Dr. Lin: Radiation therapy is one of the main modalities for cancer care. There are three main modalities. One is surgery; one is systemic treatment, such as chemotherapy, hormone therapy or immunotherapy; and, one is radiation therapy.
Radiation therapy involves using radiation beams to treat the cancer. Rather than take it out physically by surgery, we radiate that cancer and zap it.
Dr. Tripuraneni: There are two major forms of radiation therapy. Giving radiation therapy from the outside is called external radiation. That's what most patients get, using linear accelerators. There is also brachytherapy, which is internal radiation therapy where we put in radiation seeds or capsules and do radiation therapy from inside out.
Dr. Tripuraneni: Radiation therapy has been around more than 100 years. In the 1950s, there was the invention of a new machine called the linear accelerator in Palo Alto, Calif. That really opened up the Pandora's box for radiation therapy.
I've been doing radiation therapy for the past 35 years. Three major things happened in the past 35 years that really put radiation therapy in the forefront of cancer management.
The basic radiation-producing apparatus, the linear accelerator, has stayed about the same. The first major advance was the incorporation of computers. These days, the machines are really fast and highly tailor-made to deal with radiation therapy precisely where we want to treat and how we want to treat.
The second major advance was the incorporation of imaging equipment. Our linear accelerators these days come with X-ray machines built in to take regular X-rays, CAT scans and MRIs that give us the ability to look at the tumor before and during treatment so that we can safely and effectively and precisely give the treatment.
The third thing is that we now use chemotherapy, radiation therapy and immunotherapy together, making it more effective. Almost all cancers that we treat for cure these days, we use a combination of radiation therapy along with some form of chemotherapy and hormone therapy and immunotherapy.
Dr. Lin: These days, the radiation beams are much more precise. We see the target much more precisely. We have better imaging with MRIs and PET scans. We can see on the computer where that tumor is and arrange beams with various angles to treat that target while sparing normal tissue.
Dr. Tripuraneni: With high linear accelerators, we can take an X-ray or a CAT scan just before the treatment and see exactly where it is, modify what we want to treat and shift beams on a fly.
Dr. Lin: At Scripps Health, we have machines where we can actually treat in sub-millimeter precision because machines are so precise these days.
Dr. Lin: There are certain cancers that are more of what we call radioresponsive, or more radioresponsive to radiation therapy, such as lymphomas. And then there are other cancers that are more what we call radioresistant, like sarcomas. But all cancers can be treated with radiation therapy. You just have to kind of manipulate the amount of dose you get per day and how often to give it, based on the sensitivities of the tumor.
For instance, if a tumor is more sensitive, you can give less doses per day. But if a tumor is less sensitive to radiation, you just have to give a higher dose per day. So all cancers are sensitive to radiation, but some are biologically sensitive, where some are more biologically resistant.
The biologically sensitive ones would be lymphoma and seminoma, which is testicular cancer. The ones that are not so sensitive, where you can give a higher dose, would be melanomas and sarcomas. Other tumors are in between.
Dr. Tripuraneni: We treat just about every single cancer with a different radiation therapy, starting from brain tumors, throat cancers, lung cancers, breast cancers, pancreatic cancer and prostate cancer. Just about every single cancer is treated with radiation therapy.
We diagnose about 1.6 million cancers in the United States every year. More than one million patients actually get radiation therapy as the sole treatment and part of the cancer management. So that's a large number of patients. One million patients actually get cancer radiation therapy and about a third to half of them are cured solely because of radiation therapy. It's a very safe and effective and highly curative form.
Dr. Lin: I would say it depends on the type of tumor. It depends on the location. Is it easier to take out, or is it easier to radiate?
For certain cancers such as breast cancer, if a woman has lupus or some kind of autoimmune disorders, sometimes that will tip us toward doing surgery rather than radiation therapy because of the skin reaction or response to radiation therapy. Then there are certain patients who we would tip towards radiation because surgery would be harder on them.
Dr. Tripuraneni: The number of patients that actually cannot have radiation therapy because of lupus is far and few between, maybe one out of 1,000 patients or one out of 5,000 patients. I think if the cancer is localized, they can be a candidate for radiation therapy.
Dr. Tripuraneni: The most important thing is actually to have a treatment plan. That's where the radiation oncologist, surgical oncologist and medical oncologist work together and devise a plan. Sometimes, radiation therapy is the only treatment the patient is going to get. Very often these days, actually, it's a combination of multiple treatments.
Dr. Lin: After the plan is created, patients undergo immobilization and simulation, where we do a mapping of the target. We immobilize the patient so that they're treated in the same position each day. Then a planning is done in the computer in the background by a physicist and dosimetrist and radiation oncologist.
After we plan the treatment, the patient is scheduled for treatments. Radiation takes about five to 10 minutes sometimes. It's Monday through Friday treatment anywhere between one day to up to six to seven weeks, typically.
Dr. Lin: Well, it's a lot less time on the table for almost all radiation therapy equipment these days. For breast cancer, for example, we used to treat for six to seven weeks. These days, we know that a good majority of the women can probably do it in three to four weeks because there is data that shows that three to four weeks of radiation therapy by giving a slightly higher dose each day is probably equivalent to six or seven weeks of radiation therapy. The reason why we can give slightly higher doses of radiation each day is because the technology is better. It's more sophisticated in delivering the treatment.
Dr. Tripuraneni: For prostate cancer, typically, we used to give about 40 treatments over eight weeks. If you think six weeks is bad, that's eight weeks of treatment. With the older machines, you would have to be on the table for a good 20 minutes to 25 minutes. Almost half to two-thirds of patients actually only get five treatments, just one week of radiation therapy. They're on the table no more than 15 minutes, in and out so quickly. With the advent of TrueBeam STx [technology] and the like, we're much more precise. We can safely and constantly and accurately give a very high dose to the prostate and not have any damage to the rectum or bowel that's surrounding.
Dr. Tripuraneni: That's where the TrueBeam STx really comes in handy. Take prostate cancer as an example. You put the patient on the table, and then you do your X-ray measures or you do a CAT scan. You see that the prostate has actually moved either up or down or front or back right in there. You can make all the adjustments right on the table while the patient is lying down. You take one more set of X-rays to make sure that you know exactly where it is. And then you start treating. In certain cases, you can image during the treatment and make the proper adjustments while you are treating.
Dr. Lin: There was some literature recently that looked back on women who had breast cancer treatments years and years ago. And they found out that women who had left-sided breast cancer treatments were more likely to get heart disease in the future because what happens is the radiation beams could hit some of the vessels around the heart, and these vessels, they can develop plaque. It's like a hardening of the artery that can lead to an increased risk of heart disease.
But thankfully these days, the radiation therapy is no longer your mother's radiation therapy. The equipment has become so much better, so much more precise. There are so many ways to treat breast cancers now for the left side. For instance, instead of lying on your back where the beam goes across, you can lie on your stomach where the breast hangs down and treat from the bottom to avoid the heart.
I'm really happy to say that, these days with modern radiation therapy, heart risk is fairly low. As a matter of fact, last year, in the Journal of Clinical Oncology, there was a publication that stated that with modern radiation therapy the incidence of radiation therapy leading to heart-related deaths is only 0.3 percent if you're a non-smoker. If you're a smoker, it's about 1 percent. So if you have a low risk to begin with already, radiation therapy doesn't really add much more risks.
Dr. Lin: Much less side effects these days because the beams are more targeted. Before, you had many more skin burns. For prostate cancer, much more diarrhea, much more loose bowel movements, and burning with urination. These days for prostate cancer, we hardly see any side effects with radiation therapy. So much less side effects.