Circulating cell-free DNA as predictor of treatment failure after neoadjuvant chemoradiotherapy before surgery in patients with locally advanced rectal cancer: is it ready for primetime?

Pilot Study of Recurrent Ewing's Sarcoma Management with Vigil/Temozolomide/Irinotecan and Assessment of Circulating Tumor (ct) DNA

PURPOSE

Treatment options for recurrent or refractory Ewing's sarcoma (ES) are limited. Vigil is a novel autologous tumor cell therapy expressing bi-shRNA furin/GMCSF plasmid, which previously demonstrated monotherapy activity in advanced ES. Herein we report safety and evidence of benefit to Vigil for ES as potential treatment.

PATIENTS AND METHODS

In this pilot trial, eligible patients with recurrent or refractory ES who failed initial standard-of-care therapy received treatment with temozolomide (TEM) 100 mg/m2/day oral and irinotecan (IRI) 50 mg/m2/day oral, Days 1 to 5, in combination with Vigil (1 × 106-107 cells/mL/day intradermal, Day 15), every 21 days (Vigil/TEM/IRI). Objective response rate (ORR) by RECIST v1.1, progression-free survival (PFS), and overall survival (OS) were assessed. Circulating tumor (ct) DNA analysis was done by patient-specific droplet digital PCR on baseline and serially collected on-treatment samples.

RESULTS

Eight of 10 enrolled patients were evaluable for safety and efficacy (mean age 24.6; 12.6-46.1 years old); 2 did not receive Vigil. Seven of 8 patients previously received TEM/IRI. No Vigil-related adverse events were reported. Common ≥Grade 3 chemotherapy-related toxicity included neutropenia (50%) and thrombocytopenia (38%). We observed two partial response patients by RECIST; both showed histologic complete response without additional cancer therapy. Median PFS was 8.2 months (95% confidence interval, 4.3-NA). Five patients showed stable disease or better for ≥6 months. Patient-specific EWS/FLI1 ctDNA was detectable in all 8 evaluable patients at baseline. Changes in ctDNA levels corresponded to changes in disease burden.

CONCLUSIONS

Results demonstrated safety of combination Vigil/TEM/IRI.

Cell-free circulating tumor DNA in colorectal cancer: a proof of concept with simplified methodology

BACKGROUND

Cell-free DNA analysis (cfDNA) holds promise for residual disease or tumor burden quantification in colorectal cancer, with reduced costs and diagnostic equipment compared to gold standard-specific tumor DNA (ctDNA) analysis.

METHODS

This prospective case-control study included 46 colorectal cancer patients and healthy controls to perform cfDNA quantification by fluorometry using Quantus Fluorometer (Promega, Madison, WI) and using cell-free DNA ScreenTape assay (Agilent) and 4200 TapeStation instrument (Agilent Technologies, Inc., Santa Clara, CA, USA). cfDNA quantification results were correlated with stage, clinical and histopathological features.

RESULTS

33 localized (8 stage I, 12 stage II, and 13 stage III) and 13 advanced colorectal cancer patients were included. No differences in cfDNA quantification by fluorometry were demonstrated depending on stage or histopathological features in localized disease patients. Differences in cfDNA quantification by fluorometry could be demonstrated in patients with advanced disease depending on the presence of liver metastases and synchronous or metachronous metastatic disease. Differences in cfDNA quantification by fluorometry could be demonstrated between advanced colorectal cancer patients and both localized disease patients and healthy controls. Secondary cfDNA analysis by electrophoresis, although showing more specificity to measure ctDNA in cfDNA values, could not improve the capacity to detect differences between analyzed a groups beyond previously achieved with fluorometry.

CONCLUSION

This exploratory analysis of cfDNA based on fluorometry and electrophoresis methods showed promising results discriminating colorectal cancer and non-cancer patients, as well as different colorectal cancer stages and disease profiles. Further studies are needed to increase our knowledge and to help to overcome barriers to broader implementation and applications.

Nucleic acid-based markers of response to neoadjuvant chemoradiotherapy in locally advanced rectal cancer

The progress that has been made in the treatment of rectal cancer has mostly resulted from multimodality strategy approach that combines surgery, chemotherapy and radiotherapy. In locally advanced rectal cancer (LARC), surgery remains the primary treatment, while neoadjuvant chemoradiotherapy (nCRT) is used to downsize or downstage the tumor before surgical resection. Highly variable response to nCRT observed in LARC patients raises the need for biomarkers to enable prediction and evaluation of treatment response in a more efficient and timely manner than currently available tools. The search for predictive biomarkers continues beyond blood proteins, which have failed in subsequent validation studies. This review presents nucleic acids-based markers and their predictive potential in LARC patients. Most of the candidate biomarkers come from relatively small single-institution studies. The only candidate biomarker that emerged as relevant in more than a single study was elevated levels of Fusobacterium nucleatum nucleic acids in tumor tissue. Considering that this marker is easily accessible through non-invasive analysis of faecal samples, its predictive potential is worth further validation. The other candidate nucleic acid-based biomarkers require more consistent studies on larger cohorts before they can be considered for use in clinical setting.

Hypermethylation of SHISA3 DNA as a blood-based biomarker for colorectal cancer

In Taiwan, colorectal cancer (CRC) is the second most common cancer and the cancer with the third highest mortality rate. This may be because of the difficulty of detecting the disease in the early stages, as well as the fact that colonoscopy, a typical method used in screening for CRC, causes discomfort to the recipient and is prone to technical interference. For the earlier detection of CRC, finding an easier screening method with a simpler collection procedure is essential. Thus, in the present study, plasma samples from patients with CRC were analyzed to determine the extent of methylation in SHISA3 DNA. Studies have suggested that SHISA3, a newly identified tumor suppressor, can regulate tumor growth, and that the inactivation of its DNA can be traced to epigenomic alterations in CRC. Another study reported the presence of hypermethylated SHISA3 DNA in CRC biopsy specimens. In the present study, the plasma of 30 patients with CRC and nine healthy controls was collected and analyzed for the concentration of cell-free DNA through bisulfite sequencing. The methylation rates were determined. Our results have shown that an increasing amount of cell-free DNA in the group of CRC patient's plasma compared to the healthy group. Moreover, patients with later stages of CRC had higher concentrations of cell-free DNA. Notably, the methylation rate of SHISA3 was higher in the plasma of the CRC group than in that of the healthy group. The results indicated that the presence of tumor cells does not reduce the degree of SHISA3 DNA in the peripheral blood of patients with CRC. In other words, the hypermethylation of SHISA3, which inactivates the gene, is a potential cause of tumorigenesis. Furthermore, the methylation rate of SHISA3 DNA was higher in the plasma of patients with stage II CRC than in that of those with stage I CRC. In conclusion, the combination of conventional testing and screening for SHISA3 hypermethylation in plasma could improve the rate at which CRC is detected.

Assessing the Impact of Circulating Tumor DNA (ctDNA) in Patients With Colorectal Cancer: Separating Fact From Fiction

Significant advances and increased awareness have been in made in the field of non-invasive liquid biopsies for cancer, spanning several malignancies from gastrointestinal, pulmonary, and other etiologies. Broadly, the genetic source material for liquid biopsies includes circulating tumor cells, cell-free circulating tumor DNA (ctDNA), or cell-free circulating tumor microRNA (mRNA). In this review, we specifically focus on ctDNA and its current role in colorectal cancer. While there are several commercially available assays that detect ctDNA, the utility of these products is still variable and therefore the clinical applications of ctDNA in the management of patients with cancer has yet to be determined. This is reflected by the recent joint review set forth by the American Society of Clinical Oncology (ASCO) and the College of American Pathologists (CAP), clarifying and somewhat tempering the present role of ctDNA in patients with cancer. This review provides additional detail regarding ctDNA in the limited setting of colorectal cancer. The increasing importance and promise of ctDNA remains an area of active research, and further prospective studies may enhance the clinical utility of ctDNA in the future.