Problems and trends in radiotherapeutic treatment of deep-seated tumors.

The heterogeneous structure of tumors is described and the importance of oxygen is explained and analyzed. Three ways of solving the clinical problems of anoxic tumor cells are today being tried. Hyperbaric oxygen breathing before and during irradiation; using fast neutrons and thirdly the use of improved treatment schemes with low LET (i.e. low alpha-value) radiation. The various methods are described and critically evaluated. Calculations are made with the two-component model of radiation. The improved treatment schemes seem in most cases to work well and to solve the problem. If necessary, for certain radio-resistant tumors the normal treatment might also be supplemented by other methods.