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