Updates on Biomarker-Directed Therapy for Solid Tumors: Focus on NTRK, RET, and NRG-1 - Episode 4

Companion Diagnostics in Oncology for Solid Tumors

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Experts in oncology provide their insights on the use of companion diagnostics in the treatment of solid tumors. 

Mark Socinski, MD: I want to go back to Dr Patel. So many of our targeted agents historically have been developed with a companion diagnostic that is looking for whatever the target may be. Personally, I have not necessarily found them to be that helpful in day-to-day practice, but what are your thoughts? What might their impact be, and how should we look at them?

Jyoti Patel, MD, FASCO: Sure, I think that is a great question. When clinical trials are being done that examine targeted therapies, it’s advantageous for pharmaceutical companies to develop a companion diagnostic so they can quickly screen and pay for their own test…and have a homogenized set of data that they can submit to the FDA. My experience is that, after that approval, a lot about the companion diagnostic goes away. We know that we have great testing in-house as well as through multiple vendors, so I think the need for that is diminished. We use it very infrequently. I guess a good example of that, which is ubiquitous, is PD-L1 testing. That has made the interpretation of clinical trials more difficult than it needs to be, based on test characteristics and the performance of immunohistochemistry. Outside of that, I think there is great fidelity between PCR [polymerase chain reaction testing], Sanger sequencing, and NGS [next-generation sequencing]. It probably is less impactful to people who are seeing patients.

Mark Socinski, MD: Ben, what are your thoughts on companion diagnostics, specifically in lung cancer? Do you find them helpful?

Benjamin Levy, MD: Not particularly, to keep the answer short. I think there is a lot of confusion, Jyoti really highlights this. We have this PD-L1 testing; we had a companion diagnostic and a complementary diagnostic, if you recall. There was a lot of confusion around this when pembrolizumab and nivolumab were being developed. I think that, given the advent of NGS and fairly high concordance across platforms, I do not find them all that useful.

Mark Socinski, MD: Lori, I will come back to you. You had mentioned that you have 1 marker, the BRAF. I do not even know if there is a companion diagnostic for that particular regimen. I am not sure about that. What are your thoughts on companion diagnostics?

Lori Wirth, MD: I agree with the rest of the people on the panel; we live in the Wild West with so many different NGS assays available to us now. I think it makes much more sense for physicians to be able to use an assay that they know well, they know the operating characteristics, they know how to interpret the data, rather than to have to use a companion diagnostic for 1 particular diagnosis for 1 particular agent. Hopefully, we are getting away from the need to develop companion diagnostics along with targeted therapy drugs.

Mark Socinski, MD: I would think if we had to use a companion diagnostic for all the biomarkers we have in non–small cell lung cancer, we would use up tissue so quickly that….

Lori Wirth, MD: Cost would be a huge issue as well.