Observations on pulmonary metastases in patients after single doses and multiple fractions of fast neutrons and cobalt-60 gamma rays

Pulmonary metastases have been irradiated with single and fractionated doses of fast neutrons and cobalt-60 gamma rays. The response to radiation was measured on volume changes of the lesions and thus RBE values could be derived. A correlation was found between grading of the tumour and volume doubling time and also between RBE and volume doubling time. This suggests an advantage for high LET radiation of slowly growing, well differentiated tumours. Furthermore the RBE for multiple fractions tends to be higher than for single doses. Calculation of the N exponent of the Ellis formula indicated that hardly any shoulder exists when neutrons are applied.