Novel Use of ctDNA to Identify Muscle-Invasive, Non–Organ-Confined UTUC

Roger Li, MD, H. Lee Moffitt Cancer Center and Research Institute, details the current processes for clinical staging of high-risk upper tract urothelial carcinoma (UTUC), the rationale behind the presence of plasma circulating tumor DNA (ctDNA) as a predictive marker for muscle-invasive and non-organ-confined UTUC, and what his study results suggested about ctDNA’s prognostic implications for survival in this population.

Please detail the current processes for clinical staging of high-risk UTUC. What are the shortcomings of the contemporary methods, and how do these hinder the ability to select patients for neoadjuvant chemotherapy?

Dr. Li: The staging of UTUC has historically been very challenging. Despite the availability of more modern endoscopic technologies for accessing the upper tracts, it remains difficult due to the anatomical complexity of these tumors. The convoluted pathways required to access them, combined with the limitations imposed by small-sized instruments, make complete staging impossible. Similar to urothelial cancer of the bladder, upper tract disease staging relies on determining the depth of invasion into the urothelium and beyond.

Unlike bladder cancer, where resecting tumors is more feasible, accessing and fully understanding the depth of invasion for upper tract tumors is problematic due to the intricacy of access. Consequently, especially in cases of high-grade disease, accurately assessing the depth of invasion becomes a challenge.

For instance, a patient with high-grade TA disease may often receive treatment similar to a patient with what would be considered a high-grade T3 disease in the bladder. This inadequacy in staging makes selecting patients for neoadjuvant chemotherapy very challenging. Often, reliance is placed on imperfect methods like cross-sectional imaging, which may fail to detect disease extension beyond the upper tract urothelium, sometimes even affecting the kidney.

Currently, the standard approach suggests that anyone with high-grade disease should be considered for neoadjuvant chemotherapy, extrapolating evidence from bladder cancer scenarios where such treatment has shown benefits. However, the inability to distinguish between superficial high-grade disease and invasive high-grade disease leads to a considerable number of patients being potentially over-treated through this strategy.

Therefore, our study aims to explore the potential of using the ctDNA platform to refine the staging of upper tract disease. The objective is to enhance the selection process for patients who might benefit from neoadjuvant chemotherapy, aiming for a more targeted and refined approach.

What is the rationale behind the presence of plasma ctDNA as a predictive marker for muscle-invasive and non-organ-confined UTUC?

Dr. Li: Circulating tumor DNA has emerged prominently in cancer care in recent years. These are essentially DNA strands free of cells, termed cell-free DNA, detectable in various bodily fluids such as plasma, urine, saliva, and other fluid compartments. They originate from cells undergoing apoptosis or other forms of cell turnover, releasing DNA associated with the cell into these bodily fluids. Utilizing next-generation sequencing platforms, we’re now capable of identifying tumor-specific DNA within this cell-free DNA, potentially indicating the presence of tumor cells at the time of testing. By leveraging this platform, our aim is to determine whether the detection of cancer-related cell-free DNA in patients with UTUC can provide insights into the presence of invasive disease.

What did your study hope to achieve, who were the patients sampled, and what were your methods used to assess the correlation between ctDNA and muscle-invasive and non-organ-confined UTUC?

Dr. Li: We obtained consent from 30 patients diagnosed with high-risk UTUC, determined through both endoscopic examinations and cross-sectional imaging. These patients were scheduled for explorative surgery, either involving the removal of the kidney alongside the ureter or solely a segment of the ureter while reconnecting the rest of the urinary tract. Prior to their surgeries, we collected plasma samples from these patients and utilized a targeted NGS panel examining 150 genes associated with commonly discovered mutations in upper tract disease. Our goal was twofold: first, to detect these gene alterations in the preoperative phase and secondly, to compare the findings from the plasma samples with the tissue samples obtained during surgery.

All 30 patients underwent surgery without prior neoadjuvant treatments, adhering to the standard of care. Among them, 14 exhibited either muscle-invasive UTUC or non-invasive cancer with concurrent lymph node metastasis, indicating invasive disease. Notably, we detected at least 1 gene alteration in the plasma of 21 out of the 30 patients, signifying a significant presence of plasma gene alterations.

Comparing the plasma ctDNA with the whole exome sequencing of the tissue samples harvested during surgery, we discovered a 52% concordance between the 2. Taking into account previous studies utilizing bespoke ctDNA platforms, we set a threshold of at least 2 or more ctDNA alterations as a positive test result. Additionally, we integrated a copy number change derived from low-pass whole genome sequencing conducted simultaneously with the targeted panel.

Through this combined approach, we achieved a predictive ability with 79% sensitivity and 94% specificity in identifying patients with either muscle-invasive or non-organ-confined UTUC.

What did your results suggest about ctDNA’s prognostic implications for survival?

Dr. Li: One particularly exciting finding from our study is that regardless of the adjuvant or salvage treatments administered post-surgery, we observed that the ctDNA detected before surgery, irrespective of the staging at that time, had the ability to predict whether patients would experience a prolonged disease-free survival. This underscores the remarkable prognostic potential of ctDNA, enabling differentiation between patients with a heavy systemic disease burden and those without.

Moving ahead, it seems imperative that patients who test positive for ctDNA prior to surgery should strongly consider undergoing neoadjuvant treatment. This approach could potentially eliminate the micrometastatic disease that these individuals likely harbor. However, an aspect not explored in this study pertains to the kinetics of ctDNA from pre-surgery to post-surgery, which could elucidate the role of surgery in clearing out cancer. This area will be the focus of our forthcoming research endeavors.

Are there any other takeaways from the study that you would like to add?

Dr. Li: One crucial point I’d like to emphasize is the notably superior sensitivity and specificity observed in our study compared to those reported in clinical nomograms. At the outset of this discussion, I should have mentioned the current shortcomings in staging and imaging methodologies for high-risk UTUC, leading to various studies focusing on clinical nomograms. These nomograms amalgamate clinical risk factors—such as the presence of hydronephrosis in CT scans, positive urine cytology, tumor location, perinephric stranding, and other clinically derived indicators—to assess the likelihood of patients having muscle-invasive disease.

It’s noteworthy that the sensitivity of these clinical nomograms, crucial for identifying muscle-invasive disease in upper tract disease patients, typically falls within the 40 to 50% range. Sensitivity in this context holds paramount importance because missing the opportunity to administer neoadjuvant chemotherapy to these patients due to surgery-related renal function impairment is a significant concern. For many patients, post-surgery, their impaired renal function precludes them from receiving chemotherapy in the adjuvant setting. Therefore, the sensitivity of our test, its capacity to accurately identify those with muscle-invasive disease upfront, is a pivotal aspect. This accuracy can ensure that patients in need of neoadjuvant chemotherapy receive the necessary treatment to potentially prolong their lives.