Prolonged Course of COVID-19-Associated Pneumonia in a B-Cell Depleted Patient After Rituximab

Patients with pre-existing comorbidities and immunosuppression are at greater risk for SARS-CoV-2 infection and severe manifestations of COVID-19. This also includes cancer patients, who are shown to have a poor prognosis after infection. Here, we describe the case of a 72-year old male patient with B-cell depletion after maintenance treatment with rituximab for non-Hodgkin-lymphoma who had a prolonged COVID-19 course and initial false negative test results. Our case highlights the diagnostic pitfalls in diagnosing COVID-19 in B-cell depleted patients and discuss the role of B-cell depletion in the course and treatment of COVID-19. Furthermore, we investigated peripheral blood monocytes and SARS-CoV-2 specific T cells in our patient. In conclusion, our case report can help physicians to avoid diagnostic pitfalls for COVID-19 in hemato-oncological patients under chemoimmunotherapy and tries to explain the role of B-cell depletion and SARS-CoV-2 specific T cells in this context.

Changing the Use of HIV Pre-exposure Prophylaxis Among Men Who Have Sex With Men During the COVID-19 Pandemic in Melbourne, Australia

We surveyed 204 men who have sex with men (MSM) who were pre-exposure prophylaxis (PrEP) users. One in 4 daily PrEP users stopped taking PrEP during the COVID-19 pandemic, and 5% switched to on-demand PrEP. Most men reduced PrEP use because they stopped having casual sex and reduced the number of casual partners during the COVID-19 pandemic.

Combined radiotherapy and concurrent tumor treating fields (TTFields) for glioblastoma: Dosimetric consequences on non-coplanar IMRT as initial results from a phase I trial

Background

Glioblastoma is a rapidly proliferating tumor. Patients bear an inferior prognosis with a median survival time of 14-16 months. Proliferation and repopulation are a major resistance promoting factor for conventionally fractionated radiotherapy. Tumor-Treating-Fields (TTFields) are an antimitotic modality applying low-intensity (1-3 V/cm), intermediate-frequency (100-300 kHz) alternating electric-fields. More recently interference of TTFields with DNA-damage-repair and synergistic effects with radiotherapy were reported in the preclinical setting. This study aims at examining the dosimetric consequences of TTFields applied during the course of radiochemotherapy.

Methods

Cone-beam-computed-tomography (CBCT)-data from the first seven patients of the PriCoTTF-phase-I-trial were used in a predefined way for dosimetric verification and dose-accumulation of the non-coplanar-intensity-modulated-radiotherapy (IMRT)-treatment-plans as well as geometric analysis of the transducer-arrays by which TTFields are applied throughout the course of treatment. Transducer-array-position and contours were obtained from the low-dose CBCT’s routinely made for image-guidance. Material-composition of the electrodes was determined and a respective Hounsfield-unit was assigned to the electrodes. After 6D-fusion with the planning-CT, the dose-distribution was recalculated using a Boltzmann-equation-solver (Acuros XB) and a Monte-Carlo-dose-calculation-engine.

Results

Overdosage in the scalp in comparison to the treatment plan without electrodes stayed below 8.5% of the prescribed dose in the first 2 mm below and also in deeper layers outside 1cm² at highest dose as obtained from dose-volume-histogram comparisons. In the clinical target volume (CTV), underdosage was limited to 2.0% due to dose attenuation by the electrodes in terms of D95 and the effective-uniform-dose. Principal-component-analysis (PCA) showed that the first principal-position-component of the variation of repeated array-placement in the direction of the largest variations and the perpendicular second-component spanning a tangential plane on the skull had a standard deviation of 1.06 cm, 1.23 cm, 0.96 cm, and 1.11 cm for the frontal, occipital, left and right arrays for the first and 0.70 cm, 0.71 cm, 0.79 cm, and 0.68 cm, respectively for the second-principal-component. The variations did not differ from patient-to-patient (p > 0.8, Kruskal-Wallis-tests). This motion led to a diminution of the dosimetric effects of the electrodes.

Conclusion

From a dosimetric point of view, dose deviations in the CTV due to transducer-arrays were not clinically significant in the first 7 patients and confirmed feasibility of combined adjuvant radiochemotherapy and concurrent TTFields.

PriCoTTF Trial: A phase I/II trial of TTFields prior and concomitant to radiotherapy in newly diagnosed glioblastoma.

DRKS-ID: DRKS00016667.

Date of Registration in DRKS: 2019/02/26.

Investigator Sponsored/Initiated Trial (IST/IIT): yes.

Ethics Approval/Approval of the Ethics Committee: Approved.

(leading) Ethics Committee Nr.: 18–8316-MF, Ethik-Kommission der Medizinischen.

Fakultät der Universität Duisburg-Essen.

EUDAMED-No. (for studies acc. to Medical Devices act): CIV-18-08-025247.

Skeletal deterioration in COL2A1-related spondyloepiphyseal dysplasia occurs prior to osteoarthritis

OBJECTIVE

Spondyloepiphyseal dysplasia, a combination of progressive arthropathy with variable signs of skeletal dysplasia, can be a result of mutations in the collagen, type II, alpha 1 (COL2A1) gene. However, the bone involvement (e.g., density, microstructure) in this disorder has hitherto not been studied.

DESIGN

A 50-year-old female patient and her 8-year-old son with flattening of vertebral bodies and early-onset osteoarthritis were genetically tested using a custom designed gene bone panel including 386 genes. Bone microstructure and turnover were assessed using high-resolution peripheral quantitative computed tomography (HR-pQCT) and serum bone turnover markers, respectively. Furthermore, the bone and cartilage phenotype of male mice heterozygous for the loss-of-function mutation of Col2a1 (Col2a1^+/d) was analyzed compared to wildtype littermates using μ-CT and histomorphometry.

RESULTS

We identified a dominant COL2A1 mutation (c.620G > A p.(Gly207Glu)) indicating spondyloepiphyseal dysplasia in the female patient and her son, both being severely affected by skeletal deterioration. Although there was no osteoarthritis detectable at first visit, the son was affected by trabecular osteopenia, which progressed over time. In an iliac crest biopsy obtained from the mother, osteoclast indices were remarkably increased. Col2a1^+/d mice developed a moderate skeletal phenotype expressed by reduced cortical and trabecular parameters at 4 weeks. Importantly, no articular defects could be observed in the knee joints at 4 weeks, while osteoarthritis was only detectable in 12-week-old mice.

CONCLUSIONS

Our results indicate that collagen type II deficiency in spondyloepiphyseal dysplasia leads to skeletal deterioration with early-onset in humans and mice that occurs prior to the development of osteoarthritis.

Time-Integrated Neutrino Source Searches with 10 Years of IceCube Data

This Letter presents the results from pointlike neutrino source searches using ten years of IceCube data collected between April 6, 2008 and July 10, 2018. We evaluate the significance of an astrophysical signal from a pointlike source looking for an excess of clustered neutrino events with energies typically above ∼1  TeV among the background of atmospheric muons and neutrinos. We perform a full-sky scan, a search within a selected source catalog, a catalog population study, and three stacked Galactic catalog searches. The most significant point in the northern hemisphere from scanning the sky is coincident with the Seyfert II galaxy NGC 1068, which was included in the source catalog search. The excess at the coordinates of NGC 1068 is inconsistent with background expectations at the level of 2.9σ after accounting for statistical trials from the entire catalog. The combination of this result along with excesses observed at the coordinates of three other sources, including TXS 0506+056, suggests that, collectively, correlations with sources in the northern catalog are inconsistent with background at 3.3σ significance. The southern catalog is consistent with background. These results, all based on searches for a cumulative neutrino signal integrated over the 10 years of available data, motivate further study of these and similar sources, including time-dependent analyses, multimessenger correlations, and the possibility of stronger evidence with coming upgrades to the detector.

Evaluation of the inflammatory markers CCL8, CXCL5, and LIF in patients with anastomotic leakage after colorectal cancer surgery

PURPOSE

Anastomotic leakage constitutes a dreaded complication after colorectal surgery, leading to increased morbidity and mortality as well as prolonged hospitalization. Most leakages become clinically apparent about 8 days after surgery; however, early detection is quintessential to reduce complications and to improve patients' outcome. We therefore investigated the significance of specific protein expression profiles as putative biomarkers, indicating anastomotic leakage.

METHODS

In this single-center prospective cohort study serum and peritoneal fluid samples-from routinely intraoperatively inserted drainages-of colorectal cancer patients were collected 3 days after colorectal resection. Twenty patients without anastomotic leakage and 18 patients with an anastomotic leakage and without other complications were included. Protein expression of seven inflammatory markers in serum and peritoneal fluid was assessed by multiplex ELISA and correlated with patients' clinical data.

RESULTS

Monocyte chemoattractant protein 2 (CCL8/MCP-2), leukemia-inhibiting factor (LIF), and epithelial-derived neutrophil-activating protein (CXCL5/ENA-78) were significantly elevated in peritoneal fluid but not in serum samples from patients subsequently developing anastomotic leakage after colorectal surgery. No expressional differences could be found between grade B and grade C anastomotic leakages.

CONCLUSION

Measurement 3 days after surgery revealed altered protein expression patterns of the inflammatory markers CCL8/MCP2, LIF, and CXCL5/ENA-78 in peritoneal fluid from patients developing anastomotic leakage after colorectal surgery. Further studies with a larger patient cohort with inclusion of different variables are needed to evaluate their potential as predictive biomarkers for anastomotic leakage.

Elite athletes on regular training show more pronounced induction of vaccine-specific T-cells and antibodies after tetravalent influenza vaccination than controls

Compliance of elite athletes with vaccination recommendations is low mainly based on concerns about side-effects and perceived poor vaccine efficacy due to continued physical training. We therefore employed seasonal influenza vaccination to investigate the effect of regular physical training on vaccine-induced cellular and humoral immunity in elite athletes and controls. Lymphocyte subpopulations and vaccine-specific T-cells were quantified and functionally characterized from 45 athletes and 25 controls before, and 1, 2 and 26 weeks after vaccination. Moreover, influenza-specific antibodies and their neutralizing function were quantified. Both groups showed a significant increase in vaccine-reactive CD4 T-cell levels which peaked one week after vaccination (p < 0.0001). The increase was significantly more pronounced in athletes (4.1-fold) compared to controls (2.3-fold; p = 0.0007). The cytokine profile changed from multifunctional T-cells co-producing IFNγ, IL-2 and TNFα to cells with restricted cytokine expression. This change in functionality was associated with a significant increase in CTLA-4 expression (p < 0.0001), which again was more pronounced in athletes. Likewise, the increase in neutralizing antibodies was stronger in athletes (p = 0.004 for H1N1; p = 0.032 for H3N2). In conclusion, both groups mounted a strong vaccine-specific cellular and humoral immunity after standard vaccination. The more pronounced increase in specific T-cells and neutralizing antibodies indicates that high frequency and intensity of training enhance vaccine-responses in elite athletes.

Pulmonary hypertension and valvular heart disease

Pulmonary hypertension (PH) is an important contributor to morbidity and mortality in patients with left-sided heart disease, including valvular heart disease. In this context, elevated left atrial pressure primarily leads to the development of post-capillary PH. Despite the fact that repair of left-sided valvular heart disease by surgical or interventional approaches will improve PH, recent studies have highlighted that PH (pre- or post-interventional) remains an important predictor of long-term outcome. Here, we review the current knowledge on PH in valvular heart disease taking into account new hemodynamic PH definitions, and the distinction between post- and pre-capillary components of PH. A specific focus is on the precise characterization of hemodynamics and cardiopulmonary interaction, and on potential strategies for the management of residual PH after mitral or aortic valve interventions. In addition, we highlight the clinical significance of tricuspid regurgitation, which may occur as a primary condition or as a consequence of PH and right heart dilatation (functional). In this context, proper patient selection for potential tricuspid valve interventions is crucial. Finally, the article highlights gaps in evidence, and points toward future perspectives.

P1805Troponin-T, NT-proBNP and creatinine at presentation predict outcomes in patients with cardiac sarcoidosis

Background

Cardiac sarcoidosis (CS) is an infiltrative inflammatory condition defined by infiltration of noncaseating granulomas into the heart. Based on the location of sarcoid lesion involvement, patients can present with symptoms of congestive heart failure, arrhythmias, and even sudden cardiac death.

Purpose

Diagnosis of CS has been somewhat challenging, with the Heart Rhythm Society (HRS) and Japanese Ministry of Health and Welfare (JMHW) being the 2 widely accepted diagnostic guidelines. Endomyocardial biopsy is the gold standard to prove definite CS but has a low sensitivity. Imaging studies have been helpful as non-invasive methods to diagnose probable CS but these can be logistically difficult and expensive. Thus, investigating for laboratory biomarkers that can act as both diagnostic and prognostic can be crucial in how we diagnose and manage CS in the future.

Methods

Patients meeting HRS for CS were evaluated at a single institution (n=217). Biomarkers of interest included angiotensin-converting enzyme (ACE), erythrocyte sedimentation rate (ESR), C-reactive protein (CRP), N-terminal pro B-type natriuretic peptide (NT-proBNP), troponin-T, 1,25 dihydroxyvitamin D (1,25-OHVit-D), and creatinine. Biomarkers were stratified by clinical variables of interest and their association with prognosis was examined. The primary endpoint was LVAD implantation, transplantation, or death.

Results

Mean values on presentation were: ACE 32.9±28, ESR 12±13, CRP 7.4±19, NT-proBNP 1630±2923, Troponin-T 0.03±0.1, 1,25-OHVit-D 55.5±20, and creatinine 1.12±0.3. None of the biomarkers differed by sex, definite or probable CS, or a history of immunosuppression. ACE levels were associated with the presence of cardiac fibrosis on cardiac MRI (mean difference 14.7, p=0.032). Troponin-T (p=0.006; HR 1.06 per 0.01 ng/mL), NT-proBNP (p=0.0003; HR 1.31 per 1,000 pg/mL), and creatinine (p=0.01; HR 4.02 per mg/dL) were each associated with the primary endpoint (52/217 patients).

Biomarkers associated with long term outcomes in patients with cardiac sarcoidosis Biomarker Hazard ratio P value Troponin-T 1.06 (1.02–1.11)* 0.006 NT-pro BNP 1.31 (1.15–1.48)** 0.0003 Creatinine 4.02 (1.41–9.94)*** 0.01 *Per 0.01 ng/mL change; 99th percentile upper reference limit <0.01 ng/mL; **per 1,000 pg/mL change; ***per 1 mg/dL change.

Conclusion

Troponin-T, NT-proBNP, and creatinine at presentation predict outcomes in patients with CS. Further investigation on the utility of biomarkers for assessment of disease activity and treatment response is warranted.

P6491Predictive effect of mitral annular size on persistent mitral valve dysfunction after transcatheter edge-to-edge mitral valve repair for functional mitral regurgitation

Background

In patients with functional mitral regurgitation (FMR), deformation of the mitral valve (MV) apparatus leads to deteriorating coaptation of both leaflets. The MV geometry is essential to predict procedural success of using the MitraClip™ for FMR patients. Persistent such mitral regurgitation (MR) and post-procedural mitral stenosis (MS) are parameters for an increasing mortality rate after MitraClip implantation. The anterior-to-posterior mitral annulus diameter (MAD) is simple to evaluate with a high reproducibility rate. However, the predictive effect has not been determined to date.

Purpose

We evaluated the predictive effect of baseline anterior-to-posterior MAD on persistent MV dysfunctions after MitraClip™ implantation.

Methods

We investigated the prevalence of procedural failure (MR at discharge > grade 2+) and post-procedural MS (mean transmitral gradient (mTMG) at discharge ≥6 mmHg) in a patient cohort with FMR (n=190), who underwent MitraClip™ implantation. We measured the MV apparatus geometry on mid-systole using transoesophageal echocardiography before the index procedure. The MAD was stratified by interquartile ranges (IQR) in the comparison. (≤34 mm, 35 to 37 mm, 38 to 40 mm, and ≥41 mm, respectively)

Results

The mean age was 75±9 years, and 63 patients (33%) were female. The mean left ventricular ejection fraction was 34±14%. Moderate-to-severe (3+) or severe MR (4+) were documented in all patients before the procedure. Transthoracic echocardiography at discharge revealed residual MR (>2+) in 10 patients (5%) and post-procedural MS in 13 patients (7%), in which one patient presented with both residual MR and MS.

After stratification by the IQRs of MAD, there were significant differences in body weight (p<0.001), height (p<0.001), and body surface area (p<0.001), but no significant differences in the other baseline characteristics. Notably, significant differences in the prevalence of procedural failure (p=0.004) and post-procedural MS (p=0.022) were observed among the groups. (Figure) Specifically, in the cohort with the 4th IQR (MAD ≥41 mm, n=44), procedural failure was observed in 7 patients (16%), although the prevalence was only 2% in the other IQR groups. Moreover, the cohorts with the 1st and 2nd IQR presented with higher prevalence of post-procedural MS (6 of 46 patients (13%) in the 1st IQR group, and 6 of 51 (12%) in the 2nd IQR group) than those with the 3rd and 4th IQRs. (1 of 49 patients (2%) in the 3rd IQR, and none of 44 patients in the 4th IQR)

Figure 1

Conclusion

In this analysis we showed that the mitral annulus size affected MV dysfunction after MitraClip™. Anterior-to-posterior MAD was useful to predict the procedural result. For FMR candidates with dilated mitral annulus larger than 40 mm, new-generation MitraClip-XTR™ system or other therapeutic concept such as annuloplasty may be reasonable to obtain satisfactory MV function.

P14.62 Safety and adverse event profile post-market surveillance analysis of Tumor Treating Fields (TTFields) in EMEA

BACKGROUND

Tumor Treating Fields (TTFields) are established as modality in glioblastoma (GBM) therapy. GBM is the most aggressive brain tumor in adults, constituting approximately 15 % of all primary brain tumors. At diagnosis, a considerable subgroup of GBM patients is ≥65 years of age. The phase 3 EF-14 trial demonstrated a significant improvement of progression free, overall and longterm survival in newly diagnosed GBM (ndGBM) patients by the addition of TTFields compared temozolomide therapy. No treatment limiting systemic adverse events in the EF-14 trial for ndGBM or in the EF-11 trial for recurrent GBM (rGBM) were observable. Here, we present post-market surveillance data from patients in the EMEA region including elderly patients (≥ 65 years) treated with TTFields.

METHODS

Based on the MedDRA body system (system organ class) and preferred terms surveillance data of patients in the EMEA region were assessed. Additionally, surveillance data of patients < 65 as well as ≥ 65 years of age in this region were separately analyzed.

RESULTS

A total of 11,048 patients were treated with TTFields (ndGBM 53.3 %, rGBM 39.5 %, other diagnoses 7.2 %) of whom 2,252 (20.4 %) patients were treated in the EMEA region. 19.6 % of patients treated in this region were ≥65 years of age at the time of TTFields therapy initiation. One or more adverse events were reported by 64 % of EMEA patients < 65 and in 67 % of elderly EMEA patients. The most prevalent adverse event in both age groups was skin reactions, occurring in 30 % of patients < 65 years of age and 33 % elderly patients. Likewise, further adverse events in elderly patients in the EMEA region were comparable to patients younger than 65 years of age, e.g. heat sensation (< 65; ≥ 65: 4 %; 4 %) and general physical health deterioration (14 %; 18 %).

CONCLUSION

These real-life data demonstrate a good safety profile of TTFields in elderly patients as well as in patients < 65. The most frequent registered adverse event was skin reaction, which is in line with the results of the phase 3 EF-11 trial for rGBM and the EF-14 trial for ndGBM patients. In summary, these results from post-marketing surveillance emphasize the safety of TTFields in GBM treatment, particularly in the elderly population.

[Cardioband®: Where do we stand, who are suitable patients?]

Functional mitral regurgitation (FMR) is characterized by a dilatation of the mitral valve annulus resulting in an insufficient adaptation of the anterior and posterior mitral valve leaflets and/or severe tethering of the leaflets due to dilatation of the left ventricle. The Cardioband® system was introduced in 2015 and is a catheter-based direct mitral valve annuloplasty procedure for treatment of FMR. In the European CE approval study 60 patients with moderate or severe FMR were analyzed per protocol. There were no device or procedure-related deaths. The technical success rate of the procedure, defined as successful implantation and tightening was 97%. At 1 year, the overall survival and survival free of hospital readmission for heart failure were 87% and 66%, respectively. Currently, various interventional treatment procedures are available, such as the edge-to-edge technique as well as direct and indirect annuloplasty. In summary, patients with FMR as a result of a dilatation of the mitral valve annulus appear to be suitable for direct annuloplasty with the Cardioband® system.

[Social reimbursement-the Spanish-German ENT Society's (SDGHNO) Latin America project]

Nowadays, social projects are usually oriented in such a way that after a given period of time, they can either support themselves independently or even allow a pecuniary reimbursement. In the latter case, experts speak of a profit-oriented reimbursement. On the other hand, there is so-called social reimbursement, which in contrast to the abovementioned form is not profit oriented, but, for example, considers its task fulfilled by the fact of successful knowledge transfer. The Spanish-German Society for ENT Medicine and Head and Neck Surgery (SDGHNO) launched the Latin America project in 2001 under the patronage of the then President Prof. Dr. Wolfgang Draf (Fulda). The goal of the SDGHNO was and is to create a professional as well as cultural platform for Spanish- and German-speaking ENT doctors. This platform can and should be used for professional purposes, e.g., for knowledge transfer. Since the beginning of its existence, the Latin America project has thus brought numerous scientific events into being and created specific contacts which have lasted until today or have even been continued and further developed. Particularly successful examples are Chile, Colombia, and Peru. This is a vivid example of social reimbursement, because the participating German-speaking members/speakers carried out their tasks on an entirely voluntary basis. Thus, the SDGHNO did not bear any travel, catering, or accommodation costs. The activities of the SDGHNO within the framework of the Latin America project are explained.

[Therapeutic approach in oligometastatic gastric and esophageal cancer]

The therapeutic approach to patients with oligometastatic gastric cancer and esophageal cancer is currently undergoing a shift towards a more aggressive therapy including surgical resection. In the current German S3 guidelines surgical treatment of metastatic disease is not recommended; however, nowadays interdisciplinary tumor boards have to evaluate such patients increasingly more often. On an individual basis a radical surgical resection of the primary tumor and the metastases is considered and performed in patients who respond well to multimodal chemotherapy concepts. In this review article the currently available data from the literature are discussed and a foundation for individually extended surgical approaches is presented. Together with the currently available results of the FLOT 3 study and the mostly retrospective studies, it seems to be possible to identify patients who would profit from such an aggressive treatment. In the future randomized prospective studies, such as the RENAISSANCE/FLOT 5 study and the GASTRIPEC study will have to evaluate whether an aggressive surgical therapy within multimodal therapy concepts of metastatic gastric and esophageal carcinomas is warranted.

A novel pretherapeutic gene expression-based risk score for treatment guidance in gastric cancer

Background

Perioperative chemotherapy is an established treatment of advanced gastric cancer patients. Treatment selection is based on clinical staging (cT). We aimed to establish and validate a prognostic score including clinical and molecular factors, to optimize treatment decisions for these patients.

Patients and methods

We analyzed 626 carcinomas of the stomach and of the gastro-esophageal junction from two academic centers including primarily resected and pre-/perioperatively treated patients. Patients were divided into a training (N = 269) and validation (N = 357) set. Expression of 11 target genes was measured by quantitative PCR in resected tumors. A risk score to predict overall survival (OS) was generated and validated. Intra-tumoral heterogeneity was assessed by analyzing 50 tumor areas from 10 patients.

Results

A risk score including the expression of CCL5, CTNNB1, EXOSC3 and LZTR1 and the clinical parameters cT, tumor localization and histopathologic type suggested two groups with a significant difference in OS [hazard ratio (HR) 0.30; 95% confidence interval (CI) 0.17-0.52]. The risk score was successfully validated in an independent cohort (HR 0.32; 95% CI 0.21-0.51; P < 0.001) as well as in subgroups of primarily resected (HR 0.30; 95% CI 0.17-0.54; P < 0.001) and pre-/perioperatively treated patients (HR 0.37; 95% CI 0.17-0.81; P = 0.009). A significant difference in OS of high- and low-risk patients was also found in primarily resected patients with intestinal (HR 0.45; 95% CI 0.23-0.90; P = 0.020) and nonintestinal-type carcinomas (HR 0.1; 95% CI 0.02-0.42; P < 0.001). Intra-tumor heterogeneity analysis indicated a classification reliability of 95% for a supposed analysis of three biopsies.

Conclusion

The identified risk score could substantially contribute to an improved management of gastric cancer patients in the context of perioperative chemotherapy.

Constraints on Minute-Scale Transient Astrophysical Neutrino Sources

High-energy neutrino emission has been predicted for several short-lived astrophysical transients including gamma-ray bursts (GRBs), core-collapse supernovae with choked jets, and neutron star mergers. IceCube's optical and x-ray follow-up program searches for such transient sources by looking for two or more muon neutrino candidates in directional coincidence and arriving within 100 s. The measured rate of neutrino alerts is consistent with the expected rate of chance coincidences of atmospheric background events and no likely electromagnetic counterparts have been identified in Swift follow-up observations. Here, we calculate generic bounds on the neutrino flux of short-lived transient sources. Assuming an E^{-2.5} neutrino spectrum, we find that the neutrino flux of rare sources, like long gamma-ray bursts, is constrained to <5% of the detected astrophysical flux and the energy released in neutrinos (100 GeV to 10 PeV) by a median bright GRB-like source is <10^{52.5}  erg. For a harder E^{-2.13} neutrino spectrum up to 30% of the flux could be produced by GRBs and the allowed median source energy is <10^{52}  erg. A hypothetical population of transient sources has to be more common than 10^{-5}  Mpc^{-3}  yr^{-1} (5×10^{-8}  Mpc^{-3}  yr^{-1} for the E^{-2.13} spectrum) to account for the complete astrophysical neutrino flux.