Investigators Push to Leverage Liquid Biopsy As New Standard in Early Detection, Prognosis of Hematologic Malignancies

Irene Ghobrial, MD

Liquid biopsy is poised to advance the early detection and monitoring of hematologic malignancies, replacing the standard, more invasive methods of bone marrow and lymph node biopsies. Leveraging the advances made in pantumor assays and specific hematologic cancers, such as myeloma, has laid the groundwork for the shift in care by using single, or multifaceted approaches for identifying, predicting, and monitoring disease progression.

“In hematological malignancies, the hope is to take a blood sample to answer [clinical] questions instead of using either a bone marrow biopsy or lymph node biopsy,” Irene Ghobrial, MD, Lavine Family Chair for Preventative Cancer Therapies at Dana-Farber Cancer Institute, professor of medicine, and director of the Clinical Investigator Research Program at Harvard Medical School in Boston, Massachusetts. “Many studies are being done, not only in hematological malignancies, but in all cancers, but for hematologic malignancies [blood samples are] truly the way forward because we have so much information in the blood.” Ghobrial delivered the plenary lecture on the use of liquid biopsies in hematologic malignancies at the 26th Annual International Congress on Hematologic Malignancies^®: Focus on Leukemias, Lymphomas, and Myeloma.¹

“Looking at studies with liquid biopsies, you can think of circulating free DNA or circulating tumor DNA [ctDNA], RNA, proteins, and now [investigators are looking at] multiomics, which put together methylation with proteins, RNA, and DNA to try and answer [similar] questions,” Ghobrial said. “There is a second [part of liquid biopsy], which is the cellular compartment. We’ve been very lucky that many hematological malignancies have a component that circulates in the blood. We can use that for serial assessment of either [minimal residual disease] MRD or early detection and prevent of progression in many of those patients.” She noted that these assessments also include circulating tumor cells and clonal hematopoiesis of indeterminate potential (CHIP) mutations observed in white cells.

The future, Ghobrial said, is in the immune cell component of analysis, which she described as critically undermined in research. “How can we use the immune system as a biomarker of potential progression of potential response and resistance to therapy [and as a marker of] long term remission in our patients? How can we develop this immune MRD in the near future for our patients?”

Tracking Trends in Liquid Biopsy

There are 2 approaches to liquid biopsy: tumor-informed and tumor-uninformed approaches. For a tumor-informed approach, investigators develop a targeted panel based on the mutations present in the patients following whole exom or whole genome sequencing. “You can [create a] fingerprint for [a] patient throughout the course of their disease [and] multiple studies are showing that this is very deep, very sensitive, and very specific.”

For tumor-uninformed approaches, a cancer diagnosis is unknown at the offset and therefore the tests are not as sensitive, according to Ghobrial. “It’s an early detection method, and the [tests] are not as sensitive as a tumor-specific ones, but they can be done for any cancer.” Methods developed for pancancer early detection using methylation patterns have demonstrated some improvements for hematologic malignancies, including in the detection of leukemia and Hodgkin and non-Hodgkin lymphomas.² But Ghobrial said that more studies are needed specific to hematologic malignancies, including those using self-fragmentation methods that are more sensitive for detection of mutations such as CHIP in the tumor DNA.

Quantifying ctDNA using deep sequencing, such as CAPP-Seq has proven to be an effective measure in identifying B-cell lymphomas and generating targeted sequencing panels to track disease.³ “We can use next-generation sequencing [NGS] and other methods to expand the role [of liquid biopsy], and CAPP-Seq could be very [useful] in this, but can we expand it in other cancers [beyond B-cell lymphomas] in the near future?” Ghobrial asked. For example, in myeloma, she noted that the standard approach for sequencing is to have a bone marrow biopsy. “When we see a patient, we do a bone marrow biopsy, NGS, flow cytometry, [fluorescence in situ hybridization] FISH, we do immunohistochemistry, and then of course we do imaging. But can I do more in the blood?”

Serum protein electrophoresis (SPEP), an antibody test that detects cancer cells in the blood, is one such test available to investigators to identify patients with hematologic malignancies.⁴ However, improvements with mass spectrometry, such as those demonstrated in the PROMISE study (NCT03689595), may replace SPEP in the future, according to Ghobrial.

Investigators of the PROMISE study set out to find early detection of monoclonal gammopathies in high-risk populations, specifically Black Americans and those with a first- or second-degree relative with a blood cancer.⁴ A total of 7600 patients were screened using matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) as well as SPEP and immunofixation. “We wanted to see what was the lowest level that you could detect by SPEP, [and determine] the lowest you cannot detect by SPEP but can detect by mass spectrometry using a new [artificial intelligence] AI-informed algorithm to quantify the immunoglobulins and the light chains,” Ghobrial said.

The level was determined as 0.2 g/L to detect monoclonal gammopathy of undetermined significance (MGUS). “These were true monoclonal proteins [and] not abnormalities in the assay,” Ghobrial said. The overall prevalence of MGUS, as detected by MALDI-TOF MS, was 13% compared with 6% by SPEP in the high-risk population.^1,4

“Interestingly, because we had [access to] survival data [in the] electronic health record of every patient, we were able to [identify] the survival and comorbidities associated with MGs,” Ghobrial explained, adding that worse overall survival was observed with MG detection. Despite MGUS being more common among patients with myeloma, Ghobrial said that it is also associated with macroglobulinemia. “We’re starting to step back and say this is an immune dysregulation that may not be just about myeloma.”

Despite bone marrow biopsy being the gold standard for diagnosis and monitoring of patients, there is an urgent need to robust early detection methods that are tumor biology-based as well as minimally invasive, Ghobrial noted. In her laboratory, investigators began enumerating circulating tumor cells from 185 patients.¹ “Once those cells are extracted, you can perform whole genome sequencing, RNA sequencing, anything else you want and can sell, sort to have purified samples in those patients,” she said.

The samples were enriched with CD138 and enumerated using the CellSearch platform at Dana-Farber. One or more circulating tumor cells were detected in 84% of patients, with 74% of patients who had MGUS and 84% of patients with smoldering multiple myeloma having successful enumeration. Higher circulating tuor cell counts were also associated with risk classification. A median of 4, 21, and 59 circulating tumor cells were detected in patients who were in the low, intermediate, and high-risk smoldering multiple myeloma groups, respectively. “If you use the 2/20/20, [3-risk factor model], which are the clinical factors that we use for patients with smoldering myeloma, and add on circulating tumor cells we were able to find that circulating tumor cells [were associated with] worse outcomes and faster [disease] progression,” Ghobrial said. “[The presence of] circulating tumor cells tells you that there is a more biological indication of advancement of the disease beyond just an enumeration of tumor burden in those patients.”

Investigators also compared results with bone marrow biopsy using conventional methods such as FISH and whole genome sequencing without amplification, which allowed them to perform the tests on those with a lower tumor burden. “If you have only 20 or 30 cells, you need genomic amplification to try and hold genome sequencing,” Ghobrial said. “We have been able to detect every single translocation or copy number alteration [as determined by] FISH in circulating tumor cells and in the bone marrow. Cancer cell fraction, the number of mutations, and the number of clones that you can detect in the blood were also more significant than what you detect in the bone marrow.We were surprised that you can detect everything in the blood that you found in the bone marrow. Rarely we find something in the bone marrow, but the blood always gave us more mutations and a higher cancer cell fraction of certain mutations, which indicates that maybe the clones that are capable of circulating in the blood have an enhanced ability to be more important for us to understand biologically what happens with circulating clones vs bone marrow clones.”

Ghobrial returned to her discussion of leveraging the immune system and her future research is dedicated to showing these advances. “If you do immune single-cell sequencing in bone marrow, and now we can do it in the blood, they reflect each other,” she said. In examples pulled from unpublished data, Ghobrial highlighted that there was significant compositional and transcriptional change that can predict which patients would progress to myeloma the future once markers were identified. “However, what we try to do here is also using immune cell markers to decide whether a patient will have a biomarker of response to therapy, as well as after treatment, whether you have a normalization of your immune system, what we called post immunonormalization, and whether that can be predictive for long term remission.”

Ultimately, Ghobrial said there is a lot of work to improve understanding of early detection, prediction of response to therapy, of prognostic biomarkers, and then monitoring patients. “In the future these approaches will [leverage] multiomics instead [just] methylation. Hopefully [liquid biopsy] will be a clinical tool that we can use for our patients instead of using only bone marrow or lymph node biopsies or other [invasive] biopsies.”

References

1. Ghobrial I. How to harness ctDNA analysis in hematologic malignancies. Presented at: 26th Annual International Congress on Hematologic Malignancies®: Focus on Leukemias, Lymphomas, and Myeloma. February 24-27, 2022.
2. Yimer HA, Tang WHW, Tummala MK, et al. Detection of cancer signal for over 50 AJCC cancer types with a multi‑cancer early detection test. J Clin Oncol. 2021;39(suppl 15):3072. doi:10.1200/JCO.2021.39.15_suppl.3072
3. Newman AM, Bratman SV, To J, et al. An ultrasensitive method for quantitating circulating tumor DNA with broad patient coverage. Nat Med. 2014;20(5):548-54. doi:10.1038/nm.3519
4. El-Khoury H, Alberge JB, Barr H, et al. High prevalence of monoclonal gammopathy in a population at risk: the first results of the Promise study. Blood. 2021;138(suppl 1):152. doi:10.1182/blood-2021-149868