Purpose: The aim was to investigate the influence of pulmonary metastases o
f the R1H oil the radiation response Of the lung of the WAG/Rij rat.
Material and methods: Three groups of animals were metastases-free animals
treated with fractionated irradiation of the lungs; metastases-hearing anim
als receiving no irradiation: and metastases-bearing animals treated with f
ractionated irradiation initiated 14, 21 or 28 days after induction of pulm
onary metastases of the R1H-tumour by i.v. injection of viable tumour cells
. metastases were thus treated at various well-defined sizes. Total doses o
f 20 60 Gy were applied in fractions of 2 Gy within 11 days. Complication r
ate and survival time were used as endpoints.
Results: About 2 months after onset of irradiation treatment, animals had t
o he sacrificed because of severe respiratory distress either caused by irr
adiation-induced lung damage (median 57 days, range 36 77 days), or because
of development of lung metastases (65, 20 160 days). A decrease of the ED5
0 (dose required to induce lethal lung damage in 50% of irradiated animals)
, was determined for metastases-hearing animals. This effect increased with
Conclusions: The results suggest the presence of tumours in the lung decrea
sed the lung tolerance to radiation. This efect call hardly be explained by
a reduction in functional lung volume by metastatic volume.