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Imrt Radiation Therapy For Prostate Cancer

When Is Brachytherapy Alone The Right Choice

Proton Therapy, IMRT, and SBRT | Mark Scholz, MD | PCRI

For some patients with disease that is confined to the prostate and not too aggressive , brachytherapy alone is a good option. It is also convenient for the patient as it is done in an outpatient setting and most people can get back to work within a few days.

But brachytherapy is not right for everyone. For some patients with less-aggressive disease, a watch-and-wait approach would be preferred. At MSK, our philosophy is that when the disease is caught very early, it is very appropriate to do active surveillance and hold off on treatment.

This philosophy applies to patients with a low PSA level, or nonaggressive disease as reflected by a Gleason score of 6 with evidence of cancer in only a few of the biopsy samples and no evidence from the MRI of a significant amount of disease. There are also very select patients with Gleason 7 disease who may be candidates for active surveillance.

Why Do You Need Imrt And Igrt When Treating Prostate Cancer

To understand the benefits of IMRT and IGRT for prostate cancer treatment, we must first understand how radiation therapy works. Radiation is a highly effective treatment that kills cancer cells by damaging their genetic structure to prevent the tissue from growing. The problem, however, is that the radiation can also damage surrounding healthy tissue.

Steven G. Lester, M.D., F.A.C.R.O., board-certified radiation oncologist at Central Florida Cancer Care, describes how this affected prostate cancer treatments, In the past, before the technology improved, we had to take about a two-centimeter margin around the prostate to make sure we didnt miss it.

The problem is that its common for the prostate to shift. This happens throughout the day, in part, because your rectum is located behind the prostate. If the rectum is distended with gas or stool, it will push the prostate in one direction. If the rectum is empty, the prostate will drop in a different direction.

The prostate also moves depending upon how full your bladder is. Doctors generally tried to tread patients when their bladders were full, but there are variables related to how much fluid is in the bladder, which could cause the prostate to shift.

These variables made radiation oncologists strive for more innovative and accurate techniques to protect the surrounding tissue while fully treating the prostate cancer. They found innovation in IMRT and IGRT.

Cancer That Clearly Has Spread

If the cancer has spread outside the prostate, it will most likely go to nearby lymph nodes first, and then to bones. Much less often the cancer will spread to the liver or other organs.

When prostate cancer has spread to other parts of the body , hormone therapy is probably the most effective treatment. But it isnt likely to cure the cancer, and at some point it might stop working. Usually the first treatment is a luteinizing hormone-releasing hormone agonist, LHRH antagonist, or orchiectomy, sometimes along with an anti-androgen drug or abiraterone. Another option might be to get chemotherapy along with the hormone therapy. Other treatments aimed at bone metastases might be used as well.

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How Is The Procedure Performed

IMRT often requires multiple treatment sessions on different days. The radiation oncologist considers the type, location and size of the tumor, doses to normal structures, and the patient’s health to decide the number of treatments. Typically, patients are scheduled for IMRT sessions five days a week for five to eight weeks.

At the beginning of the treatment session, the radiation therapist positions the patient on the treatment table, guided by the marks on the skin defining the treatment area. If molded devices were made, they will be used to help the patient maintain the proper position. The patient may be repositioned during the procedure. Imaging systems on the treatment machine such as x-ray or CT may be used to check positioning and marker location. Treatment sessions usually take between 15 and 60 minutes.

Talk With Your Doctor About Side Effects And What To Expect

Prostate

Your doctor can help you determine whether radiation therapy is right for you.

In addition, an oncologist a doctor specializing in cancer treatment can help you learn how to minimize your chance of developing side effects.

They can also refer you to local support groups where you can get in touch with other people who have undergone or are undergoing the same treatment.

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What Are The Benefits Of Treatment With Imrt And Igrt For Prostate Cancer

One of the greatest achievements to date in treating prostate cancer is the use of sophisticated IMRT and IGRT techniques designed to target the specific instance of cancer in the organ without affecting the healthy tissue surrounding the prostate.

Once we developed image-guided radiation, it allowed us to visualize the prostate every day. Since then, we have been able to cut those margins from two centimeters to point five centimeters, says Dr. Lester. That lets us treat a lot less healthy tissue, helps us ensure were hitting the target, and it has allowed us to put in a higher dose of radiation, which has resulted in longer, better term, local control, which hopefully will translate to cures.

In the past before the technology improved, the chances of irradiating surrounding healthy tissue was high. This could result in additional health problems for the patient, something no doctor wants to occur. Thankfully, the development of new IMRT and IGRT tools allows radiation oncologists the ability to coordinate the life-saving radiation beam to within millimeters of its target. By localizing radiation treatment collateral damage to other organs is minimal.

One study compared traditional treatment with IMRT and IGRT, describing the problem with general prostate radiation therapy in this way:

Which Cancers Can Be Treated With Imrt

IMRT is used at MSK most often to treat prostate cancer, head and neck cancers, lung cancer, brain cancer, gastrointestinal cancers, and breast cancer, in part because these tumors tend to be located close to critical organs and tissues in the body. It may also be used to treat lymphoma, sarcoma, gynecologic cancers, and select pediatric cancers.

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Possible Side Effects Of Ebrt

Some of the side effects from EBRT are the same as those from surgery, while others are different.

Bowel problems: Radiation can irritate the rectum and cause a condition called radiation proctitis. This can lead to diarrhea, sometimes with blood in the stool, and rectal leakage. Most of these problems go away over time, but in rare cases normal bowel function does not return. To help lessen bowel problems, you may be told to follow a special diet during radiation therapy to help limit bowel movement during treatment. Sometimes a balloon-like device or gel is put between the rectum and the prostate before treatment to act like a spacer to lessen the amount of radiation that reaches the rectum.

Urinary problems: Radiation can irritate the bladder and lead to a condition called radiation cystitis. You might need to urinate more often, have a burning sensation while you urinate, and/or find blood in your urine. Urinary problems usually improve over time, but in some men they never go away.

Some men develop urinary incontinence after treatment, which means they cant control their urine or have leakage or dribbling. As described in the surgery section, there are different levels and types of incontinence. Overall, this side effect occurs less often with radiation therapy than after surgery. The risk is low at first, but it goes up each year for several years after treatment.

How Long Does Imrt Take

IMRT for the Teal Stage of Prostate Cancer | Prostate Cancer Staging Guide

The time it takes will depend on the nature of the cancer and treatment plan. Usually, an IMRT treatment takes about 10 to 30 minutes. You may be in the treatment room for up to an hour, but every cancer is different. Itâs a good idea to ask your doctor what to expect in your particular case.

While each procedure will be short, youâll need more than one. Doctors usually give IMRT 5 days a week for several weeks. Exactly how many times you will go also will depends on your particular cancer and treatment plan.

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Who Should Consider External Beam Radiation Therapy

In most cases, external beam radiation therapy is used for men with localized prostate cancer . The intent of EBRT in this case is to kill the tumor while sparing as much healthy tissue as possible. Sometimes it is used in more advanced cases. For example, it can be used along with hormone therapy, or used to relieve pain from bone metastases.

Clinical Applications In H& n Cancer

Radiation plays a central role in the treatment of H& N cancer. New radiation delivery techniques offer powerful potential to diminish the spectrum and severity of radiation toxicities for H& N cancer patients. For many decades, conventional H& N radiation techniques have involved treatment with generous opposed lateral beams to encompass the known primary tumour and upper cervical lymphatics. This classical technique produces a relatively homogeneous dose distribution that allows excellent target dosing while minimizing hot and cold spots. However, due to the tight proximity of tumour targets and normal tissue in the H& N region, many uninvolved structures including salivary glands, spinal cord, auditory apparatus, optic apparatus, mandible, and vocal cords can unnecessarily receive high doses of radiation.

In H& N cancer, one of the most common rationales for IMRT is to preserve salivary gland function and thereby diminish the severity of chronic xerostomia with associated adverse impact on taste, swallowing, dentition, speech, and overall quality of life. In addition, the capacity of IMRT to limit dose to normal tissue structures may also allow dose escalation and differential dose painting, thereby accomplishing in-field tumour boosting .

Isodose distributions contrasting conventional and IMRT H& N treatment plans. Significant reduction of dose to the left parotid gland is achieved with the IMRT plan.

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Low Dose Rate Brachytherapy Implants

The most common form of brachytherapy for prostate cancer, LDR involves surgically placing small radioactive pellets, about the size of a grain of rice, within the prostate. Once put in place, they remain there for life, but the radiation weakens over weeks or months, until it almost completely goes away.

What The Research Shows About Radiation Vs Surgery

Prostate

The ProtecT trial was a 10-year, randomized clinical study designed to compare radical prostatectomy, external-beam radiotherapy and active surveillance for the treatment of localized prostate cancer.

The results, published in 2016, showed that the rate of disease progression among men assigned to radiotherapy or radical prostatectomy was less than half the rate among men assigned to active monitoring. However, there was no significant difference in survival at the median 10-year mark for radiation therapy, surgery or active surveillance.

If youre interested in directly comparing treatment outcomes by treatment method and risk group , the Prostate Cancer Free Foundation provides an interactive graph on its website with information from data obtained from over 100,000 prostate cancer patients over a 15-year period.

As discussed earlier in the sections on the side effects of radiation therapy and surgery, the researchers conducting the ProtecT trial also looked at side effects and quality-of-life issues and found that the three major side effects of these two treatment options that affect quality of life after prostate cancer treatment are urinary incontinence, sexual dysfunction and bowel health.

The trial found that urinary leakage and erectile dysfunction were more common after surgery than after radiation therapy. Gastrointestinal bowel problems were more common after radiation therapy.

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What Is A Radiation Oncologist

If a patient is undergoing radiation, the cancer treatment plan may be managed by a radiation oncologist who carefully monitors the persons overall health and well-being through the process.

With advanced cancer, a patient may also be referred to a medical oncologist. This specialized doctor uses medicines such as chemotherapy and hormone therapy to treat cancers. Its common for several medical specialists to work together on a treatment plantheyre known as a cancer care team.

Heres What You Should Know About This Treatment Option

Men who get diagnosed with prostate cancer have several options to choose from for their next step. Many men with slow-growing, low-risk cancer follow active surveillance, a wait-and-see approach that monitors the cancer for changes.

But if the cancer shows higher risk or has already begun to spread, other treatments are recommended. There are two options: surgery to remove the prostate or radiation to destroy the cancer cells.

Studies comparing these two approaches demonstrate no advantage of one over the other with respect to cancer control. Your path will depend on factors like your current health, the specifics of your cancer, and personal preference. Yet for many men, radiation can be the better option.

Its much more precise than the traditional radiation used for other kinds of cancer, and research also has found that long-term quality of life is often better, with fewer adverse health effects compared to surgery, says Dr. Anthony DAmico, a radiation oncologist with Harvard-affiliated Dana-Farber Cancer Institute and Brigham and Womens Hospital.

There are two main ways to deliver radiation to the prostate: external beam radiation and brachytherapy.

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Prostate Cancer: Radiation Therapy

Radiation therapy, also called X-ray therapy, uses high levels of radiation to kill prostate cancer cells or keep them from growing and dividing while minimizing damage to healthy cells.

Radiation can be given from a machine outside the body and directed at the prostate . Or a surgeon can place radioactive materials into the tumor . These radioactive materials can be temporary or permanent.

What Equipment Is Used

Dr. Henderson on Proton Therapy Versus IMRT in Prostate Cancer

A medical linear accelerator generates the photons, or x-rays, used in IMRT. The machine is the size of a small carapproximately 10 feet high and 15 feet long. During the treatment, the patient must lie still. The intensity of each beam’s radiation dose is dynamically varied according to treatment plan. The patient will not feel any sensation while the radiation is on, but will hear noise from the machine, and may smell an odor from the electronic equipment, or see the warning indicator light. The noises and odors from the machine are normal. The patient will be in the room alone during treatment but is constantly monitored by the radiation therapists from outside the treatment room. The time in the treatment room depends on the specific plan, but usually is between 15 minutes and one hour.

See the Linear Accelerator page for more information.

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Brief History Of Imrt

Intensity-modulated radiation therapy was first conceptualised in the 1960s. However, it was not until the 1980s1990s that the computing capability required for complex inverse planning algorithms became commercially available . In 1994, the NOMOS Peacock system was introduced as the first commercial IMRT delivery unit. The Peacock system required the use of a beam modulation device known as a dynamic multivane intensity-modulating collimator . This particular form of IMRT is called serial tomotherapy, as slices could be treated by a continually rotating gantry . Step and shoot IMRT represents another commonly used technique whereby multiple static beams are subdivided into segments. In the sliding window technique, a window defined by the MLC leaves sweeps across the treatment field at variable speed, while the monitor units are delivered continuously . With serial and helical tomotherapy, the intensity modulation is achieved through the use of a binary MLC . In contrast to serial tomotherapy, helical tomotherapy is characterised by translation of the treatment couch during treatment delivery, allowing large field lengths to be treated in a single spiral . Moreover, a CT detector array diametrically opposed to the energy source allows for image and dose reconstruction capabilities during treatment. Each of these systems shares commonality of need for intensive physics support, precise anatomical target definition, and rigorous quality assurance .

What Are The Advantages Of Intensity

  • Delivers a higher dose of radiation to the tumor, with less damage to nearby healthy tissue
  • Shapes the radiation intensity to uniquely match radiation to the size and shape of the tumor
  • Is commonly used in cancers of the head and neck where many critical structures that may be near the tumor, such as the spinal cord and the salivary glands, must be avoided
  • Has been shown to be a beneficial treatment for prostate cancer because it significantly decreases the risk of rectal bleeding and provides the opportunity for dose escalation to decrease the likelihood of developing metastatic prostate cancer

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How Does Proton Therapy Compare With Imrt For Prostate Cancer Treatment Outcomes

UF Health Proton Therapy Institute published in the May 2016 issue of the International Journal of Radiation Oncology Biology Physics a study that reports 5-year outcomes of more than 1,300 prostate cancer patients treated at the Institute from 2006 to 2010. The study shows that proton therapy is a highly effective treatment for low-risk, intermediate-risk and high-risk prostate cancer. It also reports a low rate of serious side effects.

There are no prospective comparative studies for a definitive comparison of proton therapy with IMRT. The following table from the study provides some guidance on patient outcomes following prostate cancer treatment with either proton therapy or IMRT.

We at the University of Florida Health Proton Therapy Institute are fully committed to gaining a better understanding of the impact of utilizing protons to treat prostate cancer. Our published data is based on treatments delivered with well-defined dose levels and toxicity documented by detailed follow-up questions and examinations of our patients. Actual results, reported by patients and their physicians, are utilized in our research studies.

We strongly encourage all prostate patients to become better educated about their disease and the different options for treatment. We likewise encourage patients to take the time and effort to question the data from all sources.

Citations:

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