Interobserver variability in organ at risk delineation in head and neck cancer.

BACKGROUND: In radiotherapy inaccuracy in organ at risk (OAR) delineation can impact treatment plan optimisation and treatment plan evaluation. Brouwer et al. showed significant interobserver variability (IOV) in OAR delineation in head and neck cancer (HNC) and published international consensus guidelines (ICG) for OAR delineation in 2015. The aim of our study was to evaluate IOV in the presence of these guidelines. METHODS: HNC radiation oncologists (RO) from each Belgian radiotherapy centre were invited to complete a survey and submit contours for 5 HNC cases. Reference contours (OARref) were obtained by a clinically validated artificial intelligence-tool trained using ICG. Dice similarity coefficients (DSC), mean surface distance (MSD) and 95% Hausdorff distances (HD95) were used for comparison. RESULTS: Fourteen of twenty-two RO (64%) completed the survey and submitted delineations. Thirteen (93%) confirmed the use of delineation guidelines, of which six (43%) used the ICG. The OARs whose delineations agreed best with the OARref were mandible [median DSC 0.9, range (0.8-0.9); median MSD 1.1 mm, range (0.8-8.3), median HD95 3.4 mm, range (1.5-38.7)], brainstem [median DSC 0.9 (0.6-0.9); median MSD 1.5 mm (1.1-4.0), median HD95 4.0 mm (2.3-15.0)], submandibular glands [median DSC 0.8 (0.5-0.9); median MSD 1.2 mm (0.9-2.5), median HD95 3.1 mm (1.8-12.2)] and parotids [median DSC 0.9 (0.6-0.9); median MSD 1.9 mm (1.2-4.2), median HD95 5.1 mm (3.1-19.2)]. Oral cavity, cochleas, PCMs, supraglottic larynx and glottic area showed more variation. RO who used the consensus guidelines showed significantly less IOV (p = 0.008). CONCLUSIONS: Although ICG for delineation of OARs in HNC exist, they are only implemented by about half of RO participating in this study, which partly explains the delineation variability. However, this study highlights that guidelines alone do not suffice to eliminate IOV and that more effort needs to be done to accomplish further treatment standardisation, for example with artificial intelligence.

Prediction of GTV median dose differences eases Monte Carlo re-prescription in lung SBRT.

BACKGROUND AND PURPOSE: The use of Monte Carlo (MC) dose calculation algorithm for lung patients treated with stereotactic body radiotherapy (SBRT) can be challenging. Prescription in low density media and time-consuming optimization conducted CyberKnife centers to propose an equivalent path length (EPL)-to-MC re-prescription method based on GTV median dose. Unknown at the time of planning, GTV D50% practical application remains difficult. The current study aims at creating a re-prescription predictive model in order to limit conflicting dose value during EPL optimization. MATERIAL AND METHODS: 129 patients planned with EPL algorithm were recalculated with MC. Relative GTV_D50% discrepancies were assessed and influencing parameters identified using wrapper feature selection. Based on best descriptive parameters, predictive nomogram was built from multivariate linear regression. EPL-to-MC OARs near max-dose discrepancies were reported. RESULTS: The differences in GTV_D50% (median 10%, SD: 9%) between MC and EPL were significantly (p < .001) impacted by the lesion's surface-to-volume ratio and the average relative electronic density of the GTV and the GTV's 15 mm shell. Built upon those parameters, a nomogram (R2 = 0.79, SE = 4%) predicting the GTV_D50% discrepancies was created. Furthermore EPL-to-MC OAR dose tolerance limit showed a strong linear correlation with coefficient range [0.84-0.99]. CONCLUSION: Good prediction on the required re-prescription can be achieved prior planning using our nomogram. Based on strong linear correlation between EPL and MC for OARs near max-dose, further restriction on dose constraints during the EPL optimization can be warranted. This a priori knowledge eases the re-prescription process in limiting conflicting dose value.

[Multiple vertebral hemangiomas treated simultaneously with CyberKnife® Technology]. / Hémangiomes vertébraux multiples traites simultanément en condition stéréotaxique avec la technologie CyberKnife®.

Haemangioma are benign, vasoformative lesions of endothelial origin. A minority of patients with a vertebral location are symptomatic with neck or back pain. Neurological deficits due to spinal cord compression are rare and mostly observed at the thoracic and upper lumbar spine. Treatment is indicated in case of relevant symptomatology. Several invasive treatment modalities exist such as surgery and intralesional injections, but radiotherapy is the most common treatment for painful lesions. We report a case of a patient with symptomatic bifocal vertebral haemangioma (d9, l3) associated with dorsal and lumbar pain treated simultaneously using a cyberknife® vsi system, with a significant reduction of pain and a limited toxicity.

les hémangiomes sont des malformations vasculaires bénignes, d'origine endothéliale. Une minorité de patients avec des hémangiomes vertébraux sont symptomatiques et présentent des douleurs du cou ou du dos. Le déficit neurologique, occasionné par une compression de la moelle épinière, est rare et touche surtout la colonne thoracique et lombaire supérieure. Un traitement est indiqué si l'hémangiome vertébral est symptomatique. Les techniques invasives comme la chirurgie et les injections intra-lésionnelles peuvent être utilisées, mais la radiothérapie reste le traitement de choix pour les lésions douloureuses. Nous décrivons le cas d'un patient, présentant des douleurs dorso-lombaires, ayant deux hémangiomes localisés en d9 et l3 traités simultanément par le cyberknife® avec un certain succès, notamment du point de vue antalgique, et une toxicité très limitée.

Commissioning Monte Carlo algorithm for robotic radiosurgery using cylindrical 3D-array with variable density inserts.

INTRODUCTION: To commission the Monte Carlo (MC) algorithm based model of CyberKnife robotic stereotactic system (CK) and evaluate the feasibility of patient specific QA using the ArcCHECK cylindrical 3D-array (AC) with Multiplug inserts (MP). RESULTS: Four configurations were used for simple beam setup and two for patient QA, replacing water equivalent inserts by lung. For twelve collimators (5-60mm) in simple setup, mean (SD) differences between MC and RayTracing algorithm (RT) of the number of points failing the 3%/1mmgamma criteria were 1(1), 1(3), 1(2) and 1(2) for the four MP configurations. Tracking fiducials were placed within AC for patient QA. Single lung insert setup resulted in mean gamma-index 2%/2mm of 90.5% (range [74.3-95.9]) and 82.3% ([66.8-94.5]) for MC and RT respectively, while 93.5% ([86.8-98.2]) and 86.2% ([68.7-95.4]) in presence of largest inhomogeneities, showing significant differences (p<0.05). DISCUSSION: After evaluating the potential effects, 1.12g/cc PMMA and 0.09g/cc lung material assignment showed the best results. Overall, MC-based model showed superior results compared to RT for simple and patient specific testing, using a 2%/2mm criteria. Results are comparable with other reported commissionings for flattening filter free (FFF) delivery. Further improvement of MC calculation might be challenging as Multiplan has limited material library. CONCLUSIONS: The AC with Multiplug allowed for comprehensive commissioning of CyberKnife MC algorithm and is useful for patient specific QA for stereotactic body radiation therapy. MC calculation accuracy might be limited due to Multiplan's insufficient material library; still results are comparable with other reported commissioning measurements using FFF beams.

Feasibility evaluation of prone breast irradiation with the Sagittilt© system including residual-intrafractional error assessment.

PURPOSE: Feasibility evaluation of the Sagittilt© prone breast board system (Orfit Industries, Wijnegem, Belgium) for radiotherapy focusing on patient and staff satisfaction, treatment time, treatment reproducibility with the assessment of residual-intrafractional errors. MATERIAL AND METHODS: Thirty-six patients underwent whole-breast irradiation in prone position. Seventeen received a sequential boost (breast: 42.56Gy in 16 fractions, boost: 10Gy in five fractions), while 19 patients received a concomitant boost protocol (breast/boost: 45.57/55.86Gy in 21 fractions). Treatment verification included a daily online cone-beam CT (CBCT). In order to assess the residual and residual-intrafractional errors post-treatment CBCTs were performed systematically at the first five treatment sessions. Treatment time, patient comfort, staff satisfaction were also evaluated. RESULTS: The pretreatment CBCT resulted in a population systematic error of 4.5/3.9/3.3mm in lateral/longitudinal/vertical directions, while the random error was 5.4/3.8/2.8mm. Without correction these would correspond to a clinical to planning target volume margin of 15.0/12.3/10.3mm. The population systematic and random residual-intrafractional errors were 1.5/0.9/1.7mm and 1.7/1.9/1.6mm. Patient and staffs' satisfaction were considered good and average. The mean treatment session time was 21minutes (range: 13-40min). CONCLUSION: The Sagittilt© system seems to be feasible for breast irradiation and well-tolerated by patients, acceptable to radiographers and reasonable in terms of treatment times. Set-up accuracy was comparable with other prone systems; residual errors need further investigations.

Improved cone-beam computed tomography in supine and prone breast radiotherapy. Surface reconstruction, radiation exposure, and clinical workflow.

BACKGROUND AND PURPOSE: Cone-beam computerized tomography (CBCT) enables three-dimensional information of the scanned region and provides soft tissue images with good spatial resolution. Our aim was to optimize image acquisition settings for prone and supine breast radiotherapy with respect to contour accuracy, clinical practicalities, and radiation dose. PATIENTS AND METHODS: CBCT images were acquired for both prone and supine anthropomorphic phantoms and a female cadaver in supine and prone set-up. CBCT protocols were investigated by altering the tube current, exposure time, range of projection views, field of view (FOV), and starting angle. For clinical practicalities, the frequency of the use of an offset CBCT isocenter was evaluated at 558 205°-CBCTs (37 patients; 13 prone and 24 supine) and 1272 360°-CBCTs (102 patients; 13 prone and 89 supine). RESULTS: Prone and supine breast CBCT images acquired with a bowtie filter, a small FOV, a range of projection views equaling 180°, a tube current of 20 mA and an exposure time of 32 ms, demonstrated adequate contour accuracy and an elimination of the offset CBCT isocenter procedure, while this occurred in 40.7 % for the old full-rotation protocol. Furthermore a 4.3-fold dose reduction was observed for the Computed Tomography Dose Index (CTDIw) compared to the preset Chest M20 protocol. CONCLUSION: The established 180° protocol demonstrated acceptable contour accuracy, eliminated the CBCT isocenter offset procedure and reduced patient radiation exposure.

Do results of the EORTC dummy run predict quality of radiotherapy delivered within multicentre clinical trials?

OBJECTIVE: The European Organisation for the Research and Treatment of Cancer (EORTC) Radiation Oncology Group (ROG) has performed radiotherapy quality assurance (QA) in clinical trials, including dummy runs (DR) and individual case reviews (ICR), since 1991. We investigated the influence of DR results on subsequent QA and patient outcomes. METHODS: EORTC ROG studies were reviewed for DR inclusion, QA and mature clinical outcomes. A DR was classified as a failure if corrections necessitated re-submission. ICR were graded as acceptable, minor or major deviation overall. Fisher's exact test characterised potential correlations and the Mantel-Haenszel statistic quantified pooled odds ratios (OR). RESULTS: DR and ICR data were available from 12 and 3 protocols, respectively. The proportion of institutions successful at first DR attempt varied per trial from 5.6% to 68.8%. Participants were 3.2 times more likely to pass at first attempt after previous DR participation (p=0.0002). Pooled OR for an acceptable ICR was 1.69 (p=0.06) for institutions successful at DR first attempt. The effect of DR participation was not significantly correlated with patient outcome in the trial available for analysis. CONCLUSIONS: Implementing QA measures in ROG clinical trials should ensure optimal radiotherapy delivery. Centres which previously participated in a DR were significantly more likely to be successful at subsequent QA procedures.

Acute toxicity of curative radiotherapy for intermediate- and high-risk localised prostate cancer in the EORTC trial 22991.

INTRODUCTION: This trial randomly assessed short-term adjuvant hormonal therapy added to radiotherapy (RT) for intermediate- and high-risk (UICC 1997 cT2a or cT1b-c with high PSA or Gleason score) localised prostate cancer. We report acute toxicity (CTCAE v2) assessed weekly during RT in relation to radiation parameters. PATIENTS AND METHODS: Centres selected the RT dose (70, 74 or 78Gy) and RT technique. Statistical significance is at 0.05. RESULTS: Of 791 patients, 652 received 3D-CRT (70Gy: 195, 74Gy: 376, 78Gy: 81) and 139 received IMRT (74Gy: 28, 78Gy: 111). During RT, grade 3 gastrointestinal (GI) and genitourinary (GU) toxicities were reported by 7 (0.8%) and 50 (6.3%) patients, respectively. No grade 4 was reported. The risk of grade 2 GI toxicity increased significantly with increasing D50%-rectum (p=0.004) and that of grade 2 GU toxicity correlated only to Dmax-bladder (p=0.051). 3D-RT technique, increasing total dose and V95% >400 cc increased D50% and Dmax. One month after RT, only 14 patients (1.8%) reported grade 3 toxicity. AST did not seem to influence the risk of GU or GI acute toxicity. CONCLUSION: RT up to 78Gy was well tolerated. Dmax-bladder and D50%-rectum influenced the risk of grade 2 GU toxicity and GI toxicity, respectively. Both were lower with IMRT but remained high for an irradiated RT volume>400 cc for 3D-RT and for a dose of 78Gy. Hormonal treatment did not influence acute toxicity.