Early biomarkers related to secondary primary cancer risk in radiotherapy treated prostate cancer patients: IMRT versus IMAT

AbstractPurposeTo investigate whether rotational techniques (Volumetric Modulated Arc Therapy – VMAT) are associated with a higher risk for secondary primary malignancies compared to step-and-shoot Intensity Modulated Radiation Therapy (ss-IMRT). To this end, radiation therapy (RT) induced DNA double-strand-breaks and the resulting chromosomal damage were assessed in peripheral blood T-lymphocytes of prostate cancer (PCa) patients applying γH2AX foci and G0 micronucleus (MN) assays.Methods and materialsThe study comprised 33PCa patients. A blood sample was taken before start of therapy and after the 1st and 3rd RT fraction to determine respectively the RT-induced γH2AX foci and MN. The equivalent total body dose (DETB) was calculated based on treatment planning data.ResultsA linear dose response was obtained for γH2AX foci yields versus DETB while MN showed a linear-quadratic dose response. Patients treated with large volume (LV) VMAT show a significantly higher level of induced γH2AX foci and MN compared to IMRT and small volume (SV) VMAT (p<0.01). Assuming a linear-quadratic relationship, a satisfactory correlation was found between both endpoints (R2 0.86).ConclusionsBiomarker responses were governed by dose and irradiated volume of normal tissues. No significant differences between IMRT and rotational therapy inherent to the technique itself were observed

Universal evaluation of MLC models in treatment planning systems based on a common set of dynamic tests

Reference standards; Commission on professional and hospital activities; Radiotherapy, Intensity-ModulatedEstándares de referencia; Comisión sobre actividades profesionales y hospitalarias; Radioterapia de intensidad moduladaEstàndards de referència; Comissió sobre activitats professionals i hospitalàries; Radioteràpia d'intensitat moduladaPurpose: To demonstrate the feasibility of characterising MLCs and MLC models implemented in TPSs using a common set of dynamic beams. Materials and methods: A set of tests containing synchronous (SG) and asynchronous sweeping gaps (aSG) was distributed among twenty-five participating centres. Doses were measured with a Farmer-type ion chamber and computed in TPSs, which provided a dosimetric characterisation of the leaf tip, tongue-and-groove, and MLC transmission of each MLC, as well as an assessment of the MLC model in each TPS. Five MLC types and four TPSs were evaluated, covering the most frequent combinations used in radiotherapy departments. Results: Measured differences within each MLC type were minimal, while large differences were found between MLC models implemented in clinical TPSs. This resulted in some concerning discrepancies, especially for the HD120 and Agility MLCs, for which differences between measured and calculated doses for some MLC-TPS combinations exceeded 10%. These large differences were particularly evident for small gap sizes (5 and 10 mm), as well as for larger gaps in the presence of tongue-and-groove effects. A much better agreement was found for the Millennium120 and Halcyon MLCs, differences being within ± 5% and ± 2.5%, respectively. Conclusions: The feasibility of using a common set of tests to assess MLC models in TPSs was demonstrated. Measurements within MLC types were very similar, but TPS dose calculations showed large variations. Standardisation of the MLC configuration in TPSs is necessary. The proposed procedure can be readily applied in radiotherapy departments and can be a valuable tool in IMRT and credentialing audits

Petroselinic acid purification and its use for the fermentation of new sophorolipids

Petroselinic acid, a positional isomer of oleic acid, was isolated from the vegetable oil of Coriandrum sativum fruits. This uncommon fatty acid was subsequently used as substrate for sophorolipid fermentation with a Starmerella bombicola lactone esterase overexpression (oe sble) strain. A petroselinic acid based diacetylated sophorolipid lactone was obtained in high purity without incorporation of de novo synthesized fatty acids such as oleic acid. A total production of 40 g/L was obtained. The petroselinic acid based sophorolipid lactone was subsequently hydrolyzed towards the petroselinic acid based sophorolipid acid. For both compounds, their critical micelle concentration (CMC) and corresponding surface tension were compared to their oleic acid based counterparts. Both petroselinic acid based sophorolipids displayed a much lower CMC value than their oleic acid based counterparts, although their minimal surface tension was the same. Besides, the sophorolipid fermentation product was chemically modified towards a novel C12 sophorolipid aldehyde. This derivative constitutes an interesting building block for further modification towards new-to-nature sophorolipids with high potential for self-assembly applications

Longitudinal radiomics of cone-beam CT images from non-small cell lung cancer patients : evaluation of the added prognostic value for overall survival and locoregional recurrence

Background and purpose: The prognostic value of radiomics for non-small cell lung cancer (NSCLC) patients has been investigated for images acquired prior to treatment, but no prognostic model has been developed that includes the change of radiomic features during treatment. Therefore, the aim of this study was to investigate the potential added prognostic value of a longitudinal radiomics approach using cone-beam computed tomography (CBCT) for NSCLC patients. Materials and methods: This retrospective study includes a training dataset of 141 stage I-IV NSCLC patients and three external validation datasets of 94, 61 and 41 patients, all treated with curative intended (chemo) radiotherapy. The change of radiomic features extracted from CBCT images was summarized as the slope of a linear regression. The CBCT slope-features and CT-extracted features were used as input for a Cox proportional hazards model. Moreover, prognostic performance of clinical parameters was investigated for overall survival and locoregional recurrence. Model performances were assessed using the Kaplan-Meier curves and c-index. Results: The radiomics model contained only CT-derived features and reached a c-index of 0.63 for overall survival and could be validated on the first validation dataset. No model for locoregional recurrence could be developed that validated on the validation datasets. The clinical parameters model could not be validated for either overall survival or locoregional recurrence. Conclusion: In this study we could not confirm our hypothesis that longitudinal CBCT-extracted radiomic features contribute to improved prognostic information. Moreover, performance of baseline radiomic features or clinical parameters was poor, probably affected by heterogeneity within and between datasets

Interventional cardiovascular procedures in Belgium: Effective dose and conversion factors

Effective dose ( E), representing the risk of late radiation-induced effects, can be estimated by the use of conversion factors (CF), converting direct measurable quantities such as dose-area-product into E. Eight Belgian hospitals participated in the study with a total number of 318 procedures. E-values, calculated with PCXMC, were compared for the different hospitals for diagnostic and therapeutic procedures separately. E-values varied significantly depending on the hospital where the procedure was performed (P < 0.001), on filtration insertion (P < 0.001), on whether a centre is a training centre or not, the dose conscious action of the cardiologists and the complexity of the procedure ( P < 0.001). Hospital-specific CF were calculated. An average CF of 0.185 mSv Gycm(-2) was obtained with a satisfactory correlation (r = 0.966, P < 0.001). The differences in CF between hospitals were due to, a large extent, the availability of additional filtration in cinegraphy mode (P < 0.001) and not to the differences in irradiation geometries in the clinical protocol of the interventional procedures

A large-scale multicentre study in Belgium of dose area product values and effective doses in interventional cardiology using contemporary X-ray equipment

In this paper, a large-scale multicentre patient dose study performed in eight Belgian interventional cardiology departments is presented. Effective dose (E) was calculated based on a detailed dose-area product (DAP)-registration during each procedure and by using conversion coefficients generated by the Monte Carlo-based computer program PCXMC. Conversion coefficients were found to be 0.177 mSv Gycm(-2) for systems that do not use any additional copper filtration in cineradiography and 0.207 mSv Gycm(-2) for systems that use additional copper filtration in cineradiography. Mean E values of 9.6 and 15.3 mSv for diagnostic and therapeutic procedures, respectively, were obtained. DAP distributions were investigated in order to derive dose reference levels: 71 and 106 Gycm(2) for diagnostic and therapeutic procedures, respectively, are proposed. Significant differences were observed in DAP distributions taking into account whether additional copper filtration was used in the cineradiography mode. Apart from the skin, the organs most at risk are lungs and heart. The probability of fatal cancer for the studied population amounted to 1.1 x 10(-4) and 2.1 x 10(-4) for diagnostic and therapeutic procedures, respectively, for the age distribution of the patients considered in this multicentre study