Do you time initiation of definitive radiation on PSA response to neoadjuvant ADT?

Is there any benefit to delaying start of RT or perhaps changing to complete adrogen blockage if maximal PSA response is not achieved in 2 mo? What PSA metric are you using, for example, <0.3, <0.1, other? Do you feel PSA reponse to ADT is a surrogate for less agressive disease or does allowing a more robust PSA repsone actually result in "more" radiosensitization and potentially better outcome?

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Radiation Oncology · Virginia Commonwealth University Medical Center

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In the setting of definitive RT, I will generally wait 2-3 months before beginning radiation for 2 reasons. First, during that period of time the prostate may shrink by as much as a third of it's original size, which may adversely impact on the normal tissue dosimetry if this were to occur during the course of radiation. Additional shrinkage may occur beyond 3 months, but generally not to the extent seen during the first 3 months. This information has been documented in the brachytherapy literat...

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Radiation Oncology · Baylor College Of Medicine

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I would agree with @Dr. First Last in regard to timing. Practically speaking, in the US most RTOG studies started 2 months prior to RT. In Canada and Australia this could have been 6 or 8 months prior to RT, and in EORTC at the same time as RT. Nevertheless, 2-3 months is useful for volume reduction and to assess response of PSA. If deer season is coming, I've been willing to delay RT start longer and have tended to use the Canadian time of 8 months as my upper limit (in someone who will be gett...

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