Conformal Prostate Cancer Radiation Therapy
Prostate cancer radiation therapy is one of the forms of curative treatment of localized prostate cancer.Prostate cancer radiation therapy treatments use the ability of X-rays to preferentially damage cancer cells and spare normal cells to eradicate tumors without significantly affecting normal tissues. The high energy X-rays required to treat deep seated tumors within the body, such as prostate cancers, are generated by special machines called linear accelerators. The techniques of prostate cancer radiation treatment have changed dramatically over the past 10 years, mainly with the use localization CT scans and special computer softwares capable of planning individualized treatments.
For traditional radiotherapy, radiation oncologists relied mainly on an individual patient’s bony pelvic anatomy to determine the areas that needed to be treated. The prostate gland itself could not be visualized till the advent of CT scans. We now realize that prostate glands can vary tremendously in their location and shape from one patient to the other, and thus require a different approach to prostate cancer radiation treatment.
Presently, planning CT scans are performed prior to prostate cancer radiation treatment to enable the radiation oncologist to individualize, i.e. conform, the prostate cancer radiation treatment to the individual patient. Most of this planning is performed on dedicated computers that perform "virtual" 3-dimensional reconstruction of actual prostate cancer radiation treatments. Therefore, prior to the actual treatment, the radiation oncologist will accurately know the geometry and quantity of radiation delivered to an individual patient’s prostate, bladder, rectum, urethra, and bones. This process is presently called Conformal Radiotherapy (or three-dimensional conformal radiotherapy). Conformal Radiotherapy therefore allows more accurate delivery of radiation treatment in individual patients, thereby improving cure rates and decreasing complication rates. At the Cleveland Clinic Department of Radiation Oncology, 516 patients have been treated with conformal radiotherapy for prostate cancer in the past 5 years.
Conformal radiotherapy has allowed higher than standard prostate cancer radiation treatment doses to be delivered to the prostate, thereby significantly improving cure rates. The unit of radiation is 1 Gray (abbreviation: Gy). Standard radiation doses have typically been 70 Gy or less. At the Cleveland Clinic we have treated 1078 patients over the past 10 years, with 458 patients receiving >72 Gy. Our most recent patients have all been treated to 78 Gy. A total of 288 cases have received 78 Gy to the prostate and periprostatic tissues. We have observed significantly better cure rates with increasing radiation doses during prostate cancer radiation treatments.
The area within the body irradiated in prostate cancer radiation treatment is the prostate gland and the tissues in the immediate vicinity of the prostate. The normal tissues irradiated in that area are the urethra (the urinary passage going through the prostate), the bottom part of the bladder and the front part of the rectum. Other areas are not affected by the radiation. Patients receiving modern external beam radiotherapy for localized prostate cancer do not experience any hair loss, nausea, vomiting, drop in blood counts, or any significant diarrhea.
Two types of side effects can be expected following prostate cancer radiation treatment: short-term (transient) and long-term. Short-term effects caused by prostate cancer radiation treatment are related to the temporary irritation of the urethra, bladder and rectum from the radiation. During the course of radiation and for a short period after the completion of therapy, patients may experience burning on urination and some increase in the frequency of urination due to the irritation of the bladder/urethra. The symptoms from the irritation of the rectum are loosening and increase in the frequency of bowel movements. Twenty percent of patients do not experience any symptoms, 65% experience minor symptoms that do not require any intervention, and 15% require temporary medications for the control of the minor symptoms (anti-diarrheic drugs or drugs to improve the urination frequency and burning). These short-term transient effects subside within 2-3 weeks after the completion of radiation.
Long-term effects of prostate cancer radiation treatment are related to permanent changes in the linings of the rectum and bladder that can lead to spontaneous self-limited bleeding in 2-5% of patients treated with conformal radiotherapy. Only 2% of patients might require cautery of potential sites of rectal bleeding after prostate cancer radiation treatment. With respect to sexual function, 60-70% of patients retain their potency status after external beam radiotherapy. Approximately 60-70% of patients whose potency gets affected by radiation regain full potency with the use of Viagra.
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Intensity Modulated Radiotherapy
Intensity-modulated radiotherapy is the use of two separate entities; a computerized planning system that performs inverse planning and a device that is capable of changing (modulating) the intensity of the radiation beam emanating from the linear accelerator. Inverse planning is the process by which the radiation oncologist only specifies the desired doses to be delivered in different areas to the planning computer software, and the software itself determines the ideal way of delivering that plan. The devices inserted into the heads of linear accelerators are typically multi-leaf collimators. These are leaflets that are introduced in front of the radiation beam for different lengths of time, thereby changing the overall intensity of the beam, increasing the conformity of individual treatments.
Due to the nature of the planning and treatment delivery, Intensity-modulated radiotherapy (IMRT) is considered to be the ultimate conformability tool. At the Cleveland Clinic Department of Radiation Oncology, IMRT for prostate cancer is implemented with the Corvus planning software from the Nomos Corporation and the Varian Dynamic Multi-Leaf Collimator.
Localization of the Prostate
The prostate is located between the bladder and the rectum, and its position within the pelvis can change according to the degree of fullness of the bladder and rectum. Hence, on a daily basis, the position of the prostate might vary. This variation in position cannot be assessed with external skin marks or bony landmarks. With the relatively small treatment fields used with conformal and intensity-modulated radiotherapy, daily localization of the prostate becomes a necessity. The most elegant and user-friendly system available to date that is capable of localizing the prostate on a daily basis is the BAT system from the NOMOS corporation. The system is based on a trans-abdominal ultrasound connected to a special computer software that tells the radiation therapist the exact coordinates of the prostate gland in an individual patient on a daily basis. The Cleveland Clinic Radiation Oncology Department was the first test-site for the BAT system, and currently has the longest experience with this unique system.
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Short Course Intensity Modulated Radiation Therapy
The current treatment regimen for localized prostate cancer at the Cleveland Clinic Radiation Oncology Department consists of the combination of intensity-modulated radiotherapy and the BAT ultrasound system for localization of the prostate. This combination provides the delivery of a focused and individualized dose of radiation to a small area within the pelvis under the guidance of the daily trans-abdominal ultrasound system. The design and implementation of this treatment was supported by a grant from General Motors Company.
A typical prostate cancer radiation treatment used to consist of 7-9 weeks of daily treatments, 5 days per week. Our prior schedule consisted of a total of 39 treatments delivering 78.0 Gy at 2.0 Gy daily over 7 and a half weeks. Our current treatment course with intensity-modulated radiotherapy consists of a 5 and a half-week period, i.e. 28 treatment days. The radiation dose delivered on a daily basis has been increased by 40%, and the overall treatment time has been consequently reduced by 40%. Although a total of 70.0 Gy are nominally delivered to the prostate with the newer regimen, it is the biologic equivalent of 83.0-84.0 Gy delivered over 8-9 weeks. We have termed our new schedule Short Course Intensity Modulated Radiation Therapy (SCIM-RT).
Current Status of SCIM-RT at Cleveland Clinic
As of today, a total of 400 men have received SCIM-RT at the Cleveland Clinic. The patients have tolerated this regimen very well, with no significant deleterious effects observed during the course of therapy and shortly after. Patients have slightly less urinary and rectal irritation symptoms compared to our prior schedule of 7 and a half weeks. Patients are fully functional during the course of therapy, and enjoy the relative brevity of the treatment. This ensures a shorter time spent away from their work and family.
SCIM-RT Logistics
This section describes the typical course of events with SCIM-RT from the time the patient is first seen in the Department of Radiation Oncology to the time of completion of therapy.
Consultation with the Radiation Oncologist - This is the first contact with the patient. It is mainly a session during which the patient is informed about different aspects of the disease and treatment options. The Radiation Oncologist reviews all the pertinent medical information related to the patient. This includes a thorough discussion of all available treatment options for localized prostate cancer. The Radiation Oncologist specialized in prostate cancer radiotherapy at the Cleveland Clinic Foundation is Dr. Arul Mahadevan.
Planning - Once the patient decides to proceed with Intensity-modulated radiation therapy, the planning session is scheduled. This includes a marking session and CT scan, typically performed the same day. The marking session involves placing preliminary skin marks on the patient, which will be later used for the alignment during the CT scan and daily treatments. This lasts approximately 30 minutes. A special CT scan of the pelvis is then obtained. This also lasts approximately 30 minutes and involves the placement of a Foley catheter into the bladder. It does not involve any intravenous contrast injection, or any ingestion of oral contrast materials. The catheter is removed after the CT scan is obtained.
The patient is also instructed about his daily treatment appointments and given passes for free parking at an adjacent lot. The passes are valid for the duration of the treatments. Information is also given concerning the free shuttle service available to patients. The shuttle services any location within a one-hour one-way driving radius from the Cleveland Clinic main campus located at 9500 Euclid Avenue, Cleveland, Ohio.
Daily treatments - The daily treatments are delivered 5 days per week, Monday through Friday. There is a 15-20 minute waiting time. The alignment on the treatment machine last about 5 minutes. This includes the trans-abdominal ultrasound. For this procedure, the patient is asked to keep his bladder full at the time of treatment. The beam-on time for the radiation is 5-6 minutes. Therefore, the patient spends typically a total of 30-45 minutes daily in the department of Radiation Oncology.
Treatments are delivered from approximately 7:00 a.m. till 4:00 p.m. Patients are given a time that is convenient for their daily schedules. Since it is not important that treatments are delivered at the exact same time everyday, rescheduling is possible occasionally. Any missed treatment is added at the end of the treatment course; patients always receive a total of 28 treatments.
Follow-ups - Once the treatment is completed, patients are followed-up regularly. Follow-ups consist of a blood sample for PSA, and a patient questionnaire. The first PSA is obtained at 6 weeks after the completion of therapy, and subsequently at 6-month intervals.
To refer patients to the Taussig Cancer Institute for treatment evaluation, second opinion, or specialized procedures, please call 216.444.5571 or toll free 800.223.2273 ext. 4-5571.
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