JCO PO author Dr. Shilpa Gupta at Cleveland Clinic Children's Hospital shares insights into her article, "Fibroblast Growth Factor Receptor 3 (FGFR3) Alteration Status and Outcomes on Immune Checkpoint Inhibitors (ICPI) in Patients with Metastatic Urothelial Carcinoma". Host Dr. Rafeh Naqash and Dr. Gupta discuss how FGFR3 combined with TMB emerged as a biomarker that may be predictive for response to ICPI in mUC.

TRANSCRIPT

Dr. Rafeh Naqash: Hello and welcome to JCO Precision Oncology Conversations, where we bring you engaging conversations with authors of clinically relevant and highly significant JCO PO articles. I'm your host, Dr. Rafeh Naqash, podcast editor for JCO Precision Oncology and Associate Professor at the OU Health Stephenson Cancer Center.

Today I am excited to be joined by Dr. Shilpa Gupta, Director of Genitourinary Medical Oncology at the Cancer Institute and co-leader of the GU Oncology Program at the Cleveland Clinic, and also lead author of the JCO PO article titled "Fibroblast Growth Factor Receptor 3 Alteration Status and Outcomes on Immune Checkpoint Inhibitors in Patients With Metastatic Urothelial Carcinoma."

At the time of this recording, our guest's disclosures will be linked in the transcript.

Shilpa, welcome again to the podcast. Thank you for joining us today.

Dr. Shilpa Gupta: Thank you, Rafeh. Honor to be here with you again.

Dr. Rafeh Naqash: It is nice to connect with you again after two years, approximately. I think we were in our infancy of our JCO PO podcast when we had you first time, and it has been an interesting journey since then.

Dr. Shilpa Gupta: Absolutely.

Dr. Rafeh Naqash: Well, excited to talk to you about this article that you published. Wanted to first understand what is the genomic landscape of urothelial cancer in general, and why should we be interested in FGFR3 alterations specifically?

Dr. Shilpa Gupta: Bladder cancer or urothelial cancer is a very heterogeneous cancer. And while we find there is a lot of mutations can be there, you know, like BRCA1, 2, in HER2, in FGFR, we never really understood what is driving the cancer. Like a lot of old studies with targeted therapies did not really work. For example, we think VEGF can be upregulated, but VEGF inhibitors have not really shown definite promise so far.

Now, FGFR3 receptor is the only therapeutic target so far that has an FDA approved therapy for treating metastatic urothelial cancer patients, and erdafitinib was approved in 2019 for patients whose tumors overexpressed FGFR3 mutations, alterations, or fusions. And in the landscape of bladder cancer, it is important because in patients with non-muscle invasive bladder cancer, about 70 to 80% patients can have this FGFR3. But as patients become metastatic, the alterations are seen in, you know, only about 10% of patients. So the clinical trials that got the erdafitinib approved actually used archival tumor from local cancer. So when in the real world, we don't see a lot of patients if we are trying to do metastatic lesion biopsies. And why it is important to know this is because that is the only targeted therapy available for our patients right now.

Dr. Rafeh Naqash: Thank you for giving us that overview. Now, on the clinical side, there is obviously some interesting data for FGFR3 on the mutation side and the fusion side. In your clinical practice, do you tend to approach these patients differently when you have a mutation versus when you have a fusion?

Dr. Shilpa Gupta: We can use the treatment regardless of that.

Dr. Rafeh Naqash: I recently remember I had a patient with lung cancer, squamous lung cancer, who also had a synchronous bladder mass. And the first thought from multiple colleagues was that this is metastatic lung. And interestingly, the liquid biopsy ended up showing an FGFR3-TACC fusion, which we generally don't see in squamous lung cancers. And then eventually, I was able to convince our GU colleagues, urologists, to get a biopsy. They did a transurethral resection of this tumor, ended up being primary urothelial and synchronous lung, which again, going back to the FGFR3 story, I saw in your paper there is a mention of FGFR3-TACC fusions. Anything interesting that you find with these fusions as far as biology or tumor behavior is concerned?

Dr. Shilpa Gupta: We found in our paper of all the patients that were sequenced that 20% had the pathognomonic FGFR3 alteration, and the most common were the S249C, and the FGFR3-TACC3 fusion was in 45 patients. And basically I will say that we didn't want to generate too much as to fusion or the differences in that.

The key aspect of this paper was that historically there were these anecdotal reports saying that patients who have FGFR alterations or mutations, they may not respond well to checkpoint inhibitors because they have the luminal subtype. And these were backed by some preclinical data and small anecdotal reports. But since then, we have seen that, and that's why a lot of people would say that if somebody's tumor has FGFR3, don't give them immunotherapy, give them erdafitinib first, right?

So then we had this Phase 3 trial called the THOR trial, which actually showed that giving erdafitinib before pembrolizumab was not better. That debunked tha