Relative Biological Effectiveness of Carbon Ions in a Rat Prostate Carcinoma In Vivo: Comparison of 1, 2, and 6 Fractions

Journal Article · Mon Jul 01 04:00:00 EDT 2013 · International Journal of Radiation Oncology, Biology and Physics

DOI:https://doi.org/10.1016/J.IJROBP.2013.01.019· OSTI ID:22224495

Peschke, Peter ^[1]; Scholz, Michael ^[2]; Huber, Peter E. ^[1]; Debus, Jürgen ^[3]

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1. Clinical Cooperation Unit Radiation Oncology, German Cancer Research Center (DKFZ), Heidelberg (Germany)
2. Department of Biophysics, Helmholtz Center for Heavy Ion Research (GSI), Darmstadt (Germany)
3. Department of Radiation Oncology, University Hospital of Heidelberg (Germany)

Purpose: To determine the relative biological effectiveness (RBE) and the effective α/β ratio for local tumor control of a radioresistant rat prostate tumor (Dunning subline R3327-AT1) after 6 fractions of carbon ions and photons. Methods and Materials: A total of 82 animals with tumors in the distal thigh were treated with 6 fractions of either photons or carbon ions, by use of increasing dose levels and a 2-cm spread-out Bragg peak. Endpoints of the study were local control (no tumor recurrence within 300 days) and volumetric changes after irradiation. The resulting values for dose at 50% tumor control probability were used to determine RBE values. Including data for 1 and 2 fractions from a previous study, we estimated α/β ratios. Results: For 6 fractions, the values for dose at 50% tumor control probability were 116.6 ± 3.0 Gy for photons and 43.7 ± 2.3 Gy for carbon ions and the resulting RBE was 2.67 ± 0.15. The α/β ratio was 84.7 ± 13.8 Gy for photons and 66.0 ± 21.0 Gy for carbon ions. Using these data together with the linear-quadratic model, we estimated the maximum RBE to be 2.88 ± 0.27. Conclusions: The study confirmed the increased effectiveness of carbon ions relative to photons over the whole dose range for a highly radioresistant tumor. The maximum RBE below 3 is in line with other published in vivo data. The RBE values may be used to benchmark RBE models. Hypoxia seems to have a major impact on the radiation response, although this still has to be confirmed by dedicated experiments.

• OSTI ID: 22224495
• Journal Information: International Journal of Radiation Oncology, Biology and Physics, Journal Name: International Journal of Radiation Oncology, Biology and Physics Journal Issue: 3 Vol. 86; ISSN IOBPD3; ISSN 0360-3016
• Country of Publication: United States
• Language: English

Related Subjects

62 RADIOLOGY AND NUCLEAR MEDICINE
ANOXIA
BRAGG CURVE
CARBON IONS
CARCINOMAS
IN VIVO
IRRADIATION
PHOTONS
PROSTATE
RADIATION DOSES
RATS
RBE