DR RUGO: We’re still learning a lot. I think that now we believe that, as clinicians, we can pick out the AR-positive tumors that at least have a chance of responding a little better. These are indolent cancers. They act more ER-like. They tend to have more bone- and soft tissue-dominant disease and not a liver full of tumor. So these patients need to have time to respond and express the androgen receptor.

Expressing the androgen receptor alone may not be sufficient, though, because there is data from enzalutamide that suggest that potentially having an immune predictor might be a better way to understand who responds. But that was a retrospective analysis. And now they’re doing prospective studies looking to see whether or not they can predict who will benefit, both with the agent alone and in combination with chemotherapy.

DR LOVE: So again, you have the question: Antiandrogens are out there. They’re accessible, enzalutamide, bicalutamide. Of the data that you’ve seen up to this point, justify the use of this kind of strategy outside a trial setting?

DR RUGO: I think, again, I would definitely encourage the enrollment to open clinical trials, because otherwise, we’re never going to know really how these drugs work above and beyond not treating patients.

But if you have a patient who’s not eligible for any of the trials, then I think that trying to get drug, either bicalutamide or enzalutamide, on compassionate use is a reasonable option if you know the patient has AR-positive disease and can wait to have a response.

DR LOVE: What specific assay would you recommend to assess AR status?

DR RUGO: We have no idea. And that’s one of the problems is that we just don’t know what the right assay is. I think this looking at the PREDICT-AR is quite intriguing, but we don’t have any idea what is involved in that protected assay right now. So I think testing the androgen receptor with your laboratory is probably the best we can get to right now, since we have no standard approach.

DR LOVE: So what, just a regular IHC-type test?

DR RUGO: Yes. Sorry. Yes, by immunohistochemistry, not by gene expression. And that’s what the studies have done. And I think it’s the best test we have right now. It’s generally available. Certainly our lab at the university does AR testing. And central labs also provide AR testing at a very reasonable cost.

Genomic assays and (neo)adjuvant treatment decision-making

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Management of metastatic breast cancer (mBC)

CDK4/6 inhibitors for the treatment of breast cancer

Checkpoint inhibitors and other novel immunotherapeutic approaches to breast cancer

Triple-negative and BRCA mutation-positive breast cancers