The search for ways to overcome tumour radioresistance is a major
problem of experimental and clinical radiation oncology. The diffi-
culties involved in the attempts to solve this problem are a matter of
common knowledge. In many a laboratory extensive studies are un- derway
of factors determining tumour tissue response to irradiation and of
methods for exerting directional effect upon those factors. Such studies
have revealed that, at least at the cellular level, a considerable
number of factors manifest themselves which are respon- sible for
radiation effect (1] - Among those are: spatial heteroge- neity of
tumour cell population producing radioresistant cell reser- ves (hypoxic
cells of solid tumours); differing radiosensitivities of cell life cycle
phases; intrinsic dynamics of the processes of radi- ation damage and
postradiation cell recovery; induction of prolifera- tive processes in
response to the death of some cells within the po- pulation; the
stochastic nature of cell kinetics and complicated in- teraction between
individual cell subpopulations corresponding to di- fferent tumour loci.
Questions arise as to whether the researchers are now in possession of
adequate means for interpreting experimental findings and clinical
evidence and whether there are procedures for performing complex
analysis and predicting specific tumour responses to various irradiation
regimens and to combined antitumoral effects, taking into account the
complexities of the phenomena under study.