Tomotherapy: Cutting Edge Radiation Technology at MUSC
Guest: Dr. Anand Sharma – Radiation Oncology
Host: Dr. Linda Austin – Psychiatry
Dr. Linda Austin: I am Dr. Linda Austin. I am interviewing Dr. Anand Sharma who is Associate Professor of Radiation Oncology here at the Medical University of South Carolina. He is going to be talking with us today about some very exciting new technology that we have now for using radiation to more effectively pinpoint the treatment of metastatic tumors, cancer, that patients have. Dr. Sharma, let’s start with some really simple ideas. First of all, why is radiation treatment so important for cancer? Why doesn’t chemotherapy get it all?
Dr. Anand Sharma: Radiation therapy is another kind of local treatment, almost similar to surgery, except we do not cause any bleeding. Chemotherapy is systemic treatment. Radiation therapy, surgery and chemotherapy, all three, are utilized to one extent or another. But, radiation is a local treatment much like surgery while chemotherapy is a systemic treatment and usually does not work alone in solid tumors.
Dr. Linda Austin: Would it be fair to say that chemotherapy works best on smaller lesions whereas you might need radiation for larger, radiation or surgery for larger lesions?
Dr. Anand Sharma: In our context, chemotherapy works essentially in two ways. One way is that it tries to prevent the cancer cells from going from where it arises to outside its domain into the rest of the body. So, it prevents the systemic spread of cancer. The second, very effective, way is that it potentiates the effect of radiation. So, it has a radiation sensitizing effect on cancer cells. It makes cancer cells more susceptible to radiation. So, in that regard, it makes the local treatment, by radiation, more effective.
Dr. Linda Austin: Now, I understand that we have a new machine here at the medical university and that we are only the second in the state of South Carolina. There are only 160 in the world. Is that right?
Dr. Anand Sharma: That is correct.
Dr. Linda Austin: What is the name of that machine?
Dr. Anand Sharma: It is called tomotherapy. What it means, essentially, is sliced treatment. Tomo is another word for slice. That means you can treat the patient slice by slice. It is probably the most advanced way of treating patients with radiation.
Dr. Linda Austin: Now, this is effective for tumors of what parts of the body?
Dr. Anand Sharma: It is actually effective for all solid tumors in the body, particularly useful in CNS, which is brain tumors, head and neck cancers, also useful in abdominal tumors, prostate cancer, also used for some pediatric uses.
Dr. Linda Austin: What kinds of tumors is it not useful for?
Dr. Anand Sharma: It is, of course, not useful for blood cancers.
Dr. Linda Austin: Leukemias?
Dr. Anand Sharma: Leukemias, or lymphomas. What tomotherapy does is, it allows for more ways to treat a cancer. It allows a lot more freedom to use the actions of the beams than we have at our disposal right now.
Dr. Linda Austin: Can you give us a sketch of how this technology works?
Dr. Anand Sharma: Okay, well, what happens in this is that a CT scanner is combined to a linear accelerator, which is a typical radiation treatment machine. The patient goes through that scanner and is treated by a slice treatment. The machine revolves around the patient a full 360 degrees and the table on which the patient is lying moves in by a certain increment. So, a small slice of the entire slice of that patient’s body is treated at that time.
Dr. Linda Austin: So, what advantage, then, does this offer?
Dr. Anand Sharma: Advantages that it offers, compared to the conventional type of radiation, is that it allows at least 51 different angles by which beams can be applied around the body. So, it gives a circular path through which at least 51 beams, or beam arrangements, can be used compared to, say, about 7 to 9 that are used traditionally.
Dr. Linda Austin: Now, I understand this technology also allows you to take a very detailed CT image of the tumor that then will guide how you design that therapy. Can you explain that? It is a really fascinating process, I think.
Dr. Anand Sharma: As I mentioned earlier, since it is combined with a CT scanner, it can real time scan the patient’s scan and you can superimpose that, in fact, the machine automatically superimposes that, to the planning CT that was acquired at the time of simulation. Those two are combined, and if there is any change in the setup of the patient, or in even in the size of the tumor, you can see that and you can make changes accordingly. In fact, you can do that daily. So, you can see what you are treating.
Dr. Linda Austin: As you are treating?
Dr. Anand Sharma: You do the CT scan just prior to starting radiation. The duration of radiation is approximately 10 minutes, so it is not a long treatment, radiation. So, you do the setup first. The machine acquires the CT scan. You compare it to the planning CT and make adjustments as you go. You can do that everyday. This is different from the other treatment machines that we have available where you can only do that based on bony landmarks or surface marks and not based on real anatomy of the tumor and the normal structures.
After the initial simulation is done, which means you prepare for the treatment, you have a treatment plan in hand that is based on the first CT scan that is done on a conventional CT scanner. After you have done that, you bring the patient in for the first treatment. The tomotherapy machine actually acquires images first, through that area of interest, and then it compares it to your planning CT and sees if there is any disconnect. In terms of patient setup, mostly patients are set up quite accurately, but even if there is a difference of a few millimeters, it is unaccounted for and it automatically makes those changes, on the table height, on the location of the table, whether the patient needs to move to the right or to the left, inside or out, it makes all those changes. Once it is satisfied that you have a perfect match between the CT scan that you acquired just now compared to the one, say, you did about a week ago. Then, it is okay to start the treatment. So, you start the treatment and you bring the patient the next day and do the same process again. It takes about 10 minutes for the CT scan to be done and matched, before the treatment begins.
Dr. Linda Austin: So, it uses that CT scan, then, to give you absolutely accurate pinpoint information about where the tumor begins and ends and where the radiation should be directed?
Dr. Anand Sharma: It accurately localizes it. Another advantage is not just localizing where the tumor is but localizing where the normal tissues are. In my practice, I treat head and neck cancers. Some of them are quite close to the skull base and they are very close to the optic apparatus which is not too far, a few millimeters, away from the tumor. Now, if you do not have a perfect setup, you may have a high dose of radiation that was initially planned for the tumor going to those critical structures and patients may suffer from blindness or other serious side effects. So, it is really important, in those patients.
Dr. Linda Austin: So, it is really doing two things. One, it is allowing you to deliver more effective therapy and, two, it is doing so with fewer adverse effects because it is so precise.
Dr. Anand Sharma: Exactly. This is what it does. It allows you to give a high dose to the entire tumor and limiting the dose to surrounding normal critical tissues which sometimes are very close. If you do not have these benefits of this particular machine then you may underdose the tumor because you may think that the risk of causing a side effect may be high. So, it allows you to have a very sharp gradient where the tumor receives your prescribed dose but the normal tissues are spared a high dose of radiation.
Dr. Linda Austin: How long have we had this machine?
Dr. Anand Sharma: We acquired this machine just a few months ago and we are going to use it on our first few patients in the beginning of November of this year.
Dr. Linda Austin: That is so exciting, very exciting. Is there any data out yet about how this has increased survival of these head and neck cancers for patients, in other locations where it exists?
Dr. Anand Sharma: Tomotherapy has been in use for approximately four years. Tens of thousands of patients have been treated. But, in cancer parlance, it is still a short time. There have been publications that have shown that in certain tumor groups, it is superior to the existing technology, that is, step-and-shoot intensity modulated radiation therapy.
Dr. Linda Austin: Dr. Sharma, thank you so much for talking with us today.
Dr. Anand Sharma: Thank you.
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