Digital live imaging of intraoperative electrocochleography during cochlear implantation: the first 50 patients.

INTRODUCTION: Real-time visualization of intraoperative electrocochleography (ECochG) potentials via a digital microscope during cochlear implantation can provide direct feedback during electrode insertion. The aim of this prospective, randomized study of 50 patients was to obtain long-term data with a focus on residual hearing preservation and speech understanding. MATERIAL AND METHODS: Cochlear implantations were performed in 50 patients (26 female, 24 male) with residual hearing using a digital microscope. Patients were randomized into two groups. Intraoperative ECochG potentials were either displayed directly in the surgeon's field of view (picture-in-picture display, PiP) or not directly in the field of view (without picture-in-picture display, without PiP). Residual hearing preservation and speech comprehension were recorded within a 1-year follow-up period, compared between groups (PiP versus without PiP) and to a control group of 26 patients implanted without ECochG. RESULTS: Mean insertion time was significantly longer in the picture-in-picture group (p = 0.025). Residual hearing preservation after 6 weeks at 250 Hz was significantly better in the picture-in-picture group (p = 0.017). After one year, 76% of patients showed residual hearing in the picture-in-picture group (62% without picture-in-picture technique, p = n.s.). Use of the picture-in-picture technique resulted in better long-term pure tone residual hearing preservation at 250, 500, and 1000 Hz. Speech intelligibility improved by 46% in the picture-in-picture group (38% without picture-in-picture). DISCUSSION: This study is the first to describe long-term results in a large cohort of cochlear implant patients in whom digital visualization of intraoperative ECochG was used. Our results show that visualization of intraoperative ECochG has a positive effect on residual hearing preservation.

Muscular tension in ear surgeons during cochlear implantations: does a new microscope improve musculoskeletal complaints?

PURPOSE: Musculoskeletal complaints and fatigue are commonly described symptoms in daily work of ear nose and throat surgeons using a microscope. Long ear surgical procedures are associated with prolonged microscope use, which can lead to unconsciously tense and uncomfortable body posture. The digital microscope RoboticScope® allows visualization of surgical site through a Head-Mounted Display, independent from camera head and is therefore much easier on the back, as the sitting position can be adjusted flexibly. Aim of the prospective study was to investigate to what extent the use of a RoboticScope® changes the tension of neck and shoulder muscles of the surgeons in comparison to a conventional tripod microscope. METHODS: For this purpose, the electric activity of neck and shoulder muscles of surgeons was recorded using surface electromyography during cochlear implantations. Electrical potentials were derived via electrodes on neck and shoulder muscles. The basic tension of those muscles was measured in relaxed position before and after surgery. During microscope use the tension was continued to be measured. A questionnaire recorded parameters such as level of difficulty of operation as well as patient data. RESULTS: Results from 58 operations, 33 of which were performed using a conventional microscope and 25 using a Head-Mounted Display, show a significant reduction in muscular tension during surgery by 40% (p < 0.001) in experienced ear surgeons when using a RoboticScope®, regardless of the surgeon. CONCLUSION: Our results are in line with the relevance of preventive measures to avoid acute and chronic work-related illnesses/symptoms described in literature.

Bacterial biofilm formation on headpieces of Cochlear implants.

INTRODUCTION: Bacterial biofilm formation on medical devices, such as Cochlear implants (CI), can lead to chronic infections. Not only the inner parts of the implant but also the externally located headpiece might be associated with prolonged superficial skin eczema resulting in the inability of wearing the headpiece. In this study, the surface of three CI headpieces from different manufacturers were examined for bacterial biofilm formation. MATERIALS AND METHODS: Two bacterial species associated with implant-related infections were tested: Pseudomonas aeruginosa (ATCC9027) and Staphylococcus aureus (ATCC6538). Biofilms were formed over 24 h in tryptic soy broth at 36 °C. Biofilm formation was detected in form of biomass measurement by crystal violet staining. CI headpiece dummies of three manufacturers were used. RESULTS: Both tested bacterial species formed biofilms on the examined CI headpiece-surfaces in a species-dependent manner with higher biofilm formation of P. aeruginosa. For both, S. aureus and P. aeruginosa, biofilm formation on the CI components was comparable to a polystyrene control surface. Between the three manufacturers, no significant difference in biofilm formation was found. DISCUSSION: The tested bacteria displayed biofilm formation on the CI headpieces in a species-specific manner with higher amount of biofilm formed by P. aeruginosa. The biofilm formation was comparable between the manufacturers. In this study, an enhanced biofilm formation on CI headpieces could not be demonstrated. These in vitro tests suggest a minor role of bacterial biofilm on the CI headpiece in skin infections under the CI headpiece.

Abdominal ultrasound in head and neck squamous cell carcinoma staging: yes or no?

PURPOSE: Abdominal ultrasound is a diagnostic staging procedure for distant metastases in head and neck squamous cell carcinoma (HNSCC). However, currently performed abdominal staging procedures do not follow consistent standards. Therefore, this retrospective study on 498 patients aimed at investigating on abdominal ultrasound as a staging procedure in HNSCC. MATERIALS AND METHODS: A retrospective analysis of 498 head and neck cancer patients treated in our Department of Head and Neck Surgery between 2008 and 2015 was performed. Disease-related data were collected over a mean follow-up time of 30.3 months, and results of abdominal ultrasound were analyzed. RESULTS: 426 patients received abdominal ultrasound as a staging procedure. 7% (29) were suspicious for metastases. In 19 cases (66%), the detected abnormalities were masses of the liver. In four patients, abdominal metastases were confirmed at the time of initial diagnosis. 16 patients developed abdominal metastases in the course of the disease (on average 623 days after initial diagnosis). 19 out of 20 patients with abdominal metastases had an N2/N3 cervical lymph node status. In this study, the negative predictive value of abdominal ultrasound for HNSCC staging was 99.03%, while the positive predictive value yielded 5.88% (N2/N3-patients). CONCLUSION: Only in patients with locally advanced lymph-node-status (N2/N3), abdominal ultrasound can be useful as a staging investigation to exclude abdominal metastasis in HNSCC patients. For N0/N1 patients, abdominal ultrasound might be dispensed. Of note, in case of a positive result, further diagnostic procedures are mandatory.

The accuracy of clinical neck staging for p16-positive and negative oropharyngeal cancer and its therapeutic implications.

PURPOSE: Oropharyngeal squamous cell carcinoma (OPSCC) may be treated with primary surgery or primary (chemo)radiation. While surgery with concurrent neck dissection provides definitive pathological staging of the neck, non-surgical treatment relies on clinical staging for treatment planning. To assess the accuracy of clinical neck staging, we compared clinical to surgical staging after primary surgery in patients with p16-negative and p16-positive OPSCC. METHODS: Retrospective analysis of clinical, pathological, and oncologic outcome data of patients with OPSCC treated with primary surgery and bilateral neck dissection. Clinical and pathological nodal status were compared for p16-negative and p16-positive patients. Patients with occult metastatic disease were analyzed in detail. RESULTS: 95 patients were included. 60.5% of p16-negative patients and 66.6% of p16-positive patients had pathologically confirmed metastatic neck disease. p16-positive patients had improved 24-month recurrence-free survival compared to p16-negative patients at 93.3% vs. 69.6%. Pathological N-status differed from clinical N-status in 36.8% of p16-negative patients vs. 31.6% of p16-positive patients. Occult metastatic disease was more common in p16-negative patients at 18.4% vs. 8.8% for p16-positive patients. Clinical detection sensitivity for extranodal extension was low overall; sensitivity was 27.3% and specificity was 91.6% for p16-negative patients vs. 61.5% and 80.0% for p16-positive patients, respectively. CONCLUSION: Our data show a considerable degree of inaccuracy of clinical neck staging results in all OPSCC patients which needs to be taken into consideration during therapy planning. For p16-positive patients, these findings warrant attention in the context of therapy deintensification to avoid undertreatment.

ERCC2 gene single-nucleotide polymorphism as a prognostic factor for locally advanced head and neck carcinomas after definitive cisplatin-based radiochemotherapy.

Identifying patients with locally advanced head and neck carcinoma on high risk of recurrence after definitive concurrent radiochemotherapy is of key importance for the selection for consolidation therapy and for individualized treatment intensification. In this multicenter study we analyzed recurrence-associated single-nucleotide polymorphisms (SNPs) in DNA repair genes in tumor DNA from 132 patients with locally advanced head and neck carcinoma (LadHnSCC). Patients were treated with definitive radiotherapy and simultaneous cisplatin-based chemotherapy at six partner sites of the German Cancer Consortium (DKTK) Radiation Oncology Group from 2005 to 2011. For validation, a group of 20 patients was available. Score selection method using proportional hazard analysis and leave-one-out cross-validation were performed to identify markers associated with outcome. The SNPs rs1799793 and rs13181 were associated with survival and the same SNPs and in addition rs17655 with freedom from loco-regional relapse (ffLRR) in the trainings datasets from all patients. The homozygote major rs1799793 genotype at the ERCC2 gene was associated with better (Hazard ratio (HR): 0.418 (0.234-0.744), p = 0.003) and the homozygote minor rs13181 genotype at ERCC2 with worse survival (HR: 2.074, 95% CI (1.177-3.658), p = 0.017) in comparison to the other genotypes. At the ffLRR endpoint, rs1799793 and rs13181 had comparable prognostic value. The rs1799793 and rs13181 genotypes passed the leave-one-out cross-validation procedure and associated with survival and ffLRR in patients with LadHnSCC treated with definitive radiochemotherapy. While findings were confirmed in a small validation dataset, further validation is underway within a prospective biomarker study of the DKTK.

The Flex robotic system compared to transoral laser microsurgery for the resection of supraglottic carcinomas: first results and preliminary oncologic outcomes.

PURPOSE: Transoral robotic surgery (TORS) has the potential to improve some inherent disadvantages of transoral laser microsurgery (TLM). Here, we retrospectively assessed the application of the Medrobotics Flex system for the resection of supraglottic carcinomas compared to TLM. METHODS: 84 patients underwent surgery for supraglottic carcinomas with the Flex robotic system (n = 19, T-stage distribution in %: T1 42, T2 47, T3 11, T4 0) or TLM (n = 65, T-stage distribution in %: T1 40, T2 44, T3 14, T4 2). Clinical and oncologic parameters were compared. RESULTS: All surgeries were successfully completed with the Flex system and tracheostomy rate was 13%. For patients with adequate follow-up, 24-month disease-free survival was 71.4% (n = 5/7) after TORS compared to 64.9% (n = 24/37) after TLM. Local recurrence rates were 0% for TORS and 11% for TLM. CONCLUSIONS: Initial results for supraglottic carcinoma resection using the Medrobotics Flex system are encouraging with excellent local tumor control.

NAMPT signaling is critical for the proangiogenic activity of tumor-associated neutrophils.

Tumor-associated neutrophils (TANs) regulate many processes associated with tumor progression, and depending on the microenvironment, they can exhibit pro- or antitumor functions. However, the molecular mechanisms regulating their tumorigenicity are not clear. Using transplantable tumor models, we showed here that nicotinamide phosphoribosyltransferase (NAMPT), a molecule involved in CSF3R downstream signaling, is essential for tumorigenic conversion of TANs and their pro-angiogenic switch. As a result tumor vascularization and growth are strongly supported by these cells. Inhibition of NAMPT in TANs leads to their antitumor conversion. Adoptive transfer of such TANs into B16F10-tumor bearing mice attenuates tumor angiogenesis and growth. Of note, we observe that the regulation of NAMPT signaling in TANs, and its effect on the neutrophil tumorigenicity, are analogous in mice and human. NAMPT is up-regulated in TANs from melanoma and head-and-neck tumor patients, and its expression positively correlates with tumor stage. Mechanistically, we found that targeting of NAMPT suppresses neutrophil tumorigenicity by inhibiting SIRT1 signaling, thereby blocking transcription of pro-angiogenic genes. Based on these results, we propose that NAMPT regulatory axis is important for neutrophils to activate angiogenic switch during early stages of tumorigenesis. Thus, identification of NAMPT as the critical molecule priming protumor functions of neutrophils provides not only mechanistic insight into the regulation of neutrophil tumorigenicity, but also identifies a potential pathway that may be targeted therapeutically in neutrophils. This, in turn, may be utilized as a novel mode of cancer immunotherapy.

Neutrophil Maturation and Survival Is Controlled by IFN-Dependent Regulation of NAMPT Signaling.

Granulocyte-colony stimulating factor (G-CSF)/nicotinamide phosphoribosyltransferase (NAMPT) signaling has been shown to be crucial for the modulation of neutrophil development and functionality. As this signaling pathway is significantly suppressed by type I interferons (IFNs), we aimed to study how the regulation of neutrophil differentiation and phenotype is altered in IFN-deficient mice during granulopoiesis. The composition of bone marrow granulocyte progenitors and their Nampt expression were assessed in bone marrow of type I IFN receptor knockout (Ifnar1-/-) mice and compared to wild-type animals. The impact of NAMPT inhibition on the proliferation, survival, and differentiation of murine bone marrow progenitors, as well as of murine 32D and human HL-60 neutrophil-like cell lines, was estimated. The progressive increase of Nampt expression during neutrophil progenitor maturation could be observed, and it was more prominent in IFN-deficient animals. Altered composition of bone marrow progenitors in these mice correlated with the dysregulation of apoptosis and altered differentiation of these cells. We observed that NAMPT is vitally important for survival of early progenitors, while at later stages it delays the differentiation of neutrophils, with moderate effect on their survival. This study shows that IFN-deficiency leads to the elevated NAMPT expression in the bone marrow, which in turn modulates neutrophil development and differentiation, even in the absence of tumor-derived stimuli.

CD31 and VEGF are prognostic biomarkers in early-stage, but not in late-stage, laryngeal squamous cell carcinoma.

BACKGROUND: Patients suffering from squamous cell carcinoma of the larynx (LSCC) with lymphatic metastasis have a relatively poor prognosis and often require radical therapeutic management. The mechanisms which drive metastasis to the lymph nodes are largely unknown but may be promoted by a pro-angiogenic tumor microenvironment. In this study, we examined whether the number of microvessels and the expression level of vascular endothelial growth factor (VEGF) in the primary tumor are correlated with the degree of lymph node metastasis (N-stage), tumor staging (T) and survival time in LSCC patients. METHODS: Tissue-Microarrays of 97 LSCC patients were analyzed using immunohistochemistry. The expression of VEGF was scored as intensity of staining (low vs high) and the number of CD31-positive vessels (median

[The role of elective neck dissection during salvage laryngectomy - a retrospective analysis]. / Die Rolle der elektiven Neck dissection bei Salvage Laryngektomie ­ eine retrospektive Analyse.

Elective neck dissection of the N0-neck is routinely performed during salvage laryngectomy (SLE) for recurrent cancer of the larynx or hypopharynx. The therapeutic benefit of additional neck dissection must be weighed against the risk of increased morbidity. In this retrospective analysis, we assessed oncologic parameters of patients who underwent SLE with concurrent bilateral neck dissection for recurrent laryngeal or hypopharyngeal cancer. We compared these data with patients who underwent primary laryngectomy (LE) with bilateral neck dissection for laryngeal and hypopharyngeal cancer.19 patients who had undergone SLE and 83 patients after LE were included in the analysis. The majority of patients had advanced stage tumors prior to LE or primary radiation therapy, as well as advanced stage recurrent tumors prior to SLE. Prior to SLE, 5 % of all patients (n = 1) had clinically pathologic lymph nodes, compared to 47 % (n = 39) prior to LE. 17 % (n = 14) of patients with LE and bilateral neck dissection had occult lymph node metastases, compared to 5 % (n = 1) of patients who underwent SLE with bilateral neck dissection. Overall, 55 % (n = 44) of patients who underwent LE had positive cervical lymph nodes, compared to 10 % (n = 2) of SLE patients. Lymph node yield was higher in patients with LE than in SLE-patients (37.3 vs. 18.7, p < 0.001). 5-year OS was 50 % after LE and 33 % after SLE. Cervical lymph node metastases are rare in patients who undergo SLE for recurrent cancers of the larynx of hypopharynx. However, occult metastases do occur. Therefore, since SLE is the final curative therapy, additional neck dissection should be taken into consideration.

[Extracranial schwannomas of the Head and Neck: Clinical -approach based on 20 cases]. / Extrakranielle Schwannome im Kopf-Hals-Bereich: Klinische Implikationen anhand von 20 Fällen.

Background Schwannomas are rare benign tumors originating from the perineural cells forming the myelin layer in the peripheral nervous system (PNS). While well established therapeutic concepts exist for intracranial schwannomas, there is a lack of consistent clinical standards for extracranial schwannomas. Method This retrospective study describes the clinical pathway of 20 patients with histologically proven extracranial schwannomas of the head and neck. The diagnostic and therapeutic strategies for schwannomas are discussed with special emphasis on localization and functional outcome. Results Extracranial schwannomas of the head and neck region mostly originated from the facial nerve (n = 4), vagal nerve (n = 4) or sympathetic chain (n = 3). Most common symptoms were swelling (n = 12) and pain (n = 3). Preoperative imaging included MRI (n = 13), ultrasound (n = 12) and CT (n = 3). Surgical intervention was performed in 18 cases (n = 14 complete extirpation, n = 3 partial extirpation, n = 1 unknown). Regarding completely extirpated schwannomas of motor nerves (n = 10) severing the nerve of origin was more often required in patients with a preexisting functional deficit (3 out of 4 = 75 %) than in patients without preexisting deficits (2 out of 6 = 33 %). Conclusion Representing rare tumors of the head and neck region mostly originating from the facial nerve, sympathetic chain or caudal cranial nerves extracranial schwannomas require a systematic diagnostic and therapeutic approach. Postoperative functional deficits after complete extirpation must especially be anticipated in patients with a preexisting functional deficit.

Surface CD52, CD84, and PTGER2 mark mature PMN-MDSCs from cancer patients and G-CSF-treated donors.

Precise molecular characterization of circulating polymorphonuclear myeloid-derived suppressor cells (PMN-MDSCs) is hampered by their mixed composition of mature and immature cells and lack of specific markers. Here, we focus on mature CD66b+CD10+CD16+CD11b+ PMN-MDSCs (mPMN-MDSCs) from either cancer patients or healthy donors receiving G-CSF for stem cell mobilization (GDs). By RNA sequencing (RNA-seq) experiments, we report the identification of a distinct gene signature shared by the different mPMN-MDSC populations under investigation, also validated in mPMN-MDSCs from GDs and tumor-associated neutrophils (TANs) by single-cell RNA-seq (scRNA-seq) experiments. Analysis of such a gene signature uncovers a specific transcriptional program associated with mPMN-MDSC differentiation and allows us to identify that, in patients with either solid or hematologic tumors and in GDs, CD52, CD84, and prostaglandin E receptor 2 (PTGER2) represent potential mPMN-MDSC-associated markers. Altogether, our findings indicate that mature PMN-MDSCs distinctively undergo specific reprogramming during differentiation and lay the groundwork for selective immunomonitoring, and eventually targeting, of mature PMN-MDSCs.

Epithetic nasal reconstruction after total rhinectomy: Oncologic outcomes, immediate and long-term adverse effects, and quality of life.

INTRODUCTION: Total rhinectomy for tumors of the nasal cavity substantially alters patients' appearance and requires local reconstruction. While full nasal epitheses are well-established for this purpose, potential long-term adverse effects and impact on patients' quality of life are not fully understood. METHODS: Sixteen patients who underwent total rhinectomy with ensuing nasal reconstruction with a full nasal epithesis were included in the study. Oncologic outcomes were assessed, and adverse effects and quality of life analyses were performed based on a patient-reported outcomes tool. RESULTS: In patients with squamous cell carcinomas of the nasal cavity, total rhinectomy led to excellent local tumor control. Immediate and long-term adverse effects of total rhinectomy and placement of a nasal epithesis were predominantly limited to the immediate nasal region. While patients were satisfied with their nasal appearance, they reported a worse assessment of their facial appearance and a measurable long-term effect on their psychological well-being. CONCLUSION: Total rhinectomy and reconstruction with a full nasal epithesis is a safe and oncologically sound treatment approach. However, its effects on patients' overall appearance and psychological well-being need to be considered during treatment planning and follow-up.

First Use of a New Robotic Endoscope Guiding System in Endoscopic Orbital Decompression.

PURPOSE: Over the last years, robot-assisted surgery gained in importance in head and neck surgery. In our study, we used a new robotic endoscope guiding system in patients undergoing endoscopic balanced orbital decompression. The aim of the study is to evaluate the feasibility and benefit of a robotic arm in endoscopic orbital surgery. METHODS: The Medineering Robotic Endoscope Guiding System is a robotic arm designed for holding an endoscope during interventions. An endoscope equipped with a 4K camera was attached at the tip of the robotic arm and placed in the surgical field. The surgeon controlled the movements of the endoscope with foot pedal. Eight patients underwent balanced endoscopic orbital decompression showing typical symptoms of Graves' orbitopathy preoperatively. Balanced decompression was performed via a combined approach transnasally and laterally via a small skin incision. RESULTS: Attaching the endoscope to the robotic guiding system and placing it in the nasal cavity were relatively simple procedures. Setup time was less than 10 minutes. Tool motion and control using the foot pedal were comfortable and adequately precise. Movements of the attached endoscope inside the nose were feasible and allowed 2-hand surgery. The patients did not show any adverse events or complications. CONCLUSION: The Medineering Robotic Endoscope Guiding System seems to be a safe and effective support in endoscopic skull base surgery especially for orbital decompression, thus allowing 2-hand or even 4-hand settings. To the best of our knowledge, this is the first study describing the successful application of a robotic system in orbital surgery.

Digital Live Imaging of Intraoperative Electrocochleography - First Description of Feasibility and Hearing Preservation During Cochlear Implantation.

INTRODUCTION: Intraoperative electrocochleography (ECochG) during cochlear implantation is a promising tool to preserve residual hearing. However, the time gap between insertion of the electrode and acoustic feedback from the audiologist to the surgeon can cause delay and subsequently irreparable damage to cochlear structures. In this feasibility study, for the first time, real-time visualization of intraoperative ECochG via digital microscope display directly to the surgeon was successfully performed in four patients. MATERIALS AND METHODS: Four patients with residual hearing underwent cochlear implantation. Intraoperative electrocochleography responses were collected and direct visualization during the time of electrode insertion into the surgeon's field of view in the binoculars using augmented real-time digital imaging was realized. The time of electrode insertion was recorded. Hearing preservation was determined by testing postoperative changes in behavioral thresholds. RESULTS: Digital live visualization of intraoperative ECochG using image augmentation in a digital microscope was successfully performed in all cases and enabled direct adaptation of the surgeon's insertion behavior. Mean time of electrode insertion was 129.8 seconds. Postoperative behavioral thresholds were comparable to preoperative taken thresholds. Preservation of residual hearing in the low frequency range was possible. DISCUSSION: This study is the first to describe digital visualization of intraoperative electrocochleography as a new method enabling the surgeon to directly react to changes in amplitude of the cochlea microphonics. Our results show that augmentation of the intraoperative live imaging with electrical potentials could add to hearing preservation during cochlear implantation.

Imaging studies of bacterial biofilms on cochlear implants-Bioactive glass (BAG) inhibits mature biofilm.

The capability of Pseudomonas aeruginosa and Staphylococcus aureus to form biofilm on varying CI component materials differs in the presence and absence of bioactive glass (BAG). The application of BAG induces significant changes in biofilm morphology which can be visualized via scanning electron microscopy (SEM). Bacterial biofilm formation on medical devices, such as cochlear implants (CI), can lead to chronic infections. Interestingly, BAG of type S53P4 seems to be a promising tool for use in the reduction of biofilm development. Primarily, four bacterial species known to cause implant-related infections, P.aeruginosa (ATCC9027), S. aureus (ATCC6538), Staphylococcus epidermidis (ATCC12228) and Streptococcus pyogenes (ATCC19615) were analyzed regarding their capacity to form biofilm on CI components manufactured from three kinds of material: silicone, platinum and titanium. Subsequently, P. aeruginosa and S. aureus biofilms were visualized using scanning electron microscopy, comparing BAG-treated biofilm with non-treated biofilm. The four bacterial species presented biofilm-forming capabilities in a species and surface dependent manner. Metal CI components allowed for the greatest proliferation of biofilm. S. aureus and P. aeruginosa showed the highest rate of biofilm formation on polystyrene surfaces. For both species, SEM revealed altered biofilm morphology after treatment of S53P4 BAG. This study indicates that bacterial biofilm formation and structure on CI components is dependent on the surface composition, altering between metal and silicone surfaces. After application of BAG, changes in biofilm morphology on CI components were observed. These data highlight the impact of BAG on bacterial biofilm morphology.

Differential expansion of circulating human MDSC subsets in patients with cancer, infection and inflammation.

BACKGROUND: Myeloid-derived suppressor cells (MDSC) are a functional myeloid cell subset that includes myeloid cells with immune suppressive properties. The presence of MDSC has been reported in the peripheral blood of patients with several malignant and non-malignant diseases. So far, direct comparison of MDSC across different diseases and Centers is hindered by technical pitfalls and a lack of standardized methodology. To overcome this issue, we formed a network through the COST Action Mye-EUNITER (www.mye-euniter.eu) with the goal to standardize and facilitate the comparative analysis of human circulating MDSC in cancer, inflammation and infection. In this manuscript, we present the results of the multicenter study Mye-EUNITER MDSC Monitoring Initiative, that involved 13 laboratories and compared circulating MDSC subsets across multiple diseases, using a common protocol for the isolation, identification and characterization of these cells. METHODS: We developed, tested, executed and optimized a standard operating procedure for the isolation and immunophenotyping of MDSC using blood from healthy donors. We applied this procedure to the blood of almost 400 patients and controls with different solid tumors and non-malignant diseases. The latter included viral infections such as HIV and hepatitis B virus, but also psoriasis and cardiovascular disorders. RESULTS: We observed that the frequency of MDSC in healthy donors varied substantially between centers and was influenced by technical aspects such as the anticoagulant and separation method used. Expansion of polymorphonuclear (PMN)-MDSC exceeded the expansion of monocytic MDSC (M-MDSC) in five out of six solid tumors. PMN-MDSC expansion was more pronounced in cancer compared with infection and inflammation. Programmed death-ligand 1 was primarily expressed in M-MDSC and e-MDSC and was not upregulated as a consequence of disease. LOX-1 expression was confined to PMN-MDSC. CONCLUSIONS: This study provides improved technical protocols and workflows for the multi-center analysis of circulating human MDSC subsets. Application of these workflows revealed a predominant expansion of PMN-MDSC in solid tumors that exceeds expansion in chronic infection and inflammation.