Biological Gain of Carbon-ion Radiotherapy for the Early Response of Tumor Growth Delay and against Early Response of Skin Reaction in Mice

Abstract

The biological effectiveness of carbon ions relative to gamma rays (RBE) was compared between the tumor growth delay and an early skin reaction of syngeneic mice. The RBE was larger for a tumor than skin when irradiated with large doses of high-LET (linear energy transfer) carbon ions. The intra-track damage (a term of a linear quadratic model) of a tumor and skin increased equally with an increase of the LET, while the inter-track damage (beta term) of skin alone increased with the LET. These data provide evidence that high-LET radiotherapy could achieve therapeutic gain by minimizing the difference in response to fractionated irradiation between the tumor and normal tissue.

Designing a ridge filter based on a mouse foot skin reaction to spread out Bragg-peaks for carbon-ion radiotherapy

“…This implies that the LET-dependent increase of the alpha values may be independent of the cell/tissue types, while that of beta largely depends on these types. In fact, the LET-dependent increase of the beta values was also observed in our previous study in which the mouse skin reaction of legs, not foot, received fractionated doses of carbon ions spread out by a ridge filter designed based on HSG cell-kills [14]. It should be mentioned that the radiation doses used for cell survivals were below 8 Gy for photon while those used for the skin reaction were larger than 40 Gy (Fig.…”

High‐dose proton therapy and carbon‐ion therapy for stage I nonsmall cell lung cancer

“…An alternative to and possibly better treatment option than x-ray stereotactic radiotherapy is particle radiotherapy, and a comparison among these treatment modalities should be performed with respect to physical dose distribution and biological effectiveness. [8][9][10] As our facility does not perform x-ray stereotactic radiotherapy, we could not directly compare the dose distribution of particle radiotherapy with that of x-ray stereotactic radiotherapy. Generally speaking, unnecessary irradiation of the mediastinum and contralateral lung can be minimized with particle radiotherapy; the dose conformity at the target site may be better for x-ray stereotactic radiotherapy when using noncoplanar beams.…”

“…10,19,[25][26][27] However, carbon-ion therapy is more efficient against hypoxic tumor cells than x-ray radiation. The biological effects of proton irradiation have not been completely clarified, and many clinicians think that the clinical RBE of proton irradiation is higher than 1.1.…”

“…8,9 In addition, carbon-ion beams have high relative biological effectiveness, so a therapeutic gain can be expected. 10 Therefore, particle therapy can potentially deliver a higher dose to the primary tumor, leading to improved local tumor control, while simultaneously decreasing the irradiated volume and doses delivered to the surrounding critical organs such as normal lung tissue, heart, esophagus, spinal cord, and mediastinum. In April 2001, the Hyogo Ion Beam Medical Center became the first institution in the world to provide both proton therapy and carbon-ion therapy.…”

[11C]Gefitinib ([11C]Iressa): Radiosynthesis, In Vitro Uptake, and In Vivo Imaging of Intact Murine Fibrosarcoma

“…The tumor cells, originally extracted from naturally occurred fibrosarcoma-bearing mice (NFSa), have been preserved and cultivated in our institute for the past two decades [26]. NFSa cells have become standard cells for assessing the effect of CIRT in rodents in our institute [27][28][29]. A large number of results regarding the effect of CIRT on NFSa-bearing mice have been acquired.…”