Sunday, August 28, 2016

Radiation therapy may improve survival even when PSA≥75 ng/ml

Sometimes when patients originally present with very high PSA levels, a negative bone scan, and CT, they are put on permanent hormone therapy because the doctor just assumes it is micrometastatic. A closer look at the data demonstrates that an attempt at curative radiation may improve outcomes.

Lawrence et al. screened the 2004-2008 SEER database, and found 75,539 patients diagnosed with non-metastatic prostate cancer, and excluded those treated with surgery or brachytherapy. The patients had a median age of 70 years. Their findings based on a median of 60 months of follow up were:
  • ·      Use of RT was associated with a reduction in prostate cancer mortality of 59%.
  • ·      4-yr prostate cancer survival was 94% in those who had RT vs. 77% in matched patients who had no local therapy.
  • ·      The benefit held even for those with PSA≥75 ng/ml

Three important caveats:
(1) This is a retrospective study and is subject to selection bias. This means that those who received no local therapy may have done so for reasons not readily apparent in the available records. Although the authors made an attempt to account for age, grade, PSA level, stage and perhaps other variables, there may have been signs of greater progression that the doctor was aware of.
(2) The PSA values recorded in the SEER database have recently been called into question. Interested readers may read more about it here. In fact, the National Cancer Institute has withdrawn PSA data from the current files. This analysis was evidently performed before that withdrawal on April 29, 2015. This does not affect the survival data.
(3)  A median of 60 months of follow up is not long enough to determine whether survival benefits are sustained in the long run. Neither the radiation-treated cohort nor the non-treated cohort reached median survival during the time period of observation so far available.

Given those caveats, we can only conclude that there may be something to this, but that can only be determined by a clinical trial where patients with extremely high PSA levels are randomized to radiation therapy or hormone therapy only, and they are tracked for ten years or more. The study does suggest that PSA alone is not a good risk factor on which to base the decision about whether to pursue curative therapy.

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