Northern Ireland Cancer Centre Research Articles

3185: Retrospective analysis of output data for ten linear accelerators at Northern Ireland Cancer Centre

3185: Retrospective analysis of output data for ten linear accelerators at Northern Ireland Cancer Centre

Abstract A025: Elevated periprostatic fat is associated with high grade prostate cancer in radiotherapy-treated patients

Abstract Introduction Obesity is associated with poor prostate cancer-specific outcomes. Body mass index, a commonly used surrogate of obesity, does not adequately describe fat distribution, which can instead be assessed using medical imaging. Abdominal visceral obesity, a better indicator of metabolic health, has been associated with increased prostate cancer risk. Similarly, periprostatic adipose tissue (PPAT), a type of visceral fat in close proximity to the prostate has a postulated role in prostate cancer aggressiveness. We hypothesised that elevated quantities of visceral fat, both abdominal and periprostatic would be associated with increased disease aggressiveness. To gain insight into potential contributing mechanisms, we examined gene expression pathways differentially expressed in association with adiposity measures. Methods Abdominal adipose tissue, both subcutaneous and visceral (n=244), and PPAT (n=309) were quantified from the radiation planning computed tomography (CT) scans from prostate cancer patients treated with radiotherapy and ADT in the Northern Ireland Cancer Centre between 2005-2009. Abdominal fat was measured at L4/L5 and PPAT at the midpoint of pubic symphysis using a threshold of -190 to -30 Hounsfield Units to identify fat. Associations of adipose tissue quantity, categorised using tertiles of fat quantity, with Gleason score (≥4+3 versus ≤3+4) were assessed using univariable and multivariable logistic regression analysis. Associations between adipose tissue quantity and risk of biochemical recurrence and metastasis were examined using Cox regression. In a subset of patients with tumour biopsy transcriptomic data (n=183), an exploratory Gene Set Enrichment Analysis (GSEA) was performed to identify enriched gene pathways in the tumours of those with high versus low fat measures, defined using the median fat quantity. Results High PPAT was significantly associated with increased risk of high grade prostate cancer (Tertile 3 vs. Tertile 1; age adjusted OR 2.05; 95%CI 1.17-3.62; p=0.01). There was a trend for increased risk of high grade disease in those with high abdominal subcutaneous (T3 vs. T1; age adjusted OR 1.73; 95%CI 0.92-3.30) and visceral (T3 vs. T1; age adjusted OR 1.21; 95%CI 0.66-2.25) fat measures but this was not significant. In GSEA, those with high PPAT showed enrichment of the KEGG adipocytokine signalling pathway (nominal p-value=0.004) whilst those with high subcutaneous fat had enrichment of pathways involved in lipid and cholesterol metabolism. No adipose tissue measure was significantly associated with prostate cancer-specific outcomes following a median follow up of 10.1 years. Conclusions Elevated quantities of PPAT are associated with increased risk of high grade prostate cancer and enriched tumour adipocytokine signalling, suggesting a possible paracrine role of PPAT in prostate cancer aggressiveness. This is the first study to explore potential mechanisms of PPAT using tumour gene expression data. If confirmed, this may in part explain the link between obesity and aggressive prostate cancer. Citation Format: Sarah J. Winter, Suneil Jain, Gillian Prue, Conor K. McGarry, Alan R. Hounsell, Michelle Leech, Emma H. Allott. Elevated periprostatic fat is associated with high grade prostate cancer in radiotherapy-treated patients [abstract]. In: Proceedings of the AACR Special Conference: Advances in Prostate Cancer Research; 2023 Mar 15-18; Denver, Colorado. Philadelphia (PA): AACR; Cancer Res 2023;83(11 Suppl):Abstract nr A025.

P-190 The Geriatric 8 score is associated with risk of hospitalisation and 6-month survival in patients with incurable pancreatic cancer receiving gemcitabine and capecitabine

Assessing frailty in cancer patients can aid treatment decisions, target geriatric interventions and improve outcomes. The G8 score is a screening tool to detect frailty, however there are limited data on its utility in patients receiving chemotherapy for pancreatic cancer. We assessed the G8 score retrospectively in a population of older patients with incurable pancreatic cancer receiving gemcitabine and capecitabine chemotherapy. We performed a retrospective analysis of patients aged 65 or older, who had received Gemcitabine and capecitabine in the Northern Ireland Cancer Centre identified from electronic clinical databases. Clinico-pathological, treatment and outcome data were collected. Outcomes were 6-month survival, grade 3 toxicities, and hospitalisation risk 6 months from starting treatment. Toxicities were graded according to CTCAE v5. Descriptive statistics Fischer’s exact test was used to assess G8 scores and individual domains with outcomes. Univariable and multivariable analysis were undertaken assessing associations between the individual G8 domains and outcomes. Kaplan-Meier techniques were used to assess survival. SPSS version 26 was used. 95 patients treated between 11/2017 and 8/2021, were identified. Median age 73 (IQR 70 – 77) and 53% female. All G8 variables were collected except patient reported health status. 48% had metastatic disease and 52%, locally advanced disease. The median G8 score was 10.5 (IQR 9-12). Median overall survival in patients with a G8 score greater than 12 (n=22) was 13.9 months; and less than 12 (n=73), 8.6 months (log rank 2.4, p=0.118). 6 month and 12 month survival rates in the entire group were 65% and 39%, in G8 >12 77% and 50%, and in G8 12 and less 61% and 36%. Grade III toxicities were observed in 60% in both G8>12 and G8 12 and below p=0.888. Risk of hospitalisation or death in 6 months was associated with weight loss (p=0.048) and reduced BMI (p=0.04). A logistic regression model found the G8 domains were associated with risk of Hospitalisation or death at 6 months in this population (X2=29.9, p=0.008), explained 42.7% of variation of hospitalisation or death and correctly predicted 84.2% of cases. No individual variable was statistically significant in this model. This retrospective analysis suggests that the Geriatric- 8 score is associated with of risk of hospitalisation or death within 6 months of starting chemotherapy in older patients with pancreatic cancer. Given the poor survival of patients with advanced pancreatic cancer, time spent as an inpatient will have a greater proportional impact on quality of life compared to cancers with longer survival. Geriatric assessment may improve treatment decisions in these patients. Larger prospective studies are required to validate the utility of the G8 score specifically in older pancreatic cancer patients.

Alcohol intake, tobacco smoking, and esophageal adenocarcinoma survival: a molecular pathology epidemiology cohort study

PurposeTo investigate the association between cigarette smoking, alcohol consumption, and esophageal adenocarcinoma survival, including stratified analysis by selected prognostic biomarkers.MethodsA population-representative sample of 130 esophageal adenocarcinoma patients (n = 130) treated at the Northern Ireland Cancer Centre between 2004 and 2012. Cox proportional hazards models were applied to evaluate associations between smoking status, alcohol intake, and survival. Secondary analyses investigated these associations across categories of p53, HER2, CD8, and GLUT-1 biomarker expression.ResultsIn esophageal adenocarcinoma patients, there was a significantly increased risk of cancer-specific mortality in ever, compared to never, alcohol drinkers in unadjusted (HR 1.96 95% CI 1.13–3.38) but not adjusted (HR 1.70 95% CI 0.95–3.04) analysis. This increased risk of death observed for alcohol consumers was more evident in patients with normal p53 expression, GLUT-1 positive or CD-8 positive tumors. There were no significant associations between survival and smoking status in esophageal adenocarcinoma patients.ConclusionsIn esophageal adenocarcinoma patients, cigarette smoking or alcohol consumption was not associated with a significant difference in survival in comparison with never smokers and never drinkers in fully adjusted analysis. However, in some biomarker-selected subgroups, ever-alcohol consumption was associated with a worsened survival in comparison with never drinkers. Larger studies are needed to investigate these findings, as these lifestyle habits may not only be linked to cancer risk but also cancer survival.

High PTGS2 expression in post-neoadjuvant chemotherapy-treated oesophageal adenocarcinoma is associated with improved survival: a population-based cohort study.

High prostaglandin endoperoxide synthase-2 (PTGS2) enzyme expression in oesophageal adenocarcinoma has been shown to independently predict poor prognosis; however, the evidence is inconsistent. The aim of this study was to investigated the association between PTGS2 expression and prognosis in patients with oesophageal adenocarcinoma. A cohort of 135 patients with oesophageal adenocarcinoma who received neoadjuvant chemotherapy and surgery from 2004 to 2012 was identified in the Northern Ireland Cancer Centre. Tissue microarrays were created in the Northern Ireland Biobank, with triplicate cores being sampled from each tumour. Immunohistochemical PTGS2 expression was scored by two independent assessors, with intensity and proportion of tumour staining being used to calculate H-scores for each patient. Cox regression models were used to calculate hazard ratios (HRs) and 95% confidence intervals (CIs) for overall and cancer-specific survival, and recurrence-free survival by PTGS2 expression, with adjustment for potential confounders. Patients were followed up for a mean of 3.0years (standard deviation 1.8years). The PTGS2 expression cut-off value was determined from the median H-score of the cohort (270/300). High (n=79), as compared with low (n=56), PTGS2 expression was associated with improved cancer-specific survival (adjusted HR 0.56, 95% CI 0.33-0.94; P=0.03). PTGS2 expression was not significantly associated with recurrence-free survival (adjusted HR 0.85, 95% CI 0.52-1.38; P=0.51). High PTGS2 expression in oesophageal adenocarcinoma tissue was associated with improved overall and cancer-specific survival, in contrast to previous evidence. As this is the first study of its kind to include patients who had undergone neoadjuvant chemotherapy, further studies are needed to clarify these associations.

Sex hormone receptor expression and survival in esophageal adenocarcinoma: a prospective cohort study.

IntroductionA striking epidemiological feature of esophageal adenocarcinoma (EAC) is its strong, unexplained male predominance but few studies have evaluated the prevalence of sex hormone receptor expression in EAC.ResultsA low proportion of EAC tumors stained positive for ERα (4%) and AR (3%) while approximately one third stained positive for ERβ (31%). After a mean follow-up of 3 years (max 9 years), no significant associations were seen for ERα, ERβ or AR expression and EAC recurrence or survival. A non-significant reduction in mortality was observed for positive ERβ tumor expression, when restricting to patients with gastro-esophageal junctional (GEJ) cancer (HR 0.58, 95% CI 0.33, 1.03, p = 0.06).Materials and MethodsWe identified all EAC patients who underwent neo-adjuvant chemotherapy prior to surgical resection between 2004–2012 in the Northern Ireland Cancer Centre. Immunohistochemical expression of ERα, ERβ and AR was scored on triplicate cores to generate H-scores. Cox proportional hazards regression was used to evaluate the association between sex hormone receptor expression and overall, cancer-specific and recurrence-free survival.ConclusionWe found little evidence of ERα or AR expression in EAC. A moderate proportion expressed ERβ and there was suggestive evidence that its expression was associated with improved survival in GEJ cancer patients.

Vitamin D receptor as a marker of prognosis in oesophageal adenocarcinoma: a prospective cohort study.

AimsVitamin D receptor (VDR) expression has been associated with survival in several cancer sites. This study aims to evaluate the association between VDR expression and prognosis in oesophageal adenocarcinoma patients.ResultsDuring a median of 2.5 (maximum 9) years of follow-up, 75 patients died. In analysis adjusted for confounders, higher VDR expression was associated with an improved overall survival (HR 0.49 95% CI 0.25–0.96) and disease-specific survival (HR 0.50 95% CI 0.26–0.99), when comparing the highest with the lowest tertile of expression. These associations were strongest in sensitivity analysis restricted to junctional tumours.ConclusionsThis study is the first to demonstrate that patients with higher VDR expression in oesophageal adenocarcinoma have a more favourable prognosis. Further work is needed to validate these findings, and to define the role of VDR in the aetiology, progression and management of oesophageal adenocarcinoma.MethodsOesophageal adenocarcinoma specimens and clinical data were collected from 130 patients treated with neo-adjuvant chemotherapy prior to surgical resection at the Northern Ireland Cancer Centre between 2004 and 2012. Tissue microarrays were created and immunohistochemical staining for VDR was performed on triplicate tumour cores from each resection specimen. Cox proportional hazards models were applied to evaluate associations between VDR, according to tertiles of expression, and survival outcomes.

Glucose transporter 1 expression as a marker of prognosis in oesophageal adenocarcinoma.

BackgroundThe current TNM staging system for oesophageal adenocarcinoma (OAC) has limited ability to stratify patients and inform clinical management following neo-adjuvant chemotherapy and surgery.ResultsFunctional genomic analysis of the gene expression data using Gene Set Enrichment Analysis (GSEA) identified GLUT1 as putative prognostic marker in OAC.In the discovery cohort GLUT1 positivity was observed in 114 patients (80.9%) and was associated with poor overall survival (HR 2.08, 95% CI 1.1-3.94; p=0.024) following multivariate analysis. A prognostic model incorporating GLUT1, CRM and nodal status stratified patients into good, intermediate and poor prognosis groups (p< 0.001) with a median overall survival of 16.6 months in the poorest group.In the validation set 182 patients (69.5%) were GLUT1 positive and the prognostic model separated patients treated with neo-adjuvant chemotherapy and surgery (p<0.001) and surgery alone (p<0.001) into three prognostic groups.Patients and MethodsTranscriptional profiling of 60 formalin fixed paraffin-embedded (FFPE) biopsies was performed. GLUT1 immunohistochemical staining was assessed in a discovery cohort of 141 FFPE OAC samples treated with neo-adjuvant chemotherapy and surgery at the Northern Ireland Cancer Centre from 2004-2012. Validation was performed in 262 oesophageal adenocarcinomas collected at four OCCAMS consortium centres. The relationship between GLUT1 staining, T stage, N stage, lymphovascular invasion and circumferential resection margin (CRM) status was assessed and a prognostic model developed using Cox Proportional Hazards.ConclusionsGLUT1 staining combined with CRM and nodal status identifies a poor prognosis sub-group of OAC patients and is a novel prognostic marker following potentially curative surgical resection.

Radical Bladder Treatment and Outcomes in the Northern Ireland Cancer Centre

Radical Bladder Treatment and Outcomes in the Northern Ireland Cancer Centre

An audit of red flag computed tomography (CT), magnetic resonance imaging (MRI) and ultrasound (US) requests in the Northern Ireland Cancer Centre (NICC)

An audit of red flag computed tomography (CT), magnetic resonance imaging (MRI) and ultrasound (US) requests in the Northern Ireland Cancer Centre (NICC)

Identification and validation of an assay predictive of response and prognosis following anthracycline-based chemotherapy for early breast cancer.

TPS11120 Background: Currently there is no biomarker to predict specific benefit from DNA-damaging anthracycline and cyclophosphamide-based chemotherapy in the clinic. Loss of the Fanconi anemia/BRCA (FA/BRCA) DNA-damage response pathway occurs in approximately 25% of breast cancer and results in sensitivity to DNA-damaging agents. We therefore developed an assay to detect loss of the FA/BRCA pathway, for the purpose of predicting benefit from chemotherapy. Methods: 21 FA patient samples were analyzed to identify genetic processes associated with loss of the FA/BRCA pathway. Unsupervised hierarchical clustering was then performed using 60 BRCA1/2 mutant and 47 sporadic tumor samples and a molecular subgroup was identified that was defined by the molecular processes representing loss of the FA/BRCA pathway. A 44-gene DNA Damage response deficient (DDRD) assay was developed that could identify this subgroup from formalin fixed, paraffin embedded (FFPE) samples in the clinic. Results: In a publicly available independent cohort of 204 patients, the assay predicted response to neoadjuvant DNA-damaging chemotherapy (5-fluorouracil, anthracycline and cyclophosphamide) with an odds ratio of 4.01, (95% Cl:1.69-9.54). We also analysed samples from an independent cohort of 114 node-negative breast cancer patients treated with adjuvant 5-fluorouracil, epirubicin and cyclophosphamide treatment at the Northern Ireland Cancer Centre. The DDRD assay significantly predicted 5-year relapse free survival with a hazard ratio of 0.27 (95% Cl:0.10-0.83). The assay was not predictive of survival in patients who did not receive chemotherapy. Conclusions: An FFPE tissue-based assay that detects loss of the FA/BRCA pathway has been developed and independently validated as a predictor of response and prognosis following DNA damaging anthracycline/cyclophosphamide-based chemotherapy in the neoadjuvant and adjuvant settings.

Abstract P6-07-24: Prognostic Tools in Early Breast Cancer: Predicting benefit of adjuvant chemotherapy

Abstract Introduction: Adjuvant chemotherapy (CT) in early breast cancer reduces the risk of mortality. However, absolute reductions in mortality can be small. For patient with low risk disease, prognostic tools such as ‘Adjuvant! Online’ and ‘Predict’ can be used to estimate the benefit of adjuvant chemotherapy. We compare the survival gains estimated using ‘Adjuvant! Online’ and ‘Predict’ in routine clinical practice, assessing the characteristics of patients in which ‘Adjuvant! Online’ and ‘Predict’ disagree. Methods: In a retrospective study using the hospital electronic database, the clinical and pathological details of all patients with early breast cancer referred for adjuvant therapy at the Northern Ireland Cancer Centre in a 3 month period in 2011 were collected and were entered in to ‘Adjuvant! Online’ and ‘Predict’ to assess percentage benefit (absolute reduction in mortality at 10 years) from CT. We categorised patients into three prognostic groups: those where risk from CT outweighs benefit (&amp;lt;2% predicted benefit), marginal benefit (2 to 5%) and significant benefit from CT (&amp;gt;5%) We excluded patients with metastatic disease at presentation, DCIS, a second primary breast cancer or receiving neo-adjuvant treatment. Results: Of the 250 patients identified, 61 (24.4%) fell in to different prognostic groups depending on whether ‘Adjuvant! Online’ or ‘Predict’ was used to calculate benefit from CT. In those in whom there was disagreement, ‘Adjuvant! Online’ suggested marginal or significant benefit in 75.4% of patients, compared to 55.7% using ‘Predict’. Nine patients had “major” comorbidities, which is weighted only in ‘Adjuvant! Online’, and were excluded in subsequent analysis. Of those without major comorbidities, ‘Adjuvant! Online’ offered at least 2% benefit in 85% of cases, and ‘Predict’ in only 58.3%. The majority (93.3%) of cases were ER positive, and node negative (85.0%). This difference was notable in women aged 65 or less, with 86.2% with &amp;gt;2% benefit using ‘Adjuvant! Online’, compared to 55.1% using ‘Predict’. ‘Adjuvant! Online’ estimates of benefit were on average 3.7% higher for this age group. HER2 status had little impact, with similar recommendations using either ‘Adjuvant! Online’ or ‘Predict’. Conclusions: This study highlights lack of concordance between two available online prognostic tools, notably in ER positive, node negative patients. For patients with a marginal benefit from adjuvant chemotherapy, care must be used when making adjuvant treatment decisions as other prognostic tools may be of help in this group of patients. Citation Information: Cancer Res 2012;72(24 Suppl):Abstract nr P6-07-24.

288P - Prognostic Tools in Early Breast Cancer: Predicting Benefit of Adjuvant Chemotherapy

ABSTRACT Introduction Adjuvant chemotherapy (CT) in early breast cancer reduces the risk of mortality. However, absolute reductions in mortality can be small. For patient with low risk disease prognostic tools such as ‘Adjuvant! Online’ (AO) and ‘Predict’ (PD) can be used to estimate the benefit of adjuvant chemotherapy. We compare the survival gains estimated using AO and PD in routine clinical practice, assessing the characteristics of patients in which AO and PD disagree. Methods In a retrospective study using the hospital electronic database, the clinical and pathological details of all patients with early breast cancer referred for adjuvant therapy at the Northern Ireland Cancer Centre in a 3 month period in 2011 were collected and were entered in to AO and PD to assess percentage benefit (absolute reduction in mortality at 10 years) from CT. We categorised patients into three prognostic groups: those where risk from CT outweighs benefit ( 5%) We excluded patients with metastatic disease at presentation, DCIS, a second primary breast cancer or receiving neo-adjuvant treatment. Results Of the 200 patients identified, 43 (21.5%) fell in to different prognostic groups depending on whether AO or PD was used to calculate benefit from CT. In total, AO suggested marginal or significant benefit in 69.8% of patients, compared to 60.4% using PD. Eight patients had “major” comorbidities, which is weighted only in AO, and were excluded in subsequent analysis. Of those without major comorbidities, AO offered at least 2% benefit in 80% of cases, and PD in only 57.1%. The majority (91.4%) of cases were ER positive, and node negative (82.9%). This difference was notable in women aged 65 or less, with 83.3% with >2% benefit using AO, and 61.1% using PD. AO estimates of benefit were on average 3.7% higher for this age group. HER2 status had little impact, with similar recommendations using either AO or PD. Conclusions This study highlights lack of concordance between two available online prognostic tools, notably in ER positive, node negative patients. For patients with a marginal benefit from CT, care must be used when making adjuvant treatment decisions. Disclosure All authors have declared no conflicts of interest.

Management of neuroendocrine small cell carcinoma of cervix-a single centre retrospective study

AbstractPurpose: To determine disease-free and overall survival of neuroendocrine small cell cancer of cervix treated at the Northern Ireland Cancer centre between 1999 and 2010.Materials and methods: A retrospective review of all patients diagnosed and treated with neuroendocrine small cell cancer of cervix in Northern Ireland. Details of treatment modality including chemotherapy, radiotherapy and surgery were recorded.Results: Fifteen patients diagnosed with neuroendocrine small cell carcinoma (NSCC) of cervix were identified between 1999 and 2010, twelve with disease localised to the pelvis and three with metastatic disease. Three-year overall survival for all patients was 65% and disease-free survival was 45% for all patients. In patients with pelvic confined disease 3-year overall survival was 79% and disease-free survival was 57%. Median disease-free and overall survival was 30 and 39.6 months respectively. These survival rates compare very favourably to those reported in the literature. Stage of disease at diagnosis was the main determinant of survival.Conclusion: Local control and survival can be achieved in NSCC of patients with a combination of irradiation and platinum-based chemotherapy. Stage of disease determines outcomes.

Audit of Image Guided HDR Brachytherapy for Cervical Cancer in Northern Ireland

Introduction/aims: Image guided HDR brachytherapy was introduced in October 2008 at the Northern Ireland Cancer Centre. An audit was carried out to compare prescribed doses to point A and organs at risk (OAR) with standards set out in the RCR document Implementing image guided brachytherapy for cervix cancer in the UK 2009.

Response and survival in oesophageal cancer patients following neoadjuvant chemotherapy assessed by FDG-PETCT imaging and corelation to pathologic response.

e14571 Background: Combined positron emission tomography with computed tomography(PETCT) using [18F] 2-fluoro-2-deoxy-D-glucose (FDG) is an important modality for staging oesophageal cancer and may also predict pathological response to chemotherapy. We therefore conducted this retrospective review to assess the relationship between metabolic response measured by FDG-PETCT imaging following neoadjuvant chemotherapy in oesophageal cancer and survival. Methods: Oesophageal cancer patients presenting to Northern Ireland Cancer Centre between January 2003 to December 2008, who had FDG-PETCT assessment for staging and also following neoadjuvant chemotherapy before surgery were included. Routine FDG-PETCT findings were collated and metabolic response (≥ 35% reduction in the tumour standard uptake values[SUV]), evaluated. Pathologic response was assessed and stratified into five histological tumour regression grades (TRG1-5). TRG 1 and 2 groups were classified as pathological responders. Overall survival and event-free survival were obtained. Results: 81 patients with a median age of 66 years (28-77) were identified. 66 (81%) had oesophageal carcinoma and 15 (19%) had Siewart type I or type II oesophageal-gastric junction (OGJ) carcinomas. Metabolic response was identified in 67 (82.3%) of patients. After a median follow up of 25.0 months, the median overall survival in metabolic responders has not been reached. In the metabolic non responders the median overall survival was 15.7 months (p 0.005), (HR = 2.66, 95%CI 1.31-5.41) and median event-free survival was also 15.7 months (p 0.023), (HR = 2.14, 95%CI 1.09-4.21). Pathological response was seen in 14 (17.9%) and this correlates poorly with metabolic response. There is no statistically significant relationship between pathologic response and survival. Conclusions: Metabolic nonresponse to neoadjuvant chemotherapy measured by FDG-PETCT appears to be associated with a poor survival. Further work will seek to identify a molecular signature for lack of response to preoperative chemotherapy in order to minimise exposure of patients to toxic treatment where they are unlikely to benefit. No significant financial relationships to disclose.

Uptake and delivery of adjuvant chemotherapy in resected non-small cell lung cancer: experience in Northern Ireland Cancer Centre

Uptake and delivery of adjuvant chemotherapy in resected non-small cell lung cancer: experience in Northern Ireland Cancer Centre

Induction chemotherapy in non-small cell lung cancer: experience at the Northern Ireland Cancer Centre

Induction chemotherapy in non-small cell lung cancer: experience at the Northern Ireland Cancer Centre

Optimization of image quality and dose for Varian aS500 electronic portal imaging devices (EPIDs)

This study was carried out to investigate whether the electronic portal imaging (EPI) acquisition process could be optimized, and as a result tolerance and action levels be set for the PIPSPro QC-3V phantom image quality assessment. The aim of the optimization process was to reduce the dose delivered to the patient while maintaining a clinically acceptable image quality. This is of interest when images are acquired in addition to the planned patient treatment, rather than images being acquired using the treatment field during a patient's treatment. A series of phantoms were used to assess image quality for different acquisition settings relative to the baseline values obtained following acceptance testing. Eight Varian aS500 EPID systems on four matched Varian 600C/D linacs and four matched Varian 2100C/D linacs were compared for consistency of performance and images were acquired at the four main orthogonal gantry angles. Images were acquired using a 6 MV beam operating at 100 MU min−1 and the low-dose acquisition mode. Doses used in the comparison were measured using a Farmer ionization chamber placed at dmax in solid water. The results demonstrated that the number of reset frames did not have any influence on the image contrast, but the number of frame averages did. The expected increase in noise with corresponding decrease in contrast was also observed when reducing the number of frame averages. The optimal settings for the low-dose acquisition mode with respect to image quality and dose were found to be one reset frame and three frame averages. All patients at the Northern Ireland Cancer Centre are now imaged using one reset frame and three frame averages in the 6 MV 100 MU min−1 low-dose acquisition mode. Routine EPID QC contrast tolerance (±10) and action (±20) levels using the PIPSPro phantom based around expected values of 190 (Varian 600C/D) and 225 (Varian 2100C/D) have been introduced. The dose at dmax from electronic portal imaging has been reduced by approximately 28%, and while the image quality has been reduced, the images produced are still clinically acceptable.

42 Post operative radiotherapy and microscopic disease at the bronchial margin for non-small cell lung cancer (NSCLC); audit of 4 years data from the Northern Ireland Cancer Centre

42 Post operative radiotherapy and microscopic disease at the bronchial margin for non-small cell lung cancer (NSCLC); audit of 4 years data from the Northern Ireland Cancer Centre