Teaming Up To Treat Cancer
May 07, 2008
By
Dr. Laeton Pang
Radiation Oncologist
Interviewed by Melissa Moniz
How long have you been at The Queen’s Medical Center?Since 1994.
What does a radiation oncologist do?
There are various areas of oncology specialties: There’s pediatric, surgical, radiation and medical. Radiation therapy is the use of X-rays and other forms of ionizing radiation to treat patients. Most of our patients are cancer patients, but we have a few who are not. There are a few non-cancerous conditions and some benign tumors that we treat, including non-cancerous over-growth of blood vessels and other tissues or nerves in the brain.
With radiation, it’s very much a team approach. There are about 2,010 centers in the country that employ about 29,000 people nationwide. Everyone is very important in the process for safe and accurate treatment delivery. And I think we are one of the leaders in quality assurance and safety in medicine, because we really have developed procedures to make sure that patients get treatment to the right area and it’s done correctly.
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What types of cancer would you use radiation to treat?
About half of our patients either have breast, prostate or lung cancer. Those are the three most common diagnoses that we treat. About two-thirds of all cancer patients will receive radiation sometime in their lifetime. We use radiation with curative intent for about three-quarters of all of our patients. Most of our patients we’re treating with curative intent, and the other quarter of the patients are coming in for what we call palliation, which is not to cure them of their disease or extend their life, we are just trying to help them with quality-of-life issues such as pain, bleeding, blockage of blood vessels or major airways, or involvement of critical organs such as the brain.
Are there specific cancers radiation can’t treat?
All types of cancers have what we call radiosensitivity. Some cancers are much more sensitive to radiation than others. For example, lymphomas are very sensitive to radiation. Other types such as melanoma are fairly radioresistant, so it takes much higher doses of radiation to achieve an effect. Certain types of cancers like osteosarrcoma (bone cancer) are not at all radiosensitive.
How does radiation work in treating cancer?
We use high-energy X-rays that are on the order of 1,000-10,000 times more powerful than the diagnostic X-rays used in radiology. That high energy is what gives radiation its killing power. We think the main mechanism of action is to create free radicals, which then interact with the DNA and cause lethal damage on certain cells. Normal cells have mechanisms that can repair themselves, whereas cancer cells have an abnormal DNA and are not as able to repair themselves. So there’s a therapeutic ratio in that radiation kills cancer cells more than it kills normal cells. So, as a result, the cancer cells die and the body absorbs them. That’s the main mechanism of action in radiation.
How long does each radiation session take?
Minutes. We are very quick in treatment delivery. The patient has on average 10- to 15-minute time slots, and that includes the time we’re walking them in and out of the room, setting them up on the table, and delivering the treatment. So it’s very quick.
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Are there side effects when receiving radiation therapy?
The side effects depend on the area that we’re treating in the body. Unlike chemotherapy, radiation is specific to an area. Not every patient is going to lose their hair, have nausea or diarrhea. It just depends on where we’re treating.
What area is most sensitive to radiation therapy?
I think the patients who have the hardest time with it are patients who are treated to their neck or their groin region, because these are the most sensitive areas. Oftentimes those patients are also getting chemotherapy, and the added effects of radiation and chemotherapy make it somewhat difficult for those patients. Fortunately we’ve come a long way in terms of managing side effects and in terms of treatment delivery. In the past, for example, all patients who were treated to their head and neck region would develop permanent dryness to their mouth, and that was something that we couldn’t do anything about. Now we have Intensity Modulated Radiation Therapy (IMRT), which helps deliver doses more selectively. By using IMRT, we are able to spare the salivary glands, decreasing the amount of permanent dryness of the mouth. About half of the patients now have significant sparing of their salivary gland function. There also are medications we can give to help with dry mouth. In addition, there have been advances in supportive care and pain management to help patients cope with their cancers and the side effects of treatment.
Can you discuss the differences between chemotherapy and radiation and how the two are often used together to treat cancer?
Chemotherapy includes various medications given to kill cancer cells directly or help sensitize cancer to radiation. There are many different mechanisms of action for chemotherapy drugs. Chemo-therapy travels through the whole body and, for the most part, is given either through the blood stream or orally. Radiation is very selective, so we’re just treating a specific area of the body. In radiation therapy, we use two major types of radiation treatment delivery: One is external beam therapy using machines to deliver radiation from outside the body, and the other is internal radiation or implants. Radioactive particles also can be given orally or through the bloodstream, such as radioactive iodine for thyroid cancer, but this is generally done in the nuclear medicine department.
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Is radiation therapy ever painful or uncomfortable?
Not at all. Actually, when the patients are on the table, it’s just like getting an X-ray. They just lie on the table, and they get radiation treatment to whatever part of the body and they’re not feeling it at all. So the actual treatment is not painful.
When working with children and infants, is there a difference in procedure?
I don’t work much with children. One of my partners mainly does the radiotherapy for children. But the first difference with children in contrast to adults is that, when delivering radiation, one must always be aware of the potential for patient movement. A patient must be still in order for us to treat the correct area. If the child cannot cooperate and lay still for treatment, then we have to sedate them or use general anesthesia. The second difference is that while there are not many cases of childhood cancers, almost all pediatric patients are treated on clinical protocol. Only about 3-4 percent of adult patients nationwide are entered in clinical trials. By enrolling patients in trials, we learn whether newer treatment methods are better than traditional ones. Clinical trials have really advanced the treatment of children with cancer, and great strides have been made in improving survival and quality of life for childhood cancer survivors.