Brachytherapy and Size of the Prostate

Last Modified: September 16, 2007


Dear OncoLink "Ask The Experts,"

Does the size of the prostate (e.g. greater than 90cc) automatically preclude brachytherapy?


Neha Vapiwala , MD, Senior Editor of OncoLink and Chief Resident in the Department of Radiation Oncology at the Hospital of the University of Pennsylvania, responds:

No, a large prostate does not automatically preclude brachytherapy as a treatment option. However, a patient with a large prostate may be asked to undergo a temporary course of medication (drugs such as Zoladex or Lupron) in order to reduce the prostate to a size more optimal for performing brachytherapy.

In most cases, this approach works, and the ideal brachytherapy volume is successfully achieved. Also, some centers are studying and using combination external beam radiation therapy and brachytherapy for large and/or more advanced stage prostate cancers.

Having said this, many practitioners believe that the ideal prostate volume for immediate brachytherapy would be 40-50 cc or less. There are three reasons for this view:

  1. A larger prostate has a higher chance of urinary obstruction requiring catheterization after brachytherapy.
  2. Because the needles used for brachytherapy are all of the same standard size, it may be difficult or impossible to reach all the regions of a prostate that is too large with the needles that are available. A large prostate often also grows beyond the bony confines of the pelvis, so the bones may get in the way of the needles reaching all the necessary regions within the prostate.
  3. It can be more difficult to achieve a uniform dose distribution throughout the prostate if the prostate is too large. In other words, the odds of insufficient radiation dose to certain areas can be higher in a prostate that is extremely large.


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