EXTRACRANIAL TUMORS USING AN ACCELERATORClinical experience of the first thirty-one patients HENRIC BLOMGREN, INGMAR LAX, INGEMAR NASLUND and RUT SVANSTROMA stereotactic body frame with a fixation device has been developed for stereotactic radiation therapy of extracranial targets, a precision localization and positioning system in analogy with the stereotactic head frames used for intracranial targets. Results of the first 42 treated tumors in 31 patients are presented. Most of the patients had solitary tumors in liver, lung or retroperitoneal space. Clinical target volumes ranged from 2 to 622 cm3 (mean 78 cm3) and minimum doses to the planning target volumes (PTV) of 7.7-30 Gy/fraction (mean 14.2 Gy) were given on 1-4 occasions to a total minimum dose to the PTVs of 7.7-45 Gy (mean 30.2 Gy) to the periphery of the PTV and total mean doses to the PTVs of 8-66 Gy (mean 41 Gy). The central part of the tumor was usually given about 50% higher dose compared to that of the periphery of the PTV by a planned inhomogeneous dose distribution. Some of the patients received stereotactic radiation therapy concomitantly to more than one target, in others new metastases were also treated which appeared during the follow-up period. We observed a local rate of no progressive disease of 80% during a follow-up period of 1.5-38 months. Fifty percent of the tumors decreased in size or disappeared.Stereotactic radiation therapy (SRT) of brain metastases with high single doses was first given in 1975 at the Karolinska Hospital using a multi-cobalt-60 unit (gamma knife) (1). At present several thousand patients with intracranial metastases have been treated using this technique in different centers of the world ( 1-4). Local tumor control rate is around 90%. This SRT technique can frequently be used for treatment of inoperable tumors and those which are considered to be resistant to conventionally fractionated radiation. There is no other known treatment modality for solitary brain metastases which seems to

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1. Experimental growth data for Arctic charr (Salvelinus alpinus L.), all fed on excess rations, from 11 European watercourses between 54 and 70°N were analysed and fitted to a new general growth model for fish. The model was validated by comparing its predictions with the growth rate of charr in the wild. 2. Growth performance varied among populations, mainly because of variation in the maximum growth potential, whereas the thermal response curves were similar. The estimated lower and upper temperatures for growth varied between )1.7 to 5.3 and 20.8-23.2°C, respectively, while maximum growth occurred between 14.4 and 17.2°C. 3. There was no geographical or climatic trend in growth performance among populations and therefore no indication of thermal adaptation. The growth potential of charr from different populations correlated positively with fish body length at maturity and maximum weight in the wild. Charr from populations including large piscivorous fish had higher growth rates under standardised conditions than those from populations feeding on zoobenthos or zooplankton. Therefore, the adaptive variation in growth potential was related to life-history characteristics and diet, rather than to thermal conditions.

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The effects of density-dependent intercohort competition on growth and mortality in stream-resident brown trout (Salmo trutta) were tested by experimentally reducing the densities of age-1 fish and fish older than age 1 in six small streams. When densities of age-1 fish were reduced, abundance of age-0 and age-1 fish increased the following year, while age-1 fish experienced a reduced mean size. Reduced densities of fish older than age 1 resulted in increased apparent survival of age-0, age-1, and age-2 fish in the subsequent year. Mean size of age-2 fish increased as well. Many older immigrants (age >2) were found in the treatment sections where densities previously had been reduced. Data from the Swedish Electrofishing RegiSter (SERS) showed that mean body size of age-0 brown trout was negatively related to both age-0 and age >0 densities. The database also verified the inverse relationship between age-0 abundance and abundance of older cohorts. Our results indicate that intercohort competition regulates territorial fish populations, even when simple single populations in restricted environments are considered.

8-Oxo-7,8-dihydro-2'-deoxyguanosine (8-oxo-dG) is one of the mutagenic base modifications produced in DNA by the reaction of reactive oxygen species. The biological significance of 8-oxo-dG is shown by the existence of repair pathways that are able to recognize and remove this lesion from both DNA and the nucleotide pool. The final outcome of these evolutionarily conserved repair mechanisms in man is excretion of 8-oxo-dG/8-oxo-Gua from the intracellular to extracellular milieu including the blood plasma and urine. The aim of this investigation was to establish dose response relations for radiation-induced appearance of extracellular 8-oxo-dG in cellular model systems. Here we report on excretion of 8-oxo-dG after in vitro irradiation of whole blood and isolated lymphocytes with clinically relevant doses. We find that this excretion is dependent on dose and individual repair capacity, and that it saturates above doses of 0.5-1 Gy of gamma radiation. Our data also suggest that the nucleotide pool is a significant target that contributes to the levels of extracellular 8-oxo-dG; hence the mutagenic target for oxidative stress is not limited to the DNA molecule only. We conclude that extracellular 8-oxo-dG levels after in vitro irradiation have a potential to be used as a sensitive marker for oxidative stress.