Procedures for increasing the radiosensitivity of malignant tumors with special regard to synchronized radiotherapy

Two principal ways to increase the radiosensitivity of malignant tumours are described: to begin with, both the use of highly ionizing corpuscular radiation - e.g. in neutron therapy - and the simultaneous application of photons and high-pressure oxygen heighten radiosensitivity by increasing the number of secondary hit events. The second principal direction - in which the radiation intervals are timed in dependence of lifetime and division rhythm of the tumour cells - is described and illustrated by results of 5-fluorouracil and 60Co irradiation of 71 patients. The results show a particularly good response of carcinomas of the ENT region and the breast. Questions of the radiosensitive stage, the time of infusion, the influence of the generation cycle and the influence of oxygen-starved cells on the results are major points for future studies on synchronized radiotherapy. Mathematical calculations are carried out concerning the time of infusion and the influence of the generation cycle. Some consequences are mentioned which had not been dealt with so far in synchronized radiotherapy: high single doses and short intervals between sessions for tumours with short generation and duplication times, and low doses and long intervals for small tumours with slow growth rates. There is no principal difference between oxygen-starved and oxygen-rich cells as far as the dependence of radiosensitivity on the generation cycle - i.e. the starting point of synchronized radiotherapy - is concerned. (orig./AK)