Biomechanical breast modelling to improve patient positioning during breast cancer radiotherapy.

International audienceThis paper introduces a 3D FInite Element model of the breast designed to improve patient positioning during breast cancer radiotherapy. The model is used here for the design of a realistic breast phantom developed to quantify the positioning accuracy during radiotherapy

Quantitative evaluation of the impact of heterogeneity correction on left breast cancer radiotherapy performed with respiratory gating

Purpose: Our objective was to assess the impact of a heterogeneity correction to the calculated dose for left breast cancer gated radiotherapy.Methods: Ten patients with left breast cancer were studied. For each patient 2 treatment plans were generated. In plan 1 the dose was calculated using a Pencil Beam Convolution (PBC) algorithm. In plan 2 the dose was calculated using the Modified Batho's (MB) density correction method. To compare the two plans a dosimetric analysis was carried out including monitor units (MU), isodose curves, cumulative and differential dose volume histograms (cDVH, dDVH), coverage index, conformity index for target volume and the two dimensional (2D) gamma index (γ). Wilcoxon signed rank and Spearmen's tests were used to calculate p-values and correlation coefficients (r), respectively.Results: MB method reduced the MU by on average 1.12 ± 5.33%. The analysis of cDVH showed that the MB method calculated significantly higher doses for target volumes, lung and heart, p < 0.05. The data demonstrated a strong correlation between the dosimetric parameters derived from plan 1 and plan 2 with r > 0.9. The 2D γ analysis showed that the difference between plan 1 and plan 2 could reach ± 10%. The γ evaluation showed a high impact of density correction for left breast cancer with gating technique.Conclusion: This study confirms that using the MB method integrated with a PBC algorithm, the calculated dose will be increased to target volumes, lung and heart. Even more so since gating usually tends to decrease average lung density by about 39% by treating during an arrested inspiration phase. Thus, attention should be paid when changing from PBC to newer algorithms with gating techniques, since the probability of cardiac mortality and lung toxicity are correlated to absorbed dose

Atypical responses to neoadjuvant chemotherapy combined with accelerated partial breast tumor-directed radiotherapy: two cases and considerations for future clinical trials

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Prélèvement mammaire interne guidé par la lymphoscintigraphie (la désescalade raisonnée du traitement de la chaine mammaire interne ?)

Notre étude propose de déterminer si la réalisation d un prélèvement mammaire interne modifie les traitements adjuvants et le traitement de la chaîne mammaire interne (CMI). Les patientes éligibles ont bénéficié de la procédure du ganglion sentinelle entre janvier 2008 et aout 2012. Un drainage vers la CMI a été objectivé pour 114 des 401 patientes incluses (28,4 %). Ces patientes ont bénéficié d un prélèvement du ganglion sentinelle en CMI. Quarante-quatre patientes ont également bénéficié de ce prélèvement, malgré l absence de drainage lymphoscintigraphique vers la CMI, devant une suspicion clinique importante de drainage : tumeur interne et/ou profonde. L exploration chirurgicale de la CMI a été réalisée dans 158 procédures (39,4 %). Le ganglion a pu être prélevé 154 fois (97,5 %). Dans 17 cas sur 158 (10,8 %), le ganglion prélevé en CMI était envahi. Une macrométastase a été retrouvée dans 14 cas, une micrométastase dans 3 cas. Un envahissement ganglionnaire isolé en CMI est constaté dans 6 cas (3,4 %). Le prélèvement mammaire interne n a pas provoqué de complications péri ou postopératoires. Ainsi, 3 indications supplémentaires de chimiothérapie ont été proposées (1,9 %), 13 indications de radiothérapie en CMI ajoutées (8,2 %), et 3 indications d irradiation en CMI supprimées (1,9 %). Il est difficile de valider la pertinence de ce prélèvement sur cette seule étude rétrospective, mais, sans evidence based medecine cette étude peut aider la prise en charge thérapeutique en affinant le staging ganglionnaire et les indications de radiothérapie. Il serait intéressant de pouvoir apprécier l impact sur la survie et sur la toxicité de la radiothérapie.Histological evaluation of the internal mammary chain (IMC) sentinel node in breast cancer patients remains a subject of discussion. The aim of this study was to determine the impact of routinely performed IMC sentinel node biopsy on the adjuvant treatments. All patients with biopsy proven breast cancer who underwent a sentinel node procedure between 2008 and 2012 were included in a retrospective study. If the removed sentinel node contained malignant cells or not, we determined if this altered the treatment plan when practising the current guidelines. In total, 114 of the 401 included patients showed IMC drainage on lymphoscintigraphy (28.4%). Exploration of the IMC was performed in 158 (39.4%) patients; in 154/158 (97.5%) exploration was successful. In 17/158 patients (10.8%) the IMC sentinel node was tumor positive. Macro and micrometastases were found in 14 and 3 patients, respectively. CMI node was positive in 6 cases (3.8%) without positive axillary node. The surgical removement suffered no complications. In the group of patients who underwent surgical exploration of the IMC, systemic treatment was changed in 3 cases (1.9%), radiotherapy treatment in 20/158 patients (12.6%). Radiotherapy treatment is altered in a small proportion of the patients; however, solid scientific evidence for this adjustment is lacking. Involvement of stadification with involvement with FDG PET/CT seems important, to reduce and select more precisely indications of surgical removement and IMC treatments.GRENOBLE1-BU Médecine pharm. (385162101) / SudocSudocFranceF

Quantitative evaluation of the impact of heterogeneity correction on left breast cancer radiotherapy performed with respiratory gating

Purpose: Our objective was to assess the impact of a heterogeneity correction to the calculated dose for left breast cancer gated radiotherapy.Methods: Ten patients with left breast cancer were studied. For each patient 2 treatment plans were generated. In plan 1 the dose was calculated using a Pencil Beam Convolution (PBC) algorithm. In plan 2 the dose was calculated using the Modified Batho's (MB) density correction method. To compare the two plans a dosimetric analysis was carried out including monitor units (MU), isodose curves, cumulative and differential dose volume histograms (cDVH, dDVH), coverage index, conformity index for target volume and the two dimensional (2D) gamma index (γ). Wilcoxon signed rank and Spearmen's tests were used to calculate p-values and correlation coefficients (r), respectively.Results: MB method reduced the MU by on average 1.12 ± 5.33%. The analysis of cDVH showed that the MB method calculated significantly higher doses for target volumes, lung and heart, p &lt; 0.05. The data demonstrated a strong correlation between the dosimetric parameters derived from plan 1 and plan 2 with r &gt; 0.9. The 2D γ analysis showed that the difference between plan 1 and plan 2 could reach ± 10%. The γ evaluation showed a high impact of density correction for left breast cancer with gating technique.Conclusion: This study confirms that using the MB method integrated with a PBC algorithm, the calculated dose will be increased to target volumes, lung and heart. Even more so since gating usually tends to decrease average lung density by about 39% by treating during an arrested inspiration phase. Thus, attention should be paid when changing from PBC to newer algorithms with gating techniques, since the probability of cardiac mortality and lung toxicity are correlated to absorbed dose.</p

Doses delivered by portal imaging quality assurance in routine practice of adjuvant breast radiotherapy worth to by monitored and compensated in some cases

International audienceBackground: Imaging, in radiotherapy, has become a routine tool for repositioning of the target volume at each session. The repositioning precision, currently infracentimetric, evolves along with the irradiation techniques. This retrospective study aimed to identify practices and doses resulting from the use of high energy planar imaging (portal imaging) in daily practice. Methods: A retrospective survey of portal images (PIs) was carried out over 10 years for 2,403 patients and for three linacs (1 Elekta SLi, 2 Varian Clinac) for postoperative mammary irradiations. Images were taken using a standardized number of monitor units (MU) for all patients. Due to the variable sensitivities of the detectors and the possibility of adjustment of the detector-patient distance, the number of MU were 3; 2 and 1 respectively, for Elekta SLi ® , Clinac 600 ® and Clinac 2100 ®. Then, a representative cumulated dose was calculated in simplified reference conditions (5 cm depth, beam of 10 cm × 10 cm, 6 MV), considering the total number of images taken during the whole treatment course. The consistency between the representative doses and the actual absorbed doses received by the patients was verified by simulating a series of typical cases with the treatment plan dose calculation system. Results: The delivered doses differ significantly between the three linacs. The mean representative dose values by complete treatment were 0.695; 0.241 and 0.216 Gy, respectively, for SLi, Clinac 600 and Clinac 2100. However, 15 patients were exposed to a dose >2 Gy with a maximum dose of 5.05 Gy. The simulated doses were very similar to the representative doses. Conclusions: A significant dose delivery was highlighted by this study. These representative doses are presently communicated weekly to the radiation oncologist for the radiation protection of their patients. Moreover, they should be taken into account in a possible study of long-term stochastic risks

A quantitative method to implement and to assess the single isocenter technique for breast cancer radiation therapy

International audiencePurpose: We propose a process of quality assurance to validate and implement the single isocenter technique for breast cancer radiotherapy. We evaluated the dosimetric and temporal gains using the single isocenter technique compared to classic source to skin distance (SSD) technique.Methods: 6 patients of breast cancer localization were studied. For each patient 2 treatment plans were generated. In plan 1 the dose was calculated using SSD technique. In plan 2 the dose was calculated using single isocenter technique. To implement the plan 2 a dosimetric analysis including monitor units (MU), isodose curves, cumulative and differential dose volume histograms cDVH, dDVH respectively, coverage index, conformity index for planning target volume were used. The measurements using a PMMA phantom consist of measuring point dose by an ionization chamber and 2D dose distributions using 2D diodes arrays. Wilcoxon signed rank and Spearman’s tests were used to calculate p-value and correlation coefficient, respectively.Results: The single isocenter technique reduced the MU by average on -30.1 ± 13.6%, (p = 0.03). We observed an improvement with statistical significance between the two techniques for the mean dose, minimum dose and volume receiving 95% of the prescribed dose without over-dosage. The analysis for dDVH showed that the dose distribution in the target volume calculated in the single isocenter technique is more homogeneous than the SSD technique. Wilcoxon test showed that the two treatment plans had the same quality (p > 0.05). The difference between calculated and measured dose was within 2.4 ± 3.3% for absolute point dose and the percentage of points passing gamma criteria was on average 99.8 ± 0.2%.Conclusion: This method provides a quantitative evaluation and comparison of the two irradiation techniques for breast cancer and the consequences of the technical change on dose calculation

Chronic recording of cortical activity underlying vocalization in awake minipigs

International audienceBackground: Investigating brain dynamics underlying vocal production in animals is a powerful way to inform on the neural bases of human speech. In particular, brain networks underlying vocal production in non-human primates show striking similarities with the human speech production network. However, despite increasing findings also in birds and more recently in rodents, the extent to which the primate vocal cortical network model generalizes to other non-primate mammals remains unclear. Especially, no domestic species has yet been proposed to investigate vocal brain activity using electrophysiological approaches.New method: In the present study, we introduce a novel experimental paradigm to identify the cortical dynamics underlying vocal production in behaving minipigs. A key problem to chronically implant cortical probes in pigs is the presence and growth of frontal sinuses extending caudally to the parietal bone and preventing safe access to neural structures with conventional craniotomy in adult animals.Results: Here we first show that implantations of soft ECoG grids can be done safely using conventional craniotomy in minipigs younger than 5 months, a period when sinuses are not yet well developed. Using wireless recordings in behaving animals, we further show activation of the motor and premotor cortex around the onset of vocal production of grunts, the most common vocalization of pigs.Conclusion: These results suggest that minipigs, which are very loquacious and social animals, can be a good experimental large animal model to study the cortical bases of vocal production