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Background and purpose For tumor tracking, a correlation model is used to estimate internal tumor position based on external surrogate motion. When patients experience an internal/external surrogate drift, an update of the correlation model is required to continue tumor tracking. In this study, the accuracy of the internal tumor position estimation for both the clinical available update at discrete points in time (rebuild) and an in-house developed non-clinical online update approach was investigated. Methods A dynamic phantom with superimposed baseline drifts and 14 SBRT patients, treated with real-time tumor tracking (RTTT) on the Vero system, were retrospectively simulated for three update scenarios, respectively no update, clinical rebuild and 0.5 Hz automated online update of the correlation model. By comparing the target positions based on 0.5 Hz verification X-ray images with the estimated internal tumor positions regarding all three update scenarios, 95th percentile modeling errors (ME 95 ), incidences of full geometrical coverage of the CTV by a 5 mm extended PTV ( P 5mm ) and population-based PTV margins were calculated. Further, the treatment time reduction was estimated when switching from the clinical rebuild approach to the online correlation model update. Results For dynamic phantom motion with baseline drifts up to 0.4 mm/min, a 0.5 Hz intra-fraction update showed a similar accuracy in terms of ME 95 and P 5mm compared to clinical rebuild. For SBRT patients treated on Vero with RTTT, accuracy was improved by 0.5 Hz online update compared to the clinical rebuild protocol, yielding smaller PTV margins (from 3.2 mm to 2.7 mm), reduced ME 95,3D (from 4.1 mm to 3.4 mm) and an increased 5th percentile P 5mm (from 90.7% to 96.1%) for the entire patient group. Further, 80% of treatment sessions were reduced in time with on average 5.5 ± 4.1 (1 SD) min. Conclusion With a fast (0.5 Hz) automated online update of the correlation model, an efficient RTTT workflow with improved geometrical accuracy was obtained. [ABSTRACT FROM AUTHOR]

Purpose To report on the first clinical application of a real-time tumor tracking (RTTT) solution based on the Vero SBRT gimbaled linac system for treatment of moving tumors. Methods and materials A first group of 10 SBRT patients diagnosed with NSCLC or oligometastatic disease in lung or liver was treated with the RTTT technique. The PTV volumes and OAR exposure were benchmarked against the widely used ITV approach. Based on data acquired during execution of RTTT treatments, a first review was performed of the process. Results The 35% PTV volume reduction with RTTT of the studied single lesions SBRT irradiations of small target volumes is expected to result in a small (<1%) reduction of lung or liver NTCP. A GTV–PTV margin of 5.0 mm was applied for treatment planning of RTTT. From patient data on residual geometric uncertainties, a CTV–PTV margin of 3.2 mm was calculated. Reduction of the GTV–PTV margin below 5.0 mm without better understanding of biological definition of tumor boundaries was discouraged. Total treatment times were reduced to 34.4 min on average. Conclusion A considerable PTV volume reduction was achieved applying RTTT and time efficiency for respiratory correlated SBRT was reestablished with Vero RTTT. [ABSTRACT FROM AUTHOR]

Abstract: Background and purpose: The purpose of this study is to assess retrospectively secondary patient motion induced by 6D patient setup correction. Materials and methods: For 104 patients, treated with Novalis®, 6D setup correction prior to treatment was performed by ExacTrac5.0/NovalisBody® in combination with the Robotic Tilt Module™ mounted underneath the Exact Couch® top. This 6D correction might induce additional setup errors due to patient reaction against the rotations. To evaluate induced secondary motion, the 6D setup correction is verified and evaluated with respect to the tolerance limits. Results: The majority of measured secondary motions are found within the tolerance limits. Detected secondary motions are mostly found in longitudinal shifts and lateral rotations, and mainly found in only 1 dimension during the same verification. The verifications indicate that the patient population can be divided into a group that hardly moves and a group that moves throughout all 6D setup corrections. The patient’s behavior can be predicted by the evaluation of the first five fractions as none of the patients demonstrate a learning curve during the treatment. Conclusions: 6D setup correction does not induce secondary motion for the majority of the patients and can therefore be applied for all treatment indications. [Copyright &y& Elsevier]

Abstract: Purpose: To evaluate the early side effects of a short course hypofractionated radiotherapy regimen in prostate cancer. Materials and methods: Three institutions (IRE, AZ VUB, GUH) included 36 patients with T1-T3N0M0 prostate cancer in a phase II study. Patients were treated with 56Gy in 16 fractions over 4 weeks. Early side effects were scored using the RTOG/EORTC criteria and the international prostate symptom index (IPSI) weekly during treatment and 1 and 2 months afterwards. The results were compared with two control groups of patients previously treated with conventional fractionation at AZ VUB (238 patients) and GUH (114 patients). Results: None of the patients experienced grade 3–4 toxicity. Grade 1–2 Gastro-intestinal (GI), grade 2 GI, grade 1–2 Genito-urinary (GU) and grade 2 GU toxicity occurred in 75%, 36%, 75% and 44% for the hypofractionation schedule. The corresponding figures were 25–44%, 6–29%, 47–53% and 16–44% for the control groups (p <0.01 for grade 1–2 GI and GU toxicity). Two months after treatment all GU and the majority of GI symptoms had resolved. The IPSI increased from (average ±1 SD) 5.6±4 pre-treatment to 10.0±6 during week 2–4 and had normalized (5.2±4) two months after treatment. Conclusions: Though no grade 3–4 side effects were observed, the investigated schedule results in a marked increase of grade 1–2 early side effects as compared to a conventional regimen. Side effects resolved within two months post-treatment. [Copyright &y& Elsevier]

Abstract: Background and purpose: Recalculating dose distributions using measured IMRT fluence fields imported into the treatment planning system (TPS) to evaluate the technical feasibility of a prototype developed for breathing synchronized irradiation. Patients and methods: DMLC–IMRT fluence patterns acquired on radiographic film, generated by the linac in non-gated and gated mode, have been imported into the TPS. The effect of dose blurring and possible interplay between organ motion and leaf motion, and the efficacy of a breathing synchronized irradiation technique (an adapted version of a commercially available image-guidance system: NOVALIS BODY/ExacTrac4.0, BrainLAB AG) have been evaluated using radiographic film mounted to a simple phantom simulating a breathing pattern of 16 cycles per minute and covering a distance of 4cm to obtain the resulting fluence maps. Two situations have been investigated to illustrate this principle: (a) a tumor located close to the diaphragm to assess the influence of organ motion on the dose to the target volume as well as to the gastro-intestinal tract that presents a high risk at intersecting with the beam during the breathing cycle. (b) A mediastinal lesion requiring complicated fluence patterns. Results: Importing measured fluence maps yielded highly disturbed reconstructed dose distributions in case of the non-gated delivery with the phantom in motion (both orthogonal and parallel to the leaf direction), whereas the measurements from the static (film fixed in space) and the gated delivery showed good agreement with the original theoretical dose distribution. These findings have been confirmed by the dose–volume histograms, corresponding tumor control probabilities, conformity index and dose heterogeneity values. The normal tissue complication probabilities investigated in this study seem to be affected to a lesser degree, which concurs with the observation that the motion effects result in a dose spread in the direction of motion. The applied breathing synchronization technique introduced an increased treatment time with a factor 3–4. Conclusions: The use of measured fluence fields, delivered by the linac in non-gated and gated mode, as imported fluence maps for the treatment planning system is an interesting quality assurance tool and revealed the dramatic impact of dose blurring and interplay between DMLC–IMRT dose delivery and organ motion, as well as the potential of breathing synchronization to resolve this issue. The possible advantage of breathing synchronized irradiation is compromised with an increased treatment time. [Copyright &y& Elsevier]

Background and purpose: Recent and large trials of adjuvant radiotherapy for breast cancer have shown an overall survival benefit in favour of radiotherapy. However, with longer follow-up the late lethal toxicity of radiotherapy might reduce the overall survival benefits. In this paper we investigate more deeply this hypothesis.Patients and methods: Overviews of the Early Breast Cancer Trialists’ Collaborative Group provide uniform data on more than 50 unconfounded trials on adjuvant radiotherapy for early breast cancer. These data were published at regular intervals: 1987, 1990, 1995, and 2000. The odds ratios (death of any cause) were borrowed to compare the benefits of adjuvant radiotherapy between the early publications and the more mature data of the same trials. Statistical significance is calculated following logrank statistics.The comparison of odds ratios (radiotherapy versus surgery only) was done for the whole group of trials, for the older (patients accrual started in 1970 or earlier) and the more recent trials (patient accrual started after 1970), and for the large (≥600 patients) and the small trials (<600 patients).Results: Comparison of early with more mature data reveals that the odds ratios for overall survival remain stable as data become more mature. The analyses of trials’ age and trials’ size, as predictors of overall survival benefit, indicate that these factors become statistically more significant with increasing maturity of the trials.In the large recent trials an overall survival benefit due to radiotherapy (odds reduction) of 10, 10, 12 and 13%, respectively P<0.3, 0.2, 0.005 and 0.00005 is found in the successive publications. The difference in survival benefit of radiotherapy between the group of large recent trials and group of old or small trials becomes more significant at the successive updates: 10 via 9% and 12 to 13% (odds reductions), with respectively P=0.2, 0.2, 0.004 and 0.00005.Conclusions: These results support the hypothesis that the survival benefit in the recent trials is an inherent characteristic of the recent and large trials, not influenced by follow-up duration. The effect of radiotherapy as performed in the large recent trials is clinically and statistically significantly different from the effect of radiotherapy in the old or small trials. As a consequence, predictions based on pooled data including old radiotherapy trials should not be extrapolated to modern radiotherapy. [Copyright &y& Elsevier]