A Multicenter Study of Clinical to Planning Target Volume Margins for Adjuvant Partial Breast Irradiation Delivered on the 1.5T MR-Linear Accelerator

PURPOSE/OBJECTIVE(S)

Adjuvant partial breast irradiation (APBI) for early-stage breast cancer patients delivered on a conventional Linac commonly uses a clinical to planning target volume (CTV-PTV) margin of 10 mm. Published data suggest this margin could be reduced using an MR-guided workflow. This study quantifies the CTV to PTV margin for APBI delivered on the 1.5T MR-Linac (MRL) using an Adapt to Position (ATP) workflow.

MATERIALS/METHODS

All target contouring was done as per the IMPORT LOW trial and MRL Consortium guidelines. The CTV is the tumor bed defined by surgical clips including postsurgical changes. A single center cohort of ten patients was used to assess delineation error on ProKnow DS v1.28.0 by measuring CTV contour displacements on the CT planning scans (pCT) delineated by five breast radiation oncologists. All other error components were measured on treatment planning software on another single center cohort of ten patients. Target deformation error was measured as surgical clip displacements between the pCT and daily pre-treatment (pre-Tx) MRI scans. Intrafraction motion was determined by the CTV displacement between pre- and post-treatment MRIs (post-Tx) in available paired images from five patients. Matching error was estimated as the interobserver variation of three MRL radiographers registering the pCT with daily pre-Tx MRI. Technical delivery accuracy was estimated using the results from routine quality assurance measurements. Beam penumbral width (p) was estimated from the clinical treatment plans. The systematic (Σ) and random errors (σ) for each component were calculated in the left/right (X), superior/inferior (Y) and anterior/posterior (Z) directions. The contribution of these errors to the PTV margin, M was calculated using van Herk's formula with α and β being 2.50 and 1.64 respectively.

RESULTS

For APBI using an MRL ATP workflow, a CTV-PTV margin of 5.7 to 7.6 mm is required to achieve a 90% confidence of CTV coverage by the 95% isodose. Individual error components are in. Table 1 delineation error remains the largest component of error.

CONCLUSION

A minimum CTV-PTV margin of 6-8 mm is required for APBI using an MRL ATP workflow. Although smaller than margins used in conventional Linacs, the clinical benefits (in terms of fibrosis risk) of treating APBI patients on an MRL are likely to be modest. Further margin reductions may be possible using an "Adapt to Shape" workflow with daily online recontouring.

Toward Global Consensus for MR-Guided Treatment Planning for Pancreatic Tumors on a 1.5 T MR-Linac

PURPOSE/OBJECTIVE(S)

MR-guided SBRT with a 1.5 T MR-Linac is a relatively new therapy for pancreatic tumors with varying expertise levels. Moreover, treatment planning in the upper abdomen can be challenging as target coverage is often compromised by dosimetric constraints of abutting bowel structures. This may lead to large differences between centers in protocols, practices. To increase harmonization a worldwide consortium was founded among 1.5 T MR-Linac users. In this work we report on the outcome of the first phase within this collaboration, which is the assessment of the baseline variation between the treatment planning protocols and subsequent dose distributions.

MATERIALS/METHODS

Twelve centers across three continents (North America, Europe, and Australia) participated in this consortium. Each center was sent the same two anonymized data sets reflecting two cases of locally advanced pancreatic cancer of different complexity levels. The data sets included a CT scan, a predefined structure set containing the gross target volume (GTV) and the OARs, a brief medical history, tumor motion characteristics, and auxiliary CT and MR imaging. Centers were asked to create an MRgRT treatment plan according to their clinical five-fraction SBRT protocol, using their institutional margin structures, beam setup, target prescriptions, and OAR constraints. Key DVH parameters that were evaluated are D99%, D90%, D50%, D1% for the GTV and D0.5cc for the duodenum, small bowel, and stomach.

RESULTS

In general, large variations were observed in planning objectives and machine settings yielding widely varying inhomogeneous dose distributions to both the tumor and organs at risk (Table 1). This was especially manifest for case 2 where the tumor abutted with both the duodenum and small bowel over a trajectory of multiple centimeters. Not only were different trade-offs between target coverage and OAR sparing observed, but also different strategies for optimizing the integral dose to the tumor.

CONCLUSION

These results indicate a large variety in the treatment planning strategies that could well translate to differences in outcome. Based on this first evaluation, the consortium will work towards a collective consensus protocol with a second evaluation round after internal discussions.

Is the Motion Causing a Commotion? Two-Fraction Prostate SBRT on the MR-Linac

PURPOSE/OBJECTIVE(S)

In HERMES (NCT04595019) men with localized prostate cancer are treated on the Unity MR-Linac platform (MRL, Elekta AB, Stockholm) and randomized between stereotactic body radiotherapy (SBRT) with 36.25 Gy in 5 fractions and 24 Gy in 2 fractions. Patients randomized to two fractions receive 24 Gy to the high risk PTV, 20 Gy to the low risk PTV and a boost of 27 Gy to the dominant intraprostatic lesion. This study explores dose received by the target and organs at risk (OARs) when considering intrafraction motion in two fraction SBRT.

MATERIALS/METHODS

Targets and OARs were delineated and a reference plan generated on Monaco v5.40.01 (Elekta). An Adapt-to-Shape (ATS) workflow was used. Contours were propagated to the session MRI (MRIsession) and edited accordingly. Prior to delivery, a verification MRI (MRIverif) was acquired with baseline shifts corrected for using the Adapt-to-Position (ATP-of-ATS) workflow. A post treatment MRI (MRIpost) was acquired after delivery. Men in the 2-fraction arm received each fraction in 2 sub-fractions sequentially on the same day, to mitigate intrafraction motion. The plans of 5 men receiving 2 fraction SBRT were analyzed. The targets, urethra, bladder and rectum were recontoured on the MRIverif and MRIpost. Delivered plans were recalculated on the corresponding MRIverif and MRIpost. The percentage of optimal and mandatory target dose constraints met were calculated. Accumulated OAR doses were calculated by averaging their respective dose statistics across all sub-fractions, conservatively assuming that the same area of the OAR receives the maximum dose each fraction. Analysis was carried out separately for MRIverif and MRIpost as the true 'delivered dose' most likely lies between these two estimates.

RESULTS

There was good coverage across all fractions. The mandatory constraints of CTVpsv V24.0 Gy > 95% and CTVsv V20.0 Gy > 95% were met in 100% of fractions and V2700cGy > 95% in 90% on the MRIpost. Table 3 shows OAR dose.

CONCLUSION

This work demonstrates that target coverage is good, even for the GTV where no margin is applied. With our conservative dose calculation approach, we found dose constraints are exceeded for some patients. However, treatment has been well tolerated, suggesting that that our current dose constraints may be cautious. Once Elekta's True Tracking and automated gating software is implemented at our center we will be able to further improve OAR clinical goal compliance.

Prenatal Cannabis Use and Offspring Autism-Related Behaviors: Examining Maternal Stress as a Moderator in a Black American Cohort

Prenatal cannabis use and maternal stress have been proposed as risk factors for autism spectrum disorder (ASD). Black mothers and mothers of lower socioeconomic status (SES) may be especially likely to experience high levels of stress. This study examined the impact of prenatal cannabis use and maternal stress (i.e., prenatal distress, racial discrimination, and lower SES) on child ASD-related behaviors in a sample of 172 Black mother-child pairs. We found that prenatal stress was significantly associated with ASD-related behaviors. Prenatal cannabis use did not predict ASD-related behaviors and did not interact with maternal stress to predict ASD-related behaviors. These findings replicate previous work on prenatal stress-ASD associations and add to the limited literature on prenatal cannabis-ASD associations in Black samples.

Understanding the Benefit of Magnetic Resonance-guided Adaptive Radiotherapy in Rectal Cancer Patients: a Single-centre Study

AIMS

Neoadjuvant chemoradiotherapy followed by surgery is the mainstay of treatment for patients with rectal cancer. Standard clinical target volume (CTV) to planning target volume (PTV) margins of 10 mm are used to accommodate inter- and intrafraction motion of target. Treating on magnetic resonance-integrated linear accelerators (MR-linacs) allows for online manual recontouring and adaptation (MRgART) enabling the reduction of PTV margins. The aim of this study was to investigate motion of the primary CTV (CTVA; gross tumour volume and macroscopic nodes with 10 mm expansion to cover microscopic disease) in order to develop a simultaneous integrated boost protocol for use on MR-linacs.

MATERIALS AND METHODS

Patients suitable for neoadjuvant chemoradiotherapy were recruited for treatment on MR-linac using a two-phase technique; only the five phase 1 fractions on MR-linac were used for analysis. Intrafraction motion of CTVA was measured between pre-treatment and post-treatment MRI scans. In MRgART, isotropically expanded pre-treatment PTV margins from 1 to 10 mm were rigidly propagated to post-treatment MRI to determine overlap with 95% of CTVA. The PTV margin was considered acceptable if overlap was >95% in 90% of fractions. To understand the benefit of MRgART, the same methodology was repeated using a reference computed tomography planning scan for pre-treatment imaging.

RESULTS

In total, nine patients were recruited between January 2018 and December 2020 with T3a-T4, N0-N2, M0 disease. Forty-five fractions were analysed in total. The median motion across all planes was 0 mm, demonstrating minimal intrafraction motion. A PTV margin of 3 and 5mm was found to be acceptable in 96 and 98% of fractions, respectively. When comparing to the computed tomography reference scan, the analysis found that PTV margins to 5 and 10 mm only acceptably covered 51 and 76% of fractions, respectively.

CONCLUSION

PTV margins can be reduced to 3-5 mm in MRgART for rectal cancer treatment on MR-linac within an simultaneous integrated boost protocol.

MRI-guided adaptive radiotherapy for prostate cancer: When do we need to account for intra-fraction motion?

A shift of the daily plan can mitigate target position changes that occur between daily MR acquisition and treatment for MR-linac radiotherapy, but increases the session time. We demonstrated that our workflow strategy and decision-making process, to determine whether a subsequent shift is necessary, is appropriate.

Mapping Local Failure Following Bladder Radiotherapy According to Dose

AIMS

To determine the relationship between local relapse following radical radiotherapy for muscle-invasive bladder cancer (MIBC) and radiation dose.

MATERIALS AND METHODS

Patients with T2-4N0-3M0 MIBC were recruited to a phase II study assessing the feasibility of intensity-modulated radiotherapy to the bladder and pelvic lymph nodes. Patients were planned to receive 64 Gy/32 fractions to the bladder tumour, 60 Gy/32 fractions to the involved pelvic nodes and 52 Gy/32 fractions to the uninvolved bladder and pelvic nodes. Pre-treatment set-up was informed by cone-beam CT. For patients who experienced local relapse, cystoscopy and imaging (CT/MRI) was used to reconstruct the relapse gross tumour volume (GTVrelapse) on the original planning CT . GTVrelapse D98% and D95% was determined by co-registering the relapse image to the planning CT utilising deformable image registration (DIR) and rigid image registration (RIR). Failure was classified into five types based on spatial and dosimetric criteria as follows: A (central high-dose failure), B (peripheral high-dose failure), C (central elective dose failure), D (peripheral elective dose failure) and E (extraneous dose failure).

RESULTS

Between June 2009 and November 2012, 38 patients were recruited. Following treatment, 18/38 (47%) patients experienced local relapse within the bladder. The median time to local relapse was 9.0 months (95% confidence interval 6.3-11.7). Seventeen of 18 patients were evaluable based on the availability of cross-sectional relapse imaging. A significant difference between DIR and RIR methods was seen. With the DIR approach, the median GTVrelapse D98% and D95% was 97% and 98% of prescribed dose, respectively. Eleven of 17 (65%) patients experienced type A failure and 6/17 (35%) patients type B failure. No patients had type C, D or E failure. MIBC failure occurred in 10/17 (59%) relapsed patients; of those, 7/11 (64%) had type A failure and 3/6 (50%) had type B failure. Non-MIBC failure occurred in 7/17 (41%) patients; 4/11 (36%) with type A failure and 3/6 (50%) with type B failure.

CONCLUSION

Relapse following radiotherapy occurred within close proximity to the original bladder tumour volume and within the planned high-dose region, suggesting possible biological causes for failure. We advise caution when considering margin reduction for future reduced high-dose radiation volume or partial bladder radiotherapy protocols.

A Randomised Phase II Clinical Trial Comparing the Deliverability and Acute Toxicity of Wide Tangent versus Volumetric Modulated Arc Therapy to the Breast and Internal Mammary Chain

AIMS

Inclusion of the internal mammary chain in the radiotherapy target volume (IMC-RT) improves disease-free and overall survival in higher risk breast cancer patients, but increases radiation doses to heart and lungs. Dosimetric data show that either modified wide-tangential fields (WT) or volumetric modulated arc therapy (VMAT) together with [AQ1]voluntary deep inspiration breath hold (vDIBH) keep mean heart doses below 4 Gy in most patients. However, the impact on departmental resources has not yet been documented. This phase II clinical trial compared the time taken to deliver IMC-RT using either WT and vDIBH or VMAT and vDIBH, together with planning time, dosimetry, set-up reproducibility and toxicity.

MATERIALS AND METHODS

Left-sided breast cancer patients requiring IMC-RT were randomised to receive either WT(vDIBH) or VMAT radiotherapy. The primary outcome was treatment time, powered to detect a minimum difference of 75 min (5 min/fraction) between techniques. The population mean displacement, systematic error and random error for cone beam computed tomography chest wall matches in three directions of movement were calculated. Target volume and organ at risk doses were compared between groups. Side-effects, including skin (Radiation Therapy Oncology Group), lung and oesophageal toxicity (Common Terminology Criteria for Adverse Events v 4.03) rates, were compared between the groups over 3 months. Patient-reported outcome measures, including shoulder toxicity at baseline, 6 months and 1 year, were compared.

RESULTS

Twenty-one patients were recruited from a single UK centre between February 2017 and January 2018. The mean (standard deviation) total treatment time per fraction for VMAT treatments was 13.2 min (1.7 min) compared with 28.1 min (3.3 min) for WT(vDIBH). There were no statistically significant differences in patient set-up errors in between groups. The average mean heart dose for WT(vDIBH) was 2.6 Gy compared with 3.4 Gy for VMAT(vDIBH) (P = 0.13). The mean ipsilateral lung V17Gy was 32.8% in the WT(vDIBH) group versus 34.4% in the VMAT group (P = 0.2). The humeral head (mean dose 16.8 Gy versus 2.8 Gy), oesophagus (maximum dose 37.3 Gy versus 20.1 Gy) and thyroid (mean dose 22.0 Gy versus 11.2 Gy) all received a statistically significantly higher dose in the VMAT group. There were no statistically significant differences in skin, lung or oesophageal toxicity within 3 months of treatment. Patient-reported outcomes of shoulder toxicity, pain, fatigue, breathlessness and breast symptoms were similar between groups at 1 year.

CONCLUSION

VMAT(vDIBH) and WT(vDIBH) are feasible options for locoregional breast radiotherapy including the IMC. VMAT improves nodal coverage and delivers treatment more quickly, resulting in less breath holds for the patient. This is at the cost of increased dose to some non-target tissues. The latter does not appear to translate into increased toxicity in this small study.

Feasibility of tumour-focused adaptive radiotherapy for bladder cancer on the MR-linac

Bladder tumour-focused magnetic resonance image-guided adaptive radiotherapy using a 1.5 Tesla MR-linac is feasible. A full online workflow adapting to anatomy at each fraction is achievable in approximately 30 min. Intra-fraction bladder filling did not compromise target coverage with the class solution employed.

Adalimumab and Infliximab Impair SARS-CoV-2 Antibody Responses: Results from a Therapeutic Drug Monitoring Study in 11 422 Biologic-Treated Patients

BACKGROUND AND AIMS

Infliximab attenuates serological responses to SARS-CoV-2 infection. Whether this is a class effect, or if anti-tumour necrosis factor [anti-TNF] level influences serological responses, remains unknown.

METHODS

Seroprevalence and the magnitude of SARS-CoV-2 nucleocapsid antibody responses were measured in surplus serum from 11 422 (53.3% [6084] male; median age 36.8 years) patients with immune-mediated inflammatory diseases, stored at six therapeutic drug monitoring laboratories between January 29 and September 30, 2020. Data were linked to nationally held SARS-CoV-2 PCR results to July 11, 2021.

RESULTS

Rates of PCR-confirmed SARS-CoV-2 infection were similar across treatment groups. Seroprevalence rates were lower in infliximab- and adalimumab- than vedolizumab-treated patients (infliximab: 3.0% [178/5893], adalimumab: 3.0% [152/5074], vedolizumab: 6.7% [25/375], p = 0.003). The magnitude of SARS-CoV-2 reactivity was similar in infliximab- vs adalimumab-treated patients (median 4.30 cut-off index [COI] [1.94-9.96] vs 5.02 [2.18-18.70], p = 0.164), but higher in vedolizumab-treated patients (median 21.60 COI [4.39-68.10, p < 0.004). Compared to patients with detectable infliximab and adalimumab drug levels, patients with undetectable drug levels [<0.8 mg/L] were more likely to be seropositive for SARS-CoV-2 antibodies. One-third of patients who had PCR testing prior to antibody testing failed to seroconvert, all were treated with anti-TNF. Subsequent positive PCR-confirmed SARS-CoV-2 was seen in 7.9% [12/152] of patients after a median time of 183.5 days [129.8-235.3], without differences between drugs.

CONCLUSION

Anti-TNF treatment is associated with lower SARS-CoV-2 nucleocapsid seroprevalence and antibody reactivity when compared to vedolizumab-treated patients. Higher seropositivity rates in patients with undetectable anti-TNF levels support a causal relationship, although confounding factors, such as combination therapy with a immunomodulator, may have influenced the results.

A Comparison of Isotoxic Dose-escalated Radiotherapy in Lung Cancer with Moderate Deep Inspiration Breath Hold, Mid-ventilation and Internal Target Volume Techniques

AIMS

With interest in normal tissue sparing and dose-escalated radiotherapy in the treatment of inoperable locally advanced non-small cell lung cancer, this study investigated the impact of motion-managed moderate deep inspiration breath hold (mDIBH) on normal tissue sparing and dose-escalation potential and compared this to planning with a four-dimensional motion-encompassing internal target volume or motion-compensating mid-ventilation approach.

MATERIALS AND METHODS

Twenty-one patients underwent four-dimensional and mDIBH planning computed tomography scans. Internal and mid-ventilation target volumes were generated on the four-dimensional scan, with mDIBH target volumes generated on the mDIBH scan. Isotoxic target dose-escalation guidelines were used to generate six plans per patient: three with a target dose cap and three without. Target dose-escalation potential, normal tissue complication probability and differences in pre-specified dose-volume metrics were evaluated for the three motion-management techniques.

RESULTS

The mean total lung volume was significantly greater with mDIBH compared with four-dimensional scans. Lung dose (mean and V21 Gy) and mean heart dose were significantly reduced with mDIBH in comparison with four-dimensional-based approaches, and this translated to a significant reduction in heart and lung normal tissue complication probability with mDIBH. In 20/21 patients, the trial target prescription dose cap of 79.2 Gy was achievable with all motion-management techniques.

CONCLUSION

mDIBH aids lung and heart dose sparing in isotoxic dose-escalated radiotherapy compared with four-dimensional planning techniques. Given concerns about lung and cardiac toxicity, particularly in an era of consolidation immunotherapy, reduced normal tissue doses may be advantageous for treatment tolerance and outcome.

What Can Proton Beam Therapy Achieve for Patients with Pectus Excavatum Requiring Left Breast, Axilla and Internal Mammary Nodal Radiotherapy?

AIMS

Exposure of the heart to radiation increases the risk of ischaemic heart disease, proportionate to the mean heart dose (MHD). Radiotherapy techniques including proton beam therapy (PBT) can reduce MHD. The aims of this study were to quantify the MHD reduction achievable by PBT compared with volumetric modulated arc therapy in breath hold (VMAT-BH) in patients with pectus excavatum (PEx), to identify an anatomical metric from a computed tomography scan that might indicate which patients will achieve the greatest MHD reductions from PBT.

MATERIALS AND METHODS

Sixteen patients with PEx (Haller Index ≥2.7) were identified from radiotherapy planning computed tomography images. Left breast/chest wall, axilla (I-IV) and internal mammary node (IMN) volumes were delineated. VMAT and PBT plans were prepared, all satisfying target coverage constraints. Signed-rank comparisons of techniques were undertaken for the mean dose to the heart, ipsilateral lung and contralateral breast. Spearman's rho correlations were calculated for anatomical metrics against MHD reduction achieved by PBT.

RESULTS

The mean MHD for VMAT-BH plans was 4.1 Gy compared with 0.7 Gy for PBT plans. PBT reduced MHD by an average of 3.4 Gy (range 2.8-4.4 Gy) compared with VMAT-BH (P < 0.001). PBT significantly reduced the mean dose to the ipsilateral lung (4.7 Gy, P < 0.001) and contralateral breast (2.7 Gy, P < 0.001). The distance (mm) at the most inferomedial extent of IMN volume (IMN to heart distance) negatively correlated with MHD reduction achieved by PBT (Spearman's rho -0.88 (95% confidence interval -0.96 to -0.67, P < 0.001)).

CONCLUSION

For patients with PEx requiring left-sided breast and IMN radiotherapy, a clinically significant MHD reduction is achievable using PBT, compared with the optimal photon technique (VMAT-BH). This is a patient group in whom PBT could have the greatest benefit.

Non-fatal opioid overdose, naloxone access, and naloxone training among people who recently used opioids or received opioid agonist treatment in Australia: The ETHOS Engage study

BACKGROUND

Overdose is a major cause of morbidity and mortality among people who use opioids. Naloxone can reverse opioid overdoses and can be distributed and administered with minimal training. People with experience of overdose are a key population to target for overdose prevention strategies. This study aims to understand if factors associated with recent non-fatal opioid overdose are the same as factors associated with naloxone access and naloxone training in people who recently used opioids or received opioid agonist treatment (OAT).

METHODS

ETHOS Engage is an observational study of people who inject drugs in Australia. Logistic regression models were used to estimate odds ratios for non-fatal opioid overdose, naloxone access and naloxone training.

RESULTS

Between May 2018-September 2019, 1280 participants who recently used opioids or received OAT were enrolled (62% aged >40 years; 35% female, 80% receiving OAT, 62% injected drugs in the preceding month). Recent opioid overdose (preceding 12 months) was reported by 7% of participants, lifetime naloxone access by 17%, and lifetime naloxone training by 14%. Compared to people receiving OAT with no additional opioid use, recent opioid, benzodiazepine (preceding six months), and hazardous alcohol use was associated with recent opioid overdose (aOR 3.91; 95%CI: 1.68-9.10) and lifetime naloxone access (aOR 2.12; 95%CI 1.29-3.48). Among 91 people who reported recent overdose, 65% had never received take-home naloxone or naloxone training.

CONCLUSIONS

Among people recently using opioids or receiving OAT, benzodiazepine and hazardous alcohol use is associated with non-fatal opioid overdose. Not all factors associated with non-fatal overdose correspond to factors associated with naloxone access. Naloxone access and training is low across all groups. Additional interventions are needed to scale up naloxone provision.

Feasibility of magnetic resonance guided radiotherapy for the treatment of bladder cancer

Whole bladder magnetic resonance image-guided radiotherapy using the 1.5 Telsa MR-linac is feasible. Full online adaptive planning workflow based on the anatomy seen at each fraction was performed. This was delivered within 45 min. Intra-fraction bladder filling did not compromise target coverage. Patients reported acceptable tolerance of treatment.

Disease monitoring of biologic treatment in IBD: early impact and future implications of COVID-19 pandemic

COVID-19 has dominated life in 2020 with, at the time of writing, over 4.9M global cases and >320 000 deaths. The impact has been most intensely felt in acute and critical care environments. However, with most UK elective work postponed, laboratory testing of faecal calprotectin halted due to potential risk of viral transmission and non-emergency endoscopies and surgeries cancelled, the secondary impact on chronic illnesses such as inflammatory bowel disease (IBD) is becoming apparent. Data from the Scottish Biologic Therapeutic Drug Monitoring (TDM) service shows a dramatic drop in TDM testing since the pandemic onset. April 2020 saw a 75.6% reduction in adalimumab testing and a 36.2% reduction in infliximab testing when compared with February 2020 data, a reduction coinciding with the widespread cancellation of outpatient and elective activity. It is feared that disruption to normal patterns of care and disease monitoring of biologic patients could increase the risk of disease flare and adverse clinical outcomes. Urgent changes in clinical practice have been instigated to mitigate the effects of the pandemic on routine clinical care. Further transformations are needed to maintain safe, effective, patient-centred IBD care in the future.

AB0309 MEASURING THE DIFFERENCE: COMPARISON OF MEASUREMENT OF FREE INFLIXIMAB ANTI-DRUG ANTIBODIES

Background:

Infliximab (IFX) was one of the first TNF alpha inhibitors to be licenced in inflammatory arthritis and is still commonly used today. Studies have shown that approximately 50% of primary IFX responders will suffer from secondary loss of response within the first 12 months of treatment (1). The development of Anti-Drug Antibodies (ADA’s) plays a significant role in this treatment failure (2).

Monitoring of ADA’s helps identify those patients who fail to respond to treatment due to low IFX trough levels. In this scenario the presence of ADA’s can aid decision-making regarding increasing IFX dosing or switching biologic therapy to optimise treatment. (3).

Objectives:

Despite their potential importance the detection of ADAs varies widely depending on the type of assays used. The aim of this study was to determine the qualitative concordance of three commercially available ELISA kits for measurement of free ADAs to IFX on the Grifols Triturus analyser.

Methods:

150 patient samples from patients with inflammatory conditions and low IFX trough drug levels (≤0.6µg/ml) were analysed for free ADAs using Promonitor, Lisa Tracker and IDKmonitor kits on the Grifols Triturus automated ELISA analyser.

Results:

Kappa coefficient (κ) analysis indicated a moderate agreement between the Promonitor and IDKmonitor assays (κ =0.484 (95% CI, 0.357 to 0.611)) and the IDKmonitor and Lisa Tracker assays (κ = 0.485 (95% CI, 0.348-0.621)) as well as substantial agreement between the Promonitor and Lisa Tracker assays (κ =0.768 (95% CI, 0.667-0.870)). Figure 1 shows the distribution of samples identified as free ADA positive by each kit.

Figure 1.

Distribution of samples identified as free ADA positive by Promonitor, Lisa Tracker, and IDKmonitor assays. Fifty samples were considered positive by all assays. Three samples were considered positive by Promonitor and Lisa Tracker, and eight samples were considered positive by Lisa Tracker and IDKmonitor. No samples were considered positive by Promonitor and IDKmonitor. One sample was considered positive by Promonitor only, seven samples were considered positive by Lisa Tracker only, and twenty-six samples were considered positive by IDKmonitor

Conclusion:

All kits appear amenable for utilisation in a high-throughput laboratory though a true quantitative comparison between these kits was precluded by the absence of any certified reference material for free ADAs to IFX.

Although broad qualitative agreement was found between the three kits, they should not be used interchangeably for patient management.

Further research is required to estimate the impact of free ADAs on efficiency of IFX treatment and patient management.

References:

[1]Quistrebert J, Hässler S, Bachelet D et al.Incidence and risk factors for adalimumab and infliximab anti-drug antibodies in rheumatoid arthritis: A European retrospective multicohort analysis. Seminars in Arthritis and Rheumatism Volume 48, Issue 6, June 2019, Pages 967-975 2.

[2]Moots RJ, Xavier RM, Mok CC, Rahman MU, Tsai W-C, Al-Maini MH, et al. (2017)The impact of anti-drug antibodies on drug concentrations and clinical outcomes in rheumatoid arthritis patients treated with adalimumab, etanercept, or infliximab: Results from a multinational, real-world clinical practice, non-interventional study. PLoS ONE 12(4): e0175207.https://doi.org/10.1371/journal.pone.0175207

[3]Smolen JS, Landewé R, Bijlsma J, et al.EULAR recommendations for the management of rheumatoid arthritis with synthetic and biological disease-modifying antirheumatic drugs:2016 update.Annals of the Rheumatic Diseases 2017;76:960-977.

Disclosure of Interests:

Rhona Hamilton: None declared, Stephanie Shields: None declared, Andrew McGucken: None declared, Jonathan MacDonald: None declared, Martin Perry Grant/research support from: Grifols, Abbvie, Sandoz unrestricted educational grant, Consultant of: Abbvie, Gilead, Celltrion Advisory Board, Speakers bureau: Sandoz, Allan Dunlop: None declared, Elaine Gribben: None declared, Peter Galloway: None declared

AB1186 THE NHS SCOTLAND THERAPEUTIC DRUG MONITORING SERVICE FOR BIOLOGIC MEDICINES: PRELIMINARY ANALYSIS OF UTILISATION AND CLINICAL RESULTS AT YEAR 1

Background:

Anti-tumour necrosis factor α (anti-TNFα) drugs infliximab (IFX) and adalimumab (ADL) are effective treatments for several rheumatic diseases. Therapeutic drug level and anti-drug antibody monitoring (TDM) has emerged as a useful tool for optimising drug effectiveness, by identifying individuals who may benefit from dose or treatment frequency adjustment, or have secondary drug failure due to immunogenicity.

Objectives:

Ensuring safe and effective use of biologic medicines has been identified as a key priority for NHS Scotland. Inequity and inconsistency of access to TDM across the nation was recognised as a barrier to delivering best practice and so a nationally commissioned TDM service was proposed in January 2018 to support clinical practice, providing universal access to TDM for services treating inflammatory diseases across Scotland. Data collection and analysis of results regarding usage and clinical impact of the service were identified as key outcome measures to assess service success and sustainability.

Methods:

A service webpage was developed to provide guidance on testing strategies and interpretation of TDM results (1). An automated search of clinical data and test results recorded within the clinical biochemistry electronic results management system was conducted to identify all TDM tests performed between 01/01/2018 and 31/12/2018. Descriptive analysis outcomes included the number of samples received, processed, overall testing population, service utilisation by Health Board, number and results of TDM tests performed per patient. TDM results were interpreted according to published guidance on the service webpage and comparison was made with previously published data (2).

Results:

3609 specimens were received for testing, from 13 of the 14 Scottish Health Boards. 3561 drug level (DL) tests were performed; 1786IFX, 1775 ADL. 2717 total antidrug anti-body (TABT) tests and 681 free antidrug anti-body tests (FABT) were performed according to service protocol. 2791 individuals had one or more TDM tests during the 12-month period, of whom 541 were tested twice or more (range 2-5).

Table 1.

IFX & ADL DL, TABT and FABT results by category as defined in service guidance (AU/ml = Arbitrary Units/ml)]

INFLIXIMABADALIMUMABDrug level by categorySupratherapeutic DL > 8mcg/ml546 (30.6%)708 (39.9%)Supratherapeutic DL > 10 mcg/mlTherapeutic DL ≥3<8.1mcg/ml738 (41.3%)636 (35.8%)Therapeutic DL ≥5<10.1 mcg/mlSub-therapeutic DL < 3mcg/ml502 (28.1%)431 (24.3%)Sub-therapeutic DL < 5 mcg/mlTABT by categoryNegative (<10 AU/ml)791 (54.2%)905 (71.9%)Negative (<10 AU/ml)Positive (>10 AU/ml)668 (45.8%)353 (28.1%)Positive (>10 AU/ml)FABT by categoryNegative (< 5AU/ml)376 (82.8%)176 (77.6%)Negative (<10 AU/ml)Positive (> 5 AU/ml)78 (17.2%)51 (22.4%)Positive (>10 AU/ml)

Conclusion:

TDM has been enthusiastically embraced. It is estimated that > 50% of individuals treated with IFX or ADL have been tested at least once in the first year. DL results were found to be similar to previously published data, as were rates of antibody positivity. The large volume of data generated by the service may provide additional evidence regarding the utility of TDM in predicting clinical response. Next steps are to conduct a comparative effectiveness analysis where proactive vs reactive TDM testing strategies will be compared, with the primary outcome measure being the proportions of patients with secondary loss of response.

References:

[1]Scottish Biologic therapeutic Drug Monitoring Servicehttps://www.nhsggc.org.uk/about-us/professional-support-sites/biochemistry/biological-therapy-monitoring/

[2]Jani, M. Et al (2015), Clinical Utility of Random Anti–Tumor Necrosis Factor Drug–Level Testing and Measurement of Antidrug Antibodies on the Long-Term Treatment Response in Rheumatoid Arthritis. Arthritis & Rheumatology, 67: 2011-2019. doi:10.1002/art.39169

Acknowledgments:

Biogen GmbH contributed partial funding for this research. Authors had full editorial control and approval of all content

Disclosure of Interests:

Jonathan MacDonald: None declared, Martin Perry Grant/research support from: Grifols, Abbvie, Sandoz unrestricted educational grant, Consultant of: Abbvie, Gilead, Celltrion Advisory Board, Speakers bureau: Sandoz, Peter Galloway: None declared, John-Paul Seenan: None declared, Alan Dunlop: None declared

Evaluation of a Novel Field-placement Algorithm for Locoregional Breast Cancer Radiotherapy Including the Internal Mammary Chain

AIMS

Irradiation of the internal mammary chain (IMC) is increasing following recently published data, but the need for formal delineation of lymph node volumes is slowing implementation in some healthcare settings. A field-placement algorithm for irradiating locoregional lymph nodes including the IMC could reduce the resource impact of introducing irradiation of the IMC. This study describes the development and evaluation of such an algorithm.

MATERIALS AND METHODS

An algorithm was developed in which six points representing lymph node clinical target volume borders (based on European Society for Radiotherapy and Oncology consensus nodal contouring guidelines) were placed on computed tomography-defined anatomical landmarks and used to place tangential and nodal fields. Single-centre testing in 20 cases assessed the success of the algorithm in covering planning target volumes (PTVs) and adequately sparing organs at risk. Plans derived using the points algorithm were also compared with plans generated following formal delineation of nodal PTVs, using the Wilcoxon signed rank test. Timing data for point placement were collected. Multicentre testing using the same methods was then carried out to establish whether the technique was transferable to other centres.

RESULTS

Single-centre testing showed that 95% of cases met the nodal PTV coverage dose constraints (binomial probability confidence interval 75.1-99.9%) with no statistically significant reduction in mean heart dose or ipsilateral lung V17Gy associated with formal nodal delineation. In multicentre testing, 69% of cases met nodal PTV dose constraints and there was a statistically significant difference in IMC PTV coverage using the points algorithm when compared with formally delineated nodal volumes (P < 0.01). However, there was no difference in axillary level 1-4 PTV coverage (P = 0.11) with all cases meeting target volume constraints.

CONCLUSIONS

The optimal strategy for breast and locoregional lymph node radiotherapy is target volume delineation. However, use of this novel points-based field-placement algorithm results in dosimetrically acceptable plans without the need for formal lymph node contouring in a single-centre setting and for the breast and level 1-4 axilla in a multicentre setting. Further quality assurance measures are needed to enable implementation of the algorithm for irradiation of the IMC in a multicentre setting.

A Dosimetric Comparison of Breast Radiotherapy Techniques to Treat Locoregional Lymph Nodes Including the Internal Mammary Chain

AIMS

Radiotherapy target volumes in early breast cancer treatment increasingly include the internal mammary chain (IMC). In order to maximise survival benefits of IMC radiotherapy, doses to the heart and lung should be minimised. This dosimetry study compared the ability of three-dimensional conformal radiotherapy, arc therapy and proton beam therapy (PBT) techniques with and without breath-hold to achieve target volume constraints while minimising dose to organs at risk (OARs).

MATERIALS AND METHODS

In 14 patients' datasets, seven IMC radiotherapy techniques were compared: wide tangent (WT) three-dimensional conformal radiotherapy, volumetric-modulated arc therapy (VMAT) and PBT, each in voluntary deep inspiratory breath-hold (vDIBH) and free breathing (FB), and tomotherapy in FB only. Target volume coverage and OAR doses were measured for each technique. These were compared using a one-way ANOVA with all pairwise comparisons tested using Bonferroni's multiple comparisons test, with adjusted P-values ≤ 0.05 indicating statistical significance.

RESULTS

One hundred per cent of WT(vDIBH), 43% of WT(FB), 100% of VMAT(vDIBH), 86% of VMAT(FB), 100% of tomotherapy FB and 100% of PBT plans in vDIBH and FB passed all mandatory constraints. However, coverage of the IMC with 90% of the prescribed dose was significantly better than all other techniques using VMAT(vDIBH), PBT(vDIBH) and PBT(FB) (mean IMC coverage ± 1 standard deviation = 96.0% ± 4.3, 99.8% ± 0.3 and 99.0% ± 0.2, respectively). The mean heart dose was significantly reduced in vDIBH compared with FB for both the WT (P < 0.0001) and VMAT (P < 0.0001) techniques. There was no advantage in target volume coverage or OAR doses for PBT(vDIBH) compared with PBT(FB).

CONCLUSIONS

Simple WT radiotherapy delivered in vDIBH achieves satisfactory coverage of the IMC while meeting heart and lung dose constraints. However, where higher isodose coverage is required, VMAT(vDIBH) is the optimal photon technique. The lowest OAR doses are achieved by PBT, in which the use of vDIBH does not improve dose statistics.

Evaluation of a multi-atlas CT synthesis approach for MRI-only radiotherapy treatment planning

BACKGROUND AND PURPOSE

Computed tomography (CT) imaging is the current gold standard for radiotherapy treatment planning (RTP). The establishment of a magnetic resonance imaging (MRI) only RTP workflow requires the generation of a synthetic CT (sCT) for dose calculation. This study evaluates the feasibility of using a multi-atlas sCT synthesis approach (sCTa) for head and neck and prostate patients.

MATERIAL AND METHODS

The multi-atlas method was based on pairs of non-rigidly aligned MR and CT images. The sCTa was obtained by registering the MRI atlases to the patient's MRI and by fusing the mapped atlases according to morphological similarity to the patient. For comparison, a bulk density assignment approach (sCTbda) was also evaluated. The sCTbda was obtained by assigning density values to MRI tissue classes (air, bone and soft-tissue). After evaluating the synthesis accuracy of the sCTs (mean absolute error), sCT-based delineations were geometrically compared to the CT-based delineations. Clinical plans were re-calculated on both sCTs and a dose-volume histogram and a gamma analysis was performed using the CT dose as ground truth.

RESULTS

Results showed that both sCTs were suitable to perform clinical dose calculations with mean dose differences less than 1% for both the planning target volume and the organs at risk. However, only the sCTa provided an accurate and automatic delineation of bone.

CONCLUSIONS

Combining MR delineations with our multi-atlas CT synthesis method could enable MRI-only treatment planning and thus improve the dosimetric and geometric accuracy of the treatment, and reduce the number of imaging procedures.

Evaluation of radiotherapy techniques for radical treatment of lateralised oropharyngeal cancers : Dosimetry and NTCP

AIM

The aim of this study was to investigate potential advantages and disadvantages of three-dimensional conformal radiotherapy (3DCRT), multiple fixed-field intensity-modulated radiotherapy (IMRT) and volumetric-modulated arc therapy (VMAT) in terms of dose to the planning target volume (PTV), organs at risk (OARs) and normal tissue complication probability (NTCP) for delivering ipsilateral radiotherapy.

MATERIALS AND METHODS

3DCRT, IMRT and VMAT were compared in patients with well-lateralised primary tonsillar cancers who underwent primary radical ipsilateral radiotherapy. The following parameters were compared: conformity index (CI); homogeneity index (HI); dose-volume histograms (DVHs) of PTVs and OARs; NTCP, risk of radiation-induced cancer and dose accumulation during treatment.

RESULTS

IMRT and VMAT were superior to 3DCRT in terms of CI, HI and dose to the target volumes, as well as mandible and dose accumulation robustness. The techniques were equivalent in terms of dose and NTCP for the contralateral oral cavity, contralateral submandibular gland and mandible, when specific dose constraint objectives were used on the oral cavity volume. Although the volume of normal tissue exposed to low-dose radiation was significantly higher with IMRT and VMAT, the risk of radiation-induced secondary malignancy was dependant on the mathematical model used.

CONCLUSION

This study demonstrates the superiority of IMRT/VMAT techniques over 3DCRT in terms of dose homogeneity, conformity and consistent dose delivery to the PTV throughout the course of treatment in patients with lateralised oropharyngeal cancers. Dosimetry and NTCP calculations show that these techniques are equivalent to 3DCRT with regard to the risk of acute mucositis when specific dose constraint objectives were used on the contralateral oral cavity OAR.

Liver disease knowledge and acceptability of non-invasive liver fibrosis assessment among people who inject drugs in the drug and alcohol setting: The LiveRLife Study

BACKGROUND

The aim of this study was to assess factors associated with baseline knowledge of HCV and liver disease, acceptability of transient elastography (TE) assessment (FibroScan(®)), and willingness and intent to receive HCV treatment among persons with a history of injection drug use participating in a liver health promotion campaign.

METHODS

The LiveRLife campaign involved three phases: (1) campaign resource development; (2) campaign resource testing; and (3) campaign implementation. Participants were enrolled in an observational cohort study with recruitment at four clinics - one primary health care facility, two OST clinics, and one medically supervised injecting centre - in Australia between May and October 2014. Participants received educational material, nurse clinical assessment, TE assessment, dried blood spot testing, and completed a knowledge survey.

RESULTS

Of 253 participants (mean age 43 years), 68% were male, 71% had injected in the past month, and 75% self-reported as HCV positive. Median knowledge score was 16/23. In adjusted analysis, less than daily injection (AOR 5.01; 95% CI, 2.64-9.51) and no daily injection in the past month (AOR 3.54; 95% CI, 1.80-6.94) were associated with high knowledge (≥16). TE was the most preferred method both pre- (66%) and post-TE (89%) compared to liver biopsy and blood sample. Eighty-eight percent were 'definitely willing' or 'somewhat willing' to receive HCV treatment, and 56% intended to start treatment in the next 12 months. Approximately 68% had no/mild fibrosis (F0/F1, ≥2.5 to ≤7.4kPa), 13% moderate fibrosis (F2, ≥7.5 to ≤9.4kPa), 10% severe fibrosis (F3, ≥9.5 to ≤12.4kPa), and 9% had cirrhosis (F4, ≥12.5kPa).

CONCLUSION

Liver disease and HCV knowledge was moderate. High acceptability of TE by PWID provides strong evidence for the inclusion of TE in HCV-related care, and could help to prioritise HCV treatment for those at greatest risk of liver disease progression.