Of mice and men and Avodart (dutasteride)

[JimJimJimJim]

Of mice and men and Avodart (dutasteride)

 

Some men are prescribed hormone therapy (ADT) continuously. Other men are prescribed hormone therapy with periods on the drugs, and periods off the drugs (intermittent androgen deprivation therapy, IADT).

 

Some men on intermittent hormone therapy take no hormone drugs during the 'off treatment' periods.  During the 'off treatment' period other men take the drugs called 5-alpha reductase inhibitors or 5ARI drugs - either dutasteride (Avodart) or finasteride (Proscar, Propecia).

 

The reason for taking dutasteride or finasteride is that, if you are on intermittent hormone therapy, your 'off treatment' period is doubled.

 

However, though you get twice as long not on treatment, the time to become resistant to ADT (castrate resistance) is not shortened. More importantly, there appears to be no survival benefit - no extra life - from this strategy.

 

Why no extra survival?

 

The authors of the study below (Parikh et al.) set out to examine that question, working with mice with human prostate cancer.

 

They found that the beneficial effect of dutasteride activity against the cancer was only found in the first 14 days of testosterone recovery. (Some findings in men also suggest this limited early effect.)

 

When they applied a 14 day cycle, results on survival were quite positive.

 

However, in men the 'off cycle' is kept until there are signs of the cancer coming back (rising PSA). To simulate this type of intermittent therapy, the researchers kept the 'off cycle' in the mice until there were signs of the cancer coming back (cancer grown back to its original size). The result was the same as in humans - a long off cycle, but no extra survival.

 

But ...

Remember - this was in mice.

Only one sub-type of prostate cancer was looked at.

Another sub-type of prostate cancer was not influenced by dutasteride.

 

Importance to men with prostate cancer

This research may open the door to clinical studies of a new type of treatment - intermittent hormone treatment with short (14 days) or very short (4 days, in a later paper) cycle - testosterone, dutasteride, testosterone, dutasteride ...

 

Remember I am not a doctor, and my memory is not highly reliable, but I believe that such clinical trials of repeatedly stimulating and then attacking the cancer will only proceed with caution, because I remember [very lowest level of anecdotal evidence] someone saying recently in a video that a similar strategy tried with breast cancer failed because the effect of stimulating the breast cancer brought reduced survival.

 

The paper can be found here:

http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4104071/