Circulating Tumor DNA Biomarkers for Early Detection of Oligometastasis

Tumor heterogeneity and clinically invisible micrometastases in metastatic breast cancer-a call for enhanced surveillance strategies

The biology of metastatic breast cancer (MBC) is understudied, primarily due to the difficulty of procuring multiple samples from patients with oligometastatic breast cancer. We developed a rapid postmortem tissue procurement program that allows the collection and analysis of numerous metastatic lesions, subclinical locations, and potential pre-metastatic niches that fall within this scope. We conducted a rapid postmortem tissue collection study on 9 patients with MBC. Patients and their families consented to donate tissues immediately after death in an IRB-approved study. Various disease subtypes, progression histories, organ involvement, and final causes of death are reported. In patients with hormone receptor-positive (HR+) disease, estrogen receptor (ER), progesterone receptor (PR), HER2, and Ki-67 expression were heterogeneous across metastatic lesions within individual patients. Disease phenotype at the end of life trended toward complete loss of HR expression. Nearly all (n = 7) patients exhibited extensive tumor involvement of additional organs that had not been previously diagnosed clinically and were not retrospectively visible on recent imaging. Of these seven individuals, three included organs uncommonly associated with MBC: kidney, spleen, pancreas, and ovary. Finally, we identified clinically undetectable micrometastases in several organs uncommonly involved in MBC. Our findings raise several clinically relevant questions regarding the mechanisms of metastatic progression. Insights from this study argue for better surveillance strategies for monitoring MBC. We highlight the need to capture more accurate biomarker information in the context of heterogeneous disease and urge the consideration of treatment strategies that combine multiple targeted therapies.

Radiotherapy in the management of lung oligometastases

In recent years, the development of both medical imaging and new systemic agents (targeted therapy and immunotherapy) have revolutionized the field of oncology, leading to a new entity: oligometastatic disease. Adding local treatment of oligometastases to systemic treatment could lead to prolonged survival with no significant impact on quality of life. Given the high prevalence of lung oligometastases and the new systemic agents coming with increased pulmonary toxicity, this article provides a comprehensive review of the current state-of-art for radiotherapy of lung oligometastases. After reviewing pretreatment workup, the authors define several radiotherapy regimen based on the localization and size of the oligometastases. A comment on the synergistic combination of medical treatment and radiotherapy is also made, projecting on future steps in this specific clinical setting.

Node Oligorecurrence in Prostate Cancer: A Challenge

Within the oligometastatic state, oligorecurrent lymph node disease in prostate cancer represents an interesting clinical entity characterized by a relatively indolent biology that makes it unique: it can be treated radically, and its treatment is usually associated with a long period of control and excellent survival. Additionally, it is an emergent situation that we are facing more frequently mainly due to (a) the incorporation into clinical practice of the PSMA-PET that provides strikingly increased superior images in comparison to conventional imaging, with higher sensitivity and specificity; (b) the higher detection rates of bone and node disease with extremely low levels of PSA; and (c) the availability of high-precision technology in radiotherapy treatments with the incorporation of stereotaxic body radiotherapy (SBRT) or stereotaxic ablative radiotherapy (SABR) technology that allows the safe administration of high doses of radiation in a very limited number of fractions with low toxicity and excellent tolerance. This approach of new image-guided patient management is compelling for doctors and patients since it can potentially contribute to improving the clinical outcome. In this work, we discuss the available evidence, areas of debate, and potential future directions concerning the utilization of new imaging-guided SBRT for the treatment of nodal recurrence in prostate cancer.

Emerging Roles of Circulating Tumor DNA for Increased Precision and Personalization in Radiation Oncology

Recent breakthroughs in circulating tumor DNA (ctDNA) technologies present a compelling opportunity to combine this emerging liquid biopsy approach with the field of radiogenomics, the study of how tumor genomics correlate with radiotherapy response and radiotoxicity. Canonically, ctDNA levels reflect metastatic tumor burden, although newer ultrasensitive technologies can be used after curative-intent radiotherapy of localized disease to assess ctDNA for minimal residual disease (MRD) detection or for post-treatment surveillance. Furthermore, several studies have demonstrated the potential utility of ctDNA analysis across various cancer types managed with radiotherapy or chemoradiotherapy, including sarcoma and cancers of the head and neck, lung, colon, rectum, bladder, and prostate . Additionally, because peripheral blood mononuclear cells are routinely collected alongside ctDNA to filter out mutations associated with clonal hematopoiesis, these cells are also available for single nucleotide polymorphism analysis and could potentially be used to detect patients at high risk for radiotoxicity. Lastly, future ctDNA assays will be utilized to better assess locoregional MRD in order to more precisely guide adjuvant radiotherapy after surgery in cases of localized disease, and guide ablative radiotherapy in cases of oligometastatic disease.

Imaging-based prevalence of oligometastatic disease: A single-center cross-sectional study

INTRODUCTION AND BACKGROUND

Oligometastatic disease refers to a distinct state in cancer patients characterized by a low metastatic burden, with diagnosis being defined by a limited number of distant metastases in radiological imaging. However, oligometastasis remains poorly understood in terms of its biology and prevalence in the metastatic cascade. In the absence of clinically viable molecular biomarkers, this study examined the prevalence of oligometastasis using oncological imaging.

MATERIALS AND METHODS

This study is based on all consecutive FDG- and PSMA-PET scans conducted at our cancer center between January and December 2020. We identified and analyzed all PET scans from patients with maximum five distant metastases from a solid malignancy and also reviewed concurrent cMRI imaging in all candidate patients. Data on number and site of metastases were extracted from the imaging reports and verified on imaging studies in case of uncertainties.

RESULTS

In total, 7,000 PET scans were analyzed, 1,155 of which were performed in unique metastatic patients, and 637 patients showed extra-cranial oligometastatic disease (55%). Concurrent cMRI scans were available for 20% (130/637) of extracranial oligometastatic patients, 36 of which proved to be polymetastatic after combined PET and cMRI analysis. Prevalence of oligometastatic disease was influenced by primary tumor histology and most frequent in pancreatic, liver and gallbladders cancers (59%), and least frequent in cancer of unknown primary (26%). In 72% of oligometastatic cases, only one or two metastases were detected. Bone/soft tissue metastases were the most common sites of distant metastasis (41%). About three quarters of patients had metachronous oligometastatic disease.

DISCUSSION AND CONCLUSION

Our analysis suggests that about half of metastatic cancer patients are characterized by a limited tumor burden detectable on PET and cMRI imaging. This finding warrants intensified research efforts to better understand the biology of oligometastatic disease and to optimize multidisciplinary treatment strategies.

Steering decision making by terminology: oligometastatic versus argometastatic

Allowing selected patients with few distant metastases to undergo potentially curative local ablation, the designation “oligometastatic” has become a widely popular concept in oncology. However, accumulating evidence suggests that many of these patients harbour an unrecognised microscopic disease, leading either to the continuous development of new metastases or to an overt polymetastatic state and questioning thus an indiscriminate use of potentially harmful local ablation. In this paper, reviewing data on oligometastatic disease, we advocate the importance of identifying a true oligometastatic disease, characterised by a slow speed of development, instead of relying solely on a low number of lesions as the term “oligometastatic” implies. This is particularly relevant in clinical practice, where terminology has been shown to influence decision making. To define a true oligometastatic disease in the context of its still elusive biology and interaction with the immune system, we propose using clinical criteria. As discussed further in the paper, these criteria can be classified into three categories involving a low probability of occult metastases, low tumour growth rate and low tumour burden. Such cases with slow tumour-cell shedding and slow proliferation leave a sufficiently broad window-of-opportunity to detect and treat accessible lesions, increasing thus the odds of a cure.

Peptide nano-blanket impedes fibroblasts activation and subsequent formation of pre-metastatic niche

There is evidence to suggest that the primary tumor induces the formation of a pre-metastatic niche in distal organs by stimulating the production of pro-metastatic factors. Given the fundamental role of the pre-metastatic niche in the development of metastases, interruption of its formation would be a promising strategy to take early action against tumor metastasis. Here we report an enzyme-activated assembled peptide FR17 that can serve as a “flame-retarding blanket” in the pre-metastatic niche specifically to extinguish the “fire” of tumor-supportive microenvironment adaption. We show that the in-situ assembled peptide nano-blanket inhibits fibroblasts activation, suppressing the remodeling of the metastasis-supportive host stromal tissue, and reversing vascular destabilization and angiogenesis. Furthermore, we demonstrate that the nano-blanket prevents the recruitment of myeloid cells to the pre-metastatic niche, regulating the immune-suppressive microenvironment. We show that FR17 administration effectively inhibits the formation of the pulmonary pre-metastatic niche and postoperative metastasis, offering a therapeutic strategy against pre-metastatic niche formation.

Primary tumors “spread the spark” by establishing a pre-metastatic niche. Here the authors develop an in-situ assembled peptide FR17 to serve as a “flame-retarding blanket” to extinguish the “fire” of the pre-metastatic microenvironment.

The Road to Dissemination: The Concept of Oligometastases and the Barriers for Widespread Disease

Simple Summary

Oligometastatic disease is an intermediate state of metastatic dissemination with a limited number of metastatic sites and extent of disease. Tumor cells need multiple capabilities in order to migrate, survive and evolve to macroscopic metastases. These capabilities are acquired by evolutionary mechanisms and are associated with several clinical factors and biomarkers. Better understanding of these properties and biomarkers may help to select patients that can benefit from local ablative therapies, which have shown to be a promising approach in recent clinical evidence.

Abstract

Over the last years, the oligometastatic disease state has gained more and more interest, and randomized trials are now suggesting an added value of stereotactic radiotherapy on all macroscopic disease in oligometastatic patients; but what barriers could impede widespread disease in some patients? In this review, we first discuss the concept of oligometastatic disease and some examples of clinical evidence. We then explore the route to dissemination: the hurdles a tumoral clone has to overtake before it can produce efficient and widespread dissemination. The spectrum theory argues that the range of metastatic patterns encountered in the clinic is the consequence of gradually obtained metastatic abilities of the tumor cells. Tumor clones can obtain these capabilities by Darwinian evolution, hence early in their genetic progression tumors might produce only a limited number of metastases. We illustrate selective dissemination by discussing organ tropism, the preference of different cancer (sub)types to metastasize to certain organs. Finally we discuss biomarkers that may help to distinguish the oligometastatic state.

Serological cancer-associated protein biomarker levels at bowel endoscopy: Increased risk of subsequent primary malignancy

BACKGROUND

It was previously shown in three subpopulations that subjects not identified with colorectal cancer (CRC) at bowel endoscopy, but with increased serological cancer-associated protein biomarker levels had an increased risk of being diagnosed with subsequent malignant diseases.

OBJECTIVE

The aim of the present study was to perform a pooled analysis of subjects from the three subpopulations and subsequently validate the results in an independent study. The study population denoted the training set includes N = 4,076 subjects with symptoms attributable to CRC and the independent validation set N = 3,774 similar subjects.

METHODS

Levels of CEA, CA19-9, TIMP-1 and YKL-40 were determined in blood samples collected prior to diagnostic bowel endoscopy. Follow-up of subjects not diagnosed with CRC at endoscopy, was ten years and identified subjects diagnosed with primary intra- or extra-colonic malignant diseases. The primary analysis was time to a newly diagnosed malignant disease and was analyzed with death as a competing risk in the training set. Subjects with HNPCC or FAP were excluded. The cumulated incidence was estimated for each biomarker and in a multivariate model. The resulting model was then validated on the second study population.

RESULTS

In the training set primary malignancies were identified in 515 (12.6%) of the 4,076 subjects, who had a colorectal endoscopy with non-malignant findings. In detail, 33 subjects were subsequently diagnosed with CRC and 482 subjects with various extra-colonic cancers. Multivariate additive analysis of the dichotomized biomarkers demonstrated that CEA (HR = 1.50, 95% CI:1.21-1.86, p < 0.001), CA19-9 (HR = 1.41, 95% CI:1.10-1.81, p = 0.007) and TIMP-1 (HR = 1.25 95% CI: 1.01-1.54, p = 0.041) were significant predictors of subsequent malignancy. The cumulated incidence at 5 years landmark time was 17% for those subjects with elevated CEA, CA19-9 and TIMP-1 versus 6.7% for those with low levels of all. When the model was applied to the validation set the cumulated 5-year incidence was 10.5% for subjects with elevated CEA, CA19-9 and TIMP-1 and 5.6% for subjects with low levels of all biomarkers. Further analysis demonstrated a significant interaction between TIMP-1 and age in the training set. The age dependency of TIMP-1 indicated a greater risk of malignancy in younger subjects if the biomarker was elevated. This observation was validated in the second set.

CONCLUSION

Elevated cancer-associated protein biomarker levels in subjects with non-malignant findings at large bowel endoscopy identifies subjects at increased risk of being diagnosed with subsequent primary malignancy. CEA, CA19-9 and TIMP-1 were significant predictors of malignant disease in this analysis. TIMP-1 was found dependent on age. The results were validated in an independent symptomatic population.

Detectable Post-operative Circulating Tumor Human Papillomavirus (HPV) DNA And Association with Recurrence in Patients with HPV-Associated Oropharyngeal Squamous Cell Carcinoma

PURPOSE

  To determine the rate of detectability of ctHPVDNA after surgery but before adjuvant therapy in patients with HPV-associated oropharyngeal squamous cell carcinoma (HPV(+)OPSCC) and to investigate whether detectable ctHPVDNA at this time point may be associated with risk of recurrence.

METHODS AND MATERIALS

 Prospectively collected samples from patients with OPSCC were examined in a blinded fashion using a multi-analyte PCR assay. 45 samples were collected from HPV(+)OPSCC patients pre-op (prior to any treatment), and 159 samples post-op (before or at the start of adjuvant RT). Samples were identified via the radiation oncology biobank or via participation in a clinical trial. RT consisted of 60 Gy +/- cisplatin or de-escalation (30 Gy to 36 Gy in 20 b.i.d. fractions + docetaxel). 32 patients had paired samples available pre and post-op for the primary analysis. Additional exploratory analyses including associations of patient and tumor characteristics with recurrence were assessed using Cox proportional hazards models for all 159 post-op samples.. Detectability of ctHPVDNA was compared across groups utilizing logistic regression. Estimates of recurrence free survival (RFS) were made using Kaplan-Meier (KM).

RESULTS

In a paired analysis of 32 pre and post-op timepoints, 94% of patients had detectable ctHPVDNA pre-op and 41% post-op. RFS at 18 months was 83% (95% CI: 47-95%) for patients with detectable post-op ctHPVDNA compared to 100% for patients with undetectable post-op ctHPVDNA (p=.094).In an exploratory analysis of non-paired post-op samples, ctHPVDNA was detectable in 26% (41 of 159) of patients (median of 22 days post-op). Age (1.06, p=0.025), LVSI (OR 3.17, p=0.011) and ENE (OR=5.67, p=0.001) were associated with detectable ctHPVDNA after surgery. Detectable post-op ctHPVDNA was significantly associated with RFS (p<0.001).

CONCLUSION

Amongst patients with detectable pre-op ctHPVDNA, a significant proportion have detectable post-op ctHPVDNA in paired post-op samples, collected prior to the initiation of adjuvant radiation therapy. Future prospective study is warranted to investigate the association of detectable post-op ctHPVDNA with recurrence, including in comparison to established clinical and pathologic risk factors.

Development of a Prognostic Model for Overall Survival in Patients with Extracranial Oligometastatic Disease Treated with Stereotactic Body Radiation Therapy

BACKGROUND

Patients with oligometastatic disease (OMD) may experience durable disease control with ablative therapy to all sites of disease. Stereotactic body radiation therapy (SBRT) is an important modality in the management of OMD patients though a validated prognostic model for OMD patients treated with SBRT is currently lacking. The purpose of this study was to develop a prognostic model for overall survival (OS) in OMD patients treated with SBRT.

METHODS

A multi-institutional database of extracranial OMD patients treated with SBRT was used for model development. The final prognostic model was generated in a training set using recursive partitioning analysis representing 75% of the population. Model performance was evaluated in the reserved test set.

RESULTS

1,033 patients were included in the analysis. The median OS for the entire cohort was 44.2 months (95% confidence interval: 39.2-48.8 months). The variables used in the regression tree, in order of importance, were primary histology, lung-only OMD on presentation, the timing of OMD presentation and age at the start of SBRT. A full 5-category risk stratification system based on the terminal nodes possessed fair to good discriminative power with a Harrell's concordance statistic of 0.683 (0.634-0.731) and time-dependent area under the receiver operating characteristic curve of 0.709 (0706-0.711) in the test set, with good calibration. A simplified risk stratification system consisting of 3 risk categories was also proposed for greater ease-of-use with comparable performance.

CONCLUSION

A clinical prognostic model for OS in patients with extracranial OMD treated with SBRT has been developed and validated.

BC-Monitor: Towards a Routinely Accessible Circulating Tumor DNA-Based Tool for Real-Time Monitoring Breast Cancer Progression and Treatment Effectiveness

Circulating tumor DNA (ctDNA) is increasingly employed in the screening, follow-up, and monitoring of the continuously evolving tumor; however, most ctDNA assays validated for clinical use cannot maintain the right balance between sensitivity, coverage, sample requirements, time, and cost. Here, we report our BC-monitor, a simple, well-balanced ctDNA diagnostic approach using a gene panel significant in breast cancer and an optimized multiplex PCR-based NGS protocol capable of identifying allele variant frequencies below 1% in cell-free plasma DNA. We monitored a cohort of 45 breast cancer patients prospectively enrolled into our study receiving neoadjuvant chemotherapy or endocrine therapy or palliative therapy for metastatic diseases. Their tumor mutation status was examined in the archived tumor samples and plasma samples collected before and continuously during therapy. Traceable mutations of the used 38-plex NGS assay were found in approximately two-thirds of the patients. Importantly, we detected new pathogenic variants in follow-up plasma samples that were not detected in the primary tumor and baseline plasma samples. We proved that the BC-monitor can pre-indicate disease progression four-six months earlier than conventional methods. Our study highlights the need for well-designed ctDNA monitoring during treatment and follow-up, integrated into a real-time treatment assessment, which could provide information on the active tumor DNA released into the blood.

Role of 18F-Fluciclovine and Prostate-Specific Membrane Antigen PET/CT in Guiding Management of Oligometastatic Prostate Cancer: AJR Expert Panel Narrative Review

Twenty-five years ago, oligometastatic disease was proposed as an intermediary clinical state of cancer with unique implications for therapies that may impact cancer evolution and patient outcome. Identification of limited metastases that are potentially amenable to targeted therapies fundamentally depends on the sensitivity of diagnostic tools, including new-generation imaging methods. For men with biochemical recurrence after definitive therapy of the primary prostate cancer, PET/CT using either the FDA-approved radiolabeled amino acid analogue ¹⁸F-fluciclovine or investigational radiolabeled agents targeting prostate-specific membrane antigen (PSMA) enables identification of early metastases at lower serum PSA levels than was previously feasible using conventional imaging. Evidence supports PSMA PET/CT as the most sensitive imaging modality available for identifying disease sites in oligometastatic prostate cancer. PSMA PET/CT will likely become the modality of choice after regulatory approval and will drive the development of trials of emerging metastasis-directed therapies such as stereotactic ablative body radiation and radioguided surgery. Indeed, numerous ongoing or planned clinical trials are studying advances in management of oligometastatic prostate cancer based on this heightened diagnostic capacity. In this rapidly evolving clinical environment, radiologists and nuclear medicine physicians will play major roles in facilitating clinical decision making and management of patients with oligometastatic prostate cancer.