Vincent Vinh-Hung

Definition of gross tumor volume in lung cancer: inter-observer variability☆

BACKGROUND AND PURPOSEnTo determine the inter-observer variation in gross tumor volume (GTV) definition in lung cancer, and its clinical relevance.nnnMATERIALS AND METHODSnFive clinicians involved in lung cancer were asked to define GTV on the planning CT scan of eight patients. Resulting GTVs were compared on the base of geometric volume, dimensions and extensions. Judgement of invasion of lymph node (LN) regions was evaluated using the ATS/LCSG classification of LN. Clinical relevance of the variation was studied through 3D-dosimetry of standard conformal plans: volume of critical organs (heart, lungs, esophagus, spinal cord) irradiated at toxic doses, 95% isodose volumes of GTVs, normal tissue complication probabilities (NTCP) and tumor control probabilities (TCP) were compared for evaluation of observer variability.nnnRESULTSnBefore evaluation of observer variability, critical review of planning CT scan led to up- (two cases) and downstaging (one case) of patients as compared to the respective diagnostic scans. The defined GTVs showed an inter-observer variation with a ratio up to more than 7 between maximum and minimum geometric content. The dimensions of the primary tumor had inter-observer ranges of 4.2 (transversal), 7.9 (cranio-caudal) and 5.4 (antero-posterior) cm. Extreme extensions of the GTVs (left, right, cranial, caudal, anterior and posterior) varied with ranges of 2.8-7.3 cm due to inter-observer variation. After common review, only 63% of involved lymph node regions were delineated by the clinicians (i.e. 37% are false negative). Twenty-two percent of drawn in lymph node regions were accepted to be false positive after review. In the conformal plans, inter-observer ranges of irradiated normal tissue volume were on average 12%, with a maximum of 66%. The probability (in the population of all conformal plans) of irradiating at least 95% of the GTV with at least 95% of the nominal treatment dose decreased from 96 to 88% when swapping the matched GTV with an unmatched one. The average (over all patients) inter-observer range in NTCP varied from 5% (spinal cord) to 20% (ipsilateral lung), whereas the maximal ranges amounted 16% (spinal cord) to 45% (heart). The average TCP amounted 51% with an average range of 2% (maximally 5%) in case of matched GTVs. These values shifted to 42% (average TCP) with an average range of 14% (maximally 31%) when defining unmatched GTVs. Four groups of causes are suggested for the large inter-observer variation: (1) problems of methodology; (2) impossible differentiation between pathologic structures and tumor; or (3) between normal structures and tumor, and (4); lack of knowledge. Only the minority of these can be resolved objectively. For most of the causal factors agreements have to be made between clinicians, intra- and inter-departmentally. Some of the factors will never be unequivocally solved.nnnCONCLUSIONSnGTV definition in lung cancer is one of the cornerstones in quality assurance of radiotherapy. The large inter-observer variation in GTV definition jeopardizes comparison between clinicians, institutes and treatments.

Quality assurance of a system for improved target localization and patient set-up that combines real-time infrared tracking and stereoscopic X-ray imaging

BACKGROUND AND PURPOSEnThe aim of this study is to investigate the positional accuracy of a prototype X-ray imaging tool in combination with a real-time infrared tracking device allowing automated patient set-up in three dimensions.nnnMATERIAL AND METHODSnA prototype X-ray imaging tool has been integrated with a commercially released real-time infrared tracking device. The system, consisting of two X-ray tubes mounted to the ceiling and a centrally located amorphous silicon detector has been developed for automated patient positioning from outside the treatment room prior to treatment. Two major functions are supported: (a) automated fusion of the actual treatment images with digitally reconstructed radiographs (DRRs) representing the desired position; (b) matching of implanted radio opaque markers. Measurements of known translational (up to 30.0mm) and rotational (up to 4.0 degrees ) set-up errors in three dimensions as well as hidden target tests have been performed on anthropomorphic phantoms.nnnRESULTSnThe systems accuracy can be represented with the mean three-dimensional displacement vector, which yielded 0.6mm (with an overall SD of 0.9mm) for the fusion of DRRs and X-ray images. Average deviations between known translational errors and calculations varied from -0.3 to 0.6mm with a standard deviation in the range of 0.6-1.2mm. The marker matching algorithm yielded a three-dimensional uncertainty of 0.3mm (overall SD: 0.4mm), with averages ranging from 0.0 to 0.3mm and a standard deviation in the range between 0.3 and 0.4mm.nnnCONCLUSIONSnThe stereoscopic X-ray imaging device integrated with the real-time infrared tracking device represents a positioning tool allowing for the geometrical accuracy that is required for conformal radiation therapy of abdominal and pelvic lesions, within an acceptable time-frame.

Catheter tip position as a risk factor for thrombosis associated with the use of subcutaneous infusion ports

AimsThe use of subcutaneous infusion ports has become standard practice to provide a long-term venous access in oncological patients. The aim of this retrospective study was to assess the different complications of infusion ports in our population and to identify predisposing factors.Patients and methodsWe reviewed the medical records of 437 patients who were followed at the Oncology/Haematology Department of our hospital. Of these patients, there were 370 (84.4%) with solid tumours and 58 (13.2%) with haematological disease. The position of the catheter tip was evaluated by reviewing the available chest radiographs or phlebographies.Main resultsAnalysis of the records showed that 346 patients (79.17%) had no complications. The most common complications after implantation were thrombosis (8.46%), catheter dysfunction (4.8%) and infections (4.4%). Univariate and multivariate analysis showed that catheter tip positioning was the most important predisposing risk factor for thrombosis. Catheter tips positioned in the brachiocephalic vein or in the cranial part of the superior vena cava were associated with a high risk of thrombosis. Other significant risk factors were gender and initial diagnosis. Female patients and patients with lung cancer also had an elevated risk of developing a thrombosis.ConclusionsCompared to other reports, we noted a higher rate of thrombosis and port dysfunction. Since catheter tip position was a predisposing factor for developing a thrombosis, correct catheter position has to be ensured during placement. Prophylactic antithrombotic treatment might be beneficial in the event of failure to position the catheter correctly.

Prognostic value of the lymph node ratio in node positive colon cancer

Surgery is the primary treatment of non-metastatic colon cancer. En bloc removal of the colon with its associated mesenteric lymph nodes is essential. However, the number of lymph nodes reported with colectomy varies widely and may be a result of variation in the actual number of regional lymph nodes, surgical technique, or the thoroughness of the pathologist in finding lymph nodes. The number of lymph node metastases is an important negative prognostic factor and is used in stratification schemes for clinical trials.1nnRecent studies have emphasised the fact that examining a greater number of nodes increases the likelihood of correct staging and is associated with better survival, after controlling …

The effect of timing of the provision of information on anxiety and satisfaction of cancer patients receiving radiotherapy.

BACKGROUNDnTo improve the provision of information to their radiotherapy patients, the authors examined whether the timing of given written information has an effect on anxiety and satisfaction.nnnMETHODSnTwo sources of information were used: 1) a booklet with a description of radiotherapy procedures and the sensations patients can experience; 2) teaching sheets with treatment-site-related information. 68 patients were randomized to a simultaneous-information group (n = 31) and a stepwise-information group (n = 37). The patients were being treated for cancers of the breast, lung, head, and neck or the pelvic region. The authors analyzed the impacts of several variables on patient learning, including anxiety, age, gender, support, referral, stage of illness, and diagnosis. Assessments were recorded before the simulation procedure and during the second and last weeks of treatment.nnnRESULTSnThe stepwise-information group was significantly less anxious before simulation (p = 0.02) and more satisfied (p = 0.001). Of the variables studied, only the support variable was associated with high state anxiety (p < 0.0001).nnnCONCLUSIONSnProvision of patient information in a stepwise format leads to less treatment-related anxiety and greater patient satisfaction among radiation therapy patient undergoing simulation.

Initial clinical experience with infrared-reflecting skin markers in the positioning of patients treated by conformal radiotherapy for prostate cancer

PURPOSEnTo evaluate an infrared (IR) marker-based positioning system in patients receiving conformal radiotherapy for prostate cancer.nnnMETHODS AND MATERIALSnDuring 553 treatments, the ability of the IR system to automatically position the isocenter was recorded. Setup errors were measured by means of orthogonal verification films and compared to conventional positioning (using skin drawings and lasers) in 184 treatments.nnnRESULTSnThe standard deviation of anteroposterior (AP) and lateral setup errors was significantly reduced with IR marker positioning compared to conventional: 2 vs. 4.8 mm AP (p < 0.01) and 1.6 vs. 3.5 mm laterally (p < 0.01). Longitudinally, the difference was not significant (3.5 vs. 3.0 mm). Systematic errors were on the average smaller AP and laterally for the IR method: 4.1 vs. 7.8 mm AP (p = 0.01) and 3.1 vs. 5.6 mm lateral (p = 0.07). Longitudinally, the IR system resulted in somewhat larger systematic errors: 5.0 vs. 3.4 mm for conventional positioning (p = 0.03). The use of an off-line correction protocol, based on the average deviation measured over the first four fractions, allowed virtual elimination of systematic errors. Inability of the IR system to correctly locate the markers, leading to an executional failure, occurred in 21% of 553 fractions.nnnCONCLUSIONnIR marker-assisted patient positioning significantly improves setup accuracy along the AP and lateral axes. Executional failures need to be reduced.

Clinical use of stereoscopic X-ray positioning of patients treated with conformal radiotherapy for prostate cancer.

PURPOSEnTo evaluate accuracy and time requirements of a stereoscopic X-ray-based positioning system in patients receiving conformal radiotherapy to the prostate.nnnMETHODS AND MATERIALSnSetup errors of the isocenter with regard to the bony pelvis were measured by means of orthogonal verification films and compared to conventional positioning (using skin drawings and lasers) and infrared marker (IR) based positioning in each of 261 treatments. In each direction, the random error represents the standard deviation and the systematic error the absolute value of the mean position. Time measurements were done in 75 treatments.nnnRESULTSnRandom errors with the X-ray positioning system in the anteroposterior (AP), lateral, and longitudinal direction were (average +/- 1 standard deviation) 2 +/- 0.6 mm, 1.7 +/- 0.6 mm, and 2.4 +/- 0.7 mm. The corresponding values of conventional as well as IR positioning were significantly higher (p < 0.01). Systematic errors for X-ray positioning were 1.1 +/- 1.2 mm AP, 0.6 +/- 0.5 mm laterally, and 1.5 +/- 1.6 mm longitudinally. Conventional and IR marker-based positioning showed significantly larger systematic errors AP and laterally, but longitudinally, the difference was not significant. Depending on the axis looked at, errors of >or=5 mm occurred in 2%-14% of treatments after X-ray positioning, 13%-29% using IR markers, and 28%-53% with conventional positioning. Total linac time for one treatment session was 14 min 51 s +/- 4 min 18 s, half of which was used for the X-ray-assisted positioning procedure.nnnCONCLUSIONnX-ray-assisted patient positioning significantly improves setup accuracy, at the cost of an increased treatment time.

The Use of Molecular Imaging to Evaluate Radiation Fields in the Adjuvant Setting of Breast Cancer

Purpose:To evaluate standard radiation fields in locally advanced breast cancer using the information of a preoperative FDG-PET showing lymph node involvement.Patients and Methods:In 15 consecutive patients, referred for postoperative radiotherapy, a standard simulation was performed. Planning CT was fused semiautomatically with preoperative FDG-PET, and thoracic wall/breast (clinical target volume [CTV]), lungs, and location(s) of axillary nodal involvement on FDG-PET (PETax) were delineated. A dose computation was performed using the standard field simulation (plan–). If plan–resulted in inadequate dose delivery to PETax, a plan adaptation was performed to improve this deficit (plan+). Mean dose-volume histograms (DVHs) were made of the relevant structures for both plan– and plan+. Students paired t-test was performed on all mean reference values.Results:In 13 patients an image fusion could be performed. Dose computation showed underdosage to the PETax in eleven out of 13 patients. After plan adaptation, the dose delivered to PETax could be increased, with a statistically significant difference (p < 0.01) in favor of plan+ for all reference values on the DVHs. This was achieved without changes in dose delivery to CTV or lungs.Conclusion:Standard radiation portals in postoperative radiation therapy in breast cancer with lymph node involvement do not automatically result in an adequate dose delivery to the region of highest biological activity. With these preliminary results in a small series it was found feasible to correct this without compromising the dose to the CTV or lungs for patients in whom a preoperative FDG-PET shows nodal involvement.Ziel:Evaluation von Standardbestrahlungsfeldern bei lokal fortgeschrittenem Brustkrebs unter Verwendung eines präoperativen FDG-PET zur Darstellung eines Lymphknotenbefalls.Patienten und Methodik:15 aufeinanderfolgende, für eine postoperative Bestrahlung vorgesehene Patientinnen wurden einer Standardsimulation unterzogen. Das Planungs-CT wurde halbautomatisch mit dem präoperativen FDG-PET fusioniert. Brustwand/Brust (klinisches Zielvolumen [CTV]), Lungen sowie die im FDG-PET sichtbar befallenen axillären Lymphknoten (PETax) wurden konturiert. Es erfolgte eine Dosisberechnung mittels Simulation von Standardbestrahlungsfeldern (Plan–). Resultierte Plan– in einer unzureichenden Dosisverteilung hinsichtlich PETax, wurde eine Planadaptation zur Verbesserung dieses Defizits (Plan+) durchgeführt. Die mittleren Dosis-Volumen-Histogramme (DVHs) wurden für alle relevanten Strukturen sowohl für Plan– als auch für Plan+ berechnet. Auf alle Referenzmittelwerte wurde ein gepaarter Student-t-Test angewendet.Ergebnisse:Bei 13 Patientinnen war eine Bildfusion möglich. Dosisberechnungen zeigten eine Unterdosierung des PETax bei elf von 13 Patientinnen. Nach der Planadaptation konnte die PETax-Dosis mit einem statistisch signifikanten Unterschied (p < 0,01) zugunsten Plan+ für alle Referenzwerte der DVHs sowie ohne Veränderungen der Dosisbelastung für CTV und Lungen erhöht werden.Schlussfolgerung:Standardbestrahlungsfelder bei postoperativer Strahlentherapie von Brustkrebs mit Befall der Lymphknoten resultieren nicht automatisch in einer angemessenen Dosisverteilung in den biologisch hochaktiven Regionen. Bei Patientinnen, bei denen mittels FDG-PET ein Lymphknotenbefall nachgewiesen wurde, kann dies korrigiert werden, ohne Kompromisse hinsichtlich der CTV- oder Lungendosis eingehen zu müssen.

The use of molecular imaging to evaluate radiation fields in the adjuvant setting of breast cancer: A feasibility study

Purpose:To evaluate standard radiation fields in locally advanced breast cancer using the information of a preoperative FDG-PET showing lymph node involvement.Patients and Methods:In 15 consecutive patients, referred for postoperative radiotherapy, a standard simulation was performed. Planning CT was fused semiautomatically with preoperative FDG-PET, and thoracic wall/breast (clinical target volume [CTV]), lungs, and location(s) of axillary nodal involvement on FDG-PET (PETax) were delineated. A dose computation was performed using the standard field simulation (plan–). If plan–resulted in inadequate dose delivery to PETax, a plan adaptation was performed to improve this deficit (plan+). Mean dose-volume histograms (DVHs) were made of the relevant structures for both plan– and plan+. Students paired t-test was performed on all mean reference values.Results:In 13 patients an image fusion could be performed. Dose computation showed underdosage to the PETax in eleven out of 13 patients. After plan adaptation, the dose delivered to PETax could be increased, with a statistically significant difference (p < 0.01) in favor of plan+ for all reference values on the DVHs. This was achieved without changes in dose delivery to CTV or lungs.Conclusion:Standard radiation portals in postoperative radiation therapy in breast cancer with lymph node involvement do not automatically result in an adequate dose delivery to the region of highest biological activity. With these preliminary results in a small series it was found feasible to correct this without compromising the dose to the CTV or lungs for patients in whom a preoperative FDG-PET shows nodal involvement.Ziel:Evaluation von Standardbestrahlungsfeldern bei lokal fortgeschrittenem Brustkrebs unter Verwendung eines präoperativen FDG-PET zur Darstellung eines Lymphknotenbefalls.Patienten und Methodik:15 aufeinanderfolgende, für eine postoperative Bestrahlung vorgesehene Patientinnen wurden einer Standardsimulation unterzogen. Das Planungs-CT wurde halbautomatisch mit dem präoperativen FDG-PET fusioniert. Brustwand/Brust (klinisches Zielvolumen [CTV]), Lungen sowie die im FDG-PET sichtbar befallenen axillären Lymphknoten (PETax) wurden konturiert. Es erfolgte eine Dosisberechnung mittels Simulation von Standardbestrahlungsfeldern (Plan–). Resultierte Plan– in einer unzureichenden Dosisverteilung hinsichtlich PETax, wurde eine Planadaptation zur Verbesserung dieses Defizits (Plan+) durchgeführt. Die mittleren Dosis-Volumen-Histogramme (DVHs) wurden für alle relevanten Strukturen sowohl für Plan– als auch für Plan+ berechnet. Auf alle Referenzmittelwerte wurde ein gepaarter Student-t-Test angewendet.Ergebnisse:Bei 13 Patientinnen war eine Bildfusion möglich. Dosisberechnungen zeigten eine Unterdosierung des PETax bei elf von 13 Patientinnen. Nach der Planadaptation konnte die PETax-Dosis mit einem statistisch signifikanten Unterschied (p < 0,01) zugunsten Plan+ für alle Referenzwerte der DVHs sowie ohne Veränderungen der Dosisbelastung für CTV und Lungen erhöht werden.Schlussfolgerung:Standardbestrahlungsfelder bei postoperativer Strahlentherapie von Brustkrebs mit Befall der Lymphknoten resultieren nicht automatisch in einer angemessenen Dosisverteilung in den biologisch hochaktiven Regionen. Bei Patientinnen, bei denen mittels FDG-PET ein Lymphknotenbefall nachgewiesen wurde, kann dies korrigiert werden, ohne Kompromisse hinsichtlich der CTV- oder Lungendosis eingehen zu müssen.

Characteristics and clinical application of a treatment simulator with Ct-option

BACKGROUND AND PURPOSEnThe integration of a scanner for computed tomography (CT) and a treatment simulator (Sim-CT, Elekta Oncology Systems, Crawley, UK) has been studied in a clinical situation. Image quality, hounsfield units (HU) and linearity have been evaluated as well as the implications for treatment planning. The additional dose to the patient has also been highlighted.nnnMATERIAL AND METHODSnImage data is acquired using an array of solid state X-ray detectors attached externally to the simulators image intensifier. Three different fields of view (FOV: 25.0 cm, 35.0 cm and 50.0 cm) with 0.2 cm, 0.5 cm and 1.0 cm slice thickness can be selected and the system allows for an aperture diameter of 92.0 cm at standard isocentric height. The CT performance has been characterized with several criteria: spatial resolution, contrast sensitivity, geometric accuracy, reliability of hounsfield units and the radiation output level. The spatial resolution gauge of the nuclear associates quality phantom (NAQP) as well as modulation transfer functions (MTF) have been applied to evaluate the spatial resolution. Contrast sensitivity and HU measurements have been performed by means of the NAQP and a HU conversion phantom that allows inserts with different electron densities. The computed tomography dose index (CTDI) of the CT-option has been monitored with a pencil shaped ionization chamber. Treatment planning and dose calculations for heterogeneity correction based on the Sim-CT images generated from an anthropomorphic phantom as well as from ten patients have been compared with similar treatment plans based on identical, yet diagnostic CT (DCT) images.nnnRESULTSnThe last row of holes that are resolved in the spatial resolution gauge of the NAQP are either 0.150 cm or 0.175 cm depending on the FOV and the applied reconstruction filter. These are consistent with the MTF curves showing cut-off frequencies ranging from 5.3 lp/cm to 7.1 lp/cm. Linear regression analysis of HU versus electron densities revealed a correlation coefficient of 0.99. Contrast, pixel size and geometric accuracy are within specifications. Computed tomography dose index values of 0.204 Gy/As and 0.069 Gy/As have been observed with dose measurements in the center of a 16 cm diameter and 32 cm diameter phantom, respectively for large FOV. Small FOV yields CTDI values of 0.925 Gy/As and 0.358 Gy/As which is a factor ten higher than the results obtained from a DCT under similar acquisition conditions. The phantom studies showed excellent agreement between dose distributions generated with the Sim-CT and DCT HU. The deviations between the calculated settings of monitor units as well as the maximum dose in three dimensions were less than 1% for the treatment plans based on either of these HU both for pelvic as well as thoracic simulations. The patient studies confirmed these results.nnnCONCLUSIONSnThe CT-option can be considered as an added value to the simulation process and the images acquired on the Sim-CT system are adequate for dose calculation with tissue heterogeneity correction. The good image quality, however, is compromised by the relative high dose values to the patient. The considerable load to the conventional X-ray tube currently limits the Sim-CT to seven image acquisitions per patient and therefore the system is limited in its capability to perform full three-dimensional reconstruction.