Significance of early PSA response.

[pjoshea13]

New French study below.

It looked at data from clinical trials of Xtandi, Zytiga & Orteronel in CRPC.

The inclusion of Orteronel is unfortunate, since Takeda stopped producing Orteronel in 2014, because "while orteronel plus prednisone could extend the time patients lived before their cancer progressed, it did not extend overall survival in these patients."

"Early PSA response (EPR)" was "defined as a decline >50% from baseline" to "28 d after treatment initiation".

Median radiographic progression-free survival was 13.9 months in EPR cases, versus 5.6 months.

Median overall survival was 32.2 months in EPR cases, versus 15.9 months.

I'm thinking of something in the Dr Myers video I posted yesterday.  Ultimately, an effective PCa drug combo is probably going to have to achieve it's result within 3 months, in order to finesse the drug resistance problem.

From what I have read, cellular survival pathways are are fully active by the time of the 2nd treatment of drug or radiation.  The response is rapid in cells that survive the initial treatment, & it becomes much more difficult to kill them.  Meanwhile, surviving cells have time to adapt.

If a rapid PSA response is crucial to the durability of treatment, it seems to make sense to throw everything that might have additive value at the cancer.  The aim being to get the biggest possible PSA drop in the shortest possible time.  & this is the opposite of the sequential strategy of trying something until it fails, & then moving on to the next thing until that fails, etc.

-Patrick

ncbi.nlm.nih.gov/pubmed/271...

Eur J Cancer. 2016 May 2;61:44-51. doi: 10.1016/j.ejca.2016.03.070. [Epub ahead of print]

Early PSA response is an independent prognostic factor in patients with metastatic castration-resistant prostate cancer treated with next-generation androgen pathway inhibitors.

Fuerea A1, Baciarello G1, Patrikidou A1, Albigès L1, Massard C1, Di Palma M1, Escudier B1, Fizazi K1, Loriot Y2.

Author information

Abstract

BACKGROUND:

The optimal use of new therapies in metastatic castration-resistant prostate cancer (mCRPC) remains to be clarified. Prostate-specific antigen (PSA) response used as a pharmacodynamic end-point may help identify patients with early resistance to new androgen receptor-pathway inhibitors. We aimed to determine the clinical significance of early PSA response (EPR) during therapy with enzalutamide, abiraterone acetate (AA) and orteronel in mCRPC.

METHODS:

Data from patients recruited in clinical trials were studied. PSA values were obtained at baseline and 28 d after treatment initiation. EPR defined as a decline >50% from baseline was calculated according to the Prostate Cancer Working Group 2 criteria. The effects of clinical characteristics on radiographic progression-free survival (rPFS) and overall survival (OS) were examined using the Cox model.

RESULTS:

EPR was assessed in 118 patients treated in clinical trials and was found to be associated with longer rPFS and OS (P < 0.0001 for both). Median rPFS was 13.9 and 5.6 months (hazard ratio [HR]:0.38, P < 0.001) for patients with and without an EPR, respectively. Median OS was 32.2 months in patients with an EPR and 15.9 months in patients without an EPR (HR: 0.4, P < 0.01). EPR remained prognostic for OS in multivariate analyses (HR: 0.5, p=0.009) that included validated pre-therapeutic prognostic factors for mCRPC. Prognostic values of EPR for rPFS and OS were confirmed in an independent cohort of 95 AA-treated non-trial patients.

CONCLUSIONS:

EPR is an independent prognostic factor in patients with mCRPC treated with next-generation androgen pathway inhibitors and may be useful for the therapeutic management of these patients.

Copyright © 2016 Elsevier Ltd. All rights reserved.

KEYWORDS:

Abiraterone; Enzalutamide; PSA; Prostate cancer

PMID: 27151554 [PubMed - as supplied by publisher]

[Dan59]

One possible combo is xtandi plus zytiga as these two actually reach different pathways from what I understand.

Dan

[JoelT in reply to Dan59]

They do have different pathways.  One inhibits the production of testosterone (Zytiga) while the other blocks the androgen receptor (Xtandi). We are in need of a trial that would combine these two drugs, but I would bet given the very competitive nature of the two Pharmas involved it would be very difficult to envision this happening. Hopefully, I am wrong.

Joel

[afab in reply to JoelT]

Joel,  I'm in a clinical trial that has what you were questioning. I'm in Group 1 Lupron and Xtandi.  Group 2 is Lupron,  Xtandi, Zytiga and Prednisone. Participants are randomly assigned to Group 1 or 2.

[motosue in reply to JoelT]

Joel,

I'very been taking Zytga, Xtandi, Lupron, prednisone,Xgeva , met forming for a few years at least. No side effects except thin skin at forearm and ED (maybe  from Lupron.)  PSA undetectable  and testosterone below 20. Still feel good, fortunately. Take care Joel

[Dr_WHO]

I agree.  I have aggressive PCa and surgery three weeks ago but it has spread.  Next week I see both radiation and hormonal Dr.  I am going to argue for both treatments. Kick cancer  when it is down is my motto. 

[TommyTV]

My response to Zytiga with Zoladex was rapid. My PSA went from 600+ at diagnosis to immeasurable in the space of 28 days. It has stayed there for the last 4.5 years.

[Cancersucks]

Tommy,

Did you start Zoladex first or both at the same time?  We started Lupron and Flutamide 04/15, Docetaxel 07/15 and Xtandi 01/16 (lupron still).  PSA went from 2739 at initial diagnosis to nadir of 12 in October.  PSA has gone from 30 to 32 on Xtandi.  I have heard Oncs starting Xtandi or Zytiga right away with Lupron or Zoladex and I'm curious if that is your situation.

We did not get a EPR unfortunately, but Xtandi seems somewhat effective.

[TommyTV]

I'm not too familiar with brand names. I started Zoladex and within a couple of weeks I  joined the Stampede trial, getting Abiraterone and prednisone. I was very pleased at the time as Abiraterone was only just becoming available.