Intra-arterial chemotherapy for retinoblastoma treatment in Chile: Experience and results 2013-2020

OBJECTIVE

To establish the success rate of salvage intra-arterial chemotherapy (IAC), defined as the percentage of eyes that achieved tumoral remission and avoided enucleation. The second objective was the clinical characterization, catheterization results, and associated local and systemic complications.

METHODS

Retrospective, interventional case series of 29 patients (35 eyes) with persistent or recurrent retinoblastoma.

RESULTS

A total of 73 salvage IAC procedures with topotecan and melphalan were carried out. Success rate was 77% at a mean follow-up of 41.4 months. All patients with only one remaining eye avoided enucleation (10 cases). Catheterization was successful in 98.6% of cases. The types of catheterizations were as follows: 71.2% supraselective ophthalmic artery, 12.3% occlusion pump assisted supraselective ophthalmic artery, 16.4% selective external carotid with retrograde flow. 14% of patients suffered local adverse effects: 1 (2.8%) transitory ptosis, 1 (2.8%) transitory oculomotor nerve palsy, 2 (5.7%) aseptic cellulitis and 1 (2.8%) periorbitary pigmentation. 4.1% (3 cases) suffered neutropenia due to medullar chemosuppression. There were no cases of severe anemia or thrombocytopenia. There were no cerebral ischemic events or mortality associated to the procedure.

CONCLUSION

IAC with melphalan and topotecan is a safe and effective treatment option for persistent or recurrent retinoblastoma, able to reduce enucleation rates.

Mechanical Response of Polyethylene Foams with High Densities and Cell Sizes in the Microcellular Range

This article presents the compressive mechanical response at low strains for a collection of polyethylene foams with high densities and cell sizes in the microcellular range. The materials under study had a relative density between 0.27 and 0.92, a homogeneous and multi-structured cellular structure with a dense skin and a foamed core. The Young’s modulus and collapse stress were reduced when density did, the modulus following a linear trend and the collapse stress a quadratic tendency. For relative densities higher than 0.7, the materials showed Young’s modulus slightly above the limit given by a potential law with exponent equal to one. In addition, it has been proved that variations in the cell size did not influence the elastic properties. The advantages of using these materials for flat structural panels have been analyzed. A reduction of the weight of flat panels loaded in bending of up to 35% can be reached by using these foams in spite of the solid sheet from which the foam was produced.

Mechanical Behaviour at Low Strains of LDPE Foams with Cell Sizes in the Microcellular Range: Advantages of Using These Materials in Structural Elements

This paper presents the production method and the compressive mechanical response at low strains for a collection of polyethylene foams with high densities and cell sizes in the microcellular range. The materials were produced using an improved compression moulding technique that allows and independent control of density and cell size.

The materials had a relative density between 0.27 and 0.92, an homogeneous and multi-structured cellular structure with dense skin and foamed core and cell sizes in the range 30 to 100 microns. The Young's modulus decreased with density. For relative densities higher than 0.7, the reduced Young's modulus of the foams was higher than that of the solid. In addition, it has been proved that variations in the cell size at constant density did not influence the Young's modulus. The advantages of using these materials for the production of plastic pipes have been analysed. In comparison with a solid pipe a reduction of the weight of foamed pipes loaded in compression of up to 40% can be reached.

Biomass adaptation to complex substrate degradation in membrane bioreactors: appropriated operating conditions

The aim of this work is to analyse the biological performances of two immersed membranes bioreactors focusing on the biomass adaptation to complex substrate degradation and the performance in term of permeate quality. Two influents were selected: a synthetic complex influent (acetate/Viandox, MBR1) and a real seafood processing wastewater (surimi product, MBR2). The MBR systems were operated for long periods without any sludge extraction except for sampling. Organic matter removal, sludge production and quality of the treated wastewater were analysed and studied. COD removal efficiencies after a period of biomass adaptation were higher than 97% and 95% for the synthetic and real wastewater respectively. In both cases, the COD of the treated wastewater was lower than 50 mg.L(-1). In spite of salt concentration in the real wastewater a biomass adaptation process occurs. In the overall operational period, a 0.058 gCOD P.gCOD T(-1) and a 0.12 gCOD P.gCOD T(-1) observed sludge yields were obtained for the MBR1 and MBR2 respectively. These values are approximately 5 to 10 times lower than those measured in conventional activated sludge process. These results showed that the presence of particular and some of non-easily degradable compounds in the influent of MBR2 didn't limit the performance of MBR in term of COD removal achieved. The results have also confirmed the excellent permeate quality for water reuse from MBRs systems.

Continuous and sequencing membrane bioreactors applied to food industry effluent treatment

This work focuses on the performances of two immersed membrane bioreactors used for the treatment of easily biodegradable organic matter present in food industry effluents, for the purpose of water reuse. Two reactor functioning modes (continuous and sequencing) were compared in terms of organic carbon removal and of membrane permeability. For each working mode, pollutant removal was very high, treated water quality presented a low COD concentration (< 125 mg x L(-1)), no solids in suspension and low turbidity (< 0.5 NTU). The quality of the treated water (including germ removal) enabled its reuse on site. Moreover, by developing high biomass concentrations in the reactor, excess sludge production remained very low (< 0.1 gVSS x gCOD(-1)). The performances appeared slightly better for the continuous system (lower COD concentration in the effluent, < 50 mg x L(-1), and lower sludge production). In terms of filtration, a distinct difference was observed between continuous and sequencing systems; transmembrane pressure showed a small and constant evolution rate in continuous membrane bioreactor (CMBR) although it appeared more difficult to control in sequencing membrane bioreactor (SMBR) probably due to punctually higher permeate flow rate and modified suspension properties. The rapid evolution of membrane permeability observed in SMBR was such that more frequent chemical cleaning of the membrane system was required.

Effects of starvation conditions on biomass behaviour for minimization of sludge production in membrane bioreactors

The behaviour of an activated sludge system in starvation conditions was examined in batch according to substrate impulses defined by different S0/X0 ratio. The answer was characterised by an exogenous phase followed by a starvation one. If at high S0/X0 ratio, bacterial cell multiplication was the main synthesis process during exogenous phase, at low S0/X0 ratio the observed phenomenon was compound storage. In starvation conditions, for the lowest S0/X0 ratio, a rapid decrease in the MLVSS without soluble proteins production was observed. No bacterial lysis occurred and this phenomenon was due to consumption of the storage compounds with a decrease rate equal to 0.74d(-1). For high S0/X0 ratio, as soon as the exogenous phase was completed, a decrease of the MLVSS simultaneously to a soluble protein production was observed. An immediate bacterial lysis occurred with a decay rate equal to 0.53 d(-1). Because MBR systems work generally in low F/M conditions, the activity of the present microbial population is close to the one observed in starvation phase. This work points out that these conditions do not allow net bacterial growth and cells just use lysis products to satisfy their maintenance requirements. These assumptions confirm the feasibility of a decrease of the net biomass production in a MBR when high sludge retention time is operated.