External Beam Radiation Therapy:

Dose Escalation and Fractionation

Categories: Winter 2016

Included in AUA Prostate Cancer Update Course* article16.1

Radiation therapy uses high-energy rays or particles to kill cancer cells. The two main types of radiation therapy used for prostate cancer are external beam radiation and brachytherapy (internal radiation). In the last year, a number of studies reported on external beam dose and fractionation for radiation therapy.

Dose escalation

Gray, or Gy, is the unit of measurement used in photon radiation therapy. The standard dose for external beam radiation therapy ranges from 64.8 Gy to 75.6 Gy. Some recent studies suggest a role for dose escalation greater than 75.6 Gy for intermediate- and high-risk prostate cancer, including a study that found dose-escalated radiation ranging from more than 75.6 Gy to 90 Gy improved overall survival in men with intermediate- and high-risk prostate cancer. 1


Conventional radiation therapy treatment schedules typically require 40 to 45 treatments that take place from more than 8 to 9 weeks. Some research suggests that hypofractionation, which means having fewer treatments but at a higher dose per treatment, could produce outcomes similar to the conventional treatment schedule. One study found that for men with low-risk disease, having radiation therapy in 28 factions over 5.6 weeks had similar efficacy as having 41 fractions over 8.2 weeks. 2

However, there are concerns that the stronger doses would affect patient quality of life. Several randomized studies testing hypofractionated approaches highlighted concerns, including an increase in adverse gastrointestinal and genitourinary side events such as diarrhea and decreased sexual function. 2,3

However, new research presented at the 58th Annual Meeting of the American Society for Radiation Oncology (ASTRO) in September showed that patients in the hypfractionated group had similar quality of life as patients in the standard treatment group. These results were patient-reported outcomes.

  1. JAMA Oncol. 2015 Oct;1(7):897-906. doi: 10.1001/jamaoncol.2015.2316.
  2. J Clin Oncol. 2016 Jul 10;34(20):2325-32. doi: 10.1200/JCO.2016.67.0448. Epub 2016 Apr 4.
  3. Lancet Oncol. 2016 Apr;17(4):464-74. doi: 10.1016/S1470- 2045(15)00567-7. Epub 2016 Mar 9.

*Dr. Catalona’s Prostate Cancer Update Course

Dr. Catalona led the Prostate Cancer Update course at the American Urological Association annual meeting. The course highlighted important findings on prostate cancer published during the last year. The topics are wide-ranging. This issue of QUEST covers some of these articles, which we hope will be of interest to our readers.

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