Summary: The dosage of both methods of conservative therapy, i.e. of radiotherapy and of chemotherapy is the critical factor for tumor response. This review is an attempt of analysis of possibilities how to apply both treatment modalities in normal or even in escalated dosage with acceptable rate of the risk for normal tissue damage.
The results of radiotherapy and those of chemotherapy depend above all on the initial number of clonogenic cells in the tumor, on their repopulation and partially on the extent of reoxygenation during the treatment. From the point of view of tumor control and of sparing the late responding normal tissues is possible with the use of hyperfractionation to increase the total tumor dose of radiotherapy by 10—15 %. The use of antineoplastic drugs modifies the cell survival curve through the inhibition of radiation damage repair (change of alpha/beta ratio — linear-quadratic model; dose enhancement ratio).
The great problem is an optimal timing of both treatment modalities. The interdigitated alternating regimen (Prof. M. Tubiana and co-workers) seems to be very perspective, especially with the use of hyperfractionation or accelerated hyperfractionation which are able to keep step with accelerated tumor cell repopulation during radiotherapy.
Current possibilities of the radiochemotherapy optimalization from the point of view of tumour answer and toxicity by combined therapy
