Circulating tumor DNA-based molecular residual disease detection for treatment monitoring in advanced melanoma patients.

BACKGROUND: Immune checkpoint inhibitors (ICIs) have substantially improved overall survival in patients with advanced melanoma; however, the lack of biomarkers to monitor treatment response and relapse remains an important clinical challenge. Thus, a reliable biomarker is needed that can risk-stratify patients for disease recurrence and predict response to treatment. METHODS: A retrospective analysis using a personalized, tumor-informed circulating tumor DNA (ctDNA) assay on prospectively collected plasma samples (n = 555) from 69 patients with advanced melanoma was performed. Patients were divided into three cohorts: cohort A (N = 30), stage III patients receiving adjuvant ICI/observation; cohort B (N = 29), unresectable stage III/IV patients receiving ICI therapy; and cohort C (N = 10), stage III/IV patients on surveillance after planned completion of ICI therapy for metastatic disease. RESULTS: In cohort A, compared to molecular residual disease (MRD)-negative patients, MRD-positivity was associated with significantly shorter distant metastasis-free survival (DMFS; hazard ratio [HR], 10.77; p = .01). Increasing ctDNA levels from the post-surgical or pre-treatment time point to after 6 weeks of ICI were predictive of shorter DMFS in cohort A (HR, 34.54; p < .0001) and shorter progression-free survival (PFS) in cohort B (HR, 22; p = .006). In cohort C, all ctDNA-negative patients remained progression-free for a median follow-up of 14.67 months, whereas ctDNA-positive patients experienced disease progression. CONCLUSION: Personalized and tumor-informed longitudinal ctDNA monitoring is a valuable prognostic and predictive tool that may be used throughout the clinical course of patients with advanced melanoma.

Circulating tumor DNA (ctDNA) serial analysis during progression on PD-1 blockade and later CTLA-4 rescue in patients with mismatch repair deficient metastatic colorectal cancer.

Immune checkpoint inhibitors have shown great promise in treating patients with mismatch repair deficient/microsatellite instability high (dMMR/MSI-H) colorectal cancer (CRC). Although single-agent pembrolizumab has been approved for first-line treatment of dMMR/MSI-H metastatic CRC, combination therapy with cytotoxic T-lymphocyte-associated protein-4 (CTLA-4) inhibition (ipilimumab/nivolumab) has reported higher response rates. It is unclear whether patients who progress on PD-1 inhibition will respond to CTLA-4 blockade. Here, we report a case series of three patients with dMMR/MSI-H mCRC, where a durable and ongoing response to nivolumab with ipilimumab was achieved after initial progression with pembrolizumab monotherapy. Blood-based biomarkers such as carcinoembryonic antigen and CA 19-9 were employed to assess treatment response and monitor disease progression along with circulating tumor DNA (ctDNA). Our findings indicate ctDNA's potential to accurately monitor response to therapy and detect disease progression, as validated by standard imaging. This case series demonstrates that CTLA-4 rescue is worthy of additional investigation as a treatment strategy after progression on PD-1 blockade in patients with dMMR/MSI-high mCRC. Our data support the utilization and expansion of clinical studies with combination therapies and using ctDNA kinetics as early dynamic marker for therapy response assessment.

The Utility of Circulating Tumor DNA (ctDNA) Monitoring in Cancer Patients Who Are Pregnant or Planning to Become Pregnant.

The number of pregnant women with cancer is on the rise. These patients and their providers encounter complex medical management decisions. Standard-of-care systemic therapy and radiological imaging can impair fetal development and affect viability. Conversely, insufficient monitoring and treatment can lead to cancer progression, compromising the health of the patient. Personalized and tumor-informed circulating tumor DNA (ctDNA) testing (Signatera™, bespoke mPCR NGS assay) is a validated, noninvasive blood test that can accurately assess cancer progression and tumor response to treatment ahead of radiological imaging, across solid tumors. In this case series of four patients, we explore the clinical utility of longitudinal ctDNA testing in the medical management of pregnant patients with solid tumors, to aid in informed decision-making for patients and providers.

ctDNA Clearance and Radiographic Resolution of Disease in Response to Dual Checkpoint Inhibition in Metastatic Microsatellite Stable Colorectal Cancer with a High Tumor Mutation Burden.

Immunotherapy (IO) has increasingly been demonstrated to provide therapeutic benefit to patients with metastatic colorectal cancer (mCRC). However, only a subset of mCRC tumors respond to IO. Monitoring response with tumor biomarkers like carcinoembryonic antigen (CEA) has been challenging in patients with microsatellite stable (MSS) mCRC due to low expression of CEA (CEA/lo). Noninvasive blood-based biomarkers such as circulating tumor DNA (ctDNA) can inform early treatment response and augment radiographic monitoring. We describe a case study of a patient with chemotherapy-refractory CEA/lo MSS mCRC, with metastatic disease present in a cardiophrenic lymph node. The patient was given 2 cycles of combination IO (ipilimumab/nivolumab). Response was monitored by ctDNA using a multiplex PCR next-generation sequencing assay, CEA, and CT scan. After IO administration, ctDNA levels rapidly declined, becoming undetectable. This was concurrent with radiographic resolution of the lymph node metastasis. Serial monitoring of CEA during this same period was uninformative, with no significant changes observed. Significant decline in ctDNA identified metastatic response to IO in a patient with CEA/lo, MSS mCRC and was concurrently validated by CT scan. This case study provides evidence that ctDNA can be used as a prospective surrogate for radiographic tumor response.

Early Detection of Circulating Tumor DNA Postoperatively Enables Discovery of Resectable Metastatic Disease in a Patient with Colon Cancer.

Currently, serum carcinoembryonic agent (CEA) along with contrast-enhanced imaging and colonoscopy are used for evaluation of recurrence of colorectal cancer. However, CEA is an unreliable and nonspecific biomarker that may fail to rise and signal relapse. Analysis of circulating tumor DNA (ctDNA) in patients offers a minimally invasive method to assess risk of relapse several months ahead of conventional clinical means. Here, we report the case of a colon adenocarcinoma with postoperative liver metastasis diagnosed early by ctDNA measurement, using a personalized NGS-mPCR assay. While ctDNA levels continued to rise, CEA levels tested negative. Metastatic relapse to the liver was promptly confirmed by PET/CT scan. The patient underwent a successful metastasectomy with curative intent. Following surgery, the patient exhibited no evidence of disease and ctDNA levels remained negative. Our case report suggests that the early detection of postoperative molecular residual disease by means of ctDNA measurement can accurately predict mCRC relapse in cases where CEA levels fail to increase. Close monitoring of ctDNA levels during the postoperative period can allow for earlier intervention and more favorable outcomes in relapsing mCRC patients.