What is the role of external beam radiotherapy (EBRT) in the treatment of prostate cancer?

Updated: Aug 17, 2020
  • Author: Isamettin Andrew Aral, MD, MS; Chief Editor: Edward David Kim, MD, FACS  more...
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External beam radiation therapy (EBRT) remains one of the primary treatment modalities for patients with localized or locally advanced prostate cancer. The use of modern equipment has fostered greater interest in this form of treatment over the past 25 years; however, the origins of this therapy extend back to the early 20th century.

Radiation therapy for prostate cancer was first introduced to the United States in 1915 in the form of radium applicators that were positioned adjacent to the prostate (ie, in the urethra, bladder, or rectum). This form of therapy offered local treatment to the prostate but was associated with significant morbidity.

Unfortunately, the early therapy machines generated low-energy x-ray beams that lacked the ability to penetrate deep into the pelvis. As a result, treatments were often palliative and commonly caused significant skin morbidity. The technologic limitations of low-energy radiation beams greatly restricted the use of radiotherapy in advanced prostate cancer throughout the first half of the 20th century.

The role of radiotherapy in the palliative treatment of prostate cancer also was limited by discoveries regarding the endocrine-sensitive nature of this malignancy. As the androgen dependence of this tumor became increasingly clear, clinical interest turned toward eliminating the primary source of hormone production in patients with advanced disease. Accordingly, orchiectomy became an accepted form of therapy for advanced carcinoma of the prostate until estrogenic products were developed in the 1950s and 1960s.

The role of radiotherapy in the management of prostate carcinoma became clearer with technologic advancements that followed World War II. Megavoltage (> 1000 kV) radiation resulted in x-ray beams that penetrated more deeply and that were associated with significantly less skin and subcutaneous morbidity. This property prompted further investigation of the role of radiotherapy in more deeply seeded tumors.

During the 1950s and 1960s, megavoltage radiation was more commonly available from the decay of radioactive isotopes; however, in the following years, generation of high-energy x-rays became increasingly popular. Equipment names (eg, Betatron, Linear Accelerator, Proton Beam, and Neutron Beam) often indicated the mode by which the x-rays were created. By the early 1980s, the linear accelerator was established as the most common form of EBRT.

Clinical use of higher-energy radiation beams facilitated the development of radiation oncology as an accepted mode of therapy for both advanced and early-stage prostate carcinoma. This experience was largely due to the work of Bagshaw et al at Stanford University. [4] Besides allowing deeper beam penetration into tissue, linear accelerators generated a beam with more sharply delineated borders. This allowed higher doses of radiation to be directed at the clinical target (eg, prostate, seminal vesicles, or regional lymph nodes).

Improved technology, treatment planning, and dosimetry allowed localized therapy with curative intent. Heightened awareness of prostate cancer and an apparent increase in its incidence during the early 1990s served as a further stimulus for consideration of EBRT in the management of this disease.

With the evolution of improved computer-based treatment planning, conventional radiotherapy techniques have largely been supplanted by modern techniques such as 3-dimensional conformal radiotherapy (3D-CRT), intensity-modulated radiotherapy (IMRT), and image-guided radiotherapy (IGRT). The advantages of the modern approaches lie in their ability to escalate the tumor dose (thus enhancing disease control) while minimizing toxicity to normal tissue (thus improving patient compliance and satisfaction).

Nevertheless, a 2008 research summary by the Agency for Healthcare Research and Quality (AHRQ) reviewed 5 randomized controlled trials of EBRT and concluded that no regimen, whether conventional, high-dose conformal, dose fractionation, or hypofractionation, was superior in reducing overall or disease-specific mortality. [5]

For patient education information, see Prostate Cancer and Bladder Control Problems.

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