JCO PO authors Dr. Abhishek Tripathi and Dr. Salvador Jaime-Casas at City of Hope Comprehensive Cancer Center share insights into their article, "Comparative Genomic Characterization of Small Cell Carcinoma of the Bladder Compared With Urothelial Carcinoma and Small Cell Lung Carcinoma."  Host Dr. Rafeh Naqash and Drs. Tripathi and Jaime-Casas discuss a novel understanding of the genomic alterations underlying SCBC, revealing actionable mutations that could serve as potential targets for improved clinical outcomes.

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 am your host, Dr. Dr. Rafeh Naqash, Podcast Editor for JCO Precision Oncology and Associate Professor at the OU Health Stephenson Cancer Center at the University of Oklahoma.

Today, I am thrilled to be joined by Dr. Abhishek Tripathi, Associate Professor in the Department of Medical Oncology and Experimental Therapeutics Research at the City of Hope Comprehensive Cancer Center, as well as his mentee, Dr. Salvador Jaime-Casas, postdoctoral research fellow and first author of the JCO Precision Oncology article entitled "Comparative Genomic Characterization of Small Cell Carcinoma of the Bladder Compared with Urothelial Carcinoma and Small Cell Lung Carcinoma".

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

Abhishek and Salvador, welcome to our podcast and thank you for joining us today. This is a very interesting topic given that at least the landscape for neuroendocrine carcinomas, where small cell lung cancer is on one end of the spectrum, has been changing, at least on the lung cancer side, with recent approvals and some new ADCs. So, of course, understanding the genomic and transcriptomic similarities or differences between pulmonary small cell and extrapulmonary small cell is of huge interest. Could you tell us a little bit about small cell bladder cancer, current approaches to treatment of small cell bladder cancer, and then why you wanted to investigate that in this project as far as the genomic differences or similarities are concerned?

Dr. Salvador Jaime-Casas: Well, first of all, thank you very much for having me. I am very excited to be here. And really what served as backbone for this research project was the notion that there is a currently evolving genomic landscape in the area of bladder cancer. We know this is a highly heterogeneous disease when it comes to molecular underpinnings and mutational profile. Specifically, we know that the most common histologic subtype is urothelial carcinoma. Small cell bladder cancer represents a histology that is found in less than 1% of all bladder cancer cases. However, it is one of the most aggressive histologies. It presents with a very poor prognosis to patients and very poor response to treatment, which is why we attempted to really elucidate what is the mutational profile behind this and provide a comparison contrast between small cell bladder cancer, small cell lung cancer, and conventional urothelial carcinoma.

As your question mentioned, in terms of treatment, the conventional urothelial carcinoma and small cell bladder cancer are two distinct pathways when it comes to treatment algorithms. We know that in the current era there are newer and newer drugs being developed for conventional urothelial carcinoma. We have perioperative immunotherapy in the context of metastatic disease. We have antibody-drug conjugates such as enfortumab vedotin. But really, this amazing track record of drug development hasn't been mirrored in small cell bladder cancer. And here most of the therapy is usually extrapolated from studies from other small cell histologies like you mentioned earlier, small cell lung cancer has given some form of background in terms of what therapies are used here. Cytotoxic chemotherapy, for some patients with localized disease and small cell bladder cancer, concurrent chemotherapy and radiotherapy or perioperative cytotoxic chemotherapy have been the cornerstone of treatment for many years now. However, like I mentioned, the oncologic outcomes are very suboptimal when it comes to comparing it with other disease histologies, which is why we really wanted to describe the landscape here and provide this comparison across three different groups.

For this particular study, we leveraged the Tempus dataset. So, include patients with urothelial carcinoma with small cell bladder cancer and small cell lung cancer. We included their demographic information, as well as the frequency of most common genomic alterations identified. And really, it was a very comparable Table 1. We see the demographic data across the three groups was very similar. One key thing that we identified was the female prevalence was a little bit lower in patients with small cell bladder cancer when compared to small cell lung cancer. But other than that, the age, race, ethnicity, was comparable across groups, and even the smoking history. Most of the patients in this cohort were former smokers, which we believe comes to explain that regardless of any mutational profile that we talked about in a few minutes, there are shared commonalities between these histologies and shared environmental exposures and risk factors that are going to be implicated in the disease biology for these three histologies.

Dr. Rafeh Naqash: Thank you so much, Salvador, for that useful background.

I would like to shift to Abhishek real quick. Abhishek, you are a practicing clinician, you have led several studies in the GU space, especially bladder. Based on what you see in the small cell lung cancer space, how drug development is shaping up, which aligns with what you are trying to evaluate in this paper as targets, how do you see some of that being implemented for small cell bladder cancer in the current era and age?

Abhishek Tripathi: Thanks so much for the excellent question, Rafeh. As a GU investigator, small cell bladder cancer has always lagged behind in some regards regarding enrollment abilities for the novel clinical trials. And small cell lung cancer has paved the way and led the development of a lot of these drugs across the board. With the most recent sort of drugs targeting DLL3 already approved and several antibody-drug conjugates currently in development. That actually translates really well to how we should approach drug development in bladder cancer.

What we saw in the study is that although there are overlaps and similarities between small cell lung cancer and small cell bladder cancer, there are also certain differences. So the long-term assumption that all therapies for small cell bladder cancer can be extrapolated to small cell bladder], may or may not be true, and I think it is high time that we specifically investigate these novel agents in tissue-specific small cell carcinomas. To that effect, we are excited to be participating in trials that are looking at some of the novel DLL3 targeted agents, specifically bispecific antibodies and T cell engagers so to speak, and antibody-d