New high-resolution multibeam mapping images detail the southern part of Exuma Sound (Southeastern Bahamas), and its unchartered transition area to the deep abyssal plain of the Western North ...Atlantic, bounded by the Bahama Escarpment extending between San Salvador Island and Samana Cay. The transition area is locally referred to as Exuma Plateau. The newly established map reveals the detailed and complex morphology of a giant valley draining a long-lived carbonate platform from its upper slope down to the abyssal plain. This giant valley extends parallel to the slope of Long Island, Conception Island, and Rum Cay. It starts with a perched system flowing on top of a lower Cretaceous drowned main carbonate platform. The valley shows low sinuosity and is characterized by several bends and flow constrictions related to the presence of the small relict isolated platforms that kept alive longer than the main platform before drowning and merging tributaries. Turbidite levees on either side of the valley witness the pathway of multiple gravity flows, generated by upper slope over steepening around Exuma Sound through carbonate offbank transport, some of them locally >15°, and resulting slumping. In addition, additional periplatform sediments are transported to the main valley through numerous secondary slope gullies and several kilometre-long tributaries, draining the upper slopes of cays and islands surrounding Exuma Plateau. Some of them form knickpoints indicating surincision of the main Exuma Valley which is consistent with an important lateral supply of the main Exuma Valley. Prior to reaching the abyssal plain, the main valley abruptly evolves into a deep canyon, 5 km in width at its origin and as much as 10 km wide when it meets the abyssal plain, through two major knickpoints named “chutes” with outsized height exceeding several hundred of meters in height. Both chutes are associated with plunge pools, as deep as 200-m. In the deepest pools, the flows generate a hydraulic jump and resulting sediment accumulation. When the canyon opens to the San Salvador abyssal plain, the narrow, deep, and strong flows release significant volume of coarse-grained calcareous sediments in numerous turbidite layers interbedded with fine mixed siliciclastic and carbonate sediments transported by the Western Boundary Undercurrent (WBUC) along the Bahama Escarpment. Carbonate gravity flows exiting the canyon decelerate at the abyssal plain level and construct a several-kilometre-wide coarse-grained deep-sea turbidite system with well-developed lobe-shape levees, partially modified by the flow of strong contour-currents along the Bahama Escarpment.
•Giant carbonate canyon fed by longitudinal and lateral supply•Importance of gravity-driven processes in a deep-water carbonate canyons•Transition valley – canyon through gigantic chutes•Development of a large carbonate-fed turbidite system•Cenomanian flooding of the Bahamian platform and relicts drowned keep-up banks
Abstract Purpose To investigate the patterns of failure after radiotherapy for pediatric intracranial ependymoma and their correlation with dose parameters. Methods Between 2000 and 2013, 206 ...patients were treated in France. MRI scans at relapse were registered to the original planning CTs for topographic analysis of failure patterns. To compare relapse patients (RP) with non relapse patients (NRP), several dose parameters were derived from dose volume histograms. Results Over a median follow-up of 53.8 months, 84 patients presented with relapse. Topographic analysis showed 50 patients with local relapse in the radiation field, 6 in the edge of field, 6 locoregional outside the field, 10 in the spine, 5 supratentorial and 7 local and distant. The median coverage, target coverage and homogeneity indices did not differ significantly between RP and NRP. The median volume of in-field relapse was 1.25 cc 0.11, 27, with a median dose of 57.83 Gy 50.04, 61.69. Conclusions Local relapse in the tumor bed and the higher dose regions was the predominant pattern of failure. Improving coverage of the target volume and increasing the dose to the high radioresistant regions, taking into consideration other clinical and biological pronostic factors, may be an effective way of reducing local failures.
Pediatric ependymoma carries a dismal prognosis, mainly owing to local relapse within RT fields. The current prospective European approach is to increase the radiation dose with a sequential ...hypofractionated stereotactic boost. In this study, we assessed the possibility of using a simultaneous integrated boost (SIB), comparing VMAT vs. IMPT dose delivery.
The cohort included 101 patients. The dose to planning target volume (PTV59.4) was 59.4/1.8 Gy, and the dose to SIB volume (PTV67.6) was 67.6/2.05 Gy. Gross tumor volume (GTV) was defined as the tumor bed plus residual tumor, clinical target volume (CTV59.4) was GTV + 5 mm, and PTV59.4 was CTV59.4 + 3 mm. PTV67.6 was GTV+ 3 mm. After treatment plan optimization, quality indices and doses to target volume and organs at risk (OARs) were extracted and compared with the standard radiation doses that were actually delivered (median = 59.4 Gy 50.4 59.4).
In most cases, the proton treatment resulted in higher quality indices (
< 0.001). Compared with the doses that were initially delivered, mean, and maximum doses to some OARs were no higher with SIB VMAT, and significantly lower with protons (
< 0.001). In the case of posterior fossa tumor, there was a lower dose to the brainstem with protons, in terms of V59 Gy, mean, and near-maximum (D2%) doses.
Dose escalation with intensity-modulated proton or photon SIB is feasible in some patients. This approach could be considered for children with unresectable residue or post-operative FLAIR abnormalities, particularly if they have supratentorial tumors. It should not be considered for infratentorial tumors encasing the brainstem or extending to the medulla.
The purpose of this study was to determine the characteristics of early second breast cancer (SBC) among survivors of childhood and young adult malignancy treated with irradiation.
We conducted a ...multicenter retrospective study of women who presented with breast cancer aged 50 years or younger in nine French centers.
121 patients and 141 SBC were analyzed (invasive = 130; non-invasive = 11). The mean age at first cancer diagnosis was 15 years and at initial SBC diagnosis was 38 years. Bilateral disease before the age of 51 years was diagnosed in 16% of the females. The majority of SBC were invasive carcinomas (92%). Among the invasive carcinomas, 39% had a histoprognostic score of III, 3.1% overexpressed HER2 and 29% were triple negative. The proportion of triple negative phenotype SBC was higher in patients older at first cancer diagnosis RR = 1.2, 95% CI (1.1-1.3). 94% of triple negative SBCs developed in breast tissue which had received >20 Gy.
We found a high proportion of aggressive SBC following thoracic radiotherapy in childhood or early adulthood. Advances in knowledge: SBC screening is recommended by scientific societies for these child/young-adulthood cancer survivors in the same way as the one for high risk women because of constitutional mutations. Our results support these recommendations, not only because of a similar cumulative risk, but also because of the aggressive histological characteristics.
Ependymoma is the third most common brain tumor in children. Radiation therapy (RT) is systematically administered after maximum surgical resection, utilizing recent advances in radiation delivery. ...Imaging can make a significant contribution to improving treatment outcome. This prompted us to look for significant preoperative and postoperative imaging markers for survival.
We undertook a national retrospective review of 121 patients who had undergone resection followed by RT. Preoperative tumor volumes on T1 and FLAIR images were delineated, together with postoperative hyperintense volumes on FLAIR images. Overall survival (OS) and disease-free survival (DFS) analyses included clinical data and volumes extracted from images.
After a median follow-up of 38.5 months, 80.2% of patients were alive, but 39.7% had experienced at least one event. Statistically significant differences between patients with and without postoperative FLAIR abnormalities were found for both DFS (71.9% vs. 40.3%; p = 0.006) and OS (93.7% vs. 72.4%; p = 0.023) in the univariate analyses, and for OS (p = 0.049) in the multivariate analyses.
Postoperative FLAIR hyperintensities are a negative prognostic factor for intracranial ependymoma and may be a surrogate for residual disease. They could therefore prove helpful in patients' surgical and radiotherapeutic management.
To assess the relative cerebral blood volume (rCBV) and apparent diffusion coefficient (ADC) derived, respectively, from perfusion and diffusion pre-operative MRI of intracranial ependymomas and ...their predictive and prognostic values.
Pre-operative MRI and clinical data for intracranial ependymomas diagnosed between January 2000 and December 2013 were retrospectively retrieved from a web-based national database. MRI data included diffusion (62 patients) and perfusion (20 patients) MRI. Patient age, histopathological diagnosis, tumour location, ADC, relative ADC (rADC) and rCBV were considered as potential factors in a survival analysis. Survival rates were estimated using the Kaplan-Meier method. Univariate analyses were performed using the log-rank test to compare groups. We also performed a multivariate analysis, applying the Cox proportional hazards model.
ADC and rADC values within hypointense regions differed significantly between grades II and III (p = 0.01). The 75th percentile of ADC within hypointense regions and the 25th percentile of rCBV within non-enhancing lesions were prognostic of disease-free survival (p = 0.004, p = 0.05). A significant correlation was found between the 75th percentile of rCBV and the 25th percentile of rADC (p = 0.01) in enhancing regions of grade-III tumours.
Pre-operative rADC and rCBV could be used as prognostic factors for clinical outcome and to predict histological grade in paediatric ependymomas.
Prognostic value of diffusion and perfusion MRI in paediatric ependymoma was found and may play a role in the prognostic classification of patients in order to design more tailored treatment strategies.
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