[Perioperative Targeted Therapy for Operable, Early Stage NSCLC]. / Zielgerichtete Systemtherapie beim operablen Lungenkarzinom.

Non-small cell lung cancer (NSCLC) is characterized by high recurrence rates in the early stages. In a German cohort, recurrence-free survival after 5 years was 62% (stage IA1), 40.7% (stage IIA) and 28% (stage IIIA). In addition to the perioperative use of immune checkpoint inhibitors, targeted tumor therapy is also making inroads as an innovation from the palliative setting into the early stages. Of particular relevance is the use of the EGFR inhibitor osimertinib, which has been shown to improve overall survival in the adjuvant setting. In this practice-oriented review, we briefly describe the current status of adjuvant targeted therapy and the associated testing and provide an outlook on further developments.

Scribble Deficiency Promotes Pancreatic Ductal Adenocarcinoma Development and Metastasis.

Perturbation of cell polarity is a hallmark of pancreatic ductal adenocarcinoma (PDAC) progression. Scribble (SCRIB) is a well-characterized polarity regulator that has diverse roles in the pathogenesis of human neoplasms. To investigate the impact of SCRIB deficiency in PDAC development and progression, Scrib expression was genetically ablated in well-established mouse models of PDAC. Scrib loss in combination with KrasG12D did not influence development of pancreatic intraepithelial neoplasms in mice. However, Scrib deletion cooperated with KrasG12D and concomitant Trp53 heterozygous deletion to promote invasive PDAC and metastatic dissemination, leading to reduced overall survival. Immunohistochemical and transcriptome analyses revealed that Scrib-null tumors display a pronounced reduction of collagen content and an abundance of cancer-associated fibroblasts (CAF). Mechanistically, IL1α levels were reduced in Scrib-deficient tumors, and Scrib knockdown downregulated IL1α in mouse PDAC organoids (mPDO), which impaired CAF activation. Furthermore, Scrib loss increased YAP activation in mPDOs and established PDAC cell lines, enhancing cell survival. Clinically, SCRIB expression was decreased in human PDAC, and SCRIB mislocalization was associated with poorer patient outcome. These results indicate that SCRIB deficiency enhances cancer cell survival and remodels the tumor microenvironment to accelerate PDAC development and progression, establishing the tumor suppressor function of SCRIB in advanced pancreatic cancer. Significance: SCRIB loss promotes invasive pancreatic cancer development via both cell-autonomous and non-cell-autonomous processes and is associated with poorer outcomes, denoting SCRIB as a tumor suppressor and potential biomarker for the prediction of recurrence.

Multinational proficiency tests for EGFR exon 20 insertions reveal that the assay design matters.

Insertion mutations in exon 20 of the epidermal growth factor receptor gene (EGFR exon20ins) are rare, heterogeneous alterations observed in non-small cell lung cancer (NSCLC). With a few exceptions, they are associated with primary resistance to established EGFR tyrosine kinase inhibitors (TKIs). As patients carrying EGFR exon20ins may be eligible for treatment with novel therapeutics-the bispecific antibody amivantamab, the TKI mobocertinib, or potential future innovations-they need to be identified reliably in clinical practice for which quality-based routine genetic testing is crucial. Spearheaded by the German Quality Assurance Initiative Pathology two international proficiency tests were run, assessing the performance of 104 participating institutes detecting EGFR exon20ins in tissue and/or plasma samples. EGFR exon20ins were most reliably identified using next-generation sequencing (NGS). Interestingly, success rates of institutes using commercially available mutation-/allele-specific quantitative (q)PCR were below 30% for tissue samples and 0% for plasma samples. Most of these mutation-/allele-specific (q)PCR assays are not designed to detect the whole spectrum of EGFR exon20ins mutations leading to false negative results. These data suggest that NGS is a suitable method to detect EGFR exon20ins in various types of patient samples and is superior to the detection spectrum of commercially available assays.

Exceptional Response of BRAFV600E-Mutated Acinar Cell CUP to BRAF/MEK Inhibition.

Complete remission of BRAF V600E-driven ACC CUP by BRAF/MEK inhibition underscores importance of precision oncology.

Identification of novel snoRNA-based biomarkers for clear cell renal cell carcinoma from urine-derived extracellular vesicles.

BACKGROUND: Clear cell renal cell carcinoma (ccRCC) is the most common subtype of RCC with high rates of metastasis. Targeted therapies such as tyrosine kinase and checkpoint inhibitors have improved treatment success, but therapy-related side effects and tumor recurrence remain a challenge. As a result, ccRCC still have a high mortality rate. Early detection before metastasis has great potential to improve outcomes, but no suitable biomarker specific for ccRCC is available so far. Therefore, molecular biomarkers derived from body fluids have been investigated over the past decade. Among them, RNAs from urine-derived extracellular vesicles (EVs) are very promising. METHODS: RNA was extracted from urine-derived EVs from a cohort of 78 subjects (54 ccRCC patients, 24 urolithiasis controls). RNA-seq was performed on the discovery cohort, a subset of the whole cohort (47 ccRCC, 16 urolithiasis). Reads were then mapped to the genome, and expression was quantified based on 100 nt long contiguous genomic regions. Cluster analysis and differential region expression analysis were performed with adjustment for age and gender. The candidate biomarkers were validated by qPCR in the entire cohort. Receiver operating characteristic, area under the curve and odds ratios were used to evaluate the diagnostic potential of the models. RESULTS: An initial cluster analysis of RNA-seq expression data showed separation by the subjects' gender, but not by tumor status. Therefore, the following analyses were done, adjusting for gender and age. The regions differentially expressed between ccRCC and urolithiasis patients mainly overlapped with small nucleolar RNAs (snoRNAs). The differential expression of four snoRNAs (SNORD99, SNORD22, SNORD26, SNORA50C) was validated by quantitative PCR. Confounder-adjusted regression models were then used to classify the validation cohort into ccRCC and tumor-free subjects. Corresponding accuracies ranged from 0.654 to 0.744. Models combining multiple genes and the risk factors obesity and hypertension showed improved diagnostic performance with an accuracy of up to 0.811 for SNORD99 and SNORA50C (p = 0.0091). CONCLUSIONS: Our study uncovered four previously unrecognized snoRNA biomarkers from urine-derived EVs, advancing the search for a robust, easy-to-use ccRCC screening method.

Correlation of microscopic tumor extension with tumor microenvironment in esophageal cancer patients.

OBJECTIVE: In the era of image-guided adaptive radiotherapy, definition of the clinical target volume (CTV) is a challenge in various solid tumors, including esophageal cancer (EC). Many tumor microenvironmental factors, e.g., tumor cell proliferation or cancer stem cells, are hypothesized to be involved in microscopic tumor extension (MTE). Therefore, this study assessed the expression of FAK, ILK, CD44, HIF-1α, and Ki67 in EC patients after neoadjuvant radiochemotherapy followed by tumor resection (NRCHT+R) and correlated these markers with the MTE. METHODS: Formalin-fixed paraffin-embedded tumor resection specimens of ten EC patients were analyzed using multiplex immunofluorescence staining. Since gold fiducial markers had been endoscopically implanted at the proximal and distal tumor borders prior to NRCHT+R, correlation of the markers with the MTE was feasible. RESULTS: In tumor resection specimens of EC patients, the overall percentages of FAK+, CD44+, HIF-1α+, and Ki67+ cells were higher in tumor nests than in the tumor stroma, with the outcome for Ki67+ cells reaching statistical significance (p < 0.001). Conversely, expression of ILK+ cells was higher in tumor stroma, albeit not statistically significantly. In three patients, MTE beyond the fiducial markers was found, reaching up to 31 mm. CONCLUSION: Our findings indicate that the overall expression of FAK, HIF-1α, Ki67, and CD44 was higher in tumor nests, whereas that of ILK was higher in tumor stroma. Differences in the TME between patients with residual tumor cells in the original CTV compared to those without were not found. Thus, there is insufficient evidence that the TME influences the required CTV margin on an individual patient basis. TRIAL REGISTRATION NUMBER AND DATE: BO-EK-148042017 and BO-EK-177042022 on 20.06.2022, DRKS00011886, https://drks.de/search/de/trial/DRKS00011886 .

Exploring evolutionary trajectories in ovarian cancer patients by longitudinal analysis of ctDNA.

OBJECTIVES: We analysed whether temporal heterogeneity of ctDNA encodes evolutionary patterns in ovarian cancer. METHODS: Targeted sequencing of 275 cancer-associated genes was performed in a primary tumor biopsy and in ctDNA of six longitudinal plasma samples from 15 patients, using the Illumina platform. RESULTS: While there was low overall concordance between the mutational spectrum of the primary tumor biopsies vs. ctDNA, TP53 variants were the most commonly shared somatic alterations. Up to three variant clusters were detected in each tumor biopsy, likely representing predominant clones of the primary tumor, most of them harbouring a TP53 variant. By tracing these clusters in ctDNA, we propose that liquid biopsy may allow to assess the contribution of ancestral clones of the tumor to relapsed abdominal masses, revealing two evolutionary patterns. In pattern#1, clusters detected in the primary tumor biopsy were likely relapse seeding clones, as they contributed a major share to ctDNA at relapse. In pattern#2, similar clusters were present in tumors and ctDNA; however, they were entirely cleared from liquid biopsy after chemotherapy and were undetectable at relapse. ctDNA private variants were present among both patterns, with some of them mirroring subclonal expansions after chemotherapy. CONCLUSIONS: We demonstrate that tracing the temporal heterogeneity of ctDNA, even below exome scale resolution, deciphers evolutionary trajectories in ovarian cancer. Furthermore, we describe two evolutionary patterns that may help to identify relapse seeding clones for targeted therapy.

Mobocertinib in Patients with EGFR Exon 20 Insertion-Positive Non-Small Cell Lung Cancer (MOON): An International Real-World Safety and Efficacy Analysis.

EGFR exon 20 (EGFR Ex20) insertion mutations in non-small cell lung cancer (NSCLC) are insensitive to traditional EGFR tyrosine kinase inhibitors (TKIs). Mobocertinib is the only approved TKI specifically designed to target EGFR Ex20. We performed an international, real-world safety and efficacy analysis on patients with EGFR Ex20-positive NSCLC enrolled in a mobocertinib early access program. We explored the mechanisms of resistance by analyzing postprogression biopsies, as well as cross-resistance to amivantamab. Data from 86 patients with a median age of 67 years and a median of two prior lines of treatment were analyzed. Treatment-related adverse events (TRAEs) occurred in 95% of patients. Grade ≥3 TRAEs were reported in 38% of patients and included diarrhea (22%) and rash (8%). In 17% of patients, therapy was permanently discontinued, and two patients died due to TRAEs. Women were seven times more likely to discontinue treatment than men. In the overall cohort, the objective response rate to mobocertinib was 34% (95% CI, 24-45). The response rate in treatment-naïve patients was 27% (95% CI, 8-58). The median progression-free and overall survival was 5 months (95% CI, 3.5-6.5) and 12 months (95% CI, 6.8-17.2), respectively. The intracranial response rate was limited (13%), and one-third of disease progression cases involved the brain. Mobocertinib also showed antitumor activity following EGFR Ex20-specific therapy and vice versa. Potential mechanisms of resistance to mobocertinib included amplifications in MET, PIK3CA, and NRAS. Mobocertinib demonstrated meaningful efficacy in a real-world setting but was associated with considerable gastrointestinal and cutaneous toxicity.

Stratifying esophago-gastric cancer treatment using a patient-derived organoid-based threshold.

BACKGROUND AND AIMS: This study sought to determine the value of patient-derived organoids (PDOs) from esophago-gastric adenocarcinoma (EGC) for response prediction to neoadjuvant chemotherapy (neoCTx). METHODS: Endoscopic biopsies of patients with locally advanced EGC (n = 120) were taken into culture and PDOs expanded. PDOs' response towards the single substances of the FLOT regimen and the combination treatment were correlated to patients' pathological response using tumor regression grading. A classifier based on FLOT response of PDOs was established in an exploratory cohort (n = 13) and subsequently confirmed in an independent validation cohort (n = 13). RESULTS: EGC PDOs reflected patients' diverse responses to single chemotherapeutics and the combination regimen FLOT. In the exploratory cohort, PDOs response to single 5-FU and FLOT combination treatment correlated with the patients' pathological response (5-FU: Kendall's τ = 0.411, P = 0.001; FLOT: Kendall's τ = 0.694, P = 2.541e-08). For FLOT testing, a high diagnostic precision in receiver operating characteristic (ROC) analysis was reached with an AUCROC of 0.994 (CI 0.980 to 1.000). The discriminative ability of PDO-based FLOT testing allowed the definition of a threshold, which classified in an independent validation cohort FLOT responders from non-responders with high sensitivity (90%), specificity (100%) and accuracy (92%). CONCLUSION: In vitro drug testing of EGC PDOs has a high predictive accuracy in classifying patients' histological response to neoadjuvant FLOT treatment. Taking into account the high rate of successful PDO expansion from biopsies, the definition of a threshold that allows treatment stratification paves the way for an interventional trial exploring PDO-guided treatment of EGC patients.

[Advanced non-small cell lung cancer - pioneer in personalized oncology]. / Nicht kleinzelliges Lungenkarzinom ­ Vorreiter der personalisierten Onkologie.

In no other cancer is clinical practice as close to the ideals of personalized oncology as in the treatment of non-small cell lung cancer (NSCLC). Here, we briefly outline the basic principles of molecular analysis. The focus of the article is on the clinical utility of targeted therapy. Finally, we highlight the challenges for medical staff and structural solutions reflecting the situation in Germany.

PD-L1 mRNA Detection in Immunohistochemically Negative Patients: A Complementary Method for a Better Treatment Selection?

BACKGROUND/AIM: PD-L1 inhibitors have been approved for cisplatin-ineligible urothelial cancer patients relapsing after radical cystectomy. A prerequisite for therapy is a positive PD-L1 expression in the tumor tissue, whereas no options are available for patients with negative PD-L1 status. However, studies revealed that many PD-L1-negative patients also responded to PD-L1 therapy. This study investigated the feasibility of PD-L1 mRNA complementary RNA in situ hybridization (RNAish) analysis to detect PD-L1-responders independent of PD-L1 protein status. MATERIALS AND METHODS: Immunohistochemistry and RNA in situ hybridization were used to assess PD-L1 protein and mRNA in radical cystectomy tissue from patients with advanced and metastasized urothelial cancer. RESULTS: In this study, PD-L1 protein and mRNA were detected in ≥90% of the examined tissue. Positive PD-L1 mRNA expression (≥1%) on TC and IC could be evaluated in 77% and 31% of the cases, respectively. Moreover, scatterplot analysis revealed a PD-L1 mRNA positive and PD-L1 protein negative subpopulation. According to the CPS score, positive PD-L1 protein expression could be evaluated in 88% and positive PD-L1 mRNA expression in 71% of the cases. Scatterplot analysis of the CPS scores revealed a CPS protein negative but CPS mRNA positive small subpopulation. CONCLUSION: The feasibility of RNAish on formalin-fixed tissue could be proven. Moreover, complementary PD-L1 RNAish identified a sub-population of PD-L1 protein-negative and PD-L1 mRNA-positive patients, which may benefit from PD-L1 therapy.

[Ulcerative colitis-associated carcinogenesis : An update]. / Colitis-ulcerosa-assoziierte Karzinogenese : Ein Update.

Ulcerative colitis (UC) is a chronic inflammatory bowel disease beginning in the rectum and gradually extending to the right-sided colon and the terminal ileum (backwash-ileitis). Its causes are still not completely understood. Genetic susceptibility, changes in the microbiota and immune response, as well as environmental factors are thought to influence the disease course.Patients with UC are at increased risk of developing colorectal cancer (CRC) when compared to an age-matched normal population. Cancer risk increases with early onset, duration, and extent of the disease, with development of strictures, intraepithelial neoplasia, and concomitant primary sclerosing cholangitis.In contrast to the sporadic adenoma-carcinoma-sequence, UC-related CRC develops through an inflammation-intraepithelial neoplasia-carcinoma-sequence, in which genetic alterations already occur in the inflamed epithelium before the development of intraepithelial neoplasia.This article summarizes the current state of knowledge regarding UC-related carcinogenesis and its possible impact on prevention and therapy.

RAB27B expression in pancreatic cancer is predictive of poor survival but good response to chemotherapy.

BACKGROUND: Pancreatic cancer is the 4th leading cause of cancer-related death with poor survival even after curative resection. RAB27A and RAB27B are key players in the exosome pathway where they play important roles in exosome secretion. Evidence suggests that RAB27A and RAB27B expression not only leads to tumor proliferation and invasion, but also plays an important role in antigen transfer necessary for anticancer immunity. OBJECTIVE: In this study, we analyze the expression of RAB27A and RAB27B in patients after pancreatic cancer surgery with or without adjuvant chemotherapy and its influence on overall survival. METHODS: We analyzed a total of 167 patients with pancreatic cancer for their RAB27A and RAB27B expression. We dichotomized the patients along the median and compared survival in patients with high and low RAB27A and RAB27B expression with or without adjuvant chemotherapy treatment. RESULTS: We found a significant improvement in overall survival in patients with a negative resection margin (p= 0.037) and in patients who received adjuvant chemotherapy (p= 0.039). The survival benefit after chemotherapy was dependent on RAB27B expression status: only the subgroup of patients with high RAB27B expression benefited from adjuvant chemotherapy (p= 0.006), but not the subgroup with low RAB27B expression (p= 0.59). Patients with high RAB27B expression who did not receive adjuvant chemotherapy showed a trend towards worse survival compared to the other subgroups. This difference was abolished after treatment with adjuvant chemotherapy. CONCLUSION: These results suggest that RAB27B expression in pancreatic cancer might identify a subgroup of patients with poor survival who might respond well to adjuvant chemotherapy. If resectable, these patients could be considered for neoadjuvant chemotherapy to minimize the risk of not receiving adjuvant chemotherapy. Further prospective studies are needed to confirm these findings.

TIGIT Expression Delineates T-cell Populations with Distinct Functional and Prognostic Impact in Pancreatic Cancer.

PURPOSE: Immunotherapy has led to a fundamental shift in the treatment of several cancers. However, its efficacy in pancreatic ductal adenocarcinoma (PDAC) is limited. Understanding the expression of inhibitory immune checkpoint receptors (ICR) by intratumoral T cells may help to unravel their involvement in insufficient T-cell-mediated antitumor immunity. EXPERIMENTAL DESIGN: Using multicolor flow cytometry, we analyzed circulating and intratumoral T cells from blood (n = 144) and matched tumor samples (n = 107) of patients with PDAC. We determined the expression of programmed cell death protein 1 (PD-1) and T-cell immunoreceptor with Ig and immunoreceptor tyrosine-based inhibition motif (ITIM) domains (TIGIT) by CD8+ T-cells, conventional CD4+ T-cells (Tconv) and regulatory T cells (Treg) and their association with T-cell differentiation, tumor reactivity, and cytokine expression. A comprehensive follow-up was used to determine their prognostic value. RESULTS: Intratumoral T cells were characterized by increased PD-1 and TIGIT expression. Both markers delineated distinct T-cell subpopulations. PD-1+TIGIT- T cells highly expressed proinflammatory cytokines and markers of tumor reactivity (CD39, CD103), whereas TIGIT expression was linked to antiinflammatory and exhausted phenotypes. In addition, the enhanced presence of intratumoral PD-1+TIGIT- Tconv was associated with improved clinical outcomes, while high ICR expression on blood T cells was a significant hazard for overall survival (OS). CONCLUSIONS: Our results uncover the association between ICR expression and T-cell functionality. PD-1 and TIGIT characterized intratumoral T cells with highly divergent phenotypes linked to clinical outcomes, further underscoring the relevance of TIGIT for immunotherapeutic approaches in PDAC. The prognostic value of ICR expression in patient blood may be a valuable tool for patient stratification.

Label-free multiphoton microscopy enables histopathological assessment of colorectal liver metastases and supports automated classification of neoplastic tissue.

As the state of resection margins is an important prognostic factor after extirpation of colorectal liver metastases, surgeons aim to obtain negative margins, sometimes elaborated by resections of the positive resection plane after intraoperative frozen sections. However, this is time consuming and results sometimes remain unclear during surgery. Label-free multimodal multiphoton microscopy (MPM) is an optical technique that retrieves morpho-chemical information avoiding all staining and that can potentially be performed in real-time. Here, we investigated colorectal liver metastases and hepatic tissue using a combination of three endogenous nonlinear signals, namely: coherent anti-Stokes Raman scattering (CARS) to visualize lipids, two-photon excited fluorescence (TPEF) to visualize cellular patterns, and second harmonic generation (SHG) to visualize collagen fibers. We acquired and analyzed over forty thousand MPM images of metastatic and normal liver tissue of 106 patients. The morphological information with biochemical specificity produced by MPM allowed discriminating normal liver from metastatic tissue and discerning the tumor borders on cryosections as well as formalin-fixed bulk tissue. Furthermore, automated tissue type classification with a correct rate close to 95% was possible using a simple approach based on discriminant analysis of texture parameters. Therefore, MPM has the potential to increase the precision of resection margins in hepatic surgery of metastases without prolonging surgical intervention.

Identification of Epigenetically Regulated Genes Distinguishing Intracranial from Extracranial Melanoma Metastases.

Despite remarkable advances in treating patients with metastatic melanoma, the management of melanoma brain metastases remains challenging. Recent evidence suggests that epigenetic reprogramming is an important mechanism for the adaptation of melanoma cells to the brain environment. In this study, the methylomes and transcriptomes of a cohort of matched melanoma metastases were evaluated by integrated omics data analysis. The identified 38 candidate genes displayed distinct promoter methylation and corresponding gene expression changes in intracranial compared with extracranial metastases. The 11 most promising genes were validated on protein level in both tumor and surrounding normal tissue using immunohistochemistry. In accordance with the underlying promoter methylation and gene expression changes, a significantly different protein expression was confirmed for STK10, PDXK, WDR24, CSSP1, NMB, RASL11B, phosphorylated PRKCZ, PRKCZ, and phosphorylated GRB10 in the intracranial metastases. The observed changes imply a distinct intracranial phenotype with increased protein kinase B phosphorylation and a higher frequency of proliferating cells. Knockdown of PRKCZ or GRB10 altered the expression of phosphorylated protein kinase B and decreased the viability of a brain-specific melanoma cell line. In summary, epigenetically regulated cancer-relevant alterations were identified that provide insights into the molecular mechanisms that discriminate brain metastases from other organ metastases, which could be exploited by targeting the affected signaling pathways.

Neoadjuvant chemotherapy drives intratumoral T cells toward a proinflammatory profile in pancreatic cancer.

BACKGROUNDPancreatic ductal adenocarcinoma (PDAC) has a dismal prognosis. At diagnosis, only 20% of patients with PDAC are eligible for primary resection. Neoadjuvant chemotherapy can enable surgical resection in 30%-40% of patients with locally advanced and borderline resectable PDAC. The effects of neoadjuvant chemotherapy on the cytokine production of tumor-infiltrating T cells are unknown in PDAC.METHODSWe performed multiplex immunofluorescence to investigate T cell infiltration in 91 patients with PDAC. Using flow cytometry, we analyzed tumor and matched blood samples from 71 patients with PDAC and determined the frequencies of T cell subsets and their cytokine profiles. Both cohorts included patients who underwent primary resection and patients who received neoadjuvant chemotherapy followed by surgical resection.RESULTSIn human PDAC, T cells were particularly enriched within the tumor stroma. Neoadjuvant chemotherapy markedly enhanced T cell density within the ductal area of the tumor. Whereas infiltration of cytotoxic CD8+ T cells was unaffected by neoadjuvant chemotherapy, the frequency of conventional CD4+ T cells was increased, and the proportion of Tregs was reduced in the pancreatic tumor microenvironment after neoadjuvant treatment. Moreover, neoadjuvant chemotherapy increased the production of proinflammatory cytokines by tumor-infiltrating T cells, with enhanced TNF-α and IL-2 and reduced IL-4 and IL-10 expression.CONCLUSIONNeoadjuvant chemotherapy drives intratumoral T cells toward a proinflammatory profile. Combinational treatment strategies incorporating immunotherapy in neoadjuvant regimens may unleash more effective antitumor responses and improve prognosis of pancreatic cancer.FUNDINGThis work was supported by the Jung Foundation for Science and Research, the Monika Kutzner Foundation, the German Research Foundation (SE2980/5-1), the German Cancer Consortium, and the Faculty of Medicine Carl Gustav Carus, Technische Universität Dresden.

Orthotopic Glioblastoma Models for Evaluation of the Clinical Target Volume Concept.

In times of high-precision radiotherapy, the accurate and precise definition of the primary tumor localization and its microscopic spread is of enormous importance. In glioblastoma, the microscopic tumor extension is uncertain and, therefore, population-based margins for Clinical Target Volume (CTV) definition are clinically used, which could either be too small-leading to increased risk of loco-regional recurrences-or too large, thus, enhancing the probability of normal tissue toxicity. Therefore, the aim of this project is to investigate an individualized definition of the CTV in preclinical glioblastoma models based on specific biological tumor characteristics. The microscopic tumor extensions of two different orthotopic brain tumor models (U87MG_mCherry; G7_mCherry) were evaluated before and during fractionated radiotherapy and correlated with corresponding histological data. Representative tumor slices were analyzed using Matrix-Assisted Laser Desorption/Ionization (MALDI) and stained for putative stem-like cell markers as well as invasion markers. The edges of the tumor are clearly shown by the MALDI segmentation via unsupervised clustering of mass spectra and are consistent with the histologically defined border in H&E staining in both models. MALDI component analysis identified specific peaks as potential markers for normal brain tissue (e.g., 1339 m/z), whereas other peaks demarcated the tumors very well (e.g., 1562 m/z for U87MG_mCherry) irrespective of treatment. MMP14 staining revealed only a few positive cells, mainly in the tumor border, which could reflect the invasive front in both models. The results of this study indicate that MALDI information correlates with microscopic tumor spread in glioblastoma models. Therefore, an individualized CTV definition based on biological tumor characteristics seems possible, whereby the visualization of tumor volume and protein heterogeneity can be potentially used to define radiotherapy-sensitive and resistant areas.

Immunohistochemical analyses of paraffin-embedded sections after primary surgery or trimodality treatment in esophageal carcinoma.

Background: The microscopic tumor extension before, during or after radiochemotherapy (RCHT) and its correlation with the tumor microenvironment (TME) are presently unknown. This information is, however, crucial in the era of image-guided, adaptive high-precision photon or particle therapy. Materials and methods: In this pilot study, we analyzed formalin-fixed paraffin-embedded (FFPE) tumor resection specimen from patients with histologically confirmed squamous cell carcinoma (SCC; n = 10) or adenocarcinoma (A; n = 10) of the esophagus, having undergone neoadjuvant radiochemotherapy followed by resection (NRCHT + R) or resection (R)]. FFPE tissue sections were analyzed by immunohistochemistry regarding tumor hypoxia (HIF-1α), proliferation (Ki67), immune status (PD1), cancer cell stemness (CXCR4), and p53 mutation status. Marker expression in HIF-1α subvolumes was part of a sub-analysis. Statistical analyses were performed using one-sided Mann-Whitney tests and Bland-Altman analysis. Results: In both SCC and AC patients, the overall percentages of positive tumor cells among the five TME markers, namely HIF-1α, Ki67, p53, CXCR4 and PD1 after NRCHT were lower than in the R cohort. However, only PD1 in SCC and Ki67 in AC showed significant association (Ki67: p = 0.03, PD1: p = 0.02). In the sub-analysis of hypoxic subvolumes among the AC patients, the percentage of positive tumor cells within hypoxic regions were statistically significantly lower in the NRCHT than in the R cohort across all the markers except for PD1. Conclusion: In this pilot study, we showed changes in the TME induced by NRCHT in both SCC and AC. These findings will be correlated with microscopic tumor extension measurements in a subsequent cohort of patients.