Temporal Lobe Reactions After Carbon Ion Radiation Therapy: Comparison of Relative Biological Effectiveness–Weighted Tolerance Doses Predicted by Local Effect Models I and IV

Abstract Background To determine the relative biological effectiveness (RBE) and α/β-values after fractionated carbon ion irradiations of the rat spinal cord with varying linear energy transfer (LET) to benchmark RBE-model calculations. Material and methods The rat spinal cord was irradiated with 6 fractions of carbon ions at 6 positions within a 6 cm spread-out Bragg-peak (SOBP, LET: 16–99 keV/μm). TD50-values (dose at 50% complication probability) were determined from dose-response curves for the endpoint radiation induced myelopathy (paresis grade II) within 300 days after irradiation. Based on TD50-values of 15 MV photons, RBE-values were calculated and adding previously published data, the LET and fractional dose-dependence of the RBE was used to benchmark the local effect model (LEM I and IV). Results At six fractions, TD50-values decreased from 39.1 ± 0.4 Gy at 16 keV/μm to 17.5 ± 0.3 Gy at 99 keV/μm and the RBE increased accordingly from 1.46 ± 0.05 to 3.26 ± 0.13. Experimental α/β-ratios ranged from 6.9 ± 1.1 Gy to 44.3 ± 7.2 Gy and increased strongly with LET. Including all available data, comparison with model-predictions revealed that (i) LEM IV agrees better in the SOBP, while LEM I fits better in the entrance region, (ii) LEM IV describes the slope of the RBE within the SOBP better than LEM I, and (iii) in contrast to the strong LET-dependence, the RBE-deviations depend only weakly on fractionation within the measured range. Conclusions This study extends the available RBE data base to significantly lower fractional doses and performes detailed tests of the RBE-models LEM I and IV. In this comparison, LEM IV agrees better with the experimental data in the SOBP than LEM I. While this could support a model replacement in treatment planning, careful dosimetric analysis is required for the individual patient to evaluate potential clinical consequences.

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Predicting the Relative Biological Effectiveness of Carbon Ion Radiation Therapy Beams Using the Mechanistic Repair-Misrepair-Fixation (RMF) Model and Nuclear Fragment Spectra

International Journal of Radiation Oncology*Biology*Physics ◽

10.1016/j.ijrobp.2014.05.2434 ◽

2014 ◽

Vol 90 (1) ◽

pp. S849

Author(s):

F. Kamp ◽

G. Cabal ◽

A. Mairani ◽

K. Parodi ◽

J.J. Wilkens ◽

...

Keyword(s):

Radiation Therapy ◽

Relative Biological Effectiveness ◽

Carbon Ion ◽

Nuclear Fragment ◽

Biological Effectiveness ◽

Rmf Model

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Temporal Lobe Reactions After Radiotherapy With Carbon Ions: Incidence and Estimation of the Relative Biological Effectiveness by the Local Effect Model

International Journal of Radiation Oncology*Biology*Physics ◽

10.1016/j.ijrobp.2010.03.001 ◽

2011 ◽

Vol 80 (3) ◽

pp. 815-823 ◽

Cited By ~ 38

Author(s):

Ingmar Schlampp ◽

Christian P. Karger ◽

Oliver Jäkel ◽

Michael Scholz ◽

Bernd Didinger ◽

...

Keyword(s):

Temporal Lobe ◽

Relative Biological Effectiveness ◽

Local Effect ◽

Carbon Ions ◽

Effect Model ◽

Biological Effectiveness

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Mechanistic Modeling of the Relative Biological Effectiveness of Photon, Proton, and Carbon Ion Radiation Therapy

International Journal of Radiation Oncology*Biology*Physics ◽

10.1016/j.ijrobp.2010.07.149 ◽

2010 ◽

Vol 78 (3) ◽

pp. S48-S49 ◽

Cited By ~ 1

Author(s):

D.J. Carlson ◽

R.D. Stewart

Keyword(s):

Radiation Therapy ◽

Relative Biological Effectiveness ◽

Mechanistic Modeling ◽

Carbon Ion ◽

Biological Effectiveness

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Rectum Dose Constraints for Carbon Ion Therapy: Relative Biological Effectiveness Model Dependence in Relation to Clinical Outcomes

Cancers ◽

10.3390/cancers12010046 ◽

2019 ◽

Vol 12 (1) ◽

pp. 46 ◽

Cited By ~ 1

Author(s):

Kyungdon Choi ◽

Silvia Molinelli ◽

Stefania Russo ◽

Alfredo Mirandola ◽

Maria Rosaria Fiore ◽

...

Keyword(s):

Clinical Outcomes ◽

Normal Tissue ◽

Relative Biological Effectiveness ◽

Prostate Adenocarcinoma ◽

Local Effect ◽

Rectal Toxicity ◽

Carbon Ion ◽

Sacral Chordoma ◽

Biological Effectiveness ◽

Late Rectal Toxicity

The clinical application of different relative biological effectiveness (RBE) models for carbon ion RBE-weighted dose calculation hinders a global consensus in defining normal tissue constraints. This work aims to update the local effect model (LEM)-based constraints for the rectum using microdosimetric kinetic model (mMKM)-defined values, relying on RBE translation and the analysis of long-term clinical outcomes. LEM-optimized plans of treated patients, having suffered from prostate adenocarcinoma (n = 22) and sacral chordoma (n = 41), were recalculated with the mMKM using an in-house developed tool. The relation between rectum dose-volume points in the two RBE systems (DLEM|v and DMKM|v) was fitted to translate new LEM-based constraints. Normal tissue complication probability (NTCP) values, predicting late rectal toxicity, were obtained by applying published parameters. No late rectal toxicity events were reported within the patient cohort. The rectal toxicity outcome was confirmed using dosimetric analysis: DMKMVHs lay largely below original constraints; the translated DLEM|v values were 4.5%, 8.3%, 18.5%, and 35.4% higher than the nominal DMKM|v of the rectum volume, v—1%, 5%, 10% and 20%. The average NTCP value ranged from 5% for the prostate adenocarcinoma, to 0% for the sacral chordoma group. The redefined constraints, to be confirmed prospectively with clinical data, are DLEM|5cc ≤ 61 Gy(RBE) and DLEM|1cc ≤ 66 Gy(RBE).

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