Radiation question

I was wondering about PSA after radiation especially external beam. I have been told and also read that the radiation damages the DNA of both good cells and cancerous cells. Eventually the cancerous cells can not reproduce and die off. It may take a few reproductive cycles but time catches up to the cancerous cells. I am told that the healthy cells are able to repair their damage and eventually start splitting and reproducing again. ( this is over simplified ) My questions is , should you see eventually a rise in PSA as the damaged good cells come back on line. I believe normal cells don’t leak but then again we know that “normal” PSA should lie between 0 and 4 for the normal population as a whole because of some leakage .Not sure if seeds work the same . John T can you chime in here. When I asked my R/O if the good cells would repair themselves he replied they should. For five years now my PSA has stayed steady.

Glenn

corman said...

I was wondering about PSA after radiation especially external beam...

Hi Glenn,

The American Urological Association (AUA) document titled Prostate Specific Antigen Best Practice Statement:  2009 Update has an excellent response to your question regarding PSA after external beam radiation. 

I've made the title a link to the free online AUA document (check page 39), and have quoted a few relevant lines here for easy reference:

• Serum PSA should fall to a low level following radiation therapy...and should not rise on successive occasions.

• Following radiation therapy, the PSA value should fall to a low level and then remain stable. 

• PSA values <0.2 are uncommon after external beam radiotherapy, which does not ablate all prostate tissue.

• A consistently rising PSA level usually, though not always, indicates cancer recurrence.

• The number of rises needed to define a failure has been a matter of debate, but a consensus is emerging in support of the American Society for Therapeutic Radiation and Oncology (ASTRO) definition of failure: three successive rises above nadir.

• More recently it has been recognized that this endpoint is relevant only for external beam radiotherapy and even then it is easily confounded by biological variability.

• A Consensus Committee was convened in Phoenix in 2005 to reconcile these differences [discussion of PSA results after brachytherpy and external beam] and to produce a universal definition of PSA failure after all forms of radiation therapy, with or without androgen deprivation. The Committee arrived at the following conclusions: that any rise in PSA level of 2.0 ng/mL or more, over and above the nadir, predicted true failure with great sensitivity and specificity after both external beam radiotherapy and interstitial prostate brachytherapy, irrespective of whether either of these treatments was accompanied by androgen deprivation.

• This endpoint, the “Phoenix Definition,” was designed to make comparison between any radiation series possible but did not facilitate easy comparisons with surgical series. It was designed as a research tool, rather than as a trigger for a clinical intervention.

• The Consensus Committee further noted that setting a “target PSA” was not possible after external beam radiotherapy, although for interstitial prostate brachytherapy a PSA level of <0.7 ng/mL at five years would be reasonable.

 

hope this helps answer your question...

 

about the cell damage..Your prostate gland was the main target for the radiation beam...It received a high enough dose to pretty much destroy it, healthy tissue or not, along with the cancer cells..The surrounding healthy tissue was also damaged but not to the degree the prostate was. These tissues can usually repair themselves so they remain functional like your colon and urethra...The cancer, being more susceptible to damage, can not repair itself and hopefully dies off. Still, RT can cause some horrible side effects. The latest linear accelerators are much improved in their ability to hit their intended target and spare the surrounding tissue..But they are only as good as the man who writes the treatment program...