Stereotactic Body Radiotherapy

Cho, L. Chinsoo; Fonteyne, Valérie; Deneve, W.; Lo, Simon S.; Timmerman, Robert

doi:10.1007/174_2011_263

Cited by 3 publications

(3 citation statements)

References 165 publications

(176 reference statements)

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“…Likewise, SRS of cranial lesions and extracranial tumors with 15 to 25 Gy in a single dose has been shown to result in very high rates of local control (3–5). The number of viable tumor cells in 1 g of tumors has been estimated to be approximately 10 8 to 10 9 (30), implying that 8 to 9 logs of tumor cells must be sterilized for the control of 1 g of tumors.…”

Section: Discussionmentioning

confidence: 99%

Indirect Tumor Cell Death After High-Dose Hypofractionated Irradiation: Implications for Stereotactic Body Radiation Therapy and Stereotactic Radiation Surgery

Song

Lee

Griffin

et al. 2015

International Journal of Radiation Oncology*Biology*Physics

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132

103

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Summary In experimental mouse tumors, high-dose irradiation in a single fraction caused progressive increase in tumor cell death in 2 to 5 days. Such delayed tumor cell deaths appeared to be due to radiation-induced deterioration of intratumor microenvironment characterized by profound reduction of blood perfusion and increase in hypoxia. Similar secondary and indirect cell death may play an important role in clinical stereotactic body radiation therapy and stereotactic radiation surgery. Purpose The purpose of this study was to reveal the biological mechanisms underlying stereotactic body radiation therapy (SBRT) and stereotactic radiation surgery (SRS). Methods and Materials FSaII fibrosarcomas grown subcutaneously in the hind limbs of C3H mice were irradiated with 10 to 30 Gy of X rays in a single fraction, and the clonogenic cell survival was determined with in vivo—in vitro excision assay immediately or 2 to 5 days after irradiation. The effects of radiation on the intratumor microenvironment were studied using immunohistochemical methods. Results After cells were irradiated with 15 or 20 Gy, cell survival in FSaII tumors declined for 2 to 3 days and began to recover thereafter in some but not all tumors. After irradiation with 30 Gy, cell survival declined continuously for 5 days. Cell survival in some tumors 5 days after 20 to 30 Gy irradiation was 2 to 3 logs less than that immediately after irradiation. Irradiation with 20 Gy markedly reduced blood perfusion, upregulated HIF-1α, and increased carbonic anhydrase-9 expression, indicating that irradiation increased tumor hypoxia. In addition, expression of VEGF also increased in the tumor tissue after 20 Gy irradiation, probably due to the increase in HIF-1α activity. Conclusions Irradiation of FSaII tumors with 15 to 30 Gy in a single dose caused dose-dependent secondary cell death, most likely by causing vascular damage accompanied by deterioration of intratumor microenvironment. Such indirect tumor cell death may play a crucial role in the control of human tumors with SBRT and SRS.

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Section: Discussionmentioning

confidence: 99%

Indirect Tumor Cell Death After High-Dose Hypofractionated Irradiation: Implications for Stereotactic Body Radiation Therapy and Stereotactic Radiation Surgery

Song

Lee

Griffin

et al. 2015

International Journal of Radiation Oncology*Biology*Physics

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132

103

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“…An increasing number of cancer patients are treated with stereotactic body radiation therapy (SBRT) and stereotactic radiation surgery (SRS) in recent years [ 1 2 3 4 5 6 ]. The significant paradigm shift from the conventional multi-fractionated radiotherapy to hypo-fractionated SBRT and SRS has been possible owing to the remarkable technological advances for tumor imaging and also for radiation delivery systems.…”

Section: Introductionmentioning

confidence: 99%

Radiobiological mechanisms of stereotactic body radiation therapy and stereotactic radiation surgery

et al. 2015

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Despite the increasing use of stereotactic body radiation therapy (SBRT) and stereotactic radiation surgery (SRS) in recent years, the biological base of these high-dose hypo-fractionated radiotherapy modalities has been elusive. Given that most human tumors contain radioresistant hypoxic tumor cells, the radiobiological principles for the conventional multiple-fractionated radiotherapy cannot account for the high efficacy of SBRT and SRS. Recent emerging evidence strongly indicates that SBRT and SRS not only directly kill tumor cells, but also destroy the tumor vascular beds, thereby deteriorating intratumor microenvironment leading to indirect tumor cell death. Furthermore, indications are that the massive release of tumor antigens from the tumor cells directly and indirectly killed by SBRT and SRS stimulate anti-tumor immunity, thereby suppressing recurrence and metastatic tumor growth. The reoxygenation, repair, repopulation, and redistribution, which are important components in the response of tumors to conventional fractionated radiotherapy, play relatively little role in SBRT and SRS. The linear-quadratic model, which accounts for only direct cell death has been suggested to overestimate the cell death by high dose per fraction irradiation. However, the model may in some clinical cases incidentally do not overestimate total cell death because high-dose irradiation causes additional cell death through indirect mechanisms. For the improvement of the efficacy of SBRT and SRS, further investigation is warranted to gain detailed insights into the mechanisms underlying the SBRT and SRS.

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“…SBRT has been established as safe and efficacious for early stage lung cancer and selected patients with oligometastatic cancer [62, 63], and it has also been explored in the treatment of prostate cancer [43–46, 50]. SBRT can be delivered safely using any of several commercially available treatment systems.…”

Section: Stereotactic Body Radiation Therapy For Prostate Cancermentioning

confidence: 99%

Hypofractionated External-Beam Radiotherapy for Prostate Cancer

Cho

Timmerman

Kavanagh³

2013

Prostate Cancer

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There are radiobiological rationales supporting hypofractionated radiotherapy for prostate cancer. The recent advancements in treatment planning and delivery allow sophisticated radiation treatments to take advantage of the differences in radiobiology of prostate cancer and the surrounding normal tissues. The preliminary results from clinical studies indicate that abbreviated fractionation programs can result in successful treatment of localized prostate cancer without escalation of late toxicity.

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Stereotactic Body Radiotherapy

Cited by 3 publications

References 165 publications

Indirect Tumor Cell Death After High-Dose Hypofractionated Irradiation: Implications for Stereotactic Body Radiation Therapy and Stereotactic Radiation Surgery

Indirect Tumor Cell Death After High-Dose Hypofractionated Irradiation: Implications for Stereotactic Body Radiation Therapy and Stereotactic Radiation Surgery

Radiobiological mechanisms of stereotactic body radiation therapy and stereotactic radiation surgery

Hypofractionated External-Beam Radiotherapy for Prostate Cancer

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