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Biomedical subjects

P Scalliet

Publications and source records attributed to P Scalliet.

At least 73 records · Page 4Linked to original sources
PubMed1993

Influence of cisplatinum on intestinal tolerance to photon and neutron irradiation in mice.

The hypothesis that cisplatinum (c-DDP) interacts with radiation by inhibiting the cellular repair capacities, was tested by comparing the interaction of c-DDP with low-LET (60Co gamma-rays) and high-LET radiation (d(50) + Be neutrons) in mice. The biological endpoint was lethality, 6 days after total body irradiation (early intestinal tolerance). The dose modifying factor was 1.80 +/- 0.25 for c-DDP plus 60Co gamma-rays, and 1.97 +/- 0.3 for c-DDP plus neutrons. As less repairable damage is induced by fast neutrons than by photons, this suggests that, in this system, the interaction between radiation and c-DDP is not explained by repair inhibition but is purely additive.

Animals↗
PubMed1993

Commission of the European Communities "Europe Against Cancer" Programme. European school of oncology advisory report. Cancer treatment in the elderly.

Within the EC approximately one million cases of cancer are diagnosed every year. At present, more than 55% of cancers occur in subjects aged over 65 years. There has been little clinical attention to the problem of neoplasia in the elderly. They are not receiving the same standard of specialised oncological care as younger patients. Other diseases (co-morbidity conditions) associated with cancer, and influencing its treatment and outcomes are not being properly considered. Information on surgery, radiotherapy and chemotherapy in younger patients exists for all cancers and could be adapted for the elderly. Controversial aspects of neoplasia in the elderly concern the intensity of chemotherapy, extent of surgery and the relative roles of specialised cancer centres, community hospitals and primary care providers. Future research should aim to replace subjective opinions on presence of frailty with objective instruments such as the multidimensional geriatric assessment scale. New trials could then seek to improve treatment in well-defined populations in terms of both efficacy and quality of life. Funding priorities should firstly consider that clinical trials for tumours in the elderly must be organised from cancer institutes and specialised referral centres in collaboration with geriatricians, primary care and community hospital physicians. Continuing education of doctors should be reported. A document such as this with appropriate modifications might be used as an initial message on neoplasia in the elderly to be published for information to clinicians and the public throughout Europe. Specific measures of quality assurance need financial support to evaluate the improvements in patterns of care. The 10 points of the 'Europe Against Cancer Guidelines' need reemphasising.

Aged↗
PubMed1993

Radiotherapy and chemotherapy in testis tumors.

Testis tumor is rare but interesting tumor as it is a true model of curable solid tumor in adults. The use of chemotherapy constitutes one of its most successful applications. Seminoma are characterized by a great sensitivity to radiation which remains the additional adjuvant treatment for early tumors. For dysgerminoma, the authors discuss the wait and see policy for early tumors and the role of chemotherapy for advanced diseases.

Antineoplastic Combined Chemotherapy Protocols↗
PubMed1991

Application of the LQ model to the interpretation of absorbed dose distribution in the daily practice of radiotherapy.

In 1991, the vast majority of radiotherapy centers are implemented with computer treatment planning systems (TPS), and it has become routine practice to compute full absorbed dose distribution (ADD) in almost all treatment situations. Usually the target is covered by the 100% isodose and the surrounding normal tissues receive a lesser dose than the tumor. It implies, that, as the dose per fraction of, say, 2 Gy is prescribed at the 100%, normal tissues receive a daily dose different than 2 Gy. The absorbed doses delivered at different organs have therefore not the same biological effectiveness and must be corrected according to the actual dose per fraction for a proper interpretation of the treatment planning. This is of great importance since most of the "tolerance levels" used in the practice have been determined for doses per fraction around 1.8-2 Gy. The linear-quadratic (LQ) model provides a simple method for establishing biological equivalencies and has been used throughout this article to establish the difference between the absorbed dose computed by the TPS and its biological equivalent. It is shown that normal tissues receiving less than 100% of the daily dose are relatively more protected than suggested by the ADD, and, inversely, that normal structures overdosed and thus receiving more than the 100% daily dose are relatively more at risk for complications than suggested from the ADD.

Bronchial Neoplasms↗
PubMed1989

Repair kinetics as a determining factor for late tolerance of central nervous system to low dose rate irradiation.

The effect of continuous irradiation, delivered at four different dose rates (107.6, 14.7, 3.9 and 2 Gy.h-1) has been investigated using the rat cervical spinal cord biological system. The endpoint was the induction of foreleg paralysis at 9 months which corresponds, as has been described before, to white matter necrosis. Paralysis occurring in 50% of the animals was taken as the isoeffect, and the ED50 (radiation dose leading to paralysis in 50% of the animals) was calculated by probit analysis. There was a constant increase in the ED50 with the decrease in the dose rate, resulting from the repair of sublethal damage (SLD) occurring during irradiation. A comparison was made with the previously published results of high dose rate (100-120 Gy.h-1) fractionated irradiations (2, 4 and 10 fractions). alpha/beta (1.6 Gy for the pooled fractionation and dose rate data) and the half-time of SLD repair (82 min) were derived.

Animals↗
PubMed1989

Kinetics of sublethal damage recovery in mouse lip mucosa comparing low and high-LET radiation.

The effects of d(50) + Be neutrons on the lip mucosa in mice were investigated as a model of early effects. The biological endpoint eas the incidence of desquamation in the lower lip after selective irradiation of the snout of the animals. ED 50 (dose leading to desquamation in 50% of the animals) were calculated by probit analysis. Fractionated (two, four and ten fractions) and protracted (43.5, 11.5 and 0.88 Gy.h-1) irradiations have been carried out. Results were analysed using the mathematical method of Dale. An alpha/beta of 39.6 Gy and a t 1/2 of recovery of sublethal damage of 47 min have been derived. These results have been compared to data previously obtained with cobalt-60 gamma rays. Using the same mathematical approach, and comparing similar fractionated and protracted experiments, an alpha/beta of 7.4 Gy and a t 1/2 of recovery of 47 min have been calculated. There was no significant difference in the repair kinetics after irradiations with gamma rays or d(50) + Be neutrons.

Animals↗
PubMed1987

Effect of decreasing the dose rate of irradiation on the mouse lip mucosa. Comparison with fractionated irradiations.

The effect of continuous irradiation, delivered at five different dose rates (642, 76.8, 14.1, 2.9 and 1.5 Gy.h-1), has been investigated using the mouse lip mucosa. There was a striking dose rate effect (DRE) below 14.1 Gy.h-1 while above this dose rate the DRE was relatively small. No DRE was observed between irradiations delivered at 642 and 76.8 Gy.h-1. A comparison was made with the previously published results of high dose rate (84 Gy.h-1) fractionated irradiation (2, 4, 10 and 20 fractions). For both types of irradiation treatment an alpha/beta value of 7.4 Gy and a half-time for repair of 47 min was derived.

Animals↗
PubMed1987

Which RBE for iodine 125 in clinical applications?

The problem of the selection of a RBE value for 125I is discussed for clinical applications in interstitial therapy. Microdosimetric studies indicate that the emission of the 125I has a y spectra similar to X-rays of 12-140 keV (conventional X-rays), but differs from 60Co, 137Cs gamma-rays and high energy X-rays. The radiobiological data available show RBE values ranging from 1 to 2.4 for 125I (reference beam 60Co). Although obtained with different biological systems and endpoints, RBE values of 1.15-1.20 are in general observed for high doses and high dose rates. On the other hand, higher RBE values (up to 2) are observed at low doses or low dose rates, which is consistent with theoretical and microdosimetric data.

Humans↗
PubMed1987

[Effects of irradiation on the lip mucosa in the mice as a function of rate. Comparison with the effect of fractionation].

We have investigated the effect of single doses delivered at various dose rates on the mouse lip mucosa biological system. The dose rates were: 642, 76.8, 14.1, 2.9 and 1.5 Gy/h. The incidence of desquamation in the different groups of mice was used for constructing dose effect curves. The dose leading to desquamation in 50% of the animals (ED50) was obtained by probit analysis. These ED50 were 16.5, 16.7, 19, 30.2 and 33.5 Gy for the respective dose rates. Fractionated irradiations have also been performed in the same biological system (separately published), and we have therefore been able to compare the fractionated and low dose rate irradiations. The recently published model of Dale was used for this comparison. With that mathematical approach a alpha/beta value of 7.4 Gy and a half time of repair of sublethal damage of 47 minutes have been derived. These results compare well with others from the literature on biological systems with similar characteristics (rapidly proliferating systems).

Animals↗