used to fit a parametric approximation for equivalent square fieldsize.Sc factors showed agreement between the two miniphantoms atextended distances, but depended upon distance from theisocentre. Therefore, measurements in brass at isocentre werefinally used.Depth doses and 3 � 3 cm TPRs agreed with data for non-moduleaffields within 1%.Conclusion: Accuracy in positioning and conformality of this systemmust be matched by the quality of the data used in the treatmentplanning systems, and acquiring this for small fields requireda variety of techniques and detectors, considering artefacts andmeasurement effects as part of the process.

P96 The Feasibility of Selective Multiple Boosts in IMRTC. A. Walker*, G. P. Lineyy, Beavis**Radiation Physics, Hull and East Yorkshire NHS Trust andClinical Biosciences Institute, University of Hull, PrincessRoyal Hospital, Saltshouse Road, Hull, East Yorkshire, UK;yCentre for Magnetic Resonance Investigations, University ofHull, Hull Royal Infirmary, Anlaby Road, Hull, EastYorkshire, UK

Introduction: Advanced imaging techniques such as MR spectros-copy and PET provide metabolic and functional information andhave the potential to guide simultaneous boosts deliverable byIMRT. This study aims to clarify exactly what is achievable in termsof control over where and how much extra dose may be deposited.Methods: A commercial IMRT planning module (CMS XiO� 4.2) wascharacterised by investigating optimisation parameters for spher-ical and cubic ‘pseudo-boost’ volumes. Six concentric, sphericalpseudo-boosts were contoured on a brain CT dataset andexperimental treatment plans generated whereby dose objectivesand importance scaling of the individual volumes were investigat-ed. Resulting plans (for delivery using a 5 mm MLC) were evaluatedin terms of optimisation scores, target dose coverage andconformity. Secondly, 8 contiguous, cubic volumes (9 � 9 � 9 mm)were contoured to simulate large voxels of functional imaging data(e.g. MR spectroscopy) and the same methodology and analysisapplied.Results: For concentric, spherical volumes, regional dose can becontrolled at 10 and 5 mm resolution where a dose differential of 5and 3 Gy, respectively, is achievable. For neighbouring cubicvolumes, however, on a 9 mm scale, boosting one or two ‘pseudo-voxels’ by 5 Gy is possible, but prescribing a different dose to eachindividual pseudo-voxel is not. The model shows that functionalimaging for guidance of intra-PTV boosts is physically viable butthat a full voxel-by-voxel (less than 1 cm3) optimisation may not berealistic.Conclusion: Regional dose can be controlled at 5 mm resolution andimportance scaling is also effective on this scale. Given that theresolution of many functional imaging techniques is no better thanthis (typical voxel size for MR spectroscopy is 10 � 10 � 10 mm),using such images for selective multiple boosting is feasible.

P97 Study of and Correction for Intra-fraction Tumour MotionS. WebbJoint Department of Physics, Institute of Cancer Research andRoyal Marsden NHSF Trust, Downs Road, Sutton, Surrey, UK

Introduction: Intra-fraction tumour motion potentially disturbs thedelivery of a conformal high dose to a target volume by intensity-modulated radiation therapy.Methods: In this work it was assumed that the goal was to conformto a clinical target volume (CTV) not planning target volume. Acomputer-modelling technique was developed to calculate thedetrimental effect of intra-fraction motion as a model ellipsecontaining a hatchet-shaped target breathed. A technique tostretch and shift the intensity-modulated beams was then de-veloped that to a large extent rectified this problem.

Results: It was shown that the excellent conformality in the staticsituation was damaged by intra-fraction motion. The dose-volumehistograms of the CTV and of an organ at risk (OAR) which werewidely separated for the static case were closer together withintra-fraction motion. The ‘stretched beam’ change of modulationcould be (approximately) engineered through a ‘breathing multi-leaf collimator’. Specific geometrical constructions have beendeveloped that showed that, provided the body and the leavesbreathed in perfect synchrony, a pseudo-static situation resulted.The construction was amplified to explain why the DMLC techniquewith breathing is equivalent to the use of a compensator withbreathing, there being no interaction of the leaf and body motions.Intra-fraction motion that varies the density of lung would strictlyinvalidate this technique but in most cases this is a higher-orderphenomenon that can be ignored. There is a difficulty consequenton differential tissue motion and some mathematical remedieshave been developed.Conclusion: Tracking the tumour is a potential solution with a 100%duty cycle. It is far more complicated than just arranging forsynchronous motion because of the phenomena of changing tissuedensity, of latency of measurement and feedback and ofdifferential tumour motion. There is no perfect solution obtainablebut ‘near enough’ practical solutions can be engineered.

P98 Pilot Study to Assess the Quality of Life and Toxicity inPatients with Carcinoma of the Prostate undergoing ExternalBeam Radiotherapy Plus High Dose Rate Brachytherapy Boost

L. Welsh*, A. Lydon*, D. Inghamy*Torbay Hospital, South Devon NHS Healthcare Trust, Torbay,UK; yRoyal Devon & Exeter NHS Foundation Trust, UK

Aim: To evaluate the quality of life (QoL) and toxicity experiencedby patients receiving external beam radiotherapy (EBRT) plus highdose rate brachytherapy (HDR) from baseline to six monthsfollowing treatment.Background: There is clear evidence emerging that the radiationdose delivered to the prostate is an important determinant of PSAfree relapse. One approach is to deliver EBRT plus HDR boost.Although it has been suggested that men are willing to trade offsome degree of QoL to improve survival outcomes this has not beenfully evaluated in HDR brachytherapy boost.Study design: Sample size 10. Assess baseline to six months.Tools: CTC v2.0; EORTC QLQ C-30 and PR-25.Eligibility: Any patient receiving HDR brachytherapy boost foradvanced prostate cancer.Results: Patient demographics: age: mean 64.1, range 50e75;stage: T2eT3b; PSA: mean 32.4 ng/ml, range 11.9e52; Gleasonscore: 7e9.Both genitourinary (GU) and gastrointestinal (GI) toxicity increasedduring the end of treatment to six week period and had returned tonear baseline levels by six months. Only stool frequency showeda significant change over the period (P¼ 0.046). Urinary and bowelQoL followed the same pattern as toxicity and again there were nosignificant changes over the study period. Functional QoL scoresalso deteriorated at the end of treatment returning to nearbaseline by six months. However, the median scores in this cohortwere comparable with normative values.Conclusions: Data from this pilot study suggest that the impact ofHDR brachytherapy on QoL is acceptable. The service at thisinstitution has been extended so it will now be possible to powerresearch to compare EBRT plus HDR with standard EBRT alone.Further multicentre randomised studies are also required.

P99 Split-course Chemoradiotherapy: An Effective Treatment ofAnal Cancer in the Frail or Elderly

G. A. Whitfield, G. Horan, M. M. Daly, K. M. Fife, A. M. Moody,C. B. WilsonDepartment of Oncology, Addenbrooke’s Hospital,Cambridge, UK

S49CLINICAL ONCOLOGY

Purpose: To assess the effectiveness of split course chemo-radiotherapy (CRT) in the radical treatment of anal cancer inpatients in whom poor performance status, co-morbidity, advancedage or a combination thereof precluded full-dose CRT.Patients and methods: A retrospective review of patients withbiopsy-proven squamous cell carcinoma of the anus. Patients weretreated with 26 Gy in 13 fractions, followed by a minimum 2 weekbreak, then 26 Gy in 13 fractions, with concurrent chemotherapy of5-fluorouracil 1000 mg/m2/day on days 1e4 and mitomycin C 10mg/m2 bolus on day 1 in each phase. All 19 patients treated atAddenbrooke’s Hospital from 1995 to 2005 with this regimen wereincluded.Results: The median age of the 19 patients was 78 years (range 46e92 years). Seven patients (37%) were male. Sixteen (84%) had stage2 and 4 (16%) stage 3 disease. The median overall treatment timewas 58 days (range 48e70 days). The median follow up time was 2.6years (range 0.5e7.1 years). For the whole group the 5 year resultswere as follows: overall survival 51.1%, cause specific survival60.6% and relapse free survival 33.0%. For the larger stage 2subgroup, the 5 year results were: overall survival 63.3%, causespecific survival 70.3% and relapse free survival 39.9%. Using the logrank test, we demonstrated statistically significant differences inoverall survival (P¼ 0.03) and relapse free survival (P¼ 0.003) butnot in cause specific survival (P¼ 0.12) between stage 2 and stage 3patients in this series.Conclusion: This alternative regimen of split-course radiotherapywith concurrent chemotherapy is an effective treatment for analcancer in the poor performance status or elderly population.

P100 The Impact of New Ways of Working on the Job Satisfactionof Radiotherapy Treatment Radiographers

K. WilliamsonCardiff University, Cardiff, UK

Purpose: To explore the impact of specialisation and new ways ofworking within radiotherapy on the skills and job satisfaction ofradiotherapy treatment radiographers.Method: An interpretive approach was utilised in order to exploreperceptions, views and opinions of radiotherapy radiographers andto examine the ‘real world’ as experienced by these professionals.Sample: The study involved three radiotherapy departments anda non-random, purposive method was employed explicitly selectingparticipants who would generate the required data for the study.The sample consisted of 12 therapeutic radiographers, estimatedas 15% of the total available population for the study. Theseradiographers were of a range of grades and years post-qualifica-tion and identified by their managers as having non-specialist roleswithin their departments. Semi-structured, face to face interviewswere used and thematic content analysis applied to analysetranscript data.Results: The study revealed a significant correlation between jobsatisfaction and valence of radiographers working within tradi-tional professional boundaries. This was predominant in staffwhose expectations were for vocational rather than for pro-fessional rewards. Of particular significance was the identifica-tion of reframing tendencies among radiographers whoseexpectations and valence were not aligned with personalexperience. Skills and abilities of specialist radiographers wererecognised and acknowledged. However, an increasing relianceon specialist roles, as a consequence of workload pressures,prompted expressions of fear for loss of established skills amongnon-specialist staff.Conclusion: There was evidence of a perception of devaluation ofthe traditional role of radiotherapy treatment radiographer withconsequential issues for retention of more experienced staff.Managers need to address the implications of this issue in order toavoid a potential and significant impact on patient care and servicedelivery. This study highlights the need to move away from thecurrent emphasis on role development to a more balancedrhetoric, raising managers’ awareness of the needs of non-specialist staff.

P101 Evaluation of the Effects of Blood Flow on 64Cu-ATSMUptake in a Rodent Tumour Model

K. A. Wood*y, D. J. Honessy, R. J. Maxwelly, J. Wilsony,R. L. Paulz, M. J. O’Dohertyz, P. K. Marsdenz, P. J. Blowerz,B. Sangherax, W. L. Wongx, M. I. Saunders*y*University College Hospital, London, UK; Marie CurieResearch Wing, Mount Vernon Cancer Centre, Northwood,Middlesex, UK; yUniversity of Oxford Gray Cancer Institute,Northwood, Middlesex, UK; zGuy’s, King’s, St Thomas’ Schoolof Medicine, London, UK; xPaul Strickland Scanner Centre,Mount Vernon Hospital, Northwood, Middlesex, UK

Aim: Hypoxia remains a significant cause of treatment failure inhead and neck cancer. The identification of hypoxic areas withintumour may allow radiotherapy dose escalation to hypoxicsubvolumes using intensity modulated radiotherapy (IMRT). 64Cu-ATSM PET is being evaluated for imaging tumour hypoxia. Weperformed a pre-clinical study to investigate the correlation ofblood flow to the distribution of 64Cu-ATSM within a tumour.Methods: Eight BD-9 rats bearing syngeneic P22 carcinosarcomaallografts were imaged using PET and gadolinium-enhanced MRI.MRI was performed immediately prior to dynamic MicroPET . 64Cu-ATSM (10e35 MBq) was administered by iv bolus at the start of PETscanning and data were acquired for 1 hour. PET data weresegmented into 10 minute time frames. A mean standardiseduptake value (SUV) was determined for each central axial tumourslice at 0e10 minutes (SUV0e10) and 50-60 minutes (SUV50e60) post64Cu-ATSM. MRI data were processed using Varian software andMatlab. The AUC90 (area under the gadolinium uptake curve in thefirst 90 seconds, a robust indicator of tumour blood flow) wascalculated for each central axial tumour slice. Correlationcoefficients were obtained for AUC90 and SUV0e10 and AUC90 andSUV50e60.Results: The correlation coefficient for AUC90 and SUV0e10 wasstatistically significant, 0.75 (P¼ 0.034) but for AUC90 and SUV50e60

the correlation coefficient was not significant, 0.44 (P¼ 0.27).Conclusion: We found a good correlation between blood flow and64Cu-ATSM in the first 10 minutes after administration of 64Cu-ATSM, demonstrating that 64Cu-ATSM uptake is dependent ontumour blood flow initially. At 50e60 minutes there was nostatistically significant correlation. 64Cu-ATSM PET imaging ofhypoxia should not be performed immediately after 64Cu-ATSMadministration as a time interval is needed for the tracer todistribute in order to give an image more likely to represent tumourhypoxia.

P102 Multi-institutional UK Prostate Brachytherapy DatabaseJ. P. Wylie*, P. Mandall*, D. Bottomleyy, P. J. Hoskinz*Christie Hospital, Manchester, UK; yCookridge Hospital,Leeds, UK; zMount Vernon Centre for Cancer Treatment,Northwood, Middlesex, UK

Introduction: Prostate brachytherapy (BT) is an accepted curativeoption for men with localised prostate cancer. Published UK seriesreport only single centre experiences and large UK multi-in-stitutional databases detailing patient selection and outcomefollowing BT are lacking. We report an ongoing collaborationbetween Christie, Cookridge, and Mount Vernon Hospitals pro-spectively collecting demographic and outcome data on patientsundergoing I-125 implants.Method: Since April 2003 all patients undergoing BT at the threecentres have been registered on a central database. Information onpresenting demographics, baseline international prostate symptomscore (IPSS) and PSA, use of hormone therapy, additional use ofexternal beam radiotherapy (EBRT), pre- and post-implant dosim-etry, and follow up IPSS and PSA have been collected. A single datamanager (PM) is responsible for the data collection.Results: 1449 patients are currently registered with a medianfollow up of 412 days. Patient selection between centres has beensimilar. Median age 64 years (range 40e82 years), 65% T1c,median PSA 5.7 (0.1e23), median Gleason score 6 (3e9), median

S50 CLINICAL ONCOLOGY