Initiatives for education, training, and dissemination of morbidity assessment and reporting in a multiinstitutional international context: Insights from the EMBRACE studies on cervical cancer.

In 2008, the GEC ESTRO Gyn network launched the first multiinstitutional, observational, and prospective international study on MRI-guided brachytherapy in locally advanced cervical cancer patients (EMBRACE-I). EMBRACE-I was followed by EMBRACE-II from 2016 and ongoing. Among the aims of the EMBRACE studies are to benchmark morbidity outcomes and develop dose-volume effects and predictive models for morbidity. The EMBRACE studies collect both physician (CTCAE v.3) and patient (EORTC QLQ-C30/CX24) reported outcomes, including baseline information, in a regular follow-up schedule. The EMBRACE studies feature high numbers of patients (EMBRACE-I N = 1416, EMBRACE-II N = 1500 expected) enrolled from many institutions worldwide (EMBRACE-I n = 23, EMBRACE-II n = 45). This large-scale multiinstitutional approach offers a unique opportunity to investigate and develop new strategies for improving the quality of assessment and reporting of morbidity. This report presents an overview of the challenges and pitfalls regarding the assessment and reporting of morbidity encountered during more than a decade of development and research activities within the EMBRACE consortium. This includes the recognition and evaluation of inconsistencies in the morbidity assessment, and consequently, the provision of assistance and training in the scoring procedure to reduce systematic assessment bias. In parallel, a variety of methodological approaches were tested to comprehensively summarize morbidity outcomes, and a novel approach was developed to refine dose-effect models and risk factor analyses. The purpose of this report is to present an overview of these findings, describe the learning process, and the strategies that have consequently been implemented regarding educational activities, training, and dissemination.

ÖGRO survey on radiotherapy capacity in Austria : Status quo and estimation of future demands.

BACKGROUND: A comprehensive evaluation of the current national and regional radiotherapy capacity in Austria with an estimation of demands for 2020 and 2030 was performed by the Austrian Society for Radiation Oncology, Radiobiology and Medical Radiophysics (ÖGRO). MATERIALS AND METHODS: All Austrian centers provided data on the number of megavoltage (MV) units, treatment series, fractions, percentage of retreatments and complex treatment techniques as well as the daily operating hours for the year 2014. In addition, waiting times until the beginning of radiotherapy were prospectively recorded over the first quarter of 2015. National and international epidemiological prediction data were used to estimate future demands. RESULTS: For a population of 8.51 million, 43 MV units were at disposal. In 14 radiooncological centers, a total of 19,940 series with a mean number of 464 patients per MV unit/year and a mean fraction number of 20 (range 16-24) per case were recorded. The average re-irradiation ratio was 14%. The survey on waiting times until start of treatment showed provision shortages in 40% of centers with a mean waiting time of 13.6 days (range 0.5-29.3 days) and a mean maximum waiting time of 98.2 days. Of all centers, 21% had no or only a limited ability to deliver complex treatment techniques. Predictions for 2020 and 2030 indicate an increased need in the overall number of MV units to a total of 63 and 71, respectively. CONCLUSION: This ÖGRO survey revealed major regional differences in radiooncological capacity. Considering epidemiological developments, an aggravation of the situation can be expected shortly. This analysis serves as a basis for improved public regional health care planning.

Impact of hybrid PET/MR technology on multiparametric imaging and treatment response assessment of cervix cancer.

BACKGROUND AND PURPOSE: Multimodal tissue characterization by combined MRI and PET has high clinical potential in the context of sub-target definition for dose painting and response assessment but its clinical exploration is yet limited. The aim of this study was to prove the potential and feasibility of hybrid PET/MRI to non-invasively measure tumor hypoxia, perfusion and microstructure at one stop in tumors of the uterine cervix during chemoradiotherapy. MATERIAL AND METHODS: Ten cervix cancer patients were subjected to simultaneous multiparametric PET/MRI with [18F]fluoromisonidazole ([18F]FMISO). Imaging was scheduled before, twice during and after chemoradiotherapy. Intra- and inter-time point analyses of the extracted parameters (i.e. ADC, Ktrans, ABrix, [18F]FMISO-tumor to background ratio (TBR)) were performed. The [18F]FMISO uptake- and ADC-spatio-temporal changes were assessed. RESULTS: Patient averaged ADC values increased from baseline to follow up (1.03 ±â€¯0.11/1.30 ±â€¯0.13 × 10-3 mm2/s), while the TBR decreased (1.73 ±â€¯0.24/1.36 ±â€¯0.19), Ktrans dropped over time (0.17 ±â€¯0.05/0.05 ±â€¯0.05 min-1); for all above p < 0.05. None of these parameters correlated significantly on a voxel-by-voxel basis. Low-ADC regions spatially varied over time. There was pronounced reduction of the [18F]FMISO-avid volumes during treatment. CONCLUSIONS: The suggested hybrid PET/MRI protocol to non-invasively investigate tumor hypoxia, perfusion and microstructure at one stop was feasible, revealing spatio-temporal response patterns that could be utilized for comprehensive sub-target definition for dose painting and response assessment.

Assessment of Parametrial Response by Growth Pattern in Patients With International Federation of Gynecology and Obstetrics Stage IIB and IIIB Cervical Cancer: Analysis of Patients From a Prospective, Multicenter Trial (EMBRACE).

PURPOSE: To assess disease response along the parametrial space according to tumor morphology in patients with International Federation of Gynecology and Obstetrics (FIGO) stage IIB and IIIB cervical cancer at the time of image-guided adaptive brachytherapy. METHODS AND MATERIALS: Patients with FIGO stage IIB and IIIB cervical cancer registered as of November 2013 in the EMBRACE study were evaluated. Tumors were stratified according to morphologic subtype on magnetic resonance imaging (expansive and infiltrative), and the characteristics of those subtypes were analyzed. Parametrial involvement at diagnosis and at brachytherapy was evaluated, and the response to chemo-radiotherapy was classified as good, moderate, or poor. The response grade was compared between the 2 groups and analyzed with regard to tumor volumes, and dosimetric parameters. RESULTS: A total of 452 patients were evaluated, of whom 186 had expansive growth type and 266 had infiltrative morphology. Patients with infiltrative tumors had more extensive disease, as indicated by a higher rate of FIGO stage IIIB disease, as well as radiologic evidence of extension into the distal parametrial space and to the pelvic side wall on magnetic resonance imaging. Cervical necrosis was more common in the infiltrative group. Good response was more common in the expansive group (34% vs 24%; P=.02), and poor response was more common in the infiltrative group (11% and 19%; P=.02). Mean gross tumor volume at diagnosis was equal in both groups (51.7 cm(3)). The high-risk clinical target volume was larger in infiltrative tumors (37.9 cm(3) vs 33.3 cm(3), P=.005). The mean high-risk clinical target volume D90 was slightly higher in expansive tumors (92.7 Gy and 89.4 Gy, P<.001). CONCLUSION: Infiltrative tumors are more advanced at presentation and respond less favorably to chemo-radiotherapy when compared with expansive tumors that are more or less equivalent in size. The use of image-guided adaptive brachytherapy allows achieving reasonably high doses in both groups.

Carbon ion radiotherapy in Japan: an assessment of 20 years of clinical experience.

Charged particle therapy is generally regarded as cutting-edge technology in oncology. Many proton therapy centres are active in the USA, Europe, and Asia, but only a few centres use heavy ions, even though these ions are much more effective than x-rays owing to the special radiobiological properties of densely ionising radiation. The National Institute of Radiological Sciences (NIRS) Chiba, Japan, has been treating cancer with high-energy carbon ions since 1994. So far, more than 8000 patients have had this treatment at NIRS, and the centre thus has by far the greatest experience in carbon ion treatment worldwide. A panel of radiation oncologists, radiobiologists, and medical physicists from the USA and Europe recently completed peer review of the carbon ion therapy at NIRS. The review panel had access to the latest developments in treatment planning and beam delivery and to all updated clinical data produced at NIRS. A detailed comparison with the most advanced results obtained with x-rays or protons in Europe and the USA was then possible. In addition to those tumours for which carbon ions are known to produce excellent results, such as bone and soft-tissue sarcoma of the skull base, head and neck, and pelvis, promising data were obtained for other tumours, such as locally recurrent rectal cancer and pancreatic cancer. The most serious impediment to the worldwide spread of heavy ion therapy centres is the high initial capital cost. The 20 years of clinical experience at NIRS can help guide strategic decisions on the design and construction of new heavy ion therapy centres.

Use of bladder dose points for assessment of the spatial dose distribution in the posterior bladder wall in cervical cancer brachytherapy and the impact of applicator position.

PURPOSE: To validate the feasibility and use of dose points to characterize the bladder wall dose distribution and investigate potential impact of the applicator position in cervical cancer brachytherapy. METHODS AND MATERIALS: One hundred twenty-eight optimized MRI plans were evaluated. The International Commission of Radiation Units and Measurements (ICRU-38) point doses (B(ICRU)), surrogate for bladder base doses, were compared with D(2cc). Vaginal source to superior-anterior border of the symphysis distances were measured and compared within two groups, namely Group 1-B(ICRU)/D(2cc) ≥1 and Group 2-B(ICRU)/D(2cc) <1. Additionally, points at 1.5 and 2 cm cranial to the B(ICRU), parallel to the tandem and the body axis were analyzed. RESULTS: Thirty-seven percent of the patients had the ratio B(ICRU)/D(2cc) of 1 or higher, with the 2cc subvolume at the bladder base (Group 1). In 63%, BICRU/D2cc ratio was lower than 1 and the 2cc, cranial to the bladder base (Group 2). Median vaginal source-to-superior-anterior border of the symphysis line distance was -2 cm (range, -3.7 to +1.2 cm) in Group 1 and +1.8 cm (range, -2 to +4.8 cm) in Group 2 (+ cranial/- caudal direction). There was a high correlation between vaginal sources near the symphysis and the 2cc subvolume at the bladder base. The additional points provided no added value. CONCLUSIONS: Location of the 2cc subvolume varies in cervical cancer brachytherapy. Maximum doses are at the bladder base if vaginal sources are also in the vicinity of the bladder base indicated by B(ICRU)/D(2cc) ratio of 1 or higher. Such variation should be considered in dose-effect analyses and intercomparisons, as the same D(2cc) at different bladder locations may correlate with different morbidity profiles and severity Reporting D(2cc) and B(ICRU) doses together therefore remains essential.

Four years with FALCON - an ESTRO educational project: achievements and perspectives.

Variability in anatomical contouring is one of the important uncertainties in radiotherapy. FALCON (Fellowship in Anatomic deLineation and CONtouring) is an educational ESTRO (European SocieTy for Radiation and Oncology) project devoted to improve interactive teaching, the homogeneity in contouring and to compare individual contours with endorsed guidelines or expert opinions. This report summarizes the experience from the first 4 years using FALCON for educational activities within ESTRO School and presents the perspectives for the future.

Magnetic resonance imaging for assessment of parametrial tumour spread and regression patterns in adaptive cervix cancer radiotherapy.

PURPOSE: To investigate the impact of magnetic resonance imaging (MRI)-morphologic differences in parametrial infiltration on tumour response during primary radiochemotherapy in cervical cancer. MATERIAL AND METHODS: Eighty-five consecutive cervical cancer patients with FIGO stages IIB (n = 59) and IIIB (n = 26), treated by external beam radiotherapy (± chemotherapy) and image-guided adaptive brachytherapy, underwent T2-weighted MRI at the time of diagnosis and at the time of brachytherapy. MRI patterns of parametrial tumour infiltration at the time of diagnosis were assessed with regard to predominant morphology and maximum extent of parametrial tumour infiltration and were stratified into five tumour groups (TG): 1) expansive with spiculae; 2) expansive with spiculae and infiltrating parts; 3) infiltrative into the inner third of the parametrial space (PM); 4) infiltrative into the middle third of the PM; and 5) infiltrative into the outer third of the PM. MRI at the time of brachytherapy was used for identifying presence (residual vs. no residual disease) and signal intensity (high vs. intermediate) of residual disease within the PM. Left and right PM of each patient were evaluated separately at both time points. The impact of the TG on tumour remission status within the PM was analysed using χ(2)-test and logistic regression analysis. RESULTS: In total, 170 PM were analysed. The TG 1, 2, 3, 4, 5 were present in 12%, 11%, 35%, 25% and 12% of the cases, respectively. Five percent of the PM were tumour-free. Residual tumour in the PM was identified in 19%, 68%, 88%, 90% and 85% of the PM for the TG 1, 2, 3, 4, and 5, respectively. The TG 3-5 had significantly higher rates of residual tumour in the PM in comparison to TG 1 + 2 (88% vs. 43%, p < 0.01). CONCLUSION: MRI-morphologic features of PM infiltration appear to allow for prediction of tumour response during external beam radiotherapy and chemotherapy. A predominantly infiltrative tumour spread at the time of diagnosis resulted in a significantly higher rate of residual tumour in the PM at the time of brachytherapy in comparison to a predominantly expansive tumour spread.

Uncertainty analysis for 3D image-based cervix cancer brachytherapy by repetitive MR imaging: assessment of DVH-variations between two HDR fractions within one applicator insertion and their clinical relevance.

PURPOSE: To investigate dosimetric uncertainties of MRI-based cervix cancer brachytherapy, when applying two HDR fractions for each applicator insertion and their clinical relevance. METHODS: 21 patients with 84 MRI-examinations and fractions were investigated. After insertion of the MRI compatible tandem-ring applicator, an MRI-set was recorded and the treatment plan optimised for the first fraction. Prior to the second fraction 16-20 h later a second MRI-set was recorded, and the dose distribution from the plan of the previous day superimposed and analysed. The same procedure was repeated for fractions 3 and 4. Dose from EBRT and brachytherapy was normalised to 2 Gy-fractionation (EQD2), added up to a total dose, and compared to a calculated total dose if only 1 MRI-examination per insertion is available. RESULTS: The total D(90) for High risk (HR) CTV was 1.2±2.7 Gy(αß10) (1±3%) (mean±1SD) lower by individual MRI-evaluation of each fraction compared to 1 MRI per insertion. The D(2cm(3)) increased by 0.7±4.7 Gy(αß3) (1±6%) for bladder, 1.1±2.4 Gy(αß3) (2±4%) for rectum and decreased by 0.8±3.4 Gy(αß3) (1±5%) for sigmoid. For HR CTV the individual approach did not identify any case with a decrease of D(90) >5 Gy(αß10). For the bladder 3 cases, for the rectum no case and for the sigmoid 1 case was identified with an increase of D(2cm(3)) >5 Gy(αß3). For the bladder all dose variations of more than 5 Gy(αß3) could have been avoided by ensuring a constant bladder filling. Individual MRI-evaluation did not determine any case where dose constraints were not fulfilled. CONCLUSIONS: For the treatment schedule as applied in this study, geometric differences between applicator, target and OAR result in overall dosimetric changes, which seem to be of minor relevance in regard to clinical dose volume constraints applied at present.

MRI assessment of cervical cancer for adaptive radiotherapy.

PURPOSE: To assess the importance of the information obtained from MRI for adaptive cervix cancer radiotherapy. PATIENTS AND METHODS: 49 patients with cervix cancer, treated by external-beam radiotherapy (EBRT) and MRI-assisted high-dose-rate brachytherapy +/- concomitant cisplatin, underwent MRI at diagnosis and at the time of brachytherapy fractions. 190 MRI examinations were performed. Pretreatment scans were correlated with clinical examination (CE) findings. Measurements in 3-D of the tumor extension and also of the distance from the tumor to the pelvic side wall were performed using both MRI and CE. The tumor volume regression induced initially by EBRT and the subsequent regression after each brachytherapy fraction were assessed. RESULTS: MRI and CE showed 92% agreement in overall parametrial staging and 73% agreement in terms of vaginal involvement. There was, however, disagreement in parametrial side (right/left) classification in 25% of the parametria examined. These were patients with unilateral displacement of the cervix and contralateral invasion of the parametrium. The mean tumor volume on the pretreatment MRI scan (GTVD) was 61 cm(3). At the time of the four brachytherapy fractions the mean was 16 cm(3), 10 cm(3), 9 cm(3), and 8 cm(3), defined as the GTVBT plus the gray zones in the parametria. CONCLUSION: CE and MRI findings agree well in terms of overall staging. The clinical assessment of side-specific parametrial invasion improved when having access to the additional knowledge obtained from MRI. The greatest decrease in tumor volume occurs during EBRT, whereas tumor regression between the first and subsequent brachytherapy fractions is minor.

Assessment of improved organ at risk sparing for advanced cervix carcinoma utilizing precision radiotherapy techniques.

PURPOSE: To evaluate the potential benefit of proton therapy and photon based intensity-modulated radiotherapy in comparison to 3-D conformal photon radiotherapy (3D-CRT) in locally advanced cervix cancer. PATIENTS AND METHODS: In five patients with advanced cervix cancer 3D-CRT (four-field box) was compared with intensity modulated photon (IMXT) and proton therapy (IMPT) as well as proton beam therapy (PT) based on passive scattering. Planning target volumes (PTVs) included primary tumor and pelvic and para-aortic lymph nodes. Dose-volume histograms (DVHs) were analyzed for the PTV and various organs at risk (OARs) (rectal wall, bladder, small bowel, colon, femoral heads, and kidneys). In addition dose conformity, dose inhomogeneity and overall volumes of 50% isodoses were assessed. RESULTS: All plans were comparable concerning PTV parameters. Large differences between photon and proton techniques were seen in volumes of the 50% isodoses and conformity indices. DVH for colon and small bowel were significantly improved with PT and IMPT compared to IMXT, with D(mean) reductions of 50-80%. Doses to kidneys and femoral heads could also be substantially reduced with PT and IMPT. Sparing of rectum and bladder was superior with protons as well but less pronounced. CONCLUSION: Proton beam RT has significant potential to improve treatment related side effects in the bowel compared to photon beam RT in patients with advanced cervix carcinoma.

Active exercise, education, and cognitive behavioral therapy for persistent disabling low back pain: a randomized controlled trial.

STUDY DESIGN: A randomized controlled trial. OBJECTIVES: To determine 1) whether, among patients with persistent disabling low back pain (LBP), a group program of exercise and education using a cognitive behavioral therapy (CBT) approach, reduces pain and disability over a subsequent 12-month period; 2) the cost-effectiveness of the intervention; and 3) whether a priori preference for type of treatment influences outcome. SUMMARY OF BACKGROUND DATA: There is evidence that both exercise and CBT delivered in specialist settings is effective in improving LBP. There is a lack of evidence on whether such interventions, delivered by trained individuals in primary care, result in improved outcomes. METHODS: The study was conducted in nine family medical practices in East Cheshire, UK. Patients 18 to 65 years of age, consulting with LBP, were recruited; those still reporting LBP 3 months after the initial consultation were randomized between the two trial arms. The intervention arm received a program of eight 2-hour group exercise session over 6 weeks comprising active exercise and education delivered by physiotherapists using a CBT approach. Both arms received an educational booklet and audio-cassette. The primary outcome measures were pain (0-100 Visual Analogue Scale) and disability (Roland and Morris Disability Scale; score 0-24). RESULTS: A total of 196 subjects (84%) completed follow-up 12 months after the completion of the intervention program. The intervention showed only a small and nonsignificant effect at reducing pain (-3.6 mm; 95% confidence interval, -8.5, 1.2 mm) and disability (-0.6 score; 95% confidence interval, -1.6, 0.4). The cost of the intervention was low with an incremental cost-effectiveness ratio of pound5000 (U.S. $8650) per quality adjusted life year. In addition, patients allocated to the intervention that had expressed a preference for it had clinically important reductions in pain and disability. CONCLUSIONS: This intervention program produces only modest effects in reducing LBP and disability over a 1-year period. The observation that patient preference for treatment influences outcome warrants further investigation.

Uncertainties in assessment of the vaginal dose for intracavitary brachytherapy of cervical cancer using a tandem-ring applicator.

PURPOSE: The vagina has not been widely recognized as organ at risk in brachytherapy for cervical cancer. No widely accepted dose parameters are available. This study analyzes the uncertainties in dose reporting for the vaginal wall using tandem-ring applicators. METHODS AND MATERIALS: Organ wall contours were delineated on axial magnetic resonance (MR) slices to perform dose-volume histogram (DVH) analysis. Different DVH parameters were used in a feasibility study based on 40 magnetic resonance imaging (MRI)-based treatment plans of different cervical cancer patients. Dose to the most irradiated, 0.1 cm(3), 1 cm(3), 2 cm(3), and at defined points on the ring surface and at 5-mm tissue depth were reported. Treatment-planning systems allow different methods of dose point definition. Film dosimetry was used to verify the maximum dose at the surface of the ring applicator in an experimental setup. RESULTS: Dose reporting for the vagina is extremely sensitive to geometrical uncertainties with variations of 25% for 1 mm shifts. Accurate delineation of the vaginal wall is limited by the finite pixel size of MRI and available treatment-planning systems. No significant correlation was found between dose-point and dose-volume parameters. The DVH parameters were often related to noncontiguous volumes and were not able to detect very different situations of spatial dose distributions inside the vaginal wall. Deviations between measured and calculated doses were up to 21%. CONCLUSIONS: Reporting either point dose values or DVH parameters for the vaginal wall is based on high inaccuracies because of contouring and geometric positioning. Therefore, the use of prospective dose constraints for individual treatment plans is not to be recommended at present. However, for large patient groups treated within one protocol correlation with vaginal morbidity can be evaluated.

Recommendations from Gynaecological (GYN) GEC-ESTRO Working Group (I): concepts and terms in 3D image based 3D treatment planning in cervix cancer brachytherapy with emphasis on MRI assessment of GTV and CTV.

BACKGROUND AND PURPOSE: Brachytherapy (BT) plays a crucial role in the management of invasive cervix cancer from stage I to IV. Intracavitary techniques are based on afterloading devices, with different types of applicators. CT and/or MRI compatible applicators allow a sectional image based approach with a better assessment of gross tumour volume (GTV) and definition and delineation of target volume (CTV) compared to traditional approaches. Accurate and reproducible delineation of GTV, CTV and PTV, as well as of critical organs has a direct impact on BT treatment planning, especially if it is possible to adapt the pear-shape isodose by optimisation using DVH analysis. When introducing a 3D image based approach for GTV and CTV assessment, there is a need for a common language to describe the concepts and to define the terms which are to be used. METHODS: In 2000, GEC-ESTRO decided to support 3D imaging based 3D treatment planning approach in cervix cancer BT with the creation of a Working Group. The task was to describe basic concepts and terms and to work out a terminology enabling various groups working in this advanced field to use a common language. The recommendations described in this report were proposed based on clinical experience and dosimetric concepts of different institutions (IGR, Leuven, Vienna) and were stepwise validated against the background of different clinical experience. CONCLUSIONS: As GTV and CTV for BT change significantly during treatment, time frame for assessment of GTV and CTV for BT is specified in this report: at time of diagnosis GTV(D), CTV(D) and at time of BT GTV(B), CTV(B). Furthermore, CTV for BT is defined related to risk for recurrence: high risk CTV and intermediate risk CTV. Beside verbal descriptions detailed examples are given, partly in form of schematic drawings.

Basic treatment planning parameters for a 90Sr / 90Y source train used in endovascular brachytherapy.

Working groups of the AAPM, DGMP, and ESTRO have published recommendations for endovascular brachytherapy, introducing concepts of relevant parameters for dose specification and treatment planning. However, the procedures for this treatment remain often mainly based on trial protocols and manufacturer instructions. Treatment planning requires the essential knowledge of the radial and longitudinal dose distribution, as well as information about geometrical uncertainties. The present study includes a whole data set for daily clinical practice using a commercially available device for endovascular brachytherapy (Novoste Betacath). The dose distribution around the 90Sr seed train was calculated with Monte-Carlo algorithms and verified by film dosimetry. The radial dose profile was determined starting from the surface of the delivery catheter Calculated dose profiles were in good agreement to measured values. The geometrical uncertainties were estimated with a retrospective analysis of 51 patient treatments. This shows the importance of using a safety margin of at least 10 mm between Intervention Length and Reference Isodose Length. Based on the longitudinal dose profile and the necessary safety margins, the maximum treatable intervention length is 25 mm and 45 mm for a 40 mm and 60 mm source train, respectively.

Determination and application of the reference isodose length (RIL) for commercial endovascular brachytherapy devices.

BACKGROUND AND PURPOSE: During the last years endovascular brachytherapy has been established as a new field in radiotherapy. In a recent recommendation of the EndoVAscular, Groupe Européen de Curiethérapie, European Society for Therapeutic Radiation Oncology, Working Group the reference isodose length (RIL) has been introduced as a central parameter for treatment planning. It is defined as the vessel length at the reference depth enclosed by the 90% isodose. The dose is normalized to 100% at the reference depth (i.e. lumen radius plus 1 mm into the vessel wall) at the central plane. In order to avoid a geographic miss the clinical target length has to be encompassed by the RIL. MATERIAL AND METHODS: RILs are determined by Monte Carlo calculations and GafChromic film dosimetry for three endovascular brachytherapy devices currently in clinical use (192Ir seed ribbon, 32P wire source, 90Sr seed train). For all measurements, phantoms and devices the sensitive layer of GafChromic film is located in a plane at 2+/-0.1 mm parallel to the axis of the source delivery catheter. The EGSnrc code system is applied to calculate the dose profile at 2 and 3 mm distance from the source axis. RESULTS: For the ten seed 192Ir source calculated RIL at 2 mm radial distance is 30.2 mm whereas the measured RIL is 33.5 mm. In case of a 20 mm 32P wire source with two steps the calculated RIL of 36.6 mm shows excellent agreement compared with the measured value of 36.2 mm. The calculated RIL of a 40 mm 90Sr seed train was 35.8 mm compared to a measured value of 34.8 mm. CONCLUSION: As a compromise between calculated and measured RIL values at 2 and 3 mm radial distances we propose to use a RIL of 30 mm for the 192Ir ten seed ribbon, 36 mm for the32P wire source with two steps and 35 mm for the 40 mm 90Sr seed train. These parameter values can be used to define the maximum intervention length for endovascular sources.