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Biomedical subjects

H A van den Berg

Publications and source records attributed to H A van den Berg.

11 recordsLinked to original sources
PubMed2006

Greater influence of age than co-morbidity on primary treatment and complications of prostate cancer patients: an in-depth population-based study.

We investigated the influence of age and co-morbidity on treatment, the occurrence of serious non-urological complications of treatment and prognosis for prostate cancer patients diagnosed and treated in community hospitals. Additional information from a random sample of 505 prostate cancer patients (aged 40 years or older) from the Eindhoven Cancer Registry diagnosed between 1995 and 1999 was collected. In all, 43% of the prostate cancer patients aged 40-69 years and 64% of those aged 70 or older suffered from one or more serious concomitant disease that barely affected primary treatment choice. However, compared to patients without co-morbidity, patients with cardiovascular diseases underwent radical prostatectomy less often (P=0.01). In all, 38% of the patients undergoing radical prostatectomy suffered from complications during the first year after diagnosis versus about 20% of those receiving radiotherapy. The number of complications did not seem to be affected by co-morbidity. After adjustment for age, stage, grade, prostate-specific antigen level and treatment, the cumulative risk of death was almost two times higher for patients with two or more concomitant diseases than for patients without co-morbidity. After adjustment for age, prostate cancer patients with co-morbidity were not treated differently, did not suffer from more complications but had a worse prognosis, compared to those without co-morbidity.

Adult↗
PubMed2005

Impact of comorbidity on treatment and prognosis of prostate cancer patients: a population-based study.

This study investigates the independent influence of serious comorbidity and age on treatment and survival of prostate cancer patients diagnosed between 1995 and 2002 in the southern part of the Netherlands. Eight percent of patients<60 years had two or more concomitant diseases versus 27% of those aged 80 years or older. The number of patients undergoing radical prostatectomy or curative radiotherapy decreased significantly with increasing age. The proportion of patients aged 60-69 years undergoing prostatectomy decreased significantly from 32% of patients without comorbidity to 17% of patients with two or more comorbid conditions and from 8% to 3%, respectively, of those aged 70-79 years. The risk of dying was significantly higher for patients with two or more comorbid conditions compared to patients without comorbidity. Serious comorbidity led to less aggressive treatment and negatively affected the prognosis of prostate cancer patients aged 60-79 years.

Age Factors↗
PubMed2001

How microbes can achieve balanced growth in a fluctuating environment.

A microbial colony needs several essential nutrients in order to grow. Moreover, the colony requires these nutrients in fixed combinations, which are dictated by the chemical composition of its biomass. Unfortunately, ambient availabilities of the various nutrients vary all the time. This poses the question of how microbes can achieve balanced growth. The present solution to this problem is novel in that the allocation of molecular building blocks among assimilatory machineries within the cell is regarded as dynamic. This paper shows that allocation can be adapted so as to achieve balanced growth, nearly regardless of environmental conditions. Moreover, it is shown that a feedback mechanism, which monitors internal stores, is able to achieve this allocation.

Bacteria↗
PubMed2000

Definition and validation of a reference target volume in early stage node-positive cervical carcinoma, based on lymphangiograms and CT-scans.

PURPOSE: To establish a reference planning target volume for postoperative radiotherapy in stage Ib and IIa N+ cervical carcinoma, based on 47 lymphangiograms and 15 CT-scans. METHODS: Radiation oncologists (n=17) from all radiotherapy institutes in The Netherlands were asked to define the clinical target volume (CTV) and planning target volume (PTV), and to delineate (on simulation films) the radiotherapy treatment portals following a radical hysterectomy with lymph node dissection for an early stage cervical carcinoma with positive iliac lymph nodes. A reference PTV was defined by using 47 normal lymphangiograms and CT-data of the pelvis from 15 patients who underwent surgery for cervical carcinoma. The simulation films were digitized and evaluated for adequacy in covering the PTV, previously individually determined by the radiation oncologists. Subsequently, the simulation films were also evaluated for adequacy in covering the reference PTV. RESULTS: Large variations were observed in the portals used and in treatment techniques. From the digitized films, it appeared that in 50% of the cases the defined PTV was not covered adequately. Furthermore, 71% of the treatment plans would not cover the lateral borders of the reference PTV sufficiently. CONCLUSIONS: There appears to be no consensus on the target volumes to be irradiated in postoperative radiotherapy of early stage cervical carcinoma. When a PTV defined on the basis of lymphangiograms and CT-data is taken as a reference, 71% of the treatment plans would not cover this PTV adequately. These findings indicate the need for a consensus in the design of standardized treatment volumes.

Carcinoma, Squamous Cell↗
PubMed1999

Three-dimensional treatment planning for postoperative radiotherapy in patients with node-positive cervical cancer. Comparison between a conventional and a conformal technique.

PURPOSE: Reduction of irradiated small bowel volume, using a conformal three-dimensional treatment planning technique in postoperative radiotherapy of cervical cancer patients. PATIENTS AND METHODS: Large gynecological treatment fields including the para-aortic nodes were analyzed in 15 patients. A conventional treatment plan with anterior and posterior (AP-PA) parallel opposed fields and a 3D 4-field conformal radiotherapy plan with a central blocking of small bowel were compared for each patient. Dose-volume histograms and dose parameters were established. Because of the tolerance constraints of the small bowel, the cumulative dose applied to the target was 48.6 Gy. RESULTS: The mean Tumor Control Probability (TCP) values for both the conventional and the conformal technique were 0.60 and 0.61, respectively, with ranges of 0.56 to 0.67 and 0.57 to 0.66, respectively. The mean volume receiving 95% or more of the prescribed dose (V95) of the small bowel was 47.6% (32.5 to 66.3%) in the AP-PA technique and 14.9% (7.0 to 22.5%) in the conformal technique (p < 0.001), indicating a significant reduction in irradiated volume of small bowel in the higher dose range. The mean Normal Tissue Complication Probability (NTCP) decreased from 0.11 to 0.03 with the conformal plan. In patients who received a pedicled omentoplasty during surgery, the mean V95 for small bowel could be reduced to 8.5% (7.0 to 9.9%). The mean median dose to the kidneys was only slightly elevated in the conformal treatment. Especially the mean dose to the right kidney in conventional vs conformal treatment was 3.3 vs 7.9 Gy. The mean near-minimum dose (D95) to the rectosigmoid decreased from 48.4 to 30.1 Gy in the conformal plan compared to the conventional plan. CONCLUSION: The small bowel dose can be significantly reduced with 3D treatment planning, particularly if a pedicled omentoplasty is performed. This allows dose escalation to the tumor region without unacceptable toxicity for the small bowel.

Adenocarcinoma↗
PubMed1998

Multiple nutrient limitation in unicellulars: reconstructing Liebig's law.

Liebig's law of the Minimum is reformulated in terms of biomass composition dynamics. The doctrine of the single limiting nutrient is shown to be invalid generally. The nutritional status of a unicellular organism is expressed in terms of state variables; one which represents the subsistence composition and a number of reserve surplus type variables. It is proposed that the property of being limiting should be defined in terms of the reserve surplus variables. On the basis of this definition, it can be decided whether a nutrient, or combination of nutrients, is limiting, both in transient and steady states. The concept of multiple limitation is shown to have two distinct meanings on these definitions. A non-interactive minimum model, based on a 'hard' minimum operator, is introduced. Smooth interactive models may be formulated which have this minimum model as a limiting case. One such model is described. Numerical simulations show how the behaviour of this smooth model can approximate that of the minimum model: apparently hard non-linearities can arise in the smooth model, through time-scale separation.

Biomass↗
PubMed1977

I1Legal measures in behalf of veterinary medicine and public health (author's transl).

The constantly growing world population and the altered consumption pattern have considerably increased the demand for more, and more refined, food, particularly that of animal origin. Altered methods of production, highly concentrated froms of animal husbandry but also the resulting increase of the need for the cheapest possible materials for the mixed feed industry, the more rapid and greater transport facilities, the markedly increased trade in animals and particuarly in products originating fromthese animals, they all involve an increased risk of the import and outbreak of animal disease. The increased use of animal drugs, production-increasing agents and pesticides involve the danger of injurious residues being left in products of animal origin as a result of the comulative factors in animals. Therefore, the entire chain of production, beginning at the earliest possible stage, should be closely supervised. Supervisotry programmes of the Chief Veterinary Inspectorate of the Ministry of Health and of the Veterinary Service are, in a manner of speaking, the search-lights which, thanks to the refined methods of analysis developed by research workers, are able to detect and point out failings and deficiencies. An anticipated amendment of the Livestock Breeding Act, an anticipated replacement of the Antibiotics Act and a regulation forming part of the Statutory Trade Organization are designed to make it possible to respond more promptly to these signals.

Animal Husbandry↗