Blood-Based Liquid Biopsy for Patients With UTUC

Hooman Djaladat, MD, of the University of Southern California, explains his latest research into blood-based liquid biopsies for patients with UTUC, including key findings regarding rare analytes detected in preoperative samples.

Dr. Djaladat also discusses how the presence of specific biomarkers, such as CK|V oncosomes and D|CK|V cells, correlate with recurrence-free survival.

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Can you provide some background on the use of a blood-based liquid biopsy for patients with UTUC?

Dr. Djaladat: Liquid biopsy is not a novel concept; it has been employed in various cancers such as colon cancer, prostate cancer, melanoma, and lung cancers. Numerous studies have been conducted to investigate findings in the blood or to survey for cancer. The majority of past studies have concentrated on exosomes, encompassing RNAs and DNAs, notably ctDNA and cell-free DNAs. However, limited research has been undertaken on rare cell events, particularly large extracellular physicals, which are additional components potentially present in the blood and may correlate with tumors.

In urothelial cancer, there have been studies focusing on ctDNA. Currently, clinical indications exist for the use of ctDNAs, particularly in patients with invasive disease undergoing cystectomy. However, research on other components I mentioned has been limited. Although some small studies on ctDNA in upper tract urothelial carcinoma exist, there has been scant investigation specifically into circulating tumor cells and rare cell events, as I mentioned earlier. Our study, which was published in urologic oncology, focused on this aspect.

Please explain the design and methodology of your analysis. Why did you decide to focus on the presence of rare events, including circulating tumor cells and oncosomes?

Dr. Djaladat: I must clarify that I am a basic scientist, and there are likely others who can explain this more proficiently than I can. However, as part of our team engaged in a significant collaboration, we have partnered closely with our basic scientist teams at the Mickelson Cancer Institute here at USC. Together, we are investigating rare cell events specifically in the blood for detecting upper tract urothelial carcinoma. Why did we pursue this? Well, we had access to the HGSCA technology, which stands for High-Definition Single Cell Analysis. This innovative technology is something we are fortunate to have experts evaluate and work with.

Our basic scientist teams have conducted extensive studies in other cancers using this technology. Essentially, they have examined any cell that might be present in the blood, rather than solely focusing on mutation burdens through ctDNAs, and so forth. They have conducted studies in breast cancer, melanoma, lung cancer, colorectal cancer, upper tract urothelial carcinoma, and bladder cancer, some of which we have published. We have also contributed to these studies, but exploring upper tract urothelial carcinoma was the logical next step, as there has been limited research in that area.

What were the key findings regarding rare analytes detected in preoperative samples compared to those from normal donors?

Dr. Djaladat: That’s an excellent question. In this study, we specifically examined eight circulating tumor cells at the cellular level, as well as four large extracellular vesicles. Many of these extracellular vesicles are likely released by the circulating tumor cells into the bloodstream, whether through infiltration, shedding, racking, or possibly de novo production. While we’re not entirely certain of the mechanisms involved, these eight cells and four vesicles were primarily identified based on their biomarkers. We utilized immunofluorescence assays to detect cytokeratin, vimentin, and other cell surface markers at this level.

From a computational standpoint, these data were systematically saved and manually counted to ensure thoroughness in the initial stages of the study. Notably, we analyzed recent data from 28 patients with upper tract urothelial carcinoma, comparing pre-nephrectomy or discectomy samples from those with invasive disease to postoperative samples. We observed a significant correlation between pre- and post-operative evaluations in terms of total cell counts and total events, as well as for each circulating tumor cell and oncosome individually. It was particularly exciting to observe a decrease in both epithelial and mesenchymal components after surgery, indicating that the removal of primary tumors leads to observable changes in blood levels.

How did the presence of specific biomarkers, such as CK|V oncosomes and D|CK|V cells, correlate with recurrence-free survival in your study cohort?

Dr. Djaladat: This is an excellent point to emphasize. I want to reiterate that this study should not be viewed as highly conclusive or directly applicable to clinical practice. It’s important to understand that this is primarily an exploratory endeavor. To put it simply, this study serves as a pilot, an exploration, and a discovery process. Its aim is to gain a deeper understanding of what occurs beyond the markers in plasma that have already been examined. While ctDNA, which essentially represents mutations from primary tumors that are detectable in the bloodstream, has been extensively studied, there are likely other components and phenomena at play in the blood of these patients. Rare cell events represent one such aspect that warrants further investigation.

We’ve observed differences in certain markers before and after surgery, with a noticeable decline post-surgery. Additionally, we’ve identified correlations between some of these markers and oncologic outcomes, particularly recurrence. However, it’s important to note that the sample size for this specific analysis is relatively small, with a median follow-up period of only 11 months according to this report. We’re continuing to monitor these patients, and we’ve observed some changes in various cell types preoperatively that correlate with recurrence-free survival, both in terms of cells and oncosomes. While these findings provide valuable insights, it’s crucial to acknowledge that our understanding is still in the exploratory phase, and we’re not entirely certain of their significance. Further research with a larger sample size and validation is necessary to clarify the implications of these observations.

What further research do you believe is needed regarding the efficacy of blood-based liquid biopsies for UTUC?

Dr. Djaladat: We’ve also investigated the changes that occur in these biomarkers and their correlation with clinical parameters. These parameters include clinical and pathological characteristics of the tumors, demographics, and outcomes as additional variables alongside these biomarkers. When we consider all these markers in the blood, including ctDNA and rare cell events, I believe they all complement each other.

I envision consolidating all these markers into a panel that demonstrates associations with relevant oncological outcomes. This panel, ideally, would yield a high AUC (Area Under Curve) and could potentially aid in pre-surgical diagnosis, prognosis assessment before or after surgery, and guidance regarding appropriate systemic therapy for patients. Ultimately, such a panel could play a crucial role in predicting prognosis and recurrence, offering valuable assistance in clinical decision-making.

Blood-Based Liquid Biopsy for Patients With UTUC

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