Global Ring Study to Investigate the Comparability of Total Assay Performance of Commercial Claudin 18 Antibodies for Evaluation in Gastric Cancer.

Claudin 18.2 (CLDN18.2), the dominant isoform of CLDN18 in gastric tissues, is a highly specific tight junction protein of the gastric mucosa with variably retained expressions in gastric and gastroesophageal junction cancers. Additionally, CLDN18.2-targeted treatment with zolbetuximab, in combination with chemotherapy, has recently been assessed in 2 phase-III studies of patients with HER2-negative, locally advanced, unresectable, or metastatic gastric or gastroesophageal junction adenocarcinoma. These trials used the investigational VENTANA CLDN18 (43-14A) RxDx immunohistochemistry (IHC) assay on the Ventana BenchMark platform to identify patients eligible for CLDN18.2-targeted treatment. We report the findings of a global ring study evaluating the analytical comparability of concordance of the results of 3 CLDN18 antibodies (Ventana, LSBio, and Novus) stained on 3 IHC-staining platforms (Ventana, Dako, and Leica). A tissue microarray (TMA), comprising 15 gastric cancer cases, was stained by 27 laboratories across 11 countries. Each laboratory stained the TMAs using at least 2 of the 3 evaluated CLDN18 antibodies. Stained TMAs were assessed and scored using an agreed IHC-scoring algorithm, and the results were collated for statistical analysis. The data confirmed a high level of concordance for the VENTANA CLDN18 (43-14A; Ventana platform only) and LSBio antibodies on both the Dako and Leica platforms, with accuracy, precision, sensitivity, and specificity rates all reaching a minimum acceptable ≥85% threshold and good-to-excellent levels of concordance as measured by Cohen's kappa coefficient. The Novus antibody showed the highest level of variability against the reference central laboratory results for the same antibody/platform combinations. It also failed to meet the threshold for accuracy and sensitivity when used on either the Dako or Leica platform. These results demonstrated the reliability of IHC testing for CLDN18 expression in gastric tumor samples when using commercially available platforms with an appropriate methodology and primary antibody selection.

Complete Metabolic Response to Combined Immune Checkpoint Inhibition after Progression of Metastatic Colorectal Cancer on Pembrolizumab: A Case Report.

DNA mismatch repair deficient (dMMR) and microsatellite instable (MSI) metastatic colorectal cancer (mCRC) can be successfully treated with FDA- and EMA-approved immune checkpoint inhibitors (ICI) pembrolizumab and nivolumab (as single agents targeting the anti-programmed cell death protein-1 (PD-1)) or combinations of a PD-1 inhibitor with ipilimumab, a cytotoxic T-lymphocyte-associated protein 4 (CTLA-4)-targeting antibody. The best treatment strategy beyond progression on single-agent ICI therapy remains unclear. Here, we present the case of a 63-year-old male with Lynch-syndrome-associated, microsatellite instability-high (MSI-H) mCRC who achieved a rapid normalization of his tumor markers and a complete metabolic remission (CMR), currently lasting for ten months, on sequential ICI treatment with the combination of nivolumab and ipilimumab followed by nivolumab maintenance therapy after progression on single-agent anti-PD-1 ICI therapy. The therapy was well-tolerated, and no immune-related adverse events occurred. To the best of our knowledge, this is the first case of a sustained metabolic complete remission in an MSI-H mCRC patient initially progressing on single-agent anti-PD-1 therapy. Thus, dMMR mCRC patients might benefit from sequential immune checkpoint regimens even with long-term responses. However, further sophistication of clinical algorithms for treatment beyond progression on single-agent ICI therapy in MSI-mCRC is urgently needed.

Prognostic Factors for Leiomyosarcoma with Isolated Metastases to the Lungs: Impact of Metastasectomy.

BACKGROUND: Leiomyosarcoma (LMS) most frequently metastasizes to the lung. Metastatic LMS is considered incurable. Selected patients may benefit from pulmonary metastasectomy (PM) within multimodal therapy. This study analyzed the prognostic relevance of clinicopathologic factors in these patients. METHODS: Patients with metastatic LMS to the lung treated in our center from 2004 to 2020 were included in this single-center retrospective study. Overall survival (OS), progression-free survival (PFS), and prognostic factors were analyzed. RESULTS: The study had 64 patients (33 males, 52%) with metastatic LMS to the lung. The 5-year OS was 55% after the diagnosis of pulmonary metastases. Age older than 60 years at the primary tumor diagnosis, primary tumor larger than 70 mm, and five or more lung metastases were associated with poorer OS. Of the 64 patients, 44 underwent PM. The postoperative mortality rate was 0%. The patients selected for PM were younger and had smaller primary tumors, fewer metastases, and metastases that more often were metachronous. Metastasis grade (G1 vs. G2/3) and size (20-mm cutoff) were significant prognostic factors for OS (p = 0.05) and PFS (p = 0.028) after PM, respectively. The 44 patients who underwent PM had a survival benefit compared with the patients who were selected but did not undergo PM (n = 6) and the patients who were not selected for PM (n = 14). Three patients (7%) were alive and free of disease at the last follow-up visit respectively 5.5, 9, and 12 years after PM. CONCLUSIONS: For patients with leiomyosarcoma, PM is safe. Despite aggressive multimodal treatment, most patients will experience recurrence and eventually die of their disease. However, a small subgroup of patients could potentially be cured after PM.

Tropomyosin receptor kinases in sarcomas - of joy and despair.

PURPOSE OF REVIEW: The relatively recent discovery of neurotrophic tropomyosin receptor kinase (NTRK) gene arrangements as pan-tumor predictive biomarkers has led to impressive novel treatments for patients with TRK fusions. Although the number of patients who qualify for treatment is vanishingly small for cancer patients in general, a few histological subsets of sarcomas exhibit NTRK fusions more commonly leading to large expectations within the sarcoma community. RECENT FINDINGS: Larotrectenib and entrectenib have recently been approved based on durable responses in TRK positive cancers with nonresectable or metastatic disease, including many sarcomas. Identification of resistance mutations to TRKi has led to the development of novel salvage therapies which may soon further expand the armamentarium of treatments. The greatest barrier and frustration to date is the actual identification of patients who harbor the fusion. The dimension of rarity in sarcomas remains difficult to comprehend for both patients and caregivers. Diagnosis of NTRK fusions is complex, particularly in the context of sarcomas and can involve immunohistochemistry as a screening tool but frequently requires fluorescence-in-situ hybridization or next-generation sequencing (NGS) to confirm the diagnosis. SUMMARY: The growing evidence on subtype-specific incidence of NTRK fusions will help to improve strategic prioritization or exclusion of subtypes to reduce the burden of negative testing. Next-generation inhibitors provide potential salvage treatment options for patients failing first-line therapy.

Number of metastases and their response to chemotherapy impact survival of patients with isolated lung metastases from bone-derived sarcoma.

BACKGROUND: Pulmonary metastasectomy (PM) is an established treatment for selected patients with metastatic sarcomas. The aim of this study was to examine our institutional experience and evaluate factors predicting outcome. METHODS: We retrospectively reviewed all patients undergoing PM for bone sarcoma in our center from 2001 to 2019. Survival was calculated from the date of PM. Impact on survival of clinical parameters was assessed. RESULTS: Thirty-eight patients (27 males, 71%) were included. Histology was osteosarcoma (n = 20, 53%), Ewing sarcoma (n = 13, 34%) and chondrosarcoma (n = 5, 13%). Twelve patients (31.5%) had synchronous metastases, all received chemotherapy before PM. Median number of metastases was 3 (1 to 29). Twenty (53%) patients had mediastinal lymph node sampling. One patient had positive lymph nodes. Ninety-day mortality was 0%. Three and 5-year PFS were 24.5 and 21%, respectively. Three and 5-year OS were 64.5 and 38.5%, respectively. More than three metastases and progression under chemotherapy were significant independent predictors for OS. CONCLUSION: PM is a safe procedure and encouraging long-term outcome can be achieved. Patients with progression of pulmonary metastases under chemotherapy as well as patients with more than three metastases had significantly worse OS.

Surgical Treatment for Primary Chest Wall Sarcoma: A Single-Institution Study.

BACKGROUND: Primary sarcomas of the chest wall are rare aggressive tumors. Surgery is part of the multimodal treatment. We describe our institutional patient cohort and evaluate prognostic factors. METHODS: All patients who had curative intent surgery for primary chest wall sarcoma from 2004 to 2019 were retrospectively reviewed. Impact on survival-calculated from the date of surgery until last follow-up- was assessed for the following variables: age, gender, type of resection, size, grading, stage, completeness of resection, and neoadjuvant and adjuvant therapy. RESULTS: Twenty-three patients (15 males, 65%) with a median age of 54 y (4 to 82) were included. Most common histology was chondrosarcoma (n = 5, 22%). Seven patients (30%) received neoadjuvant and 13 patients (57%) received adjuvant treatment. R0 resection was achieved in 83%. Extended chest wall resection was performed in 14 patients (61%), including lung (n = 13, 57%), diaphragm (n = 2, 9%) and pericardium (n = 1, 4%). Morbidity and 90-day mortality were 23% and 0%, respectively. Three- and 5-year overall survival was 53% and 35%, respectively. R0 resection was predictor of overall survival (P = 0.029). Tumor grade and extended resections were predictors for recurrence (P = 0.034 and P = 0.018, respectively). CONCLUSIONS: Surgical resection of primary chest wall sarcoma is a safe procedure even when extended resection is required.

[Predictive diagnostics for checkpoint inhibitors]. / Prädiktive Diagnostik für Checkpoint-Inhibitoren.

Checkpoint inhibitors have revolutionized oncological treatment in many cancers and added a new immuno-oncological treatment pillar to the medicinal arsenal of conventional and molecularly targeted therapies. In monotherapy and in combination therapies, however, not all patients respond equally well, even in generally responsive tumor entities. Therefore, since the introduction of these therapies, a major focus has been the research on and implementation of predictive markers for patient selection. The first established biomarker, the expression of the target molecule PD-L1, has found its way into routine diagnostics in a large number of unfortunately very divergent diagnostic constellations in multiple entities. In addition, some molecular predictors, including the measurement of microsatellite instability and tumor mutational burden, have also been suggested and in some cases are already implemented into routine diagnostics. Additional molecular parameters have been proposed but most of them have not yet found their way into routine patient care. This review article discusses the current status and recent developments in the field of diagnostic response predictors in the context of an immune checkpoint blockade.

MSI testing : What's new? What should be considered?

Based on new trial data regarding immune checkpoint inhibitors (ICIs), the detection of high-grade microsatellite instability (MSI-H) or underlying deficient mismatch repair protein (dMMR) is now becoming increasingly important for predicting treatment response. For the first time, a PD­1 ICI (pembrolizumab) has been approved by the European Medicines Agency (EMA) for first-line treatment of advanced (stage IV) dMMR/MSI­H colorectal cancer (CRC). Further indications, such as dMMR/MSI­H endometrial carcinoma (EC), have already succeeded (Dostarlimab, 2nd line treatment) and others are expected to follow before the end of 2021. The question of optimal testing in routine diagnostics should therefore be re-evaluated. Based on a consideration of the strengths and weaknesses of the widely available methods (immunohistochemistry and PCR), a test algorithm is proposed that allows quality assured, reliable, and cost-effective dMMR/MSI­H testing. For CRC and EC, testing is therefore already possible at the primary diagnosis stage, in line with international recommendations (NICE, NCCN). The clinician is therefore enabled from the outset to consider not only the predictive but also the prognostic and predispositional implications of such a test when counseling patients and formulating treatment recommendations. As a basis for quality assurance, participation in interlaboratory comparisons and continuous documentation of results (e.g., QuIP Monitor) are strongly recommended.

[MSI testing : What is new? What should be considered? German version]. / MSI-Testung : Was ist neu? Was ist zu beachten?

Based on new trial data regarding immune checkpoint inhibitors (ICIs), the detection of high-grade microsatellite instability (MSI-H) or underlying deficient mismatch repair protein (dMMR) is now becoming increasingly important for predicting treatment response. For the first time, a PD­1 ICI (pembrolizumab) has been approved by the European Medicines Agency (EMA) for first-line treatment of advanced (stage IV) dMMR/MSI­H colorectal cancer (CRC). Further indications, such as dMMR/MSI­H endometrial carcinoma (EC), have already succeeded (Dostarlimab, 2nd line treatment) and others are expected to follow before the end of 2021. The question of optimal testing in routine diagnostics should therefore be re-evaluated. Based on a consideration of the strengths and weaknesses of the widely available methods (immunohistochemistry and PCR), a test algorithm is proposed that allows quality assured, reliable, and cost-effective dMMR/MSI­H testing. For CRC and EC, testing is therefore already possible at the primary diagnosis stage, in line with international recommendations (NICE, NCCN). The clinician is therefore enabled from the outset to consider not only the predictive but also the prognostic and predispositional implications of such a test when counseling patients and formulating treatment recommendations. As a basis for quality assurance, participation in interlaboratory comparisons and continuous documentation of results (e.g., QuIP Monitor) are strongly recommended.

Multimodality treatment including surgery for primary pulmonary sarcoma: Size does matter.

BACKGROUND AND OBJECTIVES: Primary pulmonary sarcoma (PPS) accounts for less than 1.1% of all pulmonary tumors. Few outcome data are reported. We evaluated outcome and prognostic factors in our series. METHODS: We retrospectively reviewed all patients who underwent resection for PPS in our center from 2002 to 2018. Survival was calculated from the date of surgery until last follow-up. Impact on survival of gender, type of lung resection, completeness of resection, grade, size, and TNM staging for lung cancer and soft tissue sarcoma (STS) was assessed. RESULTS: Thirteen patients were included. Eight (61.5%) patients received neoadjuvant treatment. Median tumor size at diagnosis was 11.5 cm (1-30 cm). Type of lung resection was wedge (n = 2, 15%), lobectomy (n = 4, 31%), intrapericardial (n = 3, 23%), and extrapleural pneumonectomies (n = 4, 31%). In-hospital mortality was 8%. Overall 5-year survival was 60%. Median disease-free survival was 17 months. Tumor size was a predictor for survival (P = .02) and recurrence (P = .05). Gender (P = .04) and type of lung resection (P = .04) were predictors of survival. T stage for STS of trunk and extremity, and TNM stage for lung cancer were predictors for recurrence (P = .03 and P = .04, respectively). CONCLUSION: Surgical resection within a multimodality therapy concept in highly selected patients can offer good long-term outcome.

[Immunohistochemistry-based predictive biomarkers for lung cancer]. / Immunhistochemiebasierte prädiktive Biomarker bei Lungenkarzinomen.

Predictive biomarkers play an important role in the diagnosis of lung cancer. Applied methods and technologies include molecular tests and immunohistochemistry. The latter is predominantly dedicated to the preselection of tumors for subsequent molecular analyses. Given the low prevalence of certain molecular subtypes, immunohistochemistry can contribute to a high efficacy of lung cancer diagnosis. Thus, immunohistochemistry plays a lasting and even increasing role in this context. Some assays allow a definitive predictive classification based on immunohistochemistry alone. Approval of novel therapeutics increases the number of immunohistochemistry-based predictive biomarkers. The high sensitivity of assays must be ensured by careful selection of diagnostic primary antibodies, thorough validation of staining protocols, and standardized evaluation and scoring.

[Fluorescence in situ hybridization for the diagnosis of soft-tissue and bone tumors]. / Fluoreszenz-in-situ-Hybridisierung bei der Diagnostik von Weichgewebs- und Knochentumoren.

Mesenchymal tumors, especially high-grade sarcomas, frequently harbor chaotic genotypes. Few tumors arise in association with genetic tumor predisposition syndromes with germline mutations in tumor suppressor genes. An increasing number of soft-tissue and bone tumors are characterized by recurrent genomic alterations, which can be utilized for diagnostic purposes. These include translocations and amplifications and less frequently deletions. These alterations can be detected by fluorescence in situ hybridization among other techniques. The rising number of whole genome sequencing of soft-tissue and bone tumors leads to an improved understanding of tumor genetics. On this basis, fluorescence in situ hybridization has gained relevance as a diagnostic tool. This review covers relevant genetic alterations in lipomatous tumors, soft-tissue tumors with spindle-cell and epithelioid morphology, vascular tumors, small-blue-round-cell tumors, and bone tumors that are detectable by fluorescence in situ hybridization.

Histone deacetylase class-I inhibition promotes epithelial gene expression in pancreatic cancer cells in a BRD4- and MYC-dependent manner.

Pancreatic ductal adenocarcinoma (PDAC) is a highly aggressive cancer with a particularly dismal prognosis. Histone deacetylases (HDAC) are epigenetic modulators whose activity is frequently deregulated in various cancers including PDAC. In particular, class-I HDACs (HDAC 1, 2, 3 and 8) have been shown to play an important role in PDAC. In this study, we investigated the effects of the class I-specific HDAC inhibitor (HDACi) 4SC-202 in multiple PDAC cell lines in promoting tumor cell differentiation. We show that 4SC-202 negatively affects TGFß signaling and inhibits TGFß-induced epithelial-to-mesenchymal transition (EMT). Moreover, 4SC-202 markedly induced p21 (CDKN1A) expression and significantly attenuated cell proliferation. Mechanistically, genome-wide studies revealed that 4SC-202-induced genes were enriched for Bromodomain-containing Protein-4 (BRD4) and MYC occupancy. BRD4, a well-characterized acetyllysine reader, has been shown to play a major role in regulating transcription of selected subsets of genes. Importantly, BRD4 and MYC are essential for the expression of a subgroup of genes induced by class-I HDACi. Taken together, our study uncovers a previously unknown role of BRD4 and MYC in eliciting the HDACi-mediated induction of a subset of genes and provides molecular insight into the mechanisms of HDACi action in PDAC.

PI3K: A master regulator of brain metastasis-promoting macrophages/microglia.

Mutations and activation of the PI3K signaling pathway in breast cancer cells have been linked to brain metastases. However, here we describe that in some breast cancer brain metastases samples the protein expression of PI3K signaling components is restricted to the metastatic microenvironment. In contrast to the therapeutic effects of PI3K inhibition on the breast cancer cells, the reaction of the brain microenvironment is less understood. Therefore we aimed to quantify the PI3K pathway activity in breast cancer brain metastasis and investigate the effects of PI3K inhibition on the central nervous system (CNS) microenvironment. First, to systematically quantify the PI3K pathway activity in breast cancer brain metastases, we performed a prospective biomarker study using a reverse phase protein array (RPPA). The majority, namely 30 out of 48 (62.5%) brain metastatic tissues examined, revealed high PI3K signaling activity that was associated with a median overall survival (OS) of 9.41 months, while that of patients, whose brain metastases showed only moderate or low PI3K activity, amounted to only 1.93 and 6.71 months, respectively. Second, we identified PI3K as a master regulator of metastasis-promoting macrophages/microglia during CNS colonization; and treatment with buparlisib (BKM120), a pan-PI3K Class I inhibitor with a good blood-brain-barrier penetrance, reduced their metastasis-promoting features. In conclusion, PI3K signaling is active in the majority of breast cancer brain metastases. Since PI3K inhibition does not only affect the metastatic cells but also re-educates the metastasis-promoting macrophages/microglia, PI3K inhibition may hold considerable promise in the treatment of brain metastasis and the respective microenvironment.

Context-Dependent Epigenetic Regulation of Nuclear Factor of Activated T Cells 1 in Pancreatic Plasticity.

BACKGROUND & AIMS: The ability of exocrine pancreatic cells to change the cellular phenotype is required for tissue regeneration upon injury, but also contributes to their malignant transformation and tumor progression. We investigated context-dependent signaling and transcription mechanisms that determine pancreatic cell fate decisions toward regeneration and malignancy. In particular, we studied the function and regulation of the inflammatory transcription factor nuclear factor of activated T cells 1 (NFATC1) in pancreatic cell plasticity and tissue adaptation. METHODS: We analyzed cell plasticity during pancreatic regeneration and transformation in mice with pancreas-specific expression of a constitutively active form of NFATC1, or depletion of enhancer of zeste 2 homologue 2 (EZH2), in the context of wild-type or constitutively activate Kras, respectively. Acute and chronic pancreatitis were induced by intraperitoneal injection of caerulein. EZH2-dependent regulation of NFATC1 expression was studied in mouse in human pancreatic tissue and cells by immunohistochemistry, immunoblotting, and quantitative reverse transcription polymerase chain reaction. We used genetic and pharmacologic approaches of EZH2 and NFATC1 inhibition to study the consequences of pathway disruption on pancreatic morphology and function. Epigenetic modifications on the NFATC1 gene were investigated by chromatin immunoprecipitation assays. RESULTS: NFATC1 was rapidly and transiently induced in early adaptation to acinar cell injury in human samples and in mice, where it promoted acinar cell transdifferentiation and blocked proliferation of metaplastic pancreatic cells. However, in late stages of regeneration, Nfatc1 was epigenetically silenced by EZH2-dependent histone methylation, to enable acinar cell redifferentiation and prevent organ atrophy and exocrine insufficiency. In contrast, oncogenic activation of KRAS signaling in pancreatic ductal adenocarcinoma cells reversed the EZH2-dependent effects on the NFATC1 gene and was required for EZH2-mediated transcriptional activation of NFATC1. CONCLUSIONS: In studies of human and mouse pancreatic cells and tissue, we identified context-specific epigenetic regulation of NFATc1 activity as an important mechanism of pancreatic cell plasticity. Inhibitors of EZH2 might therefore interfere with oncogenic activity of NFATC1 and be used in treatment of pancreatic ductal adenocarcinoma.

Optimization and validation of PD-L1 immunohistochemistry staining protocols using the antibody clone 28-8 on different staining platforms.

Several immunohistochemistry (IHC) assays have been developed to assess tumor programmed death-ligand 1 (PD-L1) expression levels in patients who are candidates for programmed death-1 (PD-1)/PD-L1 inhibitor therapy. The PD-L1 IHC 28-8 pharmDx kit is FDA-approved as a complementary diagnostic and CE-marked as an in vitro diagnostic device for nivolumab therapy in melanoma and specific lung cancer subtypes (and for squamous cell carcinoma of the head and neck/urothelial carcinoma in Europe only). Kit availability is limited outside the United States, and its use requires the Dako Autostainer Link 48 platform, which is unavailable in many laboratories. Validated laboratory-developed tests based on 28-8 concentrated antibody outside the kit are needed. This study compared the results from PD-L1 expression level analysis across four immunohistochemistry platforms (Dako Autostainer Link 48, Dako Omnis, Leica Bond-III, and Ventana BenchMark ULTRA) with the 28-8 pharmDx kit in lung cancer (multiple histologies), melanoma, and head and neck cancer (multiple histologies). Samples were prepared per protocol for each platform and stained using PD-L1 IHC 28-8 pharmDx kit on Dako Autostainer Link 48, and per protocol for each platform. The control samples (tonsil and placenta tissue; cell lines with prespecified PD-L1 expression levels) were tested to evaluate the specificity and the sensitivity of test assays. An agreement level of 0.90 with the pharmDx kit was set for each platform. Inter- and intra-assay reliability were assessed. Evaluable samples were lung cancer = 29; melanoma = 31; head and neck cancer = 30. Mean agreement was calculated for PD-L1 expression levels of ≥1%, ≥5%, ≥10%, and ≥50%. Mean overall agreement for all indications was 0.87-0.99. Inter- and intra-assay of scoring/classification repeatability was 100%. Analysis of PD-L1 expression levels using laboratory-developed immunohistochemistry assays with 28-8 antibody may be permissible if the platform is validated using reference samples with defined expression levels.

Interlaboratory concordance of PD-L1 immunohistochemistry for non-small-cell lung cancer.

AIMS: Programmed death ligand 1 (PD-L1) immunohistochemistry has become a mandatory diagnostic test in the treatment of lung cancer. Several research initiatives have started to harmonise the five PD-L1 immunohistochemistry assays that have been used in clinical trials. Here, we report data on interlaboratory and interassay concordance for commercial assays ('assays') and laboratory-developed tests (LDTs) at 10 German testing sites. METHODS AND RESULTS: To assess interlaboratory concordance, a tissue microarray containing 21 pulmonary carcinoma specimens was centrally prepared. Pre-cut sections were stained at 10 sites by the use of assays 28-8, 22C3, SP263, and SP142, as well as 11 LDTs. Assay performance was evaluated with a second tissue microarray containing 11 cell lines with defined PD-L1 expression. Quality control was centrally performed by manual and digital analyses. The assays yielded reproducible IHC staining patterns at all sites. In agreement with previous studies, 22C3, 28-8 and SP263 showed similar staining patterns, whereas SP142 was distinct. Among the LDTs, six of 11 protocols showed staining patterns similar to those of assays 22C3 and 28-8. Interlaboratory concordance of tumour cell scoring by use of a six-step system was moderate (Light's κ = 0.43-0.69), whereas the clinically approved cut-offs of ≥1% and ≥50% showed substantial concordance (κ = 0.73-0.89). Immune cell scoring by the use of SP142 yielded moderate concordance (κ = 0.42). CONCLUSIONS: The data confirm the previously described staining patterns of the assays, and show that they can be reproducibly employed at different sites. LDTs with staining results similar to those of the assays are implementable, but have to be carefully validated.

Current Standard and Future Perspectives in the Treatment of Gastrointestinal Stromal Tumors.

The origin of gastrointestinal stromal tumors (GIST) from interstitial cells of Cajal or their precursor cells has been understood since the early 1990s. The first mutations within the KIT-gene have been described in the late 1990s. Even though these mutations were the breakthrough of small molecular therapy, we still do not know the factors responsible for their malignant transformation. Until then, we can only speak of recurrence risk. This review gives an introduction on the current understanding of GIST and highlights the remaining questions for diagnosis, tumor progression, and treatment in progressive disease.

Harmonized PD-L1 immunohistochemistry for pulmonary squamous-cell and adenocarcinomas.

Immunohistochemistry of the PD-L1 protein may be predictive for anti-PD-1 and anti-PD-L1 immunotherapy in pulmonary adenocarcinoma and in clinically unselected cohorts of so-called non-small-cell lung cancer. Several PD-L1 immunohistochemistry assays with custom reagents and scoring-criteria are developed in parallel. Biomarker testing and clinical decision making would profit from harmonized PD-L1 diagnostics. To assess interobserver concordance and PD-L1 immunohistochemistry staining patterns, 15 pulmonary carcinoma resection specimens (adenocarcinoma: n=11, squamous-cell carcinoma: n=4) were centrally stained with the assays 28-8, 22C3, SP142, and SP263 according to clinical trial protocols. The slides were evaluated independently by nine pathologists. Proportions of PD-L1-positive carcinoma cells and immune cells were scored according to a 6-step system that integrates the criteria employed by the four PD-L1 immunohistochemistry assays. Proportion scoring of PD-L1-positive carcinoma cells showed moderate interobserver concordance coefficients for the 6-step scoring system (Light's kappa=0.47-0.50). The integrated dichotomous proportion cut-offs (≥1, ≥5, ≥10, ≥50%) showed good concordance coefficients (κ=0.6-0.8). Proportion scoring of PD-L1-positive immune cells yielded low interobserver concordance coefficients both for the 6-step-score (κ<0.2) and the dichotomous cut-offs (κ=0.12-0.25). The assays 28-8 and 22C3 stained similar proportions of carcinoma cells in 12 of 15 cases. SP142 stained fewer carcinoma cells compared to 28-8, 22C3, and SP263 in four cases, whereas SP263 stained more carcinoma cells in nine cases. SP142 and SP263 stained immune cells more intensely. The data indicate that carcinoma cells can be reproducibly scored in PD-L1 immunohistochemistry for pulmonary adenocarcinoma and squamous-cell carcinoma. No differences in interobserver concordance were noticed among the tested assays. The scoring of immune cells yielded low concordance rates and might require specific standardization. The four tested PD-L1 assays did not show comparable staining patterns in all cases. Thus, studies that correlate staining patterns and response to immunotherapy are required to test the significance of the observed differences.