Insufficient Tissue Research Articles

Image-guided stent-directed irreversible electroporation for circumferential ablation in the rat esophagus.

Background: Irreversible electroporation (IRE) has been investigated in the alimentary tract; however, the lack of dedicated electrodes and insufficient tissue responses made its application limited. The aim of this study was to investigate the efficacy and safety of image-guided stent-directed IRE in the rat esophagus. Methods: The bipolar self-expandable electrode (SE) was developed using the braiding technique. A finite element analysis was performed to validate optimal electrical field strength for the rat esophagus. A total of 40 out of 50 rats received stent-directed IRE and were sacrificed at 10h, 3days, 7days, and 28days of 10 each. The remaining ten rats underwent a sham procedure. The outcomes of stent-directed IRE were assessed by esophagography and histological responses. Results: Stent-directed IRE was technically successful in all rats with mild muscle contraction. The heart rate dropped immediately and gradually recovered at 180s. TUNEL and caspase-3 with submucosal thickness significantly increased at 10h and Day 3 compared with those of the sham control (all p < 0.001). The thickness of epithelial layers with collagen deposition significantly decreased at 10h and Day 3 (all p < 0.001), however, increased at Day 7 compared with that of the sham control (all p < 0.05). The Ki67-positive deposition significantly increased at Day 3 and 7 compared with that of the sham control (all p < 0.001). All variables were similar to those of the sham control at Day 28. Conclusion: Image-guided stent-directed IRE was effective and safe in the rat esophagus. It seems to have effectively and evenly induced cell death and gradually recovered with cellular regeneration.

CTNI-42. GENOME-WIDE DNA METHYLATION PATTERNS IN VERTU: A RANDOMIZED PHASE II TRIAL OF VELIPARIB, RADIOTHERAPY AND TEMOZOLOMIDE IN PATIENTS WITH MGMT-UNMETHYLATED GLIOBLASTOMA

Abstract BACKGROUND VERTU was a randomized phase II trial evaluating veliparib, a brain-penetrant PARP inhibitor, combined with radiotherapy and temozolomide, for patients with newly diagnosed MGMT-unmethylated glioblastoma. As part of planned correlative work after study completion, we assessed genome-wide DNA methylation patterns to predict methylation class, glioblastoma subtype and MGMT status. METHODS Patients were randomized 2:1 to experimental (60Gy/30 fractions with veliparib 200mg bid, then temozolomide 150-200mg/m2 D1-5 + veliparib 40mg bid D1-7 Q28D for 6 cycles) versus standard arm (60Gy/30 fractions with temozolomide 75mg/m2 daily, then temozolomide 150-200mg/m2 D1-5 Q28D for 6 cycles). The primary objective to improve 6-month progression-free survival (PFS-6m) was not met (doi: 10.1093/neuonc/noab111). Methylation data were generated using the Illumina Infinium Methylation EPIC bead chip array. Tumor tissues were categorized using the Heidelberg methylation-based classifier. RESULTS Methylation data were successfully generated for 98/125 patients (poor quality DNA [n = 12], no consent [n = 11], insufficient tissue [n = 4]). Those with classifier scores below 0.5 (n = 25), tumor microenvironment only (n = 6) and rediagnosis as pleomorphic xanthoastrocytoma (n = 1) were excluded, leaving n = 66. Methylation classes were GBM RTK II (n = 23, PFS-6m 43% [95%CI 23-62]), RTK I (n = 20, PFS-6m 50% [95%CI 27-69]), MES (n = 20, PFS-6m 40% [95%CI 19-60]), MID (n = 2) and G34 (n = 1). Glioblastoma subtypes were mesenchymal (n = 28, PFS-6m 50% [95%CI 30-66]), proneural (n = 24, PFS-6m 50% [95%CI 29-68]) and classical (n = 14, PFS-6m 36% [95%CI 13-59]). MGMT status were unmethylated (n = 58, PFS-6m 48% [95%CI 35-60]) and methylated (n = 8, PFS-6m 38% [95%CI 9-67]). There was no evidence of interaction between treatment arm and methylation class (excluding GBM MID and G34, P = 0.45), glioblastoma subtype (P = 0.68) or MGMT status (P = 0.52). CONCLUSIONS Genome-wide DNA methylation patterns in VERTU identified a spectrum of methylation-defined subgroups, reflecting tumoral heterogeneity. This may have utility for future clinical trials and practice. The effect of veliparib in VERTU appeared to be consistent across subgroups. ACTRN12615000407594.

Preliminary Experience of Liquid Biopsy in Lung Cancer Compared to Conventional Assessment: Light and Shadows.

To assess the qualitative relationship between liquid biopsy and conventional tissue biopsy. As a secondary target, we evaluated the relationship between the liquid biopsy results and the T stage, N stage, M stage, and compared to grading. The Local Ethics Committee of the "Università degli Studi della Campania Luigi Vanvitelli", with the internal resolution number 24997/2020 of 12.11.2020, approved this spontaneous prospective study. According to the approved protocol, patients with lung cancer who underwent Fine-Needle Aspiration Cytology (FNAC), CT-guided biopsy, and liquid biopsy were enrolled. A Yates chi-square test was employed to analyze differences in percentage values of categorical variables. A p-value &lt; 0.05 was considered statistically significant. Data analysis was performed using the Matlab Statistic Toolbox (The MathWorks, Inc., Natick, MA, USA). When a genetic mutation is present on the pathological examination, this was also detected on the liquid biopsy. ROS1 and PDL1 mutations were found in 2/29 patients, while EGFR Exon 21 was identified in a single patient. At liquid biopsy, 26 mutations were identified in the analyzed samples. The mutations with the highest prevalence rate in the study populations were: ALK (Ile1461Val), found in 28/29 patients (96.6%), EML4 (Lys398Arg), identified in 16/29 (55.2%) patients, ALK (Asp1529Glu), found in 14/29 (48.3%) patients, EGFR (Arg521Lys), found in 12/29 (41.4%) patients, ROS (Lys2228Gln), identified in 11/29 (37.9%) patients, ROS (Arg167Gln) and ROS (Ser2229Cys), identified in 10/29 (34.5%) patients, ALK (Lys1491Arg) and PIK3CA (Ile391Met), identified in 8/29 (27.6%) patients, ROS (Thr145Pro), identified in 6/29 (20.7%) patients, and ROS (Ser1109Leu), identified in 4/29 (13.8%) patients. No statistically significant differences can be observed in the mutation rate between the adenocarcinoma population and the squamous carcinoma population (p &gt; 0.05, Yates chi-square test). We showed that, when a genetic mutation was detected in pathological examination, this was always detected by liquid biopsy, demonstrating a very high concordance rate of genomic testing between tissues and their corresponding mutations obtained by liquid biopsy, without cases of false-negative results. In addition, in our study, liquid biopsy highlighted 26 mutations, with the prevalence of ALK mutation in 96.6% of patients, supporting the idea that this approach could be an effective tool in cases with insufficient tumor tissue specimens or in cases where tissue specimens are not obtainable.

Implementation Challenges and Disparities in Molecular Testing for Patients With Stage IV NSCLC: Perspectives from an Urban Safety-Net Hospital

The advent of next-generation sequencing (NGS), including both tissue assays and circulating tumor DNA (ct-DNA), has been pivotal in improving outcomes for patients with non-small cell lung cancer (NSCLC). Although molecular testing is standard of care for advanced NSCLC, challenges still exist in its implementation. This Perspective examines barriers to the widespread implementation of NGS from the vantage point of a single urban safety-net institution, with a particular focus on examining racial disparities in NGS completion. We conducted a review of patients at our institution from January 2015 through January 2022 and examined molecular testing patterns before and after the publication of updated molecular testing guidelines from the International Association for the Study of Lung Cancer (IASLC), Association for Molecular Pathology (AMP), and College of American Pathologists (CAP) in March of 2018. While NGS increased over time, we found that 43% of patients in the March 2018 through January 2022 group still did not receive NGS, and the most common reasons for the absence of testing included a lack of physician ordering and insufficient tissue on biopsy. We did not note any racial disparities in completion or time-to-adoption of NGS. Patients with squamous cell carcinoma (SCC) histology were noted to receive liquid NGS markedly less often than patients with non-squamous histology in the March 2018 through January 2022 period. Based on our own data and a review of findings from colleagues in the field, we advocate for additional physician educational programming, increased use of ct-DNA biopsy, automated (reflexive) NGS tissue testing on receipt of biopsy, and consideration for the broader molecular profiling of patients with SCC histology.

T cell aging as a risk factor for autoimmunity

Immune aging is a complex process rendering the host susceptible to cancer, infection, and insufficient tissue repair. Many autoimmune diseases preferentially occur during the second half of life, counterintuitive to the concept of excess adaptive immunity driving immune-mediated tissue damage. T cells are particularly susceptible to aging-imposed changes, as they are under extreme proliferative pressure to fulfill the demands of clonal expansion and of homeostatic T cell repopulation. T cells in older adults have a footprint of genetic and epigenetic changes, lack mitochondrial fitness, and fail to maintain proteostasis, diverging them from host protection to host injury. Here, we review recent progress in understanding how the human T-cell system ages and the evidence detailing how T cell aging contributes to autoimmune conditions. T cell aging is now recognized as a risk determinant in two prototypic autoimmune syndromes; rheumatoid arthritis and giant cell arteritis. The emerging concept adds susceptibility to autoimmune and autoinflammatory disease to the spectrum of aging-imposed adaptations and opens new opportunities for immunomodulatory therapy by restoring the functional intactness of aging T cells.

MR-CT multi-atlas registration guided by fully automated brain structure segmentation with CNNs

PurposeComputed tomography (CT) is widely used to identify anomalies in brain tissues because their localization is important for diagnosis and therapy planning. Due to the insufficient soft tissue contrast of CT, the division of the brain into anatomical meaningful regions is challenging and is commonly done with magnetic resonance imaging (MRI).MethodsWe propose a multi-atlas registration approach to propagate anatomical information from a standard MRI brain atlas to CT scans. This translation will enable a detailed automated reporting of brain CT exams. We utilize masks of the lateral ventricles and the brain volume of CT images as adjuvant input to guide the registration process. Besides using manual annotations to test the registration in a first step, we then verify that convolutional neural networks (CNNs) are a reliable solution for automatically segmenting structures to enhance the registration process.ResultsThe registration method obtains mean Dice values of 0.92 and 0.99 in brain ventricles and parenchyma on 22 healthy test cases when using manually segmented structures as guidance. When guiding with automatically segmented structures, the mean Dice values are 0.87 and 0.98, respectively.ConclusionOur registration approach is a fully automated solution to register MRI atlas images to CT scans and thus obtain detailed anatomical information. The proposed CNN segmentation method can be used to obtain masks of ventricles and brain volume which guide the registration.

Comparative characteristics of different methods of radiofrequency catheter ablation in atrial flutter

Catheter ablation occupies the first place in the treatment of atrial macro reentry arrhythmias. The main controllable parameters in ablations are energy, duration of exposure and use of catheter tip cooling. With traditional ablation techniques, there is a high risk of insufficient tissue damage due to electrode instability. Regarding the issue of stability, a new technique was proposed – reducing the application time with increasing the energy. The aim of this work was to compare the results of radiofrequency catheter ablation (RFA) using an 8 mm uncooled electrode to a 4 mm cooled electrode and a 4 mm cooled electrode with increased energy. Materials and methods. The work is based on a retrospective analysis of the results of catheter ablations in patients with atrial flutter. Patients were divided into 3 groups depending on the parameters of the used radio frequency energy and the type of ablation electrode. Results. It was found that in the group with increased energy, there were the shortest time from the start of RFA to the achievement of success criteria and the lowest radiation exposure. The obtained differences were statistically significant in comparison with two groups of patients who underwent traditional methods. Such differences were associated both with a reduction in the time of the application itself due to the use of high energy as well as the need to apply a smaller number of applications owing to a lower probability of the electrode displacement from the target area. Conclusions. The use of a high-energy protocol allows to success criteria for cavo-tricuspid isthmus ablation more quickly compared to traditional techniques (by 30 % and 22 %, respectively) with less radiation exposure (by 27 % and 24 %, respectively). The use of the high-energy protocol does not lead to an increase in the frequency of complications and can be considered safe for clinical use.

Comparison of dosimetry with magnetic resonance and computed tomography imaging delineation of surgical bed volume in breast cancer irradiation

BackgroundPostoperative radiotherapy after conservative surgery for patients with breast cancer usually includes focal over-irradiation (boost) to the surgical bed (SB). Irradiation planning using computed tomography (CT) is difficult in many cases because of insufficient intrinsic soft tissue contrast. To ensure appropriate radiation to the tumor, large boost volumes are delineated, resulting in a higher dose to the normal tissue. Magnetic resonance imaging (MRI) provides superior soft tissue contrast than CT and can better differentiate between normal tissue and the SB. However, for SB delineation CT images alone remain the pathway followed in patients undergoing breast irradiation. This study aimed to evaluate the potential advantages in boost dosimetry by using MRI and CT as pre-treatment imaging. MethodsEighteen boost volumes were drawn on CT and MRI and elastically co-registered using commercial image registration software. The radiotherapy treatment plan was optimized using the CT volumes as the baseline. The dose distributions of the target volumes on CT and MRI were compared using dose-volume histogram cutoff points. ResultsThe radiation volumes to the SB varied considerably between CT and MRI (conformity index between 0.24 and 0.67). The differences between the MRI and CT boost doses in terms of the volume receiving 98% of the prescribed dose (V98%) varied between 10% and 30%. Smaller differences in the V98% were observed when the boost volumes were delineated using MRI. ConclusionUsing MRI to delineate the volume of the SB may increase the accuracy of boost dosimetry.

Oxygen-supplied electrotherapy for enhanced photodynamic synergistic therapy overcomes hypoxia tumor microenvironment

Abstract Photodynamic therapy (PDT) has lately been identified as a promising anticancer method and gained tremendous interest due to its controllability, non-invasive nature, and negligible side effects. Nevertheless, the development of PDT is hampered by two factors. One is the insufficient tissue penetration of phototherapy laser, resulting in restricted treatment sites. Another one is the substantial dependence of reactive oxygen species (ROS) formation on oxygen concentration. Therefore, a strategy to promote ROS generation by overcoming the hypoxia microenvironment is critical to cancer therapy. Electrolysis of water is known to be a rapid and relatively secure method for producing oxygen. Thus, in this study, electrotherapy was introduced to alleviate the tumor hypoxia by producing oxygen in situ, hence boosting the PDT efficacy, namely E-PDT. Black phosphorus (BP) based nanomaterials were selected as clearable photosensitizers with outstanding PDT performance. Experiments conducted both in vitro and in vivo indicated that E-PDT performed superior therapeutic effects with the in situ generation of oxygen by electrotherapy compared with other groups. This work suggests a promising strategy for phototherapeutic anticancer efficiency enhancement.

Assessment of BRAF V600E (VE1) immunochemistry for the detection of BRAF V600E mutation in non-small cell lung carcinoma cytology specimens.

Non-small cell lung carcinoma (NSCLC) patients with BRAF V600E-mutated tumors respond to targeted therapy. Testing for BRAF V600E is commonly performed with molecular methods; however, a mutation-specific VE1 antibody clone can provide an alternative testing option using immunohistochemistry (IHC)for practices using single-gene testing and in situations when the specimen is inadequate for molecular testing. This study evaluates the usefulness of VE1 IHC in screening for BRAF V600E mutations in NSCLC cytology specimens. The authors retrospectively identified cytology cases with a diagnosis of NSCLC that had BRAF V600E IHC performed on cell block sections with the monoclonal VE1 antibody clone. The BRAF V600E IHC results were compared with those of molecular testing performed with an amplicon-based next-generation sequencing assay. There were 201 NSCLC cases evaluated. The VE1 IHC was positive in seven of seven BRAF V600E-mutated tumors (100%) and was negative in 158 of 158 nonmutated BRAF V600E tumors (100%). Thirty cases did not undergo molecular testing, primarily because of insufficient tissue or because molecular testing was performed on an alternative specimen. Six cases showed equivocal weak/focal staining: Two cases demonstrated BRAF V600E mutations, and four cases were negative by molecular testing. This study suggests that BRAF V600E IHC can be used reliably to screen NSCLC cytology specimens, and negative results strongly indicate the absence of a BRAF V600E mutation. Having a low threshold for equivocal staining is recommended with molecular confirmation of BRAF V600E for any cases demonstrating weak and/or focal cytoplasmic staining.

The Lumbar Artery Perforator Flap in Breast Reconstruction.

The lumbar artery perforator flap is a valuable alternative in breast reconstruction whenever the deep inferior epigastric perforator flap is not feasible because of insufficient or unavailable abdominal tissue. The advantage is the ideal shape and consistency of the flap, in addition to the option to perform a nerve anastomosis with the cluneal nerve. The anatomy is consistent, but there are some technical issues related to the short perforator and difficult surgical exposure in the lower back region. The inclusion of a vascular interposition graft improved the authors' results and facilitated their technical challenges and final inset of the flap. These videos guide the surgeon through the different steps involved in a breast reconstruction with the lumbar artery perforator flap.

147TiP Exactis-01 - Clinical utility of returning liquid biopsy NGS results in NSCL cancer patients: A Canadian trial through the Exactis Network

Biopsy tissue analysis is central for therapeutic decision-making in the era of precision oncology. Insufficient tumor tissue and incomplete genotyping, which prevents access to targeted therapies, are considerable challenges in lung cancer patients. Liquid biopsies, a non-invasive alternative to tissue, offer more accurate capture of tumor heterogeneity and greater flexibility for real-time disease monitoring at significantly reduced cost and risk to patients. Early evidence suggests that liquid biopsies can detect actionable biomarkers in non-small cell lung cancer (NSCLC).

S131 Clinical Application of Circulating Tumor DNA in Gastrointestinal Cancer Patients

Introduction: Circulating tumor DNA (ctDNA) derived from apoptotic tumor cells is rapidly emerging as a non-invasive biomarker to detect the presence of tumor at a molecular level and guide therapy. In this study, we present our experience with this novel marker in gastrointestinal malignancy (GIM) patients. Methods: We included all patients with GIM for whom ctDNA was ordered from January 2020 to July 2021 at our center. Patient demographics, tumor type, pathology, stage, and radiographic findings were collected. Descriptive statistics were employed to report findings. Results: We identified 62 GIM patients for whom ctDNA was ordered. Results for 6 patients were not reported due to insufficient tumor tissue. Of the 56 patients for whom ctDNA results were available, 46 (82%) had colorectal adenocarcinoma (CRC) and the rest had other GI malignancies. Of the overall cohort of 56 evaluable patients, 21 (37.5%) had metastatic disease. Imaging findings paralleled ctDNA levels and correlated with tumor burden in 30 patients (53.5%). In 13 patients (23.2%), undetectable CT DNA levels influenced decisions regarding systemic therapy in addition to acting as a surrogate for treatment response. We discontinued maintenance therapy in 5 metastatic CRC patients with negative ctDNA and imaging. These patients have been off treatment for > 12 months without evidence of recurrence. We also truncated or skipped adjuvant treatment in 6 Stage III CRC patients with negative ctDNA and imaging who had significant post-operative complications or were otherwise considered high risk for severe toxicity. In one CRC patient, ctDNA was found to be undetectable post neoadjuvant therapy which corroborated with pathological complete response on surgical pathology report. 5 patients (9.09 %) had false-negative results and 1 patient had falsely elevated levels. In 6 other patients, we could not draw significant conclusions due to the availability of only a single value. Conclusion: Our experience suggests that ctDNA is not only a sensitive tool to assess tumor burden, but can also help guide therapy in locally advanced and metastatic CRC patients. However, further prospective studies are needed to improve the accuracy of test results and integrate ctDNA in day-to-day clinical practice.

Analysis of BRCA2 Copy Number Loss and Genomic Instability in Circulating Tumor Cells from Patients with Metastatic Castration-resistant Prostate Cancer

BackgroundBRCA2 alterations predict for a response to poly-ADP-ribose polymerase inhibition in metastatic castration-resistant prostate cancer (mCRPC). However, detection is hindered by insufficient tumor tissue and low sensitivity of cell-free DNA for detecting copy number loss. ObjectiveTo evaluate the BRCA2 loss detection using single-cell, shallow whole-genome sequencing (sWGS) of circulating tumor cells (CTCs) in patients with mCRPC. Design, setting, and participantsWe analyzed CTC samples collected concurrently with tumor biopsies intended for clinical sequencing in patients with progressing mCRPC. Outcome measurements and statistical analysisDifferences in proportions were evaluated using the chi-square test. Correlations between assays were analyzed in linear regression models. Associations between alterations and genomic instability were assessed on the single-cell level using mixed-effect negative binomial models. Results and limitationsWe identified 138 patients with concurrent CTC and biopsy samples. CTC sWGS generated copy number profiles in a similar proportion of patients to biopsy samples (83% vs 78%, p = 0.23), but was more effective than bone biopsies (79% vs 50%; p = 0.009). CTC sWGS detected BRCA2 loss in more patients than tissue at the ≥1 (42% vs 16%; p < 0.001) and ≥2 (27% vs 16%; p = 0.028) CTC thresholds. The overall prevalence of BRCA2 loss was not increased in CTCs using sample-level composite z scores (p = 0.4), but was significantly increased compared with a lower-than-expected prevalence in bone samples (21% vs 3%, p = 0.014). Positive/negative predictive values for CTC BRCA2 loss were 89%/96% using the ≥1 CTC threshold and 67%/92% using the composite z score. CTC BRCA2 loss was associated with higher genomic instability in univariate (1.4-fold large-scale transition difference, 95% confidence interval [CI]: 1.2–1.6; p < 0.001) and multivariable analysis (1.4-fold difference, 95% CI: 1.2–1.6; p < 0.001). ConclusionsCopy number profiles can reliably be generated using CTC sWGS, which detected a majority of tissue-confirmed BRCA2 loss and “CTC-only” losses. BRCA2 losses were supported by increases in genomic instability. Patient summaryCurrent testing strategies have limitations in their ability to detect BRCA2 loss, a relatively common alteration in prostate cancer that is used to identify patients who may benefit from targeted therapy. In this paper, we evaluated whether we could detect BRCA2 loss in individual tumor cells isolated from patient blood samples and found this method to be suitable for further analysis.

Incidence and Factors Associated with Inadequate Endometrial Tissue for Pathological Evaluation from Uterine Curettage in Abnormal Uterine Bleeding at Udon Thani Hospital

Objective: To study the incidence and factors associated with inadequate endometrial tissue for pathological evaluation from uterine curettage in patients with abnormal uterine bleeding (AUB) at Udon Thani Hospital. Materials and Methods: The electronic medical records of women aged 35 years and older with AUB that underwent endometrial curettage in a regional hospital between October 2018 and November 2019 were retrospectively reviewed. The incidence of inadequate endometrial tissue for pathological evaluation was studied. Multiple logistic regression analysis was performed to determine the factors associated with inadequate curettage. Results: Three hundred fifty-two patients with AUB that underwent endometrial tissue curettage and had complete medical records were included in the present study. The mean age was 48.09±8.01 years. The incidence of inadequate endometrial tissue for pathological evaluation was 23.30% (95% CI 18.98 to 28.07). Postmenopausal status (adjusted OR 3.80, 95% CI 1.93 to 7.50), the low experience of the clinician (adjusted OR 2.20, 95% CI 1.15 to 3.87), and the uterine cavity length measured by uterine sound (adjusted OR 0.66 for each 1 cm increment, 95% CI 0.54 to 0.80) were significant factors associated with inadequate tissue for pathological evaluation. Conclusion: The incidence of inadequate endometrial tissue for pathological evaluation from endometrial curettage was one-quarter of all cases. The associated factors of inadequate endometrial tissue included postmenopausal status, inexperience operators, and shorter uterine length. Keywords: Endometrial tissue curettage; Insufficient endometrial tissue; Sampling adequacy; Endometrial carcinoma; Abnormal uterine bleeding

P11.73.B The diagnostic value of frame-based stereotactic biopsies in the age of precision oncology: A cross-sectional study

Abstract Background For non-resectable, eloquent, multifocal and deep-seated intracranial lesions, stereotactic frame-based biopsies can deliver a finite amount of tissue for neuropathology studies. With the increasing role of molecular genetics in the diagnostics of intracranial tumors, sufficient tissue for sequencing studies is of paramount importance. This study explored the rate of successful diagnosis after stereotactic frame-based biopsies of intracranial lesions in a high-throughput neurooncology center Material and Methods 145 consecutive patients undergoing frame-based stereotactic biopsies in 2020 and 2021 at our neurosurgical department were included in this retrospective analysis. Aspects of histological and molecular (methylomics, panel-sequencing) neuropathology analysis in addition to clinical and radiological variables were analyzed. Cases were classified as conclusive, likely-conclusive (sufficient diagnosis with non-satisfying sequencing information), and inconclusive neuropathological diagnosis. Results Of 145 cases analyzed, astrocytic tumors were suspected in n= 94 (67%) of patients. In n= 122 cases (84%), a conclusive diagnosis was possible. For 14 (11%) cases, a likely-conclusive diagnosis was established Diagnoses comprised mainly WHO 4 glioblastomas (56%), WHO 3 gliomas (2%) in addition to WHO 1 and 2 gliomas (n=7, 5%), CNS lymphomas (n=23, 16%), inflammatory diseases (n=10, 7%) and normal or reactive tissue (n=4, 3%). Methylomics were pivotal in providing an integrated diagnosis in 30% of the cases (panel sequencing in 14%). In n= 12 (8%) of the cases further testing was hindered by insufficient tissue sample DNA. Only in 3 out of 12 cases this resulted in a final inconclusive diagnosis. Conclusion Although stereotactic frame-based biopsies deliver a limited amount of tissue, they bear an excellent histopathological and molecular genetic diagnostic yield, with rare cases of missing molecular data or rarely insufficient diagnosis. Optimizing the number and representativeness of cell and DNA-rich stereotactic biopsy specimen might enhance the diagnostic and therapeutic potential of precision oncology even further.

P1.16-02 Clinical Utility of ctDNA in Advanced NSCLC at Diagnosis or Where Insufficient Tissue Was Available, Based on the ESMO ESCAT Scale

Comprehensive genomic profiling (CGP) by next generation sequencing (NGS) of ctDNA can identify a wide spectrum of genomic alterations that range from driver oncogenic alterations with FDA/EMA approved targeted therapies for routine use, to other alterations with lack of evidence for actionability. We aimed to assess the clinical utility of NGS based ctDNA genomic profiling, based on the ESMO scale for clinical actionability of molecular targets (ESCAT), in a large prospective cohort of advanced NSCLC patients.

EP08.02-110 Plasma-based Molecular Profiling to Guide Treatment Decisions in Patients with Advanced NSCLC and Limited Tissue Biopsy

Molecular profiling of tumor tissue is the gold standard for treatment decision making in advanced non-small cell lung cancer (NSCLC). However, tumor genotyping may be unavailable due to insufficient tissue samples. Plasma-based next-generation sequencing (NGS) is emerging as either complementary or alternative to standard tissue genotyping in advanced NSCLC. We present our experience using plasma-based NGS in advanced NSCLC.

1162P Tissue and liquid biopsy utilization in advanced NSCLC in a large community US practice

Professional guidelines advise broad molecular profiling for at least 8 biomarkers in non-small cell lung cancer (NSCLC) that have either approved targeted therapies or available clinical trials. Up to 38% of patients with metastatic NSCLC have inadequate tumor samples for molecular analysis at diagnosis. Professional guidelines recommend that if there is insufficient tissue to allow for testing of all biomarkers, repeat biopsy and/or plasma testing should be done. While both plasma and tissue testing are currently being incorporated into the standard workup of patients with NSCLC, there is currently no standardized workflow for testing. We performed a retrospective chart review to assess real world liquid and tissue biopsy - based biomarker testing and reflex testing dynamics to understand the current NSCLC biomarker testing scenario in a large US community practice. Advanced NSCLC patients (n=361) who were diagnosed or received first-line treatment on or after 1/1/2020 were included. Data was extracted from the electronic medical records in participating practices as well as via abstraction of patient records when available. Patient-level data was anonymized and reported in aggregate. Data collected for this analysis was evaluated in accordance with regulatory requirements for electronic records. We examined patient journeys from biopsy to treatment, determined the percentage of liquid and tissue-based testing, test failure rate, reflex testing rate, and turnaround time. 43% of NSCLC patients received both liquid and tissue testing, while 41% received only tissue testing. The median TAT for tissue testing was 10 days and for liquid testing was 7 days. Reflex testing occurred in 56% of solid tumor test failures and 31% of liquid tumor tests with negative results. Patients with both a liquid and tissue test had results in hand prior to treatment more often than those who had either test alone. In this real-world study, 43% of NSCLC patients received both liquid and tissue testing. Patients with both a liquid and solid tumor test had results in hand prior to treatment more often than those who just had a solid or liquid tumor test. These results demonstrate the utilization of tissue and liquid testing in a large US community practice.

Detection of BRCA1, BRCA2, and ATM Alterations in Matched Tumor Tissue and Circulating Tumor DNA in Patients with Prostate Cancer Screened in PROfound.

Not all patients with metastatic castration-resistant prostate cancer (mCRPC) have sufficient tumor tissue available for multigene molecular testing. Furthermore, samples may fail because of difficulties within the testing procedure. Optimization of screening techniques may reduce failure rates; however, a need remains for additional testing methods to detect cancers with alterations in homologous recombination repair genes. We evaluated the utility of plasma-derived circulating tumor DNA (ctDNA) in identifying deleterious BRCA1, BRCA2 (BRCA), and ATM alterations in screened patients with mCRPC from the phase III PROfound study. Tumor tissue samples were sequenced prospectively at Foundation Medicine, Inc. (FMI) using an investigational next-generation sequencing (NGS) assay based on FoundationOne®CDx to inform trial eligibility. Matched ctDNA samples were retrospectively sequenced at FMI, using an investigational assay based on FoundationOne®Liquid CDx. 81% (503/619) of ctDNA samples yielded an NGS result, of which 491 had a tumor tissue result. BRCA and ATM status in tissue compared with ctDNA showed 81% positive percentage agreement and 92% negative percentage agreement, using tissue as reference. At variant-subtype level, using tissue as reference, concordance was high for nonsense (93%), splice (87%), and frameshift (86%) alterations but lower for large rearrangements (63%) and homozygous deletions (27%), with low ctDNA fraction being a limiting factor. We demonstrate that ctDNA can greatly complement tissue testing in identifying patients with mCRPC and BRCA or ATM alterations who are potentially suitable for receiving targeted PARP inhibitor treatments, particularly patients with no or insufficient tissue for genomic analyses.