What is Special about Tomotherapy?
Quite simply, tomotherapy represents the future of radiation therapy. The leap in technology from regular radiation therapy is overwhelming.
Hi-Art TomotherapyÖ shares a lot of technology with CT scanners, otherwise known as computerized tomography. The machine even looks like a CT scanner. Some of its amazing capabilities are:
- Tomotherapy will do a quick CT scan before each treatment starts, to ensure the patient is aligned perfectly.
- A thin beam is rotated around the body, entering from many directions, while the couch simultaneously moves into the machine. This effectively results in thousands of little beamlets of different intensities entering the body, converging on the tumors.
- A very powerful multiple-processor computer calculates the treatment plans and coordinates treatment delivery.
- Tomo can treat big or little tumors, single or multiple tumors, one region of the body or several regions, to the same dosage in every area or to multiple different dosages. The possibilities are endless!
- Tomo can avoid organs we tell it to. We can miss the salivary glands and treat the throat tumor. Miss the spinal cord and retreat the spinal bone. Miss the kidneys and treat the pancreas.
Tomotherapy is actually a form of intensity modulated radiation therapy (IMRT). Since 1997 we have had three other IMRT machines at our center and our opinion is that tomotherapy is more advanced and versatile than other forms of IMRT. In our experience tomotherapy has been particularly valuable for the following conditions:
- Retreating previously irradiated areas of the body
- Treating multiple metastases simultaneously
- Treating all metastases throughout the body simultaneously
- Treating lung cancers, breast cancers, and prostate cancers.
CTCA's Commitment to Tomotherapy
All three radiation oncology centers in the CTCA family are utilizing tomotherapy treatment machines. The centers in Zion and Tulsa were among the first 20 centers in the world to have operational Hi-Art Tomotherapy machines since 2005.
At our Tulsa center, we have been utilizing our two tomotherapy machines in ways we could not have dreamed about a few short years ago. The demand for this technology has been so great that we frequently run treatment into the evening hours, and have treated over 1000 patients so far as of July 2007. We have treated more tomotherapy patients than any other cancer center in the world. What follows are a few of the exciting ways we are using tomotherapy.
TOMOTHERAPY TREATMENT PROTOCOLS
Many radiation oncologists are reluctanct to give repeat radiation to the same part of the body that has already received radiation in the past. It can be dangerous to re-irradiate, because you could risk complications such as excessive scarring, ulceration, or pain. However, tomotherapy is a natural choice for retreating tumors that have already been irradiated. Because tomotherapy is so targeted, it can be safer to re-irradiate, because the surrounding healthy tissues will receive less radiation dose.
Our hospital has a very large amount of experience retreating tumors with radiation, whether they be in the brain, lung, bone, breast, or other organ.
We will frequently start with a PET/CT scan to determine exactly where the recurrent active cancer is. This is important, because sometimes it is hard to distinguish between scar tissue from the previous radiation, and actively growing cancer. We usually only want to treat the active cancer. A Pet scan can distinguish between the two. We do the Pet scan as a "simulation", meaning we plan the radiation treatment directly from the PET/CT images.
We frequently add amifostine (Ethyol) as a radioprotectant drug during retreatment, to help reduce the amount of additional scarring or damage we might cause.
We choose a radiation dose that balances safety and cancer control.
Prostate cancer is treated extremely well with tomotherapy. Many men have heard about using IMRT (intensity modulated radiation therapy) for prostate cancer, and tomotherapy is a very advanced form of IMRT. We will use tomotherapy in two ways to treat prostate cancer: either by itself, or else in conjunction with high dose rate brachytherapy.
We usually place three gold VisicoilÖ markers into the prostate as the first step. The tomotherapy machine does ints own quick CT scan prior to each treatment, and the markers show up very well on the scan, and can ensure that the prostate gland is perfectly centered in the radiation field. The picture on the right shows an actual treatment set-up. This sort of accuracy in setup and treatment is referred to as Image Guided Radiation Therapy (IGRT).
When we use tomotherapy as the only treatment, we typically treat for 33 days over 6 1/2 weeks. This is faster than the treatment at most other centers, which may give 45 treatments over 9 weeks! Since tomotherapy is so precise, we have found it to be safe to give a higher dose per day so that we can finish the treatment faster.
(225 cGy/day * 33 days = 7425 cGy, is equivalent to 180 cGy/day * 45 days= 8100 cGy)
Tomotherapy by itself produces excellent PSA responses and a high cure rate. The side effects are usually mild -- the majority of patients who we see 3 months after treatment feel like they have no side effects, or almost no side effects, from the therapy. Tomotherapy plus high dose rate (HDR) brachytherapy is a very aggressive treatment combination. We recommend it for patients with aggressive tumors or men who want the most intense treatment that we offer. The tomotherapy is reduced to 20 treatments over 4 weeks when combined with HDR.
This patient was treated at Tulsa and had multiple metastases in the spinal bones. The MRI scan on the left shows "white" areas in the spinal bones where the tumors are. A tomotherapy plan was created, and all the spine metastases were treated simultaneously. With standard radiation therapy, often a different radiation therapy plan has to be created for each separate tumor treated. With tomotherapy, it is easy to treat multiple tumor simultaneously, whether they be in the brain, liver, lungs, bones, or in several organs.
Total Metastases Irradiation (TMetI)
TMetI describes the targeted and simultaneous radiation treatment of multiple tumors throughout the body. If we can treat several metastases simultaneously with tomotherapy, why not treat them all? Often, chemotherapy alone will only result in a partial response of metastatic tumors. By adding tomotherapy to all the visible areas of cancer, there can usually be an improved response, a better chance of complete response, and perhaps even a chance of cure. It is important to still use chemotherapy, because when there are multiple metastases present it usually means that there are also many "invisible" areas of micrometases that chemotherapy is particularly helpful at getting to.
According to common opinion and dogma, you should not bother to irradiate all the metastases, only the worst spots or problem areas. Fortunately, we try not to be swayed too much by dogma. With accurate PET scan identification of metastases, and with tomotherapy targeted radiation, we now have the ability to radiate all the tumors in multiple regions of the body to a high dose while limiting the amount of radiation received by healthy tissues. The whole equation of Risk vs Benefit is completely altered by these two technologies! This is similiar to the concept of aggressively treating "oligometastases", but we have increased the number and location of tumors we can treat.
Not everyone can have TMetI performed. Some guidelines are:
- Relatively few metastases, best if less than 10.
- No diffuse (widespread) involvement of any organ
- Good functioning / patient in good shape
- Every person, organ and tumor must be individually assessed!
In cases where we do not feel it is safe or effective to target all the tumors, we will evaluate to see if there is a subset of the tumors that could benefit from radiation.
Tomotherapy can be used instead of gamma-knife, cyberknife, or stereotactic radiosurgery to treat brain tumors. Tomotherapy is definitely more flexible than these therapies in that it can treat multiple tumors at the same time, can treat large or complex shaped tumors, and can be easily divided up into a series of daily treatments.
When cancer starts in another part of the body (like the lung or breast) and then spreads to the brain, it is referred to as metastatic cancer. Metastatic brain tumors are all too often treated the same way: the whole brain is radiated, hitting healthy brain cells and tumor cells with the same amount of radiation. If too low of a dose is used then the tumors will quickly grow back. If too high of a dose is used there will be brain damage. A more logical approach is a two phase treatment: first treat the entire brain to a moderately low dose -- enough to kill renegade cancer cells which are scattered throughout the brain and cannot be seen on scans, but not enough radiation to significantly harm mental functioning. Second, give some extra radiation to every visible brain tumor while avoiding the healthy brain tissue. Before IMRT and tomotherapy, there was no easy way to boost multiple brain tumors or large tumors. Now with tomotherapy, the radiation oncologist merely outlines all the tumors on a computer screen and the computer will design a treatment composed of thousands of tiny radiation beamlets which intersect on all the tumors.
Treatment of Recurrent Brain Metastases
We can also use tomotherapy to retreat brain tumors which have recurred after previous radiation. Often when brain tumors recur patients are given up on. We have retreated up to 25 separate brain tumors simultaneously by using tomotherapy. This is possibly the best technology device in existence for retreating multiple brain metastases.
Treatment of Primary Brain Tumors / Glioblastomas
Tomotherapy can do a technologically marvellous job treating glioblastoma multiforme. Using an MRI scan, and sometimes also a PET scan, we find the area of residual active cancer and have tomotherapy give this the highest dose (such as 6600 cGy). We then circle an area of brain surrounding this, where there is edema present or where we think the cancer cells might be able to spread to, and we have tomotherapy give this a lower dose (such as 4500 cGy). We can create sophisticated plans which give the highest dose right where it needs to be, and the dose will gradually taper down as you get further away from the cancer.
The tomotherapy plan on the left shows a very large lung cancer pushing against the trachea. The follow-up CT scan on the right was taken 2 months after completing radiation and it shows a compete response! These images are of the same patient, same part of the body, pre and post treatment.
We frequently treat lung cancer with our PAT treatment regimene. P.A.T. stands for Pet scan, Amifostine, and Tomotherapy. We use a Pet scan to determine where all the cancer is, tomotherapy to target it, and add amifostine (Ethyol) as a "radioprotectant" to protect the lungs against some of the damage that can be casued by radiation therapy.
This is a very advanced way to treat lung cancer. We have not yet statistically analyzed our results, but the physicians at our center have been impressed by the tumor response rates and an apparent reduction in the amount of radiation lung injuries.
After a lumpectomy (partial mastectomy), radiation therapy is usually given to the breast, to eliminate any cancer cells that may still be present. For early stage cancers, we often use breast brachytherapy, which takes only 5 days, and treats only a portion of the breast.
For more advanced breast cancers, or for women who do not want brachytherapy, we use external beam irradiation. The standard method has been to use two beams, aimed at the breast from each side. This can result in a lot of unwanted collateral radiation. The picture at the right shows all the tissue (in red) that is treated to a high dose with this standard two beam technique.
When tomotherapy is used, we are able to contour the high dose region much more precisely to the breast tissue. The high dosages can be kept off the lungs and heart. If lymph nodes such as the internal mammary nodes are also being included in the treatment, tomotherapy can result in an even more dramatic reduction in unwanted radiation. With tomotherapy we can also give a higher dose each day to the area of the breast where the tumor used to be. This can shorten the length of radiation therapy from 7 weeks down to 5 weeks.
Head and Neck Cancer
IMRT is revolutionizing the way that head and neck cancers are irradiated. With cancers of the tongue, throat, and larynx, often all the lymph glands of the neck have to be radiated along with the primary tumor. This usually results in permanent damage to the salivary glands, and a life-long dry mouth, also known as xerostomia.
With IMRT, it became possible to treat the neck lymph nodes and avoid the salivary glands. Tomotherapy, which is a special form of IMRT, has perfected this technique and reduced the parotid dose even further compared with normal IMRT.
Amifostine is also frequently added to radiation to increase the tolerance of the salivary glands to radiation. With the combination of tomotherapy and amifostine, we have a good chance of preventing this troubling and permanent symptom of dry mouth.
We always evaluate every patient's cancer uniquely to determine whether radiation therapy is appropriate, to what dose, and with what kind of radiation. Sometimes, a tumor is best treated with basic 3D-conformal radiation. Sometimes, the best choice will be IMRT. Many times, with tomotherapy. We have probably treated just about every kind of cancer and situation with tomotherapy. What we're most most excited about is our ability to treat (and retreat) cancers that would not have been possible or safe with other forms of radiation.