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Medical Forum / Diseases and Disorders / Prostate Cancer / July 2005

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Avodart

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huck - 21 Jul 2005 10:27 GMT
any one no about this new drug/ good/bad
ron - 21 Jul 2005 16:50 GMT
> any one no about this new drug/ good/bad

Hi Huck...Avodart (Dutasteride) is similar to Proscar (Finasteride) in
that it blocks the conversion of testosterone (T) to
dihydrotestosterone (DHT).  There are two pathways for the conversion
of T to DHT and they involve the 5-alpha reductase-1 (5-AR1) and 5-AR2
enzymes.  Proscar blocks only the major pathway; Avodart blocks both
pathways and is therefore usually more effective in reducing DHT
levels.  Since DHT is 3-10 times more effective than T in stimulating
hormonally dependent prostate cancer cell growth, low DHT levels are
desirable.  Proscar or Avodart are part of the ADT3 regimen often used
to reduce T and DHT levels in hormonally-dependent PCa.  Often the
Avodart or Proscar will be continued during the "off" phase if
intermittent HT is practiced.  Avodart is also used in the treatment of
BPH.  Short-term (2 year) studies have shown no increase in adverse
events when Avodart was compared to a placebo in these BHP
studies...Best wishes and good health, Ron
I. P. Freely - 21 Jul 2005 17:08 GMT
But is Avodart proven effective? My oncology team said "No" as of this
spring, and the principal ADT3 metastudy showed it to be ineffective, maybe
even harmful, after primary treatment, compared to simple ADT1. Bottom line:
Do LOTS of research before jumping into either.

I.P.

>> any one no about this new drug/ good/bad
>
[quoted text clipped - 13 lines]
> events when Avodart was compared to a placebo in these BHP
> studies...Best wishes and good health, Ron
ron - 21 Jul 2005 18:00 GMT
> But is Avodart proven effective?

It has been shown to effectively lower DHT levels.  What's the point of
lowering T to 20 and letting it be converted to the more powerful DHT?
The argument has been made that T at 20 might be equivalent to T~200 if
the T-DHT pathway is unblocked.

>My oncology team said "No" as of this spring,

Why?

> and the principal ADT3 metastudy showed it to be ineffective, maybe
> even harmful, after primary treatment, compared to simple ADT1.

While I have seen studies questioning the efficacy of Proscar or
Avodart as a preventitive, I haven't seen anything that says that
Avodart may compromise clinical results obtained when it is used in an
ADT regimen.  I'd be interested in the reference you have to it being
ineffective or harmful...Ron
I. P. Freely - 21 Jul 2005 19:50 GMT
>> But is Avodart proven effective?
>
> It has been shown to effectively lower DHT levels.

I meant effective in treating cancer.

>>My oncology team said "No" as of this spring,
>
> Why?

Because they (and I) could find no evidence it helps cure, delay, or
mitigate PC recurrence.

>> and the principal ADT3 metastudy showed it to be ineffective, maybe
>> even harmful, after primary treatment, compared to simple ADT1.
[quoted text clipped - 4 lines]
> ADT regimen.  I'd be interested in the reference you have to it being
> ineffective or harmful...Ron

I discussed last winter the metastudy (and the individual trials) that
concluded adjuvant ADT3 (aka TAB, CAB, etc.) does not help PT patients, may
cause earlier and more advanced recurrence, and WILL escalate SEs. The issue
is not the Avodart; it's ADT3 in general after primary treatment and before
ADT1 refraction (i.e., desperation). If that doesn't ring a bell, I can look
again for the source. It's widely discussed and referenced, so I'm sure
you've seen it.

I.P.
ron - 21 Jul 2005 21:28 GMT
I must have missed your earlier post last winter.  A reference would be
much appreciated...Thanks, Ron
I. P. Freely - 24 Jul 2005 23:12 GMT
>I must have missed your earlier post last winter.  A reference would be
> much appreciated...Thanks, Ron

I've not catalogued many actual links, because I've listed my sources before
(e.g., Strum, Mayo, J-H, S-K, Walsh, Harvard Med, NCS, ASCO, the PC books).
But here are some snippets from my many pages of cut'n'pastes. I'm sure none
of them is new to you. I don't have the time to repeat my research to
provide exact sources again. The bottom line for me was that asymptomatic
adjuvant CAB offers a poor theraputic index (little if any benefit over ADT1
at a significant SE cost, plus greater threat of more aggressive
recurrence).

Quick finds include http://www.jco.org/cgi/content/full/22/14/2927 ,
From which this emerges:
Is Combined Androgen Blockade Better Than Castration Alone?
Summary. Three systematic reviews (two with meta-analyses of the
literature14,15 and one meta-analysis of individualized patient data16), one
large RCT,17 and one Markov model (decision-analysis) paper18 were available
to address this question. CAB confers a statistically significant but
questionable clinical improvement in survival over orchiectomy or LHRH
monotherapy. The benefit seems to be limited to patients taking nonsteroidal
antiandrogens and seems to appear only after 5 years of follow-up.
Gastrointestinal and ophthalmologic side effects are worse on combined
androgen blockade. LHRH and nonsteroidal antiandrogens have the highest
estimated quality-adjusted survival but have an incremental cost of over $1
million (US) per quality-adjusted life-year over orchiectomy alone.

For CAB as primary therapy, this link shows some benefit:

http://www.prostateinfo.com/professional/cab/

But this one offsets that with other studies showing no benefit of adjuvant
CAB:

http://www.pcaw.com/newsite/info_articles/articles/archives/tolerability.asp

General ADT guidance from http://www.prostate-help.org/pohtwhen.htm
CONCLUSIONS
We do not believe that controlled clinical trials demonstrate clear
advantages to hormonal therapy in the following scenarios: before RP, after
RP with LN-negative disease or at the time of PSA elevation, adjuvantly with
brachytherapy, or as primary treatment for localized or locally advanced
disease. The evidence supports the use of adjuvant hormonal therapy in
subsets of men undergoing external beam radiotherapy, but only in those with
locally advanced or high-grade tumors, bulky but lowgrade tumors, and LN+
disease. Limited data suggest a possibility of a survival benefit for
adjuvant hormonal therapy in the rare patient with LN+ disease after RP. The
appropriate timing of hormonal therapy for patients with asymptomatic
metastatic disease has not been determined. Much remains to be learned,
including the most effective and best-tolerated androgen deprivation
strategy and the appropriate timing of the institution of such therapy. In
all settings in which androgen deprivation is used, the benefits must be
weighed against the significant costs and toxicities, with particular
consideration given to the expected length of exposure to hormonal therapy.

And that's for ADT1, let alone the more traumatic ADT3.

From ASCO: Recommendations for the Initial Hormonal Management of
Androgen-Sensitive Metastatic, Recurrent, or Progressive Prostate Cancer

They define Early deprivation therapy as initiation of ADT at diagnosis of
metastatic or recurrent/progressive prostate cancer, deferred deprivation
therapy as withholding ADT until the presence of clinical signs or symptoms.
Overall survival (OS) was the primary outcome of interest; QOL hardly
considered.

Loblaw, Mendelson, Talcott, et.al.

PURPOSE: To develop a clinical practice guideline for the use, combinations,
and timing of various forms of ADT for the palliation of androgen-sensitive
metastatic, recurrent, or progressive prostate carcinoma. (Attributes of
good guidelines include validity, reliability, reproducibility, clinical
applicability, clinical flexibility, clarity, multidisciplinary process,
review of evidence, and documentation.)

METHODS: An expert panel and writing committee systematically reviewed the
literature, which included a search of online databases, bibliographic
review, and consultation with content experts. A priori criteria were used
to select studies for analysis and study authors were contacted when
necessary.

RESULTS: There were 10 randomized controlled trials, six systematic reviews,
and one Markov model available to inform the guidelines.

CONCLUSION: A full discussion between practitioner and patient should occur
to determine which therapy is best for the patient. Bilateral orchiectomy or
luteinizing hormone releasing hormone agonists are the recommended initial
treatments. Nonsteroidal antiandrogen (e.g., Casodex) therapy may be
discussed as an alternative, but steroidal antiandrogens (e.g., Cyproterone
acetate, aka Androcur) should not be offered as monotherapy. Patients
willing to accept the increased toxicity of combined androgen blockage for a
small benefit in survival should be offered nonsteroidal antiandrogen in
addition to castrate therapy. Until data from studies using modern medical
diagnostic/biochemical tests and standardized follow-up schedules become
available, no specific recommendations can be issued regarding the question
of early versus deferred ADT. A discussion about the pros and cons of early
versus deferred ADT should occur.

For patients with documented metastatic disease, or whose clinical
parameters suggest too small a chance for cure to justify the toxicity of
extirpative therapy, systemic ADT through surgical or pharmacologic
castration, antiandrogen therapy, or a combination, is the standard
first-line treatment. The goal of ADT is palliation. However, there are
considerable practice variations in the use of ADT in these situations. The
possible explanations are numerous and include: the effectiveness of ADT in
suppressing the PSA; the palliative nature of ADT; its cost and toxicity;
the prolonged treatment required (further extended by PSA surveillance for
biochemical recurrence); the highly variable time lag between initial PSA
rise and symptomatic metastatic disease; and the sometimes conflicting
results of clinical trials. Because the relative efficacy of alternative
approaches to ADT appears small and its toxicity is substantial, patients
may weigh the balance between the favorable and adverse consequences of
palliative ADT differently. Therefore, shared decision-making between
patients and their physicians is necessary for optimal use of ADT.

Metastudy: early ADT for treatment of advanced PC reduces disease
progression and complications. Early ADT MAY provide a small but
statistically significant improvement in overall survival at 10 years. There
was no statistically significant difference in PC-specific survival. But
there were more frequent treatment-related adverse effects with early
therapy. Additional studies are required to evaluate more definitively the
efficacy and adverse effects of early versus delayed androgen suppression in
men with prostate cancer. In particular trials should evaluate patients with
advanced prostate cancer diagnosed by PSA testing and men with persistent or
rising PSA levels following treatment options (e.g. radical prostatectomy,
radiation therapy or observation) for clinically localized disease.
Antiandrogen monotherapy is not recommended. Patients should be followed
clinically and started on ADT once symptoms of locally progressive or
metastatic disease present.

I.P.
ron - 25 Jul 2005 15:27 GMT
I.P...Thanks for taking the time to pull this information together.
The following  paragraph  in Loblaw's paper caught my eye,

"The most recent review (21 RCTs; 6,871 men) by Samson et al,14
compared androgen deprivation alone (orchiectomy or LHRH agonist)
versus combined blockade combined with steroidal or nonsteroidal
antiandrogens. Overall, the review found a larger survival improvement
than the previous meta-analyses favoring combined androgen blockade,
which first appeared at 5 years for men receiving (HR = 0.871; 95% CI,
0.805 to 0.942). Five years follow-up data were only provided in ten of
the 21 studies."

I would suspect that, as with primary treatment comparisons, more
significant differences, assuming they do exist, would emerge as
studies move out towards the 10 year timeframe.  It is not surprising
that HT comparisons show little or no difference in overall survival
when periods less than 5 years are examined.
Please understand that I am in no way criticizing your choices.  You
have very clearly thought through your treatment alternatives and made
the right choice for you.  For me, this discussion is part of the
discovery process and I hope it helps whoever may follow...Best wishes
and good health, Ron
Ed Friedman - 21 Jul 2005 18:28 GMT
> any one no about this new drug/ good/bad

Huck,

As others have said, this drug works similarly to finasteride as a 5AR2
inhibitor.  They both slow down the rate of growth of prostate cancer
approximately 5 fold.  However, if you take soy, flaxseed, or any other
food that binds preferentially to estrogen receptor-beta while taking
5AR2 inhibitors, then the rate of apoptosis (programmed cell death) will
decrease so much that the population doubling time for the prostate
cancer will actually become shorter.

As far as I know, of the doctors who use triple androgen blockade, only
Dr. Leibowitz and Dr. Tucker are aware of this fact, which is why their
results are so much better than anyone elses (unless you think a 0%
chance of death from prostate cancer when at stage T1-T3 is not that great).

This reason that soy is bad when on 5AR2 inhibitors is very complicated,
but is demonstrated in my paper at:

http://www.tbiomed.com/content/2/1/10

The paper is quite technical, but explains just about everything there
is to know about prostate cancer.

Ed Friedman
 
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