Slow vs fast doubling time and radiation effectiveness

Goodlife,

Little confused by the question. Systemic vs local are not apples to apples. If the cancer is local, then radiation or a combination of radiation and HT will normally do the trick. Systemic is not local and is outside the field of radation, except in those cases where the cancer is located in the pelvic lymph nodes and is also radiated.

It's more nuanced than a simple doubling time. There are multiple factors that are used in prediction , and even then it's only a predictor of odds for large groups of men.

In my case--bearing in mind that I am a person, not a study of thousands of men--my doubling time, post surgery, was rapid. It was doubling every 2.7 months. And yet I seem to have done fine, now nearly 4 years later, my PSA is still less than 0.1.

I would not sweat doubling time too much, but I would pay attention to the pre-SRT PSA level, since multiple studies have identified that as a crucial parameter.

Goodlife - here is my limited understanding from reading some of the documents. It seems there are several different dynamics going on. It is not simple.

1.) If the cancer has a fast PSA doubling time, that is a sign of greater likelihood that it is no longer in the prostate bed and nearby lymph nodes but has become a metastatic, systemic disease. In that case local radiation will do no good whatsoever, since the cancer is no longer local. MRI and other imaging can often but not always reveal if this is the case. Also if you have a psa recurrence after having negative margins at RP it is more likely to be systemic but if you have a psa recurrence after having positive margins at RP it is more likely to be a local recurrence.

2.) If it is a fast doubling time, but it has not yet spread, that is all the more reason to hit it with radiation and hit it hard, before it spreads. PC with a fast doubling time is not always systemic.

3.) If it is localized and it is slow growing (PSADT > 15 months) there is an argument to be made for *not* doing RT even if the cancer appears to be localized, because most patients would die of something else before the PC ever got big enough to be symptomatic. This depends somewhat on age and co-morbidity of course.

Just because a cancer is no longer localized does not mean it is androgen-independent. It could go either way.

So you have to take multiple considerations into account. So perhaps think of it as a two by two matrix:
>> localized and slow growing - radiation can help but probably not needed, why suffer with the side effects?
>> localized and fast growing - nuke it
>> Systemic and slow growing - radiation can't help but you don't really need it.
>> Systemic and fast growing - radiation won't help at this point; seek to treat it by some other means.

The harder calls are when it is ambiguous whether localized or not, and when the growth rate is in the middle of the range between fast and slow.

Dr. Myers' video which purg posted recently has a lot of good thinking on this issue; I encourage you to review it.

Post Edited (proscapt) : 2/10/2011 6:21:08 PM (GMT-7)

Thanks. I did watch Snuffy's video, and he made some kind of comment about fast doubling times should be treated with HT, between 3 and 6 month doubling times is a gray area, and longer doubling times are treated in a conservative manner. Not really consistent with the Trock report.