jim’s initial diagnosis of Stage IIIB NSCLC, the oncologists prescribed chemotherapy followed by radiation. Still reeling from the unexpected diagnosis and poor prognosis, I didn’t have time to worry about how it worked; I only cared that it did work. When he had the first recurrence, five years later, there were more options and I gave more time to researching those that were available.

You may be , as I was at first, not particularly interested in what is going on in the body during these treatments. But if you are interested, I can share my simple version of radiology for beginners.

X-rays, gamma rays, and charged particles are forms of electromagnetic radiation (as are light, microwaves, and radio waves) used for cancer treatment. X rays are basically the same thing as visible light waves but they have a higher energy level—enough energy to disrupt molecular bonds. These highly energetic waves can be harnessed for medical purposes such as imaging and diagnostic testing. Certain forms with even more energy are used to shrink tumors and kill cancer cells.

Radiation therapy kills cancer cells by damaging their DNA (the molecules inside cells that carry genetic information and pass it from one generation to the next). Radiation therapy can either damage DNA directly or create charged particles (free radicals) within the cells that can in turn damage the DNA. Cancer cells whose DNA is damaged beyond repair stop dividing or die. When the damaged cells die, they are broken down and eliminated by the body’s natural processes. This explains the post treatment effects of radiation. Side effects are experienced as the cancerous cells die off.

The radiation may be delivered by a machine outside the body (external-beam radiation therapy). This machine, a linear accelerator, uses microwave technology (similar to that used for radar) to accelerate electrons, then allows these electrons to collide with a heavy metal target. As a result of the collisions, high-energy x-rays are produced. X-rays are emitted when a highly energetic beam of charged particles such as electrons is rapidly decelerated — because it runs into a metal target, for example.

In 2003, for Jim, the doctors used standard radiation treatments five days a week for six weeks.The side effects included extreme, even debilitating fatigue, nausea, and some difficulty swallowing.

In 2008, they chose to treat a metastasis next to the spine with Intensity-Modulated Radiation Therapy, IMRT stereotactic radiation, a specialized type of external beam radiation targeting a well-defined tumor using extremely detailed imaging scans. Stereotactic treatments can be confusing because many hospitals call the treatments by the name of the manufacturer rather than calling it SRS or SBRT. Brand names for these treatments include Axesse, Cyberknife, Gamma Knife, Novalis, Primatom, Synergy, X-Knife, TomoTherapy, Trilogy and Truebeam. This list changes as equipment manufacturers continue to develop new, specialized technologies to treat cancers. Jim received TomoTherapy from Dr. Brian Butler and his staff at Methodist Hospital in Houston. As with any complicated medical procedure, choosing the doctor is as important or more important than choosing the type.

The advantage of stereotactic radiation is they deliver the right amount of radiation to the tumor in a shorter period of time with less damage to adjacent healthy tissue. Instead of thirty days of treatments, the mission is accomplished in five or so treatments spread over two weeks.

Why then don’t all oncologists prescribe stereotactic radiation instead of standard radiation?

It is suitable for only certain small tumors.
The preparation for treatment is longer and requires specially trained medical personnel. This is because physicians must manually delineate the tumors one CT image at a time through the entire disease site which can take much longer than 3DCRT preparation. Then, medical physicists and dosimetrists must be engaged to create a viable treatment plan.
Not every facility has the necessary equipment and personnel to administer the treatment.

Targeted radiation is not without side-effects. Jim still experienced fatigue that lasted weeks beyond treatment but it was not as severe or debilitating as the same amount of radiation spread over a six or ten week time period. A few years ago after three TomoTherapy treatments landed him in the hospital with pericarditis, inflammation of the tissue around the heart, an extremely painful, though not life threatening condition. And he has nerve damage resulting in pain and numbness. Still, in his opinion, radiotherapy is much easier to take than chemotherapy—and it’s over sooner.

However, the doctors have warned us that radiotherapy of any kind will probably not be an option if the cancer comes back to the same areas that have been treated repeatedly. Hopefully, if and when than happens, researchers will have found an alternative treatment.

No comments:

Post a Comment