Dose equivalents of tumour repopulation during radiotherapy: the potential for confusion.

Dale, Roger G.; Jones, Bleddyn; Sinclair, J A

doi:10.1259/bjr.73.872.11026867

Cited by 14 publications

(6 citation statements)

References 6 publications

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“…The animals were kept anesthetized (1.5% isoflurane, 30% O 2 ) during irradiation. The hypofractionated doses were determined by a calculation based on the linear quadratic formula for cell survival to calculate the “standard equivalent dose (SED)” for planning hypofractionated stereotactic radiotherapy (34, 35). The fractions of 4.8 Gy × 10, 5.7 Gy × 8, 7 Gy × 6 and 9.3 Gy × 4 approximate the biological effect of a 70 Gy (35 fractions of 2 Gy each) dose plan for 9L and C6 tumors (36).…”

Section: Methodsmentioning

confidence: 99%

Assessment of the Changes in 9L and C6 Glioma pO₂by EPR Oximetry as a Prognostic Indicator of Differential Response to Radiotherapy

Hou

Mupparaju²,

Lariviere

et al. 2013

Radiation Research

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Tumor hypoxia impedes the outcome of radiotherapy. As the extent of hypoxia in solid tumors varies during the course of radiotherapy, methods that can provide repeated assessment of tumor pO2 such as EPR oximetry may enhance the efficacy of radiotherapy by scheduling irradiations when the tumors are oxygenated. The repeated measurements of tumor pO2 may also identify responders, and thereby facilitate the design of better treatment plans for nonresponding tumors. We have investigated the temporal changes in the ectopic 9L and C6 glioma pO2 irradiated with single radiation doses less than 10 Gy by EPR oximetry. The 9L and C6 tumors were hypoxic with pO2 of approximately 5–9 mmHg. The pO2 of C6 tumors increased significantly with irradiation of 4.8–9.3 Gy. However, no change in the 9L tumor pO2 was observed. The irradiation of the oxygenated C6 tumors with a second dose of 4.8 Gy resulted in a significant delay in growth compared to hypoxic and 2 Gy × 5 treatment groups. The C6 tumors with an increase in pO2 of greater than 50% from the baseline of irradiation with 4.8 Gy (responders) had a significant tumor growth delay compared to nonresponders. These results indicate that the ectopic 9L and C6 tumors responded differently to radiotherapy. We propose that the repeated measurement of the oxygen levels in the tumors during radiotherapy can be used to identify responders and to design tumor oxygen guided treatment plans to improve the outcome.

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Section: Methodsmentioning

confidence: 99%

Assessment of the Changes in 9L and C6 Glioma pO₂by EPR Oximetry as a Prognostic Indicator of Differential Response to Radiotherapy

Hou

Mupparaju²,

Lariviere

et al. 2013

Radiation Research

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show abstract

“…The choice of the 9.3 Gy dose was determined by a calculation based on the linear quadratic formula for cell survival that calculates “standard equivalent dose (SED)” for planning hypofractionated stereotactic radiotherapy (24, 25). The dose of 9.3 Gy × 4 fractions approximates the biological effect of a 70 Gy dose fractionation plan for F98 gliomas.…”

Section: Methodsmentioning

confidence: 99%

Effect of Hyperoxygenation on Tissue pO2 and Its Effect on Radiotherapeutic Efficacy of Orthotopic F98 Gliomas

Khan

Mupparaju

Hekmatyar

et al. 2010

International Journal of Radiation Oncology*Biology*Physics

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Purpose-Lack of methods for repeated assessment of tumor pO 2 limits the ability to test and optimize hypoxia modifying procedures being developed for clinical applications. We report the repeated measurements of orthotopic F98 tumor pO 2 , and relate this to the effect of carbogen inhalation on tumor growth when combined with hypofractionated radiotherapy. Methods and Materials-ElectronParamagnetic Resonance (EPR) oximetry was used for repeated measurements of tumor and contralateral brain pO 2 in rats during 30% O 2 and carbogen inhalation for 5 consecutive days. The T 1 enhanced volumes and diffusion coefficients of the tumors were assessed by MRI. The tumors were irradiated with 9.3 Gy × 4 in rats breathing 30% O 2 or carbogen to determine the effect on tumor growth.Results-The pre-treatment F98 tumor pO 2 varied between 8 -16 mmHg, while the contralateral brain had 41 -45 mmHg pO 2 during repeated measurements. Carbogen breathing led to a significant increase in tumor and contralateral brain pO 2 ; however this effect declined over days. Irradiation of the tumors in rats breathing carbogen resulted in a significant decrease in tumor growth and an increase in the diffusion coefficient measured by MRI. Conclusions-The results provide quantitative measurements of the effect of carbogen inhalation on intracerebral tumor pO 2 and its consequence on therapeutic outcome. Such direct repeated pO 2 measurements by EPR oximetry can provide temporal information that could be used to improve therapeutic outcome by scheduling doses at times of improved tumor oxygenation. EPR oximetry is currently being tested for clinical applications.

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“…Whereas cell repopulation is usually ignored in the LQ model for conventional external beam radiotherapy or HF-SRS due to the relatively shorter radiation delivery time and a shorter interval between two consecutive deliveries compared to cell repair time, because of the considerably longer treatment interval between two Staged-SRS sessions, tumor cell survival would be undesirably increased due to cell repopulation. In order to reflect the potential decrease in tumor local control, a subtractive repopulation factor ( 17 , 21 ) was included in the calculation of BED to account for potential tumor proliferation during the intentional interval. Therefore, the total BED delivered to a tumor voxel of a complete Staged-SRS treatment course could be calculated as…”

Section: Methodsmentioning

confidence: 99%

Evaluation of Biological Effective Dose in Gamma Knife Staged Stereotactic Radiosurgery for Large Brain Metastases

et al. 2022

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ObjectiveGamma knife (GK) staged stereotactic radiosurgery (Staged-SRS) has become an effective treatment option for large brain metastases (BMs); however, it has been challenging to evaluate the total dose because of tumor shrinkage between two staged sessions. This study aims to evaluate total biological effective dose (BED) in Staged-SRS, and to compare the BED with those in single-fraction SRS (SF-SRS) and hypo-fractionated SRS (HF-SRS).MethodsPatients treated with GK Staged-SRS at a single institution were retrospectively included. The dose delivered in two sessions of Staged-SRS was summed using the deformable image registration. Each patient was replanned for SF-SRS and HF-SRS. The total BEDs were computed using the linear-quadratic model. Tumor BED98% and brain V84Gy2, equivalent to V12Gy in SF-SRS, were compared between SF-SRS, HF-SRS, and Staged-SRS plans with the Wilcoxon test.ResultsTwelve patients with 24 BMs treated with GK Staged-SRS were identified. We observed significant differences (p < 0.05) in tumor BED98% but comparable brain V84Gy2 (p = 0.677) between the Staged-SRS and SF-SRS plans. No dosimetric advantages of Staged-SRS over HF-SRS were observed. Tumor BED98% in the HF-SRS plans were significantly higher than those in the Staged-SRS plans (p < 0.05). Despite the larger PTVs, brain V84Gy2 in the HF-SRS plans remained lower (p < 0.05).ConclusionWe presented an approach to calculate the composite BEDs delivered to both tumor and normal brain tissue in Staged-SRS. Compared to SF-SRS, Staged-SRS delivers a higher dose to tumor but maintains a comparable dose to normal brain tissue. Our results did not show any dosimetric advantages of Staged-SRS over HF-SRS.

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Dose equivalents of tumour repopulation during radiotherapy: the potential for confusion.

Cited by 14 publications

References 6 publications

Assessment of the Changes in 9L and C6 Glioma pO₂by EPR Oximetry as a Prognostic Indicator of Differential Response to Radiotherapy

Assessment of the Changes in 9L and C6 Glioma pO₂by EPR Oximetry as a Prognostic Indicator of Differential Response to Radiotherapy

Effect of Hyperoxygenation on Tissue pO2 and Its Effect on Radiotherapeutic Efficacy of Orthotopic F98 Gliomas

Evaluation of Biological Effective Dose in Gamma Knife Staged Stereotactic Radiosurgery for Large Brain Metastases

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Dose equivalents of tumour repopulation during radiotherapy: the potential for confusion.

Cited by 14 publications

References 6 publications

Assessment of the Changes in 9L and C6 Glioma pO2by EPR Oximetry as a Prognostic Indicator of Differential Response to Radiotherapy

Assessment of the Changes in 9L and C6 Glioma pO2by EPR Oximetry as a Prognostic Indicator of Differential Response to Radiotherapy

Effect of Hyperoxygenation on Tissue pO2 and Its Effect on Radiotherapeutic Efficacy of Orthotopic F98 Gliomas

Evaluation of Biological Effective Dose in Gamma Knife Staged Stereotactic Radiosurgery for Large Brain Metastases

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Assessment of the Changes in 9L and C6 Glioma pO₂by EPR Oximetry as a Prognostic Indicator of Differential Response to Radiotherapy

Assessment of the Changes in 9L and C6 Glioma pO₂by EPR Oximetry as a Prognostic Indicator of Differential Response to Radiotherapy