Radiotherapy of the R1H-tumor: dose-rate effect on tumor response in brachytherapy with 106-ruthenium eye applicators.
OBJECTIVE
The influence of the dose-rate on tumor response in radiotherapy with 106-Ruthenium eye plaques has been investigated in an experimental tumor system.


METHODS
The identical total dose was applied within three different overall treatment times (42 hr, 192 hr and 312 hr), corresponding to dose-rates of 6.0 Gy/hr, 1.3 Gy/hr and 0.8 Gy/hr.


RESULTS
The therapeutic outcome of brachytherapy varied significantly between the three groups of animals treated with different dose-rates. At a dose-rate of 1.3 Gy/hr all tumors were locally controlled, but no local control was observed when a dose-rate of 6.0 Gy/hr was delivered. 0.8 Gy/hr was less effective than 1.3 Gy/hr but more effective than 6.0 Gy/hr.


CONCLUSIONS
These results were unexpected but they might be explained by an incomplete reoxygenation if the overall treatment time is too short (42 hr, dose-rate 6.0 Gy/hr) and by proliferation of tumor cells under treatment if the overall treatment time is too long (312 hr, 0.8 Gy/hr).
Kleineidam
M
M
Institute of Biophysics and Radiobiology, University Hospital Hamburg-Eppendorf, Germany.
Guthoff
R
R
Schiller
F
F
Chumbley
L
L
Beck-Bornholdt
H P
HP
D000818:Animals; D001918:Brachytherapy / Q000295:instrumentation*; D005260:Female; D009368:Neoplasm Transplantation; D011879:Radiotherapy Dosage; D051381:Rats; D012208:Rhabdomyosarcoma / Q000532:radiotherapy*; D012429:Ruthenium Radioisotopes / Q000008:administration & dosage / Q000627:therapeutic use*
D012429:Ruthenium Radioisotopes