Quality assurance in radiotherapy: analysis of the causes of not starting or early radiotherapy withdrawal.

BACKGROUND: The aim of this study was to analyse the reasons for not starting or for early of radiotherapy at the Radiation Oncology Department. METHODS: All radiotherapy treatments from March 2010 to February 2012 were included. Early withdrawals from treatment those that never started recorded. Clinical, demographic and dosimetric variables were also noted. RESULTS: From a total of 3250 patients treated and reviewed, 121 (4%) did not start or complete the planned treatment. Of those, 63 (52%) did not receive any radiotherapy fraction and 58 (48%) did not complete the course, 74% were male and 26% were female. The mean age was 67 ± 13 years. The most common primary tumour was lung (28%), followed by rectum (16%). The aim of treatment was 62% radical and 38% palliative, 44% of patients had metastases; the most common metastatic site was bone, followed by brain. In 38% of cases (46 patients) radiotherapy was administered concomitantly with chemotherapy (10 cases (22%) were rectal cancers). The most common reason for not beginning or for early withdrawal of treatment was clinical progression (58/121, 48%). Of those, 43% died (52/121), 35 of them because of the progression of the disease and 17 from other causes. Incomplete treatment regimens were due to toxicity (12/121 (10%), of which 10 patients underwent concomitant chemotherapy for rectal cancer). CONCLUSIONS: The number of patients who did not complete their course of treatment is low, which shows good judgement in indications and patient selection. The most common reason for incomplete treatments was clinical progression. Rectal cancer treated with concomitant chemotherapy was the most frequent reason of the interruption of radiotherapy for toxicity

Sediment undulations on the Llobregat prodelta: Signs of early slope instability or sedimentary bedforms?

A field of sediment undulations has been mapped by means of high resolution multibeam bathymetry and seismic reflection profiles in the Llobregat River prodelta, off the city of Barcelona, Catalonia, Spain. Similar features had previously been recognized in other prodelta environments and interpreted either as downslope sediment deformation or sedimentary structures induced by bottom currents or hyperpycnal flows. Since the study area is undergoing significant offshore development, proper interpretation of such sediment undulations is needed for a correct risk assessment. The occurrence of the sediment undulations is restricted to the prodelta front on slope gradients between 3 and 0.2º. The undulations have developed at the edge and atop an area of gas bearing sediments within the Late-Holocene high-stand mud wedge. An evaluation is made of the characteristics of the sediment undulations in order to determine the most likely process for the origin of these structures. Amongst these characteristics are the continuity of the reflections and lack of diffractions in between different undulations, their size distribution (large to small) both from shallow to deep and with depth in section, the asymmetry (decreasing from proximal to distal), the crest to trough vertical distance on the landward side of the undulations (up to 0.5 m), and the lack of features that could indicate a progressive movement such as growth structures and drag folds. These characteristics indicate that the sediment undulations on the Llobregat River prodelta do not result from sediment deformation, but rather from the interaction of bottom currents generated by hyperpycnal flows from the Llobregat River with regional sea water circulation. Their identification as sediment waves implies that such features do not pose a major hazard for urther offshore development

Quality assurance in radiotherapy: analysis of the causes of not starting or early radiotherapy withdrawal.

BACKGROUND: The aim of this study was to analyse the reasons for not starting or for early of radiotherapy at the Radiation Oncology Department. METHODS: All radiotherapy treatments from March 2010 to February 2012 were included. Early withdrawals from treatment those that never started recorded. Clinical, demographic and dosimetric variables were also noted. RESULTS: From a total of 3250 patients treated and reviewed, 121 (4%) did not start or complete the planned treatment. Of those, 63 (52%) did not receive any radiotherapy fraction and 58 (48%) did not complete the course, 74% were male and 26% were female. The mean age was 67 ± 13 years. The most common primary tumour was lung (28%), followed by rectum (16%). The aim of treatment was 62% radical and 38% palliative, 44% of patients had metastases; the most common metastatic site was bone, followed by brain. In 38% of cases (46 patients) radiotherapy was administered concomitantly with chemotherapy (10 cases (22%) were rectal cancers). The most common reason for not beginning or for early withdrawal of treatment was clinical progression (58/121, 48%). Of those, 43% died (52/121), 35 of them because of the progression of the disease and 17 from other causes. Incomplete treatment regimens were due to toxicity (12/121 (10%), of which 10 patients underwent concomitant chemotherapy for rectal cancer). CONCLUSIONS: The number of patients who did not complete their course of treatment is low, which shows good judgement in indications and patient selection. The most common reason for incomplete treatments was clinical progression. Rectal cancer treated with concomitant chemotherapy was the most frequent reason of the interruption of radiotherapy for toxicity

The influence of overpressure and focused fluid flow on subaquatic slope stability in a formerly glaciated basin : Lake Villarrica (South-Central Chile)

Pore fluid pressure is a key parameter for subaquatic slope stability and has been put forward to explain the development of many submarine landslides, especially when occurring on very gentle slopes or in areas with high sedimentation rate. Due to the sparse availability of in-situ pore pressure data, a profound understanding and quantification of excess pore pressure development and its influence on subaquatic landslide processes is still missing. In this study, we use glacigenic Lake Villarrica (Chile) as a model basin, in which we document in-situ excess pore pressure, focused fluid escape features and subaquatic slope failures at relatively shallow subsurface depth (< 10 m). A subaquatic slope was characterized in great detail by a dense network of high-resolution seismic-reflection profiles, multibeam bathymetry and sediment cores. In-situ undrained shear strength and formation pore fluid pressures were documented using free-fall piezocone penetrometer (CPTU) and subsequent pore pressure dissipation tests. We show four independent lines of evidence for overpressure of variable magnitude within the sedimentary slopes: i) pockmarks and other fluid escape features on seismic profiles and bathymetric maps, ii) estimation of ambient in-situ pore pressure via CPTU dissipation tests, iii) underconsolidation and downward decrease in in-situ undrained shear strength within units of uniform lithology, and iv) hydrofractured glacio-lacustrine sediments. Locally, overpressure reaches about 80-90% of the hydrostatic vertical effective stress. We hypothesize that glacier-proximal sediments are strongly underconsolidated and overpressured due to rapid deposition and/or subglacial meltwater pumping. Postglacial consolidation of a thick glacier-proximal unit leads to the upward expulsion of excess pore water. A permeability barrier is formed by the overlying glacio-lacustrine clays and fine silts, focusing these migrating fluids to topographic highs. There, very high overpressure ratios facilitate the development of hydro-fractures, repeated fluid escape and pockmarks on the lake bottom. Overpressure may decrease slope stability in Lake Villarrica in different manners: by focused fluid escape weakening sediments, by generating underconsolidated sequences of low undrained shear strength, and by facilitating static failure. Based on high-quality in-situ data, this study confirms that high overpressure ratios in shallow sediments may be a typical feature at formerly-glaciated marine and lacustrine environments and highlights the major role of pore fluid overpressure for preconditioning subaquatic slopes to failure.(VLID)1569165Accepted versio

Sediment undulations on the Llobregat prodelta: Signs of early slope instability or sedimentary bedforms?

A field of sediment undulations has been mapped by means of high resolution multibeam bathymetry and seismic reflection profiles in the Llobregat River prodelta, off the city of Barcelona, Catalonia, Spain. Similar features had previously been recognized in other prodelta environments and interpreted either as downslope sediment deformation or sedimentary structures induced by bottom currents or hyperpycnal flows. Since the study area is undergoing significant offshore development, proper interpretation of such sediment undulations is needed for a correct risk assessment. The occurrence of the sediment undulations is restricted to the prodelta front on slope gradients between 3 and 0.2º. The undulations have developed at the edge and atop an area of gas bearing sediments within the Late-Holocene high-stand mud wedge. An evaluation is made of the characteristics of the sediment undulations in order to determine the most likely process for the origin of these structures. Amongst these characteristics are the continuity of the reflections and lack of diffractions in between different undulations, their size distribution (large to small) both from shallow to deep and with depth in section, the asymmetry (decreasing from proximal to distal), the crest to trough vertical distance on the landward side of the undulations (up to 0.5 m), and the lack of features that could indicate a progressive movement such as growth structures and drag folds. These characteristics indicate that the sediment undulations on the Llobregat River prodelta do not result from sediment deformation, but rather from the interaction of bottom currents generated by hyperpycnal flows from the Llobregat River with regional sea water circulation. Their identification as sediment waves implies that such features do not pose a major hazard for urther offshore development