الفهرس 
Cancer Prostate OverviewOnly 14 pages are availabe for public view
 |  | from | 158 |  |  |
| | | from | 158 | | |
Abstract
Worldwide; prostate Cancer is the third most common cancer in men with an estimated 543,000 new cases each year. In Egypt; they represented 2% of all incident cancers and 3.9% of all newly diagnosed male cancers. Although radical prostatectomy is an effective treatment for many patients with clinically localized prostate cancer, treatment may fail in up to 20–40% of the cases, depending on prognostic factors and patient selection. Treatment planning and delivery of radiation therapy are undergoing significant change with continuous advancements in computer hardware computational power and computer graphics. The original radiotherapy technique was known as “two-dimensional” radiation and relied upon standard X-rays to define the treatment volume. This technique was the standard method in most radiotherapy practices until the 1990s. Essentially, this process used landmarks such as the pubic bone, bladder and rectum (filled with contrast material) to align the radiation beams. Conventional radiation therapy has contributed to the ineffectiveness of external-beam radiation therapy because of its insufficient dose distribution and overdoses to organs at risk (OARs) such as the bladder and rectum. Three-dimensional conformal radiotherapy (3DCRT) became the standard at most radiotherapy centers during the 1990s. It resulted in both higher cure rates and lower complication rates compared with “two-dimensional radiotherapy,” because a higher radiation dose could be accurately delivered to the prostate target volume, even as the dose to surrounding tissues was reduced depending on CT-based planning. The next major advance in external beam radiotherapy was the development of intensity-modulated radiation therapy (IMRT). Intensity Modulated Radiation Therapy (IMRT) allows a much greater degree of control of the radiation volume, by varying the strength of a beam across its entire area. Effectively, this converts one large beam into many tiny “beamlets,” each with its own customized intensity. Each beamlet arrangement is then computer-programmed to hit areas within the target for a specific amount of time, and then move in rapid succession to the next beamlet arrangement, until the entire coverage objective has been met. This process is repeated from multiple different angles. Brachytherapy is the use of sealed radioactive sources placed in close proximity to the treatment target volume, either by directly inserting them into the tumor, or by loading them into instruments (applicators) which were previously inserted into cavities inside the body at close distance to the tumor. Stereotactic procedures in modern radiation therapy require a stereotactic device, medical imaging, computer treatment planning, and a radiation source. Stereotactic radiotherapy attempts to preserve the function of normal cells within the target volume and surrounding normal tissues by the use of multiple, smaller dose fractions, while using very tight margins around the intended target. In both cases, highly accurate positioning of radiation beams and rapid dose fall-off outside the target volume are required.