Catheter ablation for atrial fibrillation in adult congenital heart disease: an international registry study

Background

Life expectancies for patients with congenital heart disease (CHD) have dramatically increased in recent years, accompanied by a rise in atrial fibrillation (AF) prevalence. Data on AF ablation strategy and outcomes are limited in CHD.

Purpose

We aimed to investigate the characteristics of CHD patients presenting for AF ablation and their outcomes.

Methods

A multicenter, retrospective analysis was performed of CHD patients undergoing AF ablation between 2004 and 2020 at 13 participating centers. The severity of CHD was classified using the 2014 PACES/HRS guidelines. Clinical data were collected including ablation strategy and follow up. One-year procedural success was defined as freedom from AF in the absence of antiarrhythmic drugs (AADs, complete) or including previously failed AADs (partial).

Results

Of 240 patients, 127 (53.4%) had persistent AF, 62.5% were male, and mean age was 55.2±0.9 years. CHD complexity categories included 147 (61.3%) simple, 69 (28.8%) intermediate and 25 (10.4%) severe. The most common CHD type was atrial septal defect (n=78). More complex CHD conditions included transposition of the great arteries (n=14), anomalous pulmonary veins (n=13), tetralogy of Fallot (n=8), cor triatriatum (n=7), single ventricle physiology (n=2), among others. The majority (71.3%) of patients had AF despite at least one AAD. 46 patients (22.1%) had a reduced systemic ventricular ejection fraction <50%, and the mean left atrial diameter was 44.1±0.7 mm. PV isolation (PVI) was performed in 227 patients (94.6%); additional ablation strategies included left atrial linear ablations (25.4%), CFAE (19.2%), and cavotricuspid isthmus ablation (40.8). One-year complete and partial success rates were 45.0% and 20.5%, respectively, with no significant difference in the rate of complete success between complexity groups. Overall, 38 patients (15.8%) required more than one ablation procedure. There were 3 (1.3%) major and 13 (5.4%) minor procedural complications.

Conclusion

AF ablation in this complex population was safe and resulted in AF control in the majority of patients. Future work should address the most appropriate ablation targets in the challenging population.

Funding Acknowledgement

Type of funding sources: None.

1060 Surgical Currency - the Link Between Skill Fade and Safe Practice

Aim

Surgical currency refers to the operating time required per year before a surgeon's skill fade could negatively affect patient outcomes. Increased surgical experience and volume of operating hours directly improves patient outcomes. There is no clear guidance from the NHS or Defence Medical Services on amount of experience needed to maintain current. This paper highlights the importance of surgical currency, investigates if skill fade occurs faster than knowledge, and looks to ensure surgeons are not deployed beyond the point of currency. It explores methods to prevent skill fade and reintegrate surgeons following absence.

Method

A thorough literature search was performed. Currency protocols across Royal Colleges, healthcare systems and other industries were studied, including systems installed to mitigate skill fade during COVID-19.

Results

An average deployment for a military surgeon will be three months, but pre-deployment training can make this six. The AMRC states an absence over three months affects medical knowledge. Skill fade occurs more rapidly than knowledge, but research remains limited for how long a well-practiced skill is retained. The aviation industry clearly stipulates a pilot's currency, and simulator training is provided following absence. US surgical simulator training proved effective in maintaining skills during the pandemic. Health Education England and Royal College of Surgeons Edinburgh provides return programs for trainees but not consultants.

Conclusions

Careful consideration should be given before extending surgical deployments. Surgical simulation could be used while deployed to maintain currency. Return-to-work programs should be available to consultants. Further research should be done on currency and prevention of skill fade.

Raman Interferometry between Autoionizing States to Probe Ultrafast Wave-Packet Dynamics with High Spectral Resolution

Photoelectron interferometry with femtosecond and attosecond light pulses is a powerful probe of the fast electron wave-packet dynamics, albeit it has practical limitations on the energy resolution. We show that one can simultaneously obtain both high temporal and spectral resolution by stimulating Raman interferences with one light pulse and monitoring the modification of the electron yield in a separate step. Applying this spectroscopic approach to the autoionizing states of argon, we experimentally resolved its electronic composition and time evolution in exquisite detail. Theoretical calculations show remarkable agreement with the observations and shed light on the light-matter interaction parameters. Using appropriate Raman probing and delayed detection steps, this technique enables highly sensitive probing and control of electron dynamics in complex systems.

Autoionizing Polaritons in Attosecond Atomic Ionization

Light-induced states and Autler-Townes splitting of laser-coupled states are common features in the photoionization spectra of laser-dressed atoms. The entangled light-matter character of metastable Autler-Townes multiplets, which makes them autoionizing polaritons, however, is still largely unexplored. We employ attosecond transient-absorption spectroscopy in argon to study the formation of polariton multiplets between the 3s^{-1}4p and several light-induced states. We measure a controllable stabilization of the polaritons against ionization, in excellent agreement with ab initio theory. Using an extension of the Jaynes-Cummings model to autoionizing states, we show that this stabilization is due to the destructive interference between the Auger decay and the radiative ionization of the polaritonic components. These results give new insights into the optical control of electronic structure in the continuum and unlock the door to applications of radiative stabilization in metastable polyelectronic systems.

POS0838 EPIDEMIOLOGY AND TRENDS IN SURVIVAL OF SYSTEMIC SCLEROSIS IN OLMSTED COUNTY: A POPULATION-BASED STUDY (1980-2018)

Background:

Systemic sclerosis (SSc) is a complex immune-mediated disease with heterogeneous manifestations, which is characterized by vasculopathy and fibrosis of the skin and visceral organs. Mortality associated with SSc exceeds that of other rheumatic diseases, though population-based studies assessing recent trends in survival are lacking.

Objectives:

We aimed to determine the incidence and prevalence of physician-diagnosed SSc in a population-based cohort over a 39-year time period, and assess for trends in survival over time.

Methods:

Medical records of patients with a diagnosis or suspicion of SSc in a geographically well-defined area from Jan 1, 1980 to Dec 31, 2018 were reviewed to identify incident cases of SSc. Cases were defined by physician diagnosis of SSc, and fulfillment of the 2013 ACR/EULAR classification criteria was ascertained. Prevalent cases of SSc on Jan 1, 2015 were also identified. Incidence and prevalence rates were age- and sex-adjusted to the 2010 U.S. white population. Survival rates were compared with expected rates in the general population.

Results:

85 incident cases of SSc (91% female, mean age 55.4 ± 16 y) and 49 prevalent cases on Jan 1, 2015 were identified. Patients had a mean 11.7 (SD 9.4) years of follow-up available. The overall age and sex adjusted annual incidence for 1980-2018 was 2.5 (95% CI: 2.0-3.1) per 100,000 population, with no change in incidence over time (p=0.32). The age-adjusted incidence was 4.4 (95% CI: 3.4-5.4) for females, and 0.56 (95% CI: 0.16-0.96) for males per 100,000 population. The age- and sex-adjusted prevalence on Jan 1, 2015 was 43.6 (95% CI: 31.3-55.8) per 100,000 population.

77 (91%) patients fulfilled the 2013 classification criteria; 38 (45%) fulfilled 1980 criteria. 70 (82%) had limited cutaneous involvement, 12 (14%) had diffuse cutaneous involvement, and 3 (4%) had sine scleroderma. At SSc diagnosis, 80 (94%) patients had Raynaud’s, 43 (51%) had sclerodactyly, 39 (46%) had telangiectasias, 14/48 (29%) had abnormal nailfold capillaries, 16/35 (46%) had digital ulcers or fingertip scarring, 8 (9%) had interstitial lung disease (ILD), and 7 (8%) had pulmonary arterial hypertension (PAH). 77/82 patients (91%) had a positive antinuclear antibody. 44 (52%) had a known SSc-related autoantibody: 32 (73%) with anti-centromere, 9 (20%) with anti-Scl-70, and 4 (9%) with anti-RNA-polymerase III.

Survival was 77% (95% CI: 69-87) at 5 years, 66% (95% CI: 56-78) at 10 years, and 42% (95% CI: 30-57) at 20 years, with no evidence of improved survival over time (p=0.46). Age (Hazard ratio [HR]: 1.49 per 10 year increase; 95% CI 1.19-1.88), smoking at time of diagnosis (HR: 2.37; 95% CI: 1.05-5.34), digital ischemia (HR: 2.54; 95% CI: 1.33-4.87), ILD (HR: 4.00; 95% CI: 2.11-7.59), and PAH (HR: 4.30; 95% CI: 2.24-8.25) had significant associations with mortality. Survival of patients with SSc was poorer than the general population (standardized mortality ratio: 2.48; 95% CI: 1.76-3.39).

Conclusion:

The average incidence of SSc in this population-based cohort spanning 39 years was 2.5 per 100,000 population, with no change in incidence over time. Age, smoking, digital ischemia, ILD and PAH were risk factors for poorer survival. Overall survival for patients with SSc is worse than that of the general population and shows no improvement over time, suggesting continued need for improved diagnostic and treatment measures.

Figure 1.

Survival of 85 Olmsted County residents with SSc compared with expected survival rates from Minnesota lifetables (observed: solid line, expected: dashed line).

Disclosure of Interests:

None declared

POS0836 CONDUCTION AND RHYTHM DISORDERS AMONG PATIENTS WITH SYSTEMIC SCLEROSIS: A US POPULATION BASED STUDY

Background:

Systemic sclerosis (SSc) can impact multiple areas of the heart through fibrotic and vascular processes; leading to variable cardiac involvement including electrocardiogram (ECG) abnormalities. Conduction and rhythm disorders are associated with worse prognosis in patients with SSc. (1, 2)

Objectives:

To study the incidence, risk factors and outcomes of conduction and rhythm disorders in a US population-based cohort of patients with SSc and non-SSc comparators from the same geographic area.

Methods:

A previously identified incident cohort of SSc patients (1980-2016) in a well-defined geographic area was compared to a randomly selected 2:1 cohort of age- and sex-matched non-SSc subjects from the same population base. Demographics, disease characteristics, cardiovascular risk factors and laboratory tests were abstracted by manual record review. ECGs and Holter ECGs were reviewed to determine the occurrence of any conduction or rhythm abnormalities. The need for cardiac interventions was also abstracted.

Results:

78 incident SSc cases and 156 non-SSc comparators were identified [age 56 years± 15.7, 91% female]. Prevalence of any conduction disorders before SSc diagnosis compared to non-SSc comparators was 15% vs. 7% (p=0.06), and any rhythm disorder was 18% vs. 13% (p=0.33). During a median follow up of 10.5 years in patients with SSc and 13.0 years in non-SSc comparators, conduction disorders developed in 25 SSc patients with a cumulative incidence (ci) of 20.5% (95% CI: 12.4-34.1%) compared to 28 non-SSc patients with ci of 10.4% (95% CI: 6.2-17.4%) (HR: 2.57; 95% CI: 1.48-4.45), while rhythm disorders developed in 27 SSc patients with ci of 27.3% (95% CI: 17.9-41.6%) vs 43 non-SSc patients with ci of 18.0% (95% CI: 12.3-26.4%) (HR: 1.62; 95% CI: 1.00-2.64). (Figure 1).

Conduction disorders in patients with SSc during follow up included: 1st-degree atrioventricular block (AVB) (n=12), 2nd-degree AVB (n=1), 3rd-degree AVB (n=1), right bundle branch block (n=10), left bundle branch block (n=4), bifascicular block (n=6), and prolonged-QT (n=13). Rhythm disorders included: atrial fibrillation (n=10), atrial flutter (n=4), supraventricular tachycardia (n=4), ventricular tachycardia (n=1), and premature ventricular contractions (n=16).

Pulmonary hypertension (PHT) was the only significant risk factor identified for development of both conduction and rhythm disorders (HR=8.38, 95% CI: 1.32-53.40 and HR=8.07, 95% CI: 1.60-40.74, respectively). Current smoking significantly increased the risk for development of rhythm disorders (HR=2.91, 95% CI: 1.19-7.12). Conduction and rhythm disorders were associated with increased mortality among patients with SSc (HR=7.60, 95% CI: 3.49-16.55 and HR=4.87, 95% CI: 2.28-10.42, respectively, after adjusting for age, sex and calendar year of diagnosis).

Conclusion:

Patients with SSc have a significantly higher prevalence of conduction disorders at disease onset than non-SSc comparators. During the course of their disease, their risk of developing conduction disorders is 2.6-fold, and risk of rhythm disorders is 1.6-fold increased, compared to non-SSc subjects.

PHT was significantly associated with increased risk of developing conduction and rhythm disorders among patients with SSc, a finding that should warrant increased vigilance and screening for ECG abnormalities in this population.

References:

[1]Tyndall A.J. et al. Ann Rheum Dis, 2010. 69(10): p. 1809-15.

[2]Desai C.S. et al. Curr Opin Rheumatol, 2011. 23(6): p. 545-54.

Figure 1.

Cumulative incidence of any conduction or any rhythm disorder in SSc (solid line) vs non-SSc comparators (dashed line).

Disclosure of Interests:

None declared

Stereotactic body radiation therapy as palliative management for incurable thoracic malignancies

e24097

Background: Radiation therapy plays an important role in symptom palliation for patients with incurable cancer. Currently limited data exists regarding the role of SBRT vs conformal radiation for the palliation of symptoms due to malignancy. We report the symptom management and local control of palliative SBRT for incurable thoracic malignancies at a single institution. Methods: We retrospectively identified patients who underwent palliative SBRT between Jan 1st, 2009 and March 26th, 2019. Patients all had thoracic tumors that were not candidates for curative radiation due to age, stage, comorbidity, and/or prior treatment. We identified courses with total doses between 25-50 Gy (median 40) and total fractions between 3-10 (median 5). Symptoms such as cough, chest pain, hemoptysis, and shortness of breath were assessed at time of consult and first follow-up between 1-6 months post treatment. We also reviewed follow-up CT imaging to evaluate for local control using RECIST criteria. Descriptive statistics were used to evaluate patients’ clinicopathologic data and symptom palliation. Local control was analyzed via Kaplan-Meier method. Results: Of the 76 patients who completed palliative SBRT to 92 total lung lesions, 45 patients reported symptoms at consult and completed 50 courses of radiation to 55 lesions. Within this symptomatic cohort, average age was 71 (range, 42-93), 32 were female (58%), and most were stage IV (n = 42, 76%). Most lesions treated were non-small cell lung cancer (n = 34, 62%) while the most common primary site of metastatic lesions was colorectal (n = 6, 11%). Additional primary sites included breast, renal, sarcoma, and others (n = 15, 27%). Of the 53 lesions treated with follow-up within 6 months, 21 (40%) showed relief of at least 1 symptom and 31 (58%) showed stable symptoms. Only 1 patient (2%) showed symptom progression. All patients with hemoptysis at presentation achieved hemostasis following SBRT. Among 48 treated lesions with follow-up CT imaging, 1 (2%) showed complete response, 28 (58%) showed partial response (PR), 15 (31%) showed stable disease (SD), and 4 (8%) showed progressive disease. With further follow-up (median 23 months), 30 of the 53 lesions with initial PR or SD demonstrated local control until death. Conclusions: There is conflicting literature regarding the ideal palliative radiation dose for thoracic tumors. SBRT has the advantage of allowing a higher biologic dose without protracted treatment courses in the setting of palliation of symptoms. Our symptomatic cohort showed good symptom palliation and long-term local control of treated lesions. Prospective studies are required to further confirm the role of palliative SBRT for symptomatic thoracic tumors.

Radiation Recall Pneumonitis After Treatment With Checkpoint Blockade Immunotherapy: A Case Series and Review of Literature

BACKGROUND

Radiation recall pneumonitis (RRP) is a poorly understood clinical syndrome in which patients develop radiation pneumonitis triggered by a systemic agent, often years after the completion of radiation therapy. Immune checkpoint blockade agents have only recently been posited as a trigger for RRP. Here, we present three cases of immunotherapy-induced RRP.

CASE PRESENTATION

Our first patient was diagnosed with primary lung adenocarcinoma, and 4.5 years after completing radiation therapy developed symptomatic RRP immediately following a second dose of nivolumab-containing immunotherapy regimen. Our second patient was diagnosed with primary bladder cancer metastatic to the mediastinum, which was treated twice with radiation therapy. He developed RRP in the days following his second course of ipilimumab-pembrolizumab which was months after his second course of radiation that he received. Our final patient was diagnosed with metastatic small cell lung cancer and received local consolidative radiation therapy in addition to whole-brain radiation. He developed RRP on the 11th day after concluding his 4th cycle of nivolumab-ipilimumab, approximately 7 months after having had completed chest radiation therapy.

CONCLUSIONS

Immunotherapy-induced RRP is a rare diagnosis which can present more focally than traditional immunotherapy pneumonitis and which must be clinically differentiated from other local processes such as pneumonia. Further research should explore the mechanisms underlying these radiation recall reactions as many patients receive radiation and immunotherapy during the course of their cancer treatment.

Association of Health-Care System with Prostate Cancer-Specific Mortality in African American and Non-Hispanic White Men

BACKGROUND

Disparities in prostate cancer-specific mortality (PCSM) between African American and non-Hispanic White (White) patients have been attributed to biological and systemic factors. We evaluated drivers of these disparities in the Surveillance, Epidemiology and End Results (SEER) national registry and an equal-access system, the Veterans Health Administration (VHA).

METHODS

We identified African American and White patients diagnosed with prostate cancer between 2004-2015 in SEER (N = 311,691) and the VHA (N = 90,749). We analyzed the association between race and metastatic disease at presentation using multivariable logistic regression adjusting for sociodemographic factors, and PCSM using sequential competing-risks regression adjusting for disease and sociodemographic factors.

RESULTS

The median follow-up was 5.3 years in SEER and 4.7 years in the VHA. African American men were more likely than White men to present with metastatic disease in SEER (adjusted odds ratio = 1.23, 95% confidence interval [CI] = 1.17-1.30), but not in the VHA (adjusted odds ratio = 1.07, 95% CI = 0.98-1.17). African American versus White race was associated with an increased risk of PCSM in SEER (subdistribution hazard ratio [SHR] = 1.32, 95% CI = 1.10-1.60), but not in the VHA (SHR = 1.00, 95% CI: 0.93-1.08). Adjusting for disease extent, PSA, and Gleason score eliminated the association between race and PCSM in SEER (aSHR 1.04, 95% CI 0.93-1.16).

CONCLUSIONS

Racial disparities in PCSM were present in a nationally representative registry, but not in an equal-access healthcare system, due to differences in advanced disease at presentation. Strategies to increase healthcare access may bridge the racial disparity in outcomes. Longer follow-up is needed to fully assess mortality outcomes.Disparities between African American and non-Hispanic White (White) patients in cancer-specific mortality have been described across numerous cancer types and healthcare systems[1-5]. The survival gap between African American and White patients with prostate cancer has been well-characterized, with two-fold higher prostate cancer-specific mortality (PCSM) rates among African American patients depending on the setting[1, 6-10]. This disparity has been attributed to differences in prostate cancer biology in African American men, in addition to systemic factors in mediating this disparity, such as differential access to healthcare, Prostate-Specific Antigen (PSA) screening, and distrust in the healthcare system[1, 11-16].The Veterans Health Administration (VHA) is a relatively equal-access healthcare system that treats a large, ethnically diverse population of veterans. The Surveillance, Epidemiology and End Results (SEER) program is a national cancer registry program that collects data from the general United States (US) population. The goals of the present investigation were to 1) Compare PCSM between African American and White men within SEER and the VHA and 2) Identify modifiable system-level contributors to these disparities. We hypothesized that PCSM would be comparable among African American and White men in an equal-access setting, the VHA, but not in a national registry, SEER, and that this disparity in SEER would be in part driven by more advanced disease at presentation.

A134 A MULTI-CENTRE RANDOMIZED CONTROLLED TRIAL TO COMPARE TWO BOWEL CLEANSING REGIMENS AFTER A COLONOSCOPY WITH INADEQUATE BOWEL PREPARATION

Aims

Failed bowel preparation is common during colonoscopy, yet the optimal purgative regimen to use for the next attempt is unknown. The objective of this study was to compare the efficacy, tolerability, and safety of two regimens at supratherapeutic doses for use after failed bowel preparation.

Methods

A multi-centre phase III endoscopist blinded randomized controlled trial (NCT02976805) was conducted in patients who failed bowel preparation, using the US Multi-Society Task Force (USMSTF) definition of inability to exclude polyps >5 mm in size and requiring a shortened interval to next colonoscopy. Regimen A consisted of 15 mg of bisacodyl and 2 + 2 L of split dose polyethylene glycol electrolyte solution (PEG) and Regimen B consisted of 15 mg of bisacodyl and 4 + 2 L of split dose PEG. The primary outcome was adequate bowel preparation, defined as a Boston Bowel Preparation Scale (BBPS) total score ≥ 6 with all segment scores ≥ 2. Secondary outcomes were adequate bowel preparation using the USMSTF definition, median BBPS, adenoma detection (ADR), advanced adenoma detection (aADR), sessile serrated polyp detection (SSPDR), and cecal intubation (CIR). Adverse events were assessed at the time of the colonoscopy and 14 days later.

Results

Between February 2017 and December 2019, 250 subjects were screened at four academic centres in Canada, of which 195 were randomized: 96 to Regimen A and 99 to Regimen B. The mean (SD) age was 60.6 (11.4) years, 87 (45.1%) were female, and the median (IQR) total BBPS score at previous failed colonoscopy was 3 (1,4). Regimen B was not superior to Regimen A in achieving adequate bowel preparation using the BBPS definition (87.6% vs. 91.1%, p=0.45) or the USMSTF definition (85.4% vs 91.1%, p=0.24), nor was it superior with respect to the median BBPS score (7 vs 7, p=0.50), mean ADR (31.5% vs 37.8%, p=0.37), aADR (11.2% vs 18.9%, p=0.15), SSPDR (5.6% vs 8.9%, p=0.40) or CIR (92.1% vs 96.7%, p=0.19). Regimen A had a higher adherence rate (88.2% vs. 74.7%, p=0.02) and greater willingness to undergo the bowel preparation again (91.2% vs. 66.2%, p<0.001). The only serious adverse event occurred in a patient randomized to Regimen B who was admitted to hospital for vomiting after colonoscopy.

Conclusions

Split dose 4L PEG with 15mg of bisacodyl is highly efficacious, well tolerated, and can be used for patients who previously failed first line bowel preparations. The additional 2L of PEG in Regimen B did not improve bowel preparation and was not as well tolerated.

Funding Agencies

AMOSO Opportunities Grant, Pharmascence Inc.

Clinical outcomes after faecal microbiota transplant by retention enema in both immunocompetent and immunocompromised patients with recurrent Clostridioides difficile infections at an academic medical centre

BACKGROUND

Recurrent Clostridioides difficile infection (CDI) is one of the most common and challenging infections to treat in healthcare facilities. Faecal microbiota transplantation (FMT) is recommended as a definitive treatment option.

METHODS

We performed a retrospective review of 50 patients from January 2015 to December 2019 who underwent FMT for recurrent CDI. Primary outcome was recurrence of CDI within 12-weeks of FMT and secondary outcomes were the need for repeat FMT, serious adverse outcomes related to FMT and all-cause mortality.

RESULTS

Fifty charts were reviewed, of which 47 cases comprising 17 immunocompromised patients treated with FMT via retention enema were included in the study. The majority of the patients had ≥3 recurrent CDIs (62%). Nine (19%) patients failed to respond to the first FMT and five underwent repeat FMT within four to 12 weeks. The cure rate was 81% after the first FMT (38/47) and 91% after the second FMT treatment (43/47). Serious adverse events occurred in 2% and all-cause mortality was 2% at 90-day follow up.

CONCLUSION

Our study demonstrated the safety and efficacy of FMT administered via retention enema, a simple bedside procedure, for the treatment and prevention of recurrent non-severe and severe CDI with an overall cure rate of 91%.

Perioperative intravenous contrast administration and the incidence of acute kidney injury after major gastrointestinal surgery: prospective, multicentre cohort study

BACKGROUND

This study aimed to determine the impact of preoperative exposure to intravenous contrast for CT and the risk of developing postoperative acute kidney injury (AKI) in patients undergoing major gastrointestinal surgery.

METHODS

This prospective, multicentre cohort study included adults undergoing gastrointestinal resection, stoma reversal or liver resection. Both elective and emergency procedures were included. Preoperative exposure to intravenous contrast was defined as exposure to contrast administered for the purposes of CT up to 7 days before surgery. The primary endpoint was the rate of AKI within 7 days. Propensity score-matched models were adjusted for patient, disease and operative variables. In a sensitivity analysis, a propensity score-matched model explored the association between preoperative exposure to contrast and AKI in the first 48 h after surgery.

RESULTS

A total of 5378 patients were included across 173 centres. Overall, 1249 patients (23·2 per cent) received intravenous contrast. The overall rate of AKI within 7 days of surgery was 13·4 per cent (718 of 5378). In the propensity score-matched model, preoperative exposure to contrast was not associated with AKI within 7 days (odds ratio (OR) 0·95, 95 per cent c.i. 0·73 to 1·21; P = 0·669). The sensitivity analysis showed no association between preoperative contrast administration and AKI within 48 h after operation (OR 1·09, 0·84 to 1·41; P = 0·498).

CONCLUSION

There was no association between preoperative intravenous contrast administered for CT up to 7 days before surgery and postoperative AKI. Risk of contrast-induced nephropathy should not be used as a reason to avoid contrast-enhanced CT.

0614 Diurnal Patterning of Autonomic Measures in Sleep Apnea and Paroxysmal Atrial Fibrillation and Response to Continuous Positive Airway Pressure Therapy

Introduction

Diurnal patterning of autonomic function in paroxysmal atrial fibrillation (PAF) and sleep disordered breathing (SDB) is unknown. We hypothesize heart rate variability (HRV) as surrogates of autonomic function, exhibit diurnal differences in PAF relative to SDB severity and treatment.

Methods

We leveraged the Sleep Apnea and Atrial Fibrillation Biomarkers and Electrophysiologic Atrial Triggers (SAFEBEAT,NCT02576587) study focused on participants with PAF and SDB (apnea hypopnea index,AHI≥15,3% oxygen desaturation hypopnea). Attended 16-channel polysomnography (PSG) and continuous ECG monitoring (Heartrak Telemetry®) for 7-21 days was performed at baseline and after 3-months of continuous positive airway pressure (CPAP). Linear mixed-effects models (least square means,95%CI) were used to assess relationships between daily average HRV measures (frequency domain:LF,HF,LF/HF;time domain:MNN,RMSSD,SD1,SD ratio and novel non-linear:DFA-alpha measures) with SDB (AHI),%sleep time with SaO2<90%(TRT<90): per 5-unit increase),effect of 3-month CPAP relative to sleep-wake and statistical interaction of sleep-wake. Analyses were conducted using SAS version v.9.4, Cary, NC.

Results

The analytic sample was comprised of 33 cases with PAF and SDB:61.1±11.7 years,62.5% male, BMI:33.9±7.2kg/m2,75% Caucasian,AHI 15.1 (IQR: 4.4,29.4) and 68.8% on atrioventricular nodal blocking medications. AHI was associated with frequency (HF:0.08[0.01,0.16] and LF/HF:-0.11[-0.20, -0.01]), time (SD1:0.08[0.02,0.14] and SD ratio: 0.09[0.04,0.14]) and non-linear (DFA-alpha1: -0.02[-0.036,-0.003]) domain measures during wake, but not sleep. Significant sleep-wake and AHI as well as TRT<90 interactions relative to HRV measures were observed (p≤0.001). Only SD ratio was associated with TRT<90 (0.12[0.03,0.24]). Baseline to follow-up CPAP time domain measures were altered mainly during wake versus sleep with MNN increased 0.13: [0.08,0.19],p<0.001; RMSSD increased 0.13 [0.08,0.19], p<0.001; SD1 increased 30% [0.09,0.55], p=0.004; SD ratio increased 20% [0.01,0.43], p=0.033,and also frequency domain: HF increased 33%[0.03,0.72], p=0.028.

Conclusion

SDB defined by AHI--more so than nocturnal hypoxia--was associated with surrogate autonomic measures impacted by CPAP intervention during wake and not sleep in PAF. SDB-related autonomic influences in PAF appear to be more pronounced during wakefulness suggesting long-term potentiation-like influences.

Support

This study was supported by the National Heart, Lung and Blood Institute (NHLBI) [Grant R01 HL108493] and National Institutes of Health (NIH) National Center for Research Resources [Grant UL1 RR024989]

Combined Androgen Blockade in Localized Prostate Cancer Treated With Definitive Radiation Therapy

BACKGROUND

The addition of androgen deprivation therapy to radiation therapy (RT) improves survival in patients with intermediate- and high-risk prostate cancer (PCa), but it is not known whether combined androgen blockade (CAB) with a gonadotropin-releasing hormone agonist (GnRH-A) and a nonsteroidal antiandrogen improves survival over GnRH-A monotherapy.

METHODS

This study evaluated patients with intermediate- and high-risk PCa diagnosed in 2001 through 2015 who underwent RT with either GnRH-A alone or CAB using the Veterans Affairs Informatics and Computing Infrastructure. Associations between CAB and prostate cancer-specific mortality (PCSM) and overall survival (OS) were determined using multivariable regression with Fine-Gray and multivariable Cox proportional hazards models, respectively. For a positive control, the effect of long-term versus short-term GnRH-A therapy was tested.

RESULTS

The cohort included 8,423 men (GnRH-A, 4,529; CAB, 3,894) with a median follow-up of 5.9 years. There were 1,861 deaths, including 349 resulting from PCa. The unadjusted cumulative incidences of PCSM at 10 years were 5.9% and 6.9% for those receiving GnRH-A and CAB, respectively (P=.16). Compared with GnRH-A alone, CAB was not associated with a significant difference in covariate-adjusted PCSM (subdistribution hazard ratio [SHR], 1.05; 95% CI, 0.85-1.30) or OS (hazard ratio, 1.02; 95% CI, 0.93-1.12). For high-risk patients, long-term versus short-term GnRH-A therapy was associated with improved PCSM (SHR, 0.74; 95% CI, 0.57-0.95) and OS (SHR, 0.82; 95% CI, 0.73-0.93).

CONCLUSIONS

In men receiving definitive RT for intermediate- or high-risk PCa, CAB was not associated with improved PCSM or OS compared with GnRH alone.

Association between Radical Prostatectomy and Survival in Men with Clinically Node-positive Prostate Cancer

Evidence supporting radical prostatectomy (RP) for men with clinically node-positive (cN+) prostate cancer (PC) is limited. In a US national database, we identified 741 men with cN+ nonmetastatic PC diagnosed during 2000-2015 who underwent definitive local therapy with RP (n=78), radiotherapy (RT) with neoadjuvant androgen deprivation therapy (ADT) (n=193), or nondefinitive therapy with ADT alone (n=445) or observation (n=25). We compared PC-specific mortality (PCSM) and all-cause mortality (ACM) using multivariable Fine-Gray competing risk regression and Cox regression, respectively. Compared to nondefinitive therapy, RP was associated with significantly better PCSM (subdistribution hazard ratio [SHR] 0.32, 95% confidence interval [CI] 0.16-0.66; p=0.002) and ACM (HR 0.36, 95% CI 0.21-0.61; p<0.001). Compared to RT, RP was not associated with a significant difference in PCSM (SHR 0.47, 95% CI 0.19-1.17; p=0.1) or ACM (HR 0.88, 95% CI 0.46-1.70; p=0.71). These data suggest that RP is associated with favorable survival outcomes that appear to be superior to those for patients who did not receive definitive therapy and comparable to those for patients receiving definitive ADT/RT. Randomized trials of surgery with multimodal therapy are needed. PATIENT SUMMARY: We found that in clinically node-positive prostate cancer, radical prostatectomy was associated with a cancer-specific and overall survival benefit compared to nondefinitive therapy. Randomized clinical trials are required to determine the best treatment approach in this patient population.

Wheat ms5 male-sterility is induced by recessive homoeologous A and D genome non-specific lipid transfer proteins

Nuclear male-sterile mutants with non-conditional, recessive and strictly monogenic inheritance are useful for both hybrid and conventional breeding systems, and have long been a research focus for many crops. In allohexaploid wheat, however, genic redundancy results in rarity of such mutants, with the ethyl methanesulfonate-induced mutant ms5 among the few reported to date. Here, we identify TaMs5 as a glycosylphosphatidylinositol-anchored lipid transfer protein required for normal pollen exine development, and by transgenic complementation demonstrate that TaMs5-A restores fertility to ms5. We show ms5 locates to a centromere-proximal interval and has a sterility inheritance pattern modulated by TaMs5-D but not TaMs5-B. We describe two allelic forms of TaMs5-D, one of which is non-functional and confers mono-factorial inheritance of sterility. The second form is functional but shows incomplete dominance. Consistent with reduced functionality, transcript abundance in developing anthers was found to be lower for TaMs5-D than TaMs5-A. At the 3B homoeolocus, we found only non-functional alleles among 178 diverse hexaploid and tetraploid wheats that include landraces and Triticum dicoccoides. Apparent ubiquity of non-functional TaMs5-B alleles suggests loss-of-function arose early in wheat evolution and, therefore, at most knockout of two homoeoloci is required for sterility. This work provides genetic information, resources and tools required for successful implementation of ms5 sterility in breeding systems for bread and durum wheats.

An epigenetic breeding system in soybean for increased yield and stability

Epigenetic variation has been associated with a wide range of adaptive phenotypes in plants, but there exist few direct means for exploiting this variation. RNAi suppression of the plant-specific gene, MutS HOMOLOG1 (MSH1), in multiple plant species produces a range of developmental changes accompanied by modulation of defence, phytohormone and abiotic stress response pathways along with methylome repatterning. This msh1-conditioned developmental reprogramming is retained independent of transgene segregation, giving rise to transgene-null 'memory' effects. An isogenic memory line crossed to wild type produces progeny families displaying increased variation in adaptive traits that respond to selection. This study investigates amenability of the MSH1 system for inducing agronomically valuable epigenetic variation in soybean. We developed MSH1 epi-populations by crossing with msh1-acquired soybean memory lines. Derived soybean epi-lines showed increase in variance for multiple yield-related traits including pods per plant, seed weight and maturity time in both glasshouse and field trials. Selected epi-F2:4 and epi-F2:5 lines showed an increase in seed yield over wild type. By epi-F2:6, we observed a return of MSH1-derived enhanced growth back to wild-type levels. Epi-populations also showed evidence of reduced epitype-by-environment (e × E) interaction, indicating higher yield stability. Transcript profiling of epi-lines identified putative signatures of enhanced growth behaviour across generations. Genes related to cell cycle, abscisic acid biosynthesis and auxin response, particularly SMALL AUXIN UP RNAs (SAURs), were differentially expressed in epi-F2:4 lines that showed increased yield when compared to epi-F2:6 . These data support the potential of MSH1-derived epigenetic variation in plant breeding for enhanced yield and yield stability.

Molecular identification of the wheat male fertility gene Ms1 and its prospects for hybrid breeding

The current rate of yield gain in crops is insufficient to meet the predicted demands. Capturing the yield boost from heterosis is one of the few technologies that offers rapid gain. Hybrids are widely used for cereals, maize and rice, but it has been a challenge to develop a viable hybrid system for bread wheat due to the wheat genome complexity, which is both large and hexaploid. Wheat is our most widely grown crop providing 20% of the calories for humans. Here, we describe the identification of Ms1, a gene proposed for use in large-scale, low-cost production of male-sterile (ms) female lines necessary for hybrid wheat seed production. We show that Ms1 completely restores fertility to ms1d, and encodes a glycosylphosphatidylinositol-anchored lipid transfer protein, necessary for pollen exine development. This represents a key step towards developing a robust hybridization platform in wheat.Heterosis can rapidly boost yield in crop species but development of hybrid-breeding systems for bread wheat remains a challenge. Here, Tucker et al. describe the molecular identification of the wheat Ms1 gene and discuss its potential for large-scale hybrid seed production in wheat.

MutS HOMOLOG1-derived epigenetic breeding potential in tomato

Evidence is compelling in support of a naturally occurring epigenetic influence on phenotype expression in land plants, although discerning the epigenetic contribution is difficult. Agriculturally important attributes like heterosis, inbreeding depression, phenotypic plasticity, and environmental stress response are thought to have significant epigenetic components, but unequivocal demonstration of this is often infeasible. Here, we investigate gene silencing of a single nuclear gene, MutS HOMOLOG1 (MSH1), in the tomato (Solanum lycopersicum) 'Rutgers' to effect developmental reprogramming of the plant. The condition is heritable in subsequent generations independent of the MSH1-RNA interference transgene. Crossing these transgene-null, developmentally altered plants to the isogenic cv Rutgers wild type results in progeny lines that show enhanced, heritable growth vigor under both greenhouse and field conditions. This boosted vigor appears to be graft transmissible and is partially reversed by treatment with the methylation inhibitor 5-azacytidine, implying the influence of mobile, epigenetic factors and DNA methylation changes. These data provide compelling evidence for the feasibility of epigenetic breeding in a crop plant.

High photosensitivity few-layered MoSe2 back-gated field-effect phototransistors

In this paper, we report on the fabrication and optoelectronic properties of high sensitive phototransistors based on few-layered MoSe2 back-gated field-effect transistors, with a mobility of 19.7 cm² V⁻¹ s⁻¹ at room temperature. We obtained an ultrahigh photoresponsivity of 97.1 AW⁻¹ and an external quantum efficiency (EQE) of 22 666% using 532 nm laser excitation at room temperature. The photoresponsivity was improved near the threshold gate voltage; however, the selection of the silicon dioxide as a gate oxide represents a limiting factor in the ultimate performance. Thanks to their high photoresponsivity and external quantum efficiency, the few-layered MoSe2-based devices are promising for photoelectronic applications.

Gate dependent Raman spectroscopy of graphene on hexagonal boron nitride

Raman spectroscopy, a fast and nondestructive imaging method, can be used to monitor the doping level in graphene devices. We fabricated chemical vapor deposition (CVD) grown graphene on atomically flat hexagonal boron nitride (hBN) flakes and SiO2 substrates. We compared their Raman response as a function of charge carrier density using an ion gel as a top gate. The G peak position, the 2D peak position, the 2D peak width and the ratio of the 2D peak area to the G peak area show a dependence on carrier density that differs for hBN compared to SiO2. Histograms of two-dimensional mapping are used to compare the fluctuations in the Raman peak properties between the two substrates. The hBN substrate has been found to produce fewer fluctuations at the same charge density owing to its atomically flat surface and reduced charged impurities.

Spinal 5-HT3 receptors facilitate behavioural hypersensitivity induced by elevated calcium channel alpha-2-delta-1 protein

BACKGROUND

Peripheral nerve injury induces up-regulation of the calcium channel alpha-2-delta-1 proteins in the dorsal root ganglia and dorsal spinal cord that correlates with neuropathic pain development. Similar behavioural hypersensitivity was also observed in injury-free transgenic (TG) mice over-expressing the alpha-2-delta-1 proteins in neuronal tissues. To investigate pathways regulating alpha-2-delta-1 protein-mediated behavioural hypersensitivity, we examined whether spinal serotonergic 5-HT3 receptors are involved similarly in the modulation of behavioural hypersensitivity induced by either peripheral nerve injury in a nerve injury model or neuronal alpha-2-delta-1 over-expression in the TG model.

METHODS

The effects of blocking behavioural hypersensitivity in these two models by intrathecal or systemic injections of 5-HT3 receptor antagonist, ondansetron, were compared.

RESULTS

Our data indicated that the TG mice displayed similar behavioural hypersensitivities to non-painful mechanical stimulation (tactile allodynia) and painful thermal stimulation (thermal hyperalgesia) as that observed in the nerve injury model. Interestingly, tactile allodynia and thermal hyperalgesia in both models can be blocked similarly by intrathecal, but not systemic, injection of ondansetron.

CONCLUSIONS

Our data suggest that spinal 5-HT3 receptors are likely to play a role in alpha-2-delta-1-mediated behavioural hypersensitivities through a descending serotonergic facilitation.

Prognostic value of cardiac troponins in elderly patients with hip fracture--a systematic review

Cardiac troponins can be elevated in cardiac ischemic conditions or other diseases such as pulmonary embolism or renal failure, where they may predict outcome. We hypothesized that cardiac troponins offer useful prognostic information regarding morbidity and mortality in elderly hip fracture patients undergoing surgical therapy. A literature review was conducted using PubMed and CINAHL plus with full text (EBSCOhost). Articles with original data relating troponins to prognosis in elderly hip fracture patients were reviewed. Studies with patients not undergoing surgery or undergoing elective or nonhip fracture surgery were excluded. Six papers met inclusion criteria. Troponin elevation was seen in 26.7-39% of patients, while myocardial infarction, cardiac complications, and cardiac death occurred in ≤35% troponin-positive patients in four of six studies. Several noncardiac factors were associated with elevated troponin including higher American Society of Anaesthesiologists score, current smoking, reduced mobility/activity level, lower hemoglobin, and living in residential care. Patients with elevated troponin had longer lengths of stay, increased risk for discharge to long-term care facilities, and higher mortality. Increased age, male sex, and higher American Society of Anaesthesiologists score were also associated with mortality. Elevated troponin can be used as a marker of increased morbidity/mortality in elderly hip fracture patients undergoing surgery, as hypothesized, even in the absence of cardiac complications. Perioperative troponin evaluation may be useful for risk stratification, but further studies are needed to clarify risks and benefits of such testing.

Stereotactic body radiation therapy (SBRT) for multiple primary lung cancers (MPLC): a review and case series

OBJECTIVES

To review the literature and report our experience with the use of stereotactic body radiation therapy (SBRT) to treat multiple primary lung cancers (MPLCs).

METHODS

A retrospective review of 18 patients with 36 separate MPLC lesions (6 synchronous pairs and 12 metachronous pairs) was performed. Of these 18 patients, 16 were not surgical candidates and 2 declined to have surgery. Of the 36 lesions treated, 27 received SBRT, 6 had received prior fractionated RT, and 3 had prior surgical resection. Radiotherapy doses for SBRT ranged from 48 to 56 Gy (Median = 50 Gy) in 4 to 13 fractions (Median = 5 fractions) and treatment plans used 4D-CT simulation scans in all patients.

RESULTS

The median follow-up was 20 months after initial SBRT. We observed local control in 22 of 27 (81.5%) of the lesions treated with SBRT. The actuarial overall survival at 2 years from completion of initial SBRT course was 62%. Metastatic disease occurred in 3 of the 6 deceased patients. Clinically evident pneumonitis was observed in 3 of the 18 pts (17%), which resolved completely with steroid therapy.

CONCLUSIONS

SBRT appears to be a safe and effective treatment for MPLC both solely or after prior fractionated RT or surgical resection. SBRT for MPLC is a reasonable treatment option for patients who are not optimal candidates for surgery or who decline surgery.

The safety and efficacy of antitumour necrosis factor-alpha therapy for inflammatory bowel disease in patients post liver transplantation: a case series

BACKGROUND

The role of antitumour necrosis factor-alpha (anti-TNF) therapy for inflammatory bowel disease (IBD) among liver transplant recipients is largely unknown given the rarity of this population and the paucity of literature on the subject.

AIM

To investigate the safety and efficacy of anti-TNF therapy for refractory IBD in the post liver transplant population.

METHODS

The liver transplant database at London Health Sciences Centre was searched to identify adult patients with IBD treated with anti-TNF therapy post transplantation.

RESULTS

Six patients (five men, one woman) were identified, aged 28-65. All patients had cadaveric orthotopic liver transplants. Four patients required transplantation due to primary sclerosing cholangitis, one due to autoimmune hepatitis, and one due to biliary atresia. Five patients suffered from Crohn's disease and the remaining patient from indeterminate colitis. All patients were treated with infliximab 5 mg/kg every 8 weeks after undergoing induction at weeks 0, 2 and 6, with the exception of one patient. The duration of infliximab therapy ranged from 8 weeks to 4 years. Four patients treated with infliximab experienced sustained improvement of their IBD symptoms post transplantation, as documented by Harvey-Bradshaw Index scores demonstrating clinical remission. Of the remaining two patients, neither had sustained improvement of their IBD with infliximab or subsequent adalimumab. One patient was diagnosed with systemic lupus erythematosus and another with colorectal adenocarcinoma following anti-TNF therapy. Otherwise, no side effects were attributed to anti-TNF therapy.

CONCLUSIONS

Based on this case series, anti-TNF therapy appears to be safe and effective for treating refractory IBD in patients post liver transplantation. These patients respond to anti-TNF therapy similar to those who have not been previously transplanted.

GateCT™ surface tracking system for respiratory signal reconstruction in 4DCT imaging

PURPOSE

To assess the temporal and spatial accuracy of the GateCT™ system (VisionRT, London, UK), a recently released respiratory tracking system for 4DCT, under both ideal and nonideal respiratory conditions.

METHODS

Three experiments were performed by benchmarking and comparing its results with the ground-truth input data and those generated by the widely used Varian RPM™ system (Real-time Position Management, Varian, Palo Alto, CA). The first experiment used 10 sinusoidal breathing patterns (constant amplitude and frequency using sin(6)ωt), 10 "consistent" patient breathing patterns, and 10 "sporadic" patient breathing patterns. Motion was simulated with the quasar™ Programmable Respiratory Motion Platform (MODUS, London, Canada) as the surrogate. The GateCT™ and RPM™ systems were used to track the breathing patterns. The data from both systems were then analyzed in the Fourier domain, to evaluate temporal/phase accuracy, using the Pearson's correlation coefficient (PCC). The analysis correlated the ground-truth input data against the GateCT™ and RPM™ tracking results, respectively. The second experiment used 10 ideal sinusoidal breathing patterns, five of period 2.0 s, and five of period 5.0 s, with varying abdominal amplitudes found in clinical cases (peak-to-peak range: 1.67-10 mm) to test the sensitivity of the system to reconstruct various range of motion. And, the third experiment used 12 consecutive clinical patients to track the abdominal motion simultaneously by the GateCT™ and RPM™ systems. The baseline of the tracking results from both the two systems was analyzed via the mean-position-estimate (MPE) calculations. All experiments were tracked for at least 120 s.

RESULTS

In the first experiment, the average PCC values (±SD) of all thirty breathing patterns were 0.9995 ± 0.00035 and 0.9994 ± 0.00041 for the GateCT™ and the RPM™ system, respectively. These nearly identical results demonstrated similar temporal/phase tracking accuracy for the two systems. The results in the second experiment, however, revealed a pattern for the GateCT™ system in which the uncertainty of its mean-position tracking increased as the amplitude of the breathing pattern decreased. For example, a non-negligible baseline drift of up to 29.3% with respect to the peak-to-peak amplitude of 1.67-mm was observed. On the contrary, the RPM™ system displayed a more consistent recording of amplitudes over time with the greatest drift being <7.7%. The third experiment confirmed these findings in the clinical setting. Consistent decrease in PCC values due to the increase in artificial amplitude drifts, as the breathing amplitude decreased, was found. The lowest PCC value was 0.7239 for a patient with 1.57-mm peak-to-peak amplitude.

CONCLUSIONS

The GateCT™ system revealed its consistency in temporal/phase tracking but had limitations in accurately tracking the absolute abdominal positions, thus suggesting its appropriateness for phase-sorting of 4DCT rather than amplitude-sorting. In contrast, the RPM™ system demonstrated stable respiratory signal tracking in all ranges and accurately both in phase and amplitude, and is a robust system to use for both phase-sorting and amplitude-sorting techniques. The impact of the observed mean-position drift in the GateCT™ system on the resulting 4DCT image quality, in amplitude-sorting, needs further investigation.

Fluid biopsy for circulating tumor cell identification in patients with early-and late-stage non-small cell lung cancer: a glimpse into lung cancer biology

Circulating tumor cell (CTC) counts are an established prognostic marker in metastatic prostate, breast and colorectal cancer, and recent data suggest a similar role in late stage non-small cell lung cancer (NSCLC). However, due to sensitivity constraints in current enrichment-based CTC detection technologies, there are few published data about CTC prevalence rates and morphologic heterogeneity in early-stage NSCLC, or the correlation of CTCs with disease progression and their usability for clinical staging. We investigated CTC counts, morphology and aggregation in early stage, locally advanced and metastatic NSCLC patients by using a fluid-phase biopsy approach that identifies CTCs without relying on surface-receptor-based enrichment and presents them in sufficiently high definition (HD) to satisfy diagnostic pathology image quality requirements. HD-CTCs were analyzed in blood samples from 78 chemotherapy-naïve NSCLC patients. 73% of the total population had a positive HD-CTC count (>0 CTC in 1 mL of blood) with a median of 4.4 HD-CTCs mL⁻¹ (range 0-515.6) and a mean of 44.7 (±95.2) HD-CTCs mL⁻¹. No significant difference in the medians of HD-CTC counts was detected between stage IV (n = 31, range 0-178.2), stage III (n = 34, range 0-515.6) and stages I/II (n = 13, range 0-442.3). Furthermore, HD-CTCs exhibited a uniformity in terms of molecular and physical characteristics such as fluorescent cytokeratin intensity, nuclear size, frequency of apoptosis and aggregate formation across the spectrum of staging. Our results demonstrate that despite stringent morphologic inclusion criteria for the definition of HD-CTCs, the HD-CTC assay shows high sensitivity in the detection and characterization of both early- and late-stage lung cancer CTCs. Extensive studies are warranted to investigate the prognostic value of CTC profiling in early-stage lung cancer. This finding has implications for the design of extensive studies examining screening, therapy and surveillance in lung cancer patients.

Intensity-modulated radiosurgery with rapidarc for multiple brain metastases and comparison with static approach

Rotational RapidArc (RA) and static intensity-modulated radiosurgery (IMRS) have been used for brain radiosurgery. This study compares the 2 techniques from beam delivery parameters and dosimetry aspects for multiple brain metastases. Twelve patients with 2-12 brain lesions treated with IMRS were replanned using RA. For each patient, an optimal 2-arc RA plan from several trials was chosen for comparison with IMRS. Homogeneity, conformity, and gradient indexes have been calculated. The mean dose to normal brain and maximal dose to other critical organs were evaluated. It was found that monitor unit (MU) reduction by RA is more pronounced for cases with larger number of brain lesions. The MU-ratio of RA and IMRS is reduced from 104% to 39% when lesions increase from 2 to 12. The dose homogeneities are comparable in both techniques and the conformity and gradient indexes and critical organ doses are higher in RA. Treatment time is greatly reduced by RA in intracranial radiosurgery, because RA uses fewer MUs, fewer beams, and fewer couch angles.