Compatibility of the Linear-Quadratic Formalism and Biologically Effective Dose Concept to High-Dose-Per-Fraction Irradiation in a Murine Tumor

Otsuka, Shinya; Shibamoto, Yuta; Iwata, Hiromitsu; Murata, Rumi; Sugie, Chikao; Ito, Masato; Ogino, Hiroyuki

doi:10.1016/j.ijrobp.2011.05.034

Cited by 44 publications

(30 citation statements)

References 26 publications

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“…The exact calculation method to obtain the proper SDE of 14 Gy in three-fraction radiotherapy has still not yet been established [24]. Animal experiments have shown that equivalent single doses for two or three fractions calculated from the L–Q formula were lower than the actual measured doses by 21–31% [25]. However, the accumulation of clinical data regarding the use of the V14, which can be converted for proper SDE in the future, may support the creation of an ideal calculation method for converting to SDE from hypofractionation.…”

Section: Discussionmentioning

confidence: 99%

Three-fraction CyberKnife radiotherapy for brain metastases in critical areas: referring to the risk evaluating radiation necrosis and the surrounding brain volumes circumscribed with a single dose equivalence of 14 Gy (V14)

Inoué¹,

Seto²,

Nozaki³

et al. 2013

Journal of Radiation Research

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The efficacy and toxicity of three-fraction CyberKnife radiotherapy were evaluated in patients with brain metastases in critical areas. One hundred and fifty-nine metastases in 145 patients including tumors >10 cm3 were treated with three-fraction CyberKnife radiotherapy with a median marginal dose of 27 Gy at a median prescribed isodose of 60%. Changes in the neurological manifestations, local tumor control and adverse effects were investigated after treatment. The surrounding brain volumes circumscribed with 23.1 Gy (single dose equivalence of 14 Gy: V14) were measured to evaluate the risk of adverse effects. Neurological manifestations, such as motor weakness, visual disturbances and aphasia improved in 26 of 97 patients (26.8%). Local tumor control was obtained in 137 of 143 metastases (95.8%) during a median follow-up of 7 months. Nine patients had symptomatic edema and three of them (2.1%) required surgical resection because of radiation necrosis. The V14 of these patients was 4.6–31.5 cm3. There were 35 lesions with a V14 of 7 cm3 or more and three of them developed extensive brain edema due to radiation necrosis. None of the patients with a V14 of <7 cm3 exhibited edema requiring an operation. We therefore conclude that a high rate of local tumor control and low rates of complications are obtained after three-fraction CyberKnife radiotherapy for metastases in critical areas. The V14 of the surrounding brain therefore seems to be a useful indicator for the risk evaluation of radiation necrosis in patients with larger metastases.

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Section: Discussionmentioning

confidence: 99%

Three-fraction CyberKnife radiotherapy for brain metastases in critical areas: referring to the risk evaluating radiation necrosis and the surrounding brain volumes circumscribed with a single dose equivalence of 14 Gy (V14)

Inoué¹,

Seto²,

Nozaki³

et al. 2013

Journal of Radiation Research

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“…This mathematical tool was developed to estimate radiation damage on normal (and neoplastic tissue), and has proved useful for designing and comparing effects of new fractionation protocols (48). The LQ-model is suggested valid up to 8–10 Gy per fraction (49), but considered inappropriate for the high-dose regimens delivered by SRS and (lung) SART (50), presumably underestimating tumor control in the high-dose range (51, 52). Therefore, based on the recent success and widespread use of ablative RT, adapted tools for comparing dose and fractionation are being discussed (53–56).…”

Section: The Evolution Of Radiation Therapy and Treatment Regimensmentioning

confidence: 99%

Radiotherapy and the Tumor Stroma: The Importance of Dose and Fractionation

2014

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Ionizing radiation is a non-specific but highly effective way to kill malignant cells. However, tumor recurrence sustained by a minor fraction of surviving tumor cells is a commonplace phenomenon caused by the activation of both cancer cell intrinsic resistance mechanisms, and also extrinsic intermediaries of therapy resistance, represented by non-malignant cells and structural components of the tumor stroma. The improved accuracy offered by advanced radiotherapy (RT)-technology permits reduced volume of healthy tissue in the irradiated field, and has been triggering an increase in the prescription of high-dose oligofractionated regimens in the clinics. Given the remarkable clinical success of high-dose RT and the current therapeutic shift occurring in the field, in this review we revise the existing knowledge on the effects that different radiation regimens exert on the different compartments of the tumor microenvironment, and highlight the importance of anti-tumor immunity and other tumor cell extrinsic mechanisms influencing therapeutic responses to high-dose radiation.

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“…In a recent review, Shibamoto et al . [5] stated that the LQ model might be applicable up to a fractional dose approximately twofold the α/β ratio. The basis for this statement was as follows.…”

Section: Discussionmentioning

confidence: 99%

Applicability of the linear-quadratic model to single and fractionated radiotherapy schedules: an experimental study

Miyakawa

Shibamoto

Otsuka

et al. 2013

Journal of Radiation Research

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The aim of this study was to examine the applicability of the linear-quadratic (LQ) model to single and fractionated irradiation in EMT6 cells. First, the α/β ratio of the cells was determined from single-dose experiments, and a biologically effective dose (BED) for 20 Gy in 10 fractions (fr) was calculated. Fractional doses yielding the same BED were calculated for 1-, 2-, 3-, 4-, 5-, 7-, 15- and 20-fraction irradiation using LQ formalism, and then irradiation with these schedules was actually given. Cell survival was determined by a standard colony assay. Differences in cell survival between pairs of groups were compared by t-test. The α/β ratio of the cells was 3.18 Gy, and 20 Gy in 10 fr corresponded to a BED3.18 of 32.6 Gy. The effects of 7-, 15- and 20-fraction irradiation with a BED3.18 of 32.6 Gy were similar to those of the 10-fraction irradiation, while the effects of 1- to 5-fraction irradiation were lower. In this cell line, the LQ model was considered applicable to 7- to 20-fraction irradiation or doses per fraction of 2.57 Gy or smaller. The LQ model might be applicable in the dose range below the α/β ratio.

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Compatibility of the Linear-Quadratic Formalism and Biologically Effective Dose Concept to High-Dose-Per-Fraction Irradiation in a Murine Tumor

Cited by 44 publications

References 26 publications

Three-fraction CyberKnife radiotherapy for brain metastases in critical areas: referring to the risk evaluating radiation necrosis and the surrounding brain volumes circumscribed with a single dose equivalence of 14 Gy (V14)

Three-fraction CyberKnife radiotherapy for brain metastases in critical areas: referring to the risk evaluating radiation necrosis and the surrounding brain volumes circumscribed with a single dose equivalence of 14 Gy (V14)

Radiotherapy and the Tumor Stroma: The Importance of Dose and Fractionation

Applicability of the linear-quadratic model to single and fractionated radiotherapy schedules: an experimental study

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