Disease Sites

Intensity Modulated Radiation Therapy (IMRT) / Image Guided Radiation Therapy (IGRT)

What is Conformal Therapy?

One of the most important advances in the delivery of external beam radiation therapy has been the development of conformal therapy. Traditional conventional radiation therapy is targeted only by the location of pelvic bones seen on plain x-rays which cannot show the actual prostate gland. These bony landmarks do not show the unique prostate anatomy of any particular man. The fields therefore tend to be large, square shaped and generic. This results in more unnecessary radiation to the surrounding tissues. 

What is IMRT?
The state of the art technology allows for the ultimate in conformal external beam. Like no other technology IMRT allows us to treat the prostate while severely limiting the dose delivered to adjacent normal structures such as the bladder, rectum and small bowel. This reduction in dose to these normal structures often results in a reduction in the rate of side effects. IMRT is sometimes used for dose escalation which may result in superior local control of the disease in the treatment site.

Conversely, 3D conformal therapy allows for the customization of treatment for each particular individual. Every man has a prostate of unique size and shape, a different extent of cancer, and a unique location of his nearby normal organs (bladder and bowel). Conformal radiation is the process of accurately determining this unique anatomy and tailoring the radiation treatment such that it "conforms" to every patient. Where conventional therapy would treat all prostates within the same big square beams, conformal radiation treats a round prostate by round beams and an oblong shaped prostate with oblong shaped beams. 

3D Conformal treatment is a complex process which involves three basic components. The first is patient immobilization. Special body casts are created to improve the reproducibility of the patients position on the machine. The second step is computed tomography (CT) assisted organ identification. The precise location and shape of the prostate as well as the bladder and rectum is determined. The final step involves the use of powerful computer tools to generate the specific beams which will differentially deliver the radiation to the prostate while sparing the surrounding normal tissues. Specialized blocks are created to shape the beams which have been generated. This improvement in technology means that the radiation beams can be made the smallest size possible to safely treat the cancer while avoiding normal tissues. In fact, 14% less dose on average is given to the bladder and rectum by conformal treatment compared to conventional methods. The less normal tissue irradiated results in less unwanted side effects. 

The Treatment Process 

Simulation: This is the first step of conformal radiation. The total time needed for this first day is about 90 minutes. A custom body mold is made (that extends from the abdomen to thighs). By lying in the mold, you will be in the same position on the treatment table every day - up to 67% more accurately than without the cast. Next is the CT scan in our department. Claustrophobia, a fear of close places, is rarely a problem. Contrast dye is used during the CT scan to improve the image of the prostate and bladder on the film. Please tell your doctor or nurse if you are allergic to contrast dye or iodine. Three tattoos the size of a pencil point are then placed around the waistline to be used every day for accurate positioning of the treatment beams. They are permanent but small and in locations that will not be publicly visible. 


IMRT/3-D Treatment planning: This process takes place behind the scenes over a 1 week period - you do not need to be present. The CT scan taken at simulation is examined by the physician who contours the important body organs which are then inputted into the computer. The physician then directs specially trained physicists and dosimetrist in designing the conformal shape of the radiation beams. This is the custom tailoring - the radiation beams are designed to mimic the shape of the target with the narrowest margin of normal tissue possible. 

Set-up: We check the accuracy of your specific treatment on the actual therapy machine before starting radiation. 

Radiation Treatments: A course of IMRT or 3D conformal radiation will take approximately 7 weeks, Monday through Friday, except for major holidays. The actual time in the treatment room is 10-30 minutes. Please allow 45-60 minutes total each day for parking, dressing and small delays. Treatment times are flexible from 7:30 - 4:00 - most requests for a specific time of day can be met. 

Reduction in Side Effects with 3D Conformal Radiation / IMRT  

Similar to a regular X-ray, there is no pain, nausea, vomiting, burning or sensation of any kind from the radiation beam. Most men are able to continue to work, to drive, to exercise, to be sexually active, or to do any other usual activity during the 7 weeks of radiation. Patients meet with their physician and nurse at least once per week to discuss questions or side effects during the treatment. Common side effects during conformal radiation treatment are mild fatigue, dryness of the irradiated skin, changes with urination including increased frequency, and changes in bowel function including increased frequency or diarrhea. Side effects during treatment are easily managed as an outpatient. The radiation will not cause hair loss. Increased stool frequency or diarrhea will respond to changes in diet, such as more fiber, or medications, such as Imodium and Lomotil. Medications including Hytrin, Cardura or Flomax are occasionally needed for temporary symptoms of bladder irritation. By irradiating less normal tissue, our conformal techniques have markedly reduced the side effects that most men experience during and after their course of radiation. Over the seven week course, patients treated with conformal techniques use less medication because of fewer symptoms than patients treated previously with conventional radiation. 

Serious side effects after IMRT or 3-D conformal radiation therapy are very uncommon. In patients treated with this technique urinary incontinence occurs in only 1% of patients. Serious bowel problems are also rare. Approximately 20% of patients experience some degree of rectal bleeding, however only 2% of patients develop rectal bleeding that requires coagulation or laser treatments to stop the process. These rates are far below those observed with conventional treatment, despite delivering 10-20% more radiation to the prostate cancer. 

Treatment Options and Outcomes 

Multiple studies have now confirmed that the most important factors prior to treatment for prostate cancer are a patients stage (disease within the gland, direct extension outside the gland, or spread to other areas of the body), Gleason score (microscopic assessment of the biologic aggressiveness of the cancer cells) and the prostatic ?specific antigen (PSA). Based on these factors (see below) patients are stratified into certain risk groups which can aid patients and physicians select the most appropriate management. 

PSA

Gleason Score

Stage(1992)                                      Stage1997

Early Stage Prostate Cancer 


This favorable group is generally defined as men with disease limited to the prostate (T1-T2A/B), a Gleason score of 6 or less and a PSA < 10 ng/ml. Men with early stage prostate cancer have a choice of treatment between surgery, conformal external beam radiation or radioactive seed implants. 

T1C Prostate Cancer 

The PSA blood test for the screening of men without symptoms of prostate cancer has led to a large increase in the diagnosis of tumors that are too small to be felt (non palpable) by a physicians digital rectal examination. These early stage prostate cancers have been given a new name - T1C tumors. Men who with this type of prostate cancer are rapidly becoming the majority of all patients treated for prostate cancer each year. Conformal external beam radiation has been highly effective for the treatment of these early stage cancers. After conformal treatment, 85-90% of men with a non-palpable, T1C tumor and a PSA level of less than 10 ng/ml remain free of any evidence of disease five years later. 

The number of patients with palpable disease contained within the prostate gland is also on the rise. A summary of favorable patients treated with conformal external beam radiation at Fox Chase Cancer Center was recently published in the journal of Urology. Analysis demonstrated that with 3-D conformal therapy the patients with no biochemical ( a non-rising PSA) or clinical evidence of cancer was 85% for patients with a gleason score 6 or less and a pretreatment PSA of less than 10. This result compares favorably to a similar group of patients treated by radical surgery at Johns Hopkins University Hospital.

An assessment of sexual potency following treatment with conformal radiation has also been performed. Of the young men (age < 65) who were potent before radiation, 73% remained potent after radiation. These potency reports after conformal therapy are similar to those reported after nerve sparing surgery for prostate cancer. 

Intermediate Risk Prostate Cancer 

This group includes men with stage T1-T3, a Gleason score of 7 or less and a PSA between 10-20 ng/ml. Certain men in this diverse group can effectively be managed with either surgery or radiation therapy. The combination of the Gleason score, PSA and stage are utilized to determine the risk of extra-prostatic (tumor cells beyond the prostatic capsule) disease. Patients with a high risk of tumor cells extending outside the prostatic capsule are not good candidates for radical prostatectomy, as the surgeon cannot remove all of the malignant cells. Since radiation can be delivered to the regions surrounding the capsule these patients are candidates for external radiation. 

These patients are also candidates for innovative treatment strategies which combine external beam radiation with some form of implant. The implants can be performed either as the conventional permanent seed type or by the newly developed high dose rate temporary implants. 

Locally Advanced Prostate Cancer 

For men with more advanced cancers - men whose cancers involve both lobes or extending outside of their prostate, men with a high PSA level (>20 ng/ml) or a tumor designated "high grade" by the pathologist (gleason score 8-10)--we often recommend the addition of hormone therapy to radiation. Hormone treatment calls for a simple injection once every one to four months, beginning just before or at the start of radiation and continuing for one year. Occasionally, a longer period of hormone use may be recommended. In these groups of patients, it has been demonstrated that the addition of hormones to radiation results in a large increase in freedom from failure at 5 years. Cancer free rates increased from 34% to 64%. 

There is emerging evidence that long-term hormones may improve the length of survival in these patients as well. In a large European randomized trial one group of patients received three years of hormones (Zoladex) plus radiation while a second group was treated with radiation therapy alone. After 5 years, the survival in the hormone plus radiation group was 79% compared to 62% in the radiation therapy alone group. Similar results were reported from a randomized RTOG study of high risk patients. Zoladex was administered during the last week of radiation and continued until there was evidence of disease progression in one group while a second group was randomized to receive hormones only after they had signs of progression. The use of early (adjuvant) long term Zoladex produced a five year overall survival benefit. However, it was limited only to patients with high grade (gleason 8-10) tumors. 

While these two important studies suggest a benefit to long term hormonal suppression in high risk men, there is no evidence that short term hormones offer a similar advantage. Studies to date utilizing 2 to 4 months of hormones prior to definitive management (either surgery or radiation) have failed to demonstrate any long term survival benefit. It is important to note, however that hormones are beneficial in certain situations to shrink the gland to improve urinary problems or make the gland more amenable to implant. Therefore, the benefit of their use in these situations may be applied on an individual basis. 

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