Evaluation of SCCVII tumor cell survival in clamped and non-clamped solid tumors exposed to carbon-ion beams in comparison to X-rays.

The aim of this study was to measure the RBE (relative biological effectiveness) and OER (oxygen enhancement ratio) for survival of cells within implanted solid tumors following exposure to 290MeV/nucleon carbon-ion beams or X-rays. Squamous cell carcinoma cells (SCCVII) were transplanted into the right hind legs of syngeneic C3H male mice. Irradiation with either carbon-ion beams with a 6-cm spread-out Bragg peak (SOBP, at 46 and 80keV/µm) or X-rays was delivered to 5-mm or less diameter tumors. We defined three different oxygen statuses of the irradiated cells. Hypoxic and normoxic conditions in tumors were produced by clamping or not clamping the leg to avoid blood flow. Furthermore, single-cell suspensions were prepared from non-irradiated tumors and directly used to determine the radiation response of aerobic cells. Single-cell suspensions (aerobic condition) were fully air-saturated. Single-cell suspensions were prepared from excised and trypsinized tumors, and were used for in vivo-in vitro colony formation assays to obtain cell survival curves. The RBE values increased with increasing LET in SOBP beams. The maximum RBE values in three different oxygen conditions; hypoxic tumor, normoxic tumor and aerobic cells, were 2.16, 1.76 and 1.66 at an LET of 80keV/µm, respectively. After X-ray irradiation the OERh/n values (hypoxic tumor/normoxic tumor) were lower than the OERh/a (hypoxic tumor/aerobic cells), and were 1.87±0.13 and 2.52±0.11, respectively. The OER values of carbon-ion irradiated samples were small in comparison to those of X-ray irradiated samples. However, no significant changes of the OER at proximal and distal positions within the SOBP carbon-ion beams were observed. To conclude, we found that the RBE values for cell survival increased with increasing LET and that the OER values changed little with increasing LET within the SOBP carbon-ion beams.

Dose- and LET-dependent changes in mouse skin contracture up to a year after either single dose or fractionated doses of carbon ion or gamma rays.

Time dependence of relative biological effectiveness (RBE) of carbon ions for skin damage was investigated to answer the question of whether the flat distribution of biological doses within a Spread-Out Bragg peak (SOBP) which is designed based on in vitro cell kill could also be flat for in vivo late responding tissue. Two spots of Indian ink intracutaneously injected into the legs of C3H mice were measured by calipers. An equieffective dose to produce 30% skin contraction was calculated from a dose-response curve and used to calculate the RBE of carbon ion beams. We discovered skin contraction progressed after irradiation and then reached a stable/slow progression phase. Equieffective doses decreased with time and the decrease was most prominent for gamma rays and least prominent for 100 keV/µm carbon ions. Survival parameter of alpha but not beta in the linear-quadratic model is closely related to the RBE of carbon ions. Biological doses within the SOBP increased with time but their distribution was still flat up to 1 year after irradiation. The outcomes of skin contraction studies suggest that (i) despite the higher RBE for skin contracture after carbon ions compared to gamma rays, gamma rays can result in a more severe late effect of skin contracture. This is due to the carbon effect saturating at a lower dose than gamma rays, and (ii) the biological dose distribution throughout the SOBP remains approximately the same even one year after exposure.

A Potential Renewed Use of Very Heavy Ions for Therapy: Neon Minibeam Radiation Therapy.

(1) Background: among all types of radiation, very heavy ions, such as Neon (Ne) or Argon (Ar), are the optimum candidates for hypoxic tumor treatments due to their reduced oxygen enhancement effect. However, their pioneering clinical use in the 1970s was halted due to severe side effects. The aim of this work was to provide a first proof that the combination of very heavy ions with minibeam radiation therapy leads to a minimization of toxicities and, thus, opening the door for a renewed use of heavy ions for therapy; (2) Methods: mouse legs were irradiated with either Ne MBRT or Ne broad beams at the same average dose. Skin toxicity was scored for a period of four weeks. Histopathology evaluations were carried out at the end of the study; (3) Results: a significant difference in toxicity was observed between the two irradiated groups. While severe da-mage, including necrosis, was observed in the broad beam group, only light to mild erythema was present in the MBRT group; (4) Conclusion: Ne MBRT is significantly better tolerated than conventional broad beam irradiations.

Apparent absence of a proton beam dose rate effect and possible differences in RBE between Bragg peak and plateau.

PURPOSE: Respiration-gated irradiation for a moving target requires a longer time to deliver single fraction in proton radiotherapy (PRT). Ultrahigh dose rate (UDR) proton beam, which is 10-100 times higher than that is used in current clinical practice, has been investigated to deliver daily dose in single breath hold duration. The purpose of this study is to investigate the survival curve and relative biological effectiveness (RBE) of such an ultrahigh dose rate proton beam and their linear energy transfer (LET) dependence. METHODS: HSG cells were irradiated by a spatially and temporally uniform proton beam at two different dose rates: 8 Gy/min (CDR, clinical dose rate) and 325 Gy/min (UDR, ultrahigh dose rate) at the Bragg peak and 1.75 (CDR) and 114 Gy/min (UDR) at the plateau. To study LET dependence, the cells were positioned at the Bragg peak, where the absorbed dose-averaged LET was 3.19 keV/microm, and at the plateau, where it was 0.56 keV/microm. After the cell exposure and colony assay, the measured data were fitted by the linear quadratic (LQ) model and the survival curves and RBE at 10% survival were compared. RESULTS: No significant difference was observed in the survival curves between the two proton dose rates. The ratio of the RBE for CDR/UDR was 0.98 +/- 0.04 at the Bragg peak and 0.96 +/- 0.06 at the plateau. On the other hand, Bragg peak/plateau RBE ratio was 1.15 +/- 0.05 for UDR and 1.18 +/- 0.07 for CDR. CONCLUSIONS: Present RBE can be consistently used in treatment planning of PRT using ultrahigh dose rate radiation. Because a significant increase in RBE toward the Bragg peak was observed for both UDR and CDR, further evaluation of RBE enhancement toward the Bragg peak and beyond is required.

Microscope-assisted reduction clitoroplasty used to treat two patients with clitoromegaly.

We report 2 cases of clitoromegaly, 1 in a patient with true hermaphroditism, and the other in a patient with adrenogenital syndrome. Both were treated surgically with reduction clitoroplasty. There are 3 different clitoroplasty procedures: clitorectomy, clitoral recession, and reduction clitoroplasty. Reduction clitoroplasty with preservation of the neurovascular bundle is considered superior in terms of formation of the external genitals and sensation. However, the disadvantages are that detachment of the neurovascular bundle from the clitoral shaft is difficult and that there is a high possibility of sensory and blood flow disorders in the clitoris. In an attempt to achieve safe and reliable surgical manipulation, we used a surgical microscope (OPMI 6-SDFC, Carl Zeiss Surgical GmbH, magnification x8) to detach the neurovascular bundle from the clitoral shaft in our 2 patients. Our impression is that our efforts were extremely effective. Furthermore, our experience leads us to believe that the procedure for neurovascular bundle detachment required in reduction clitoroplasty is not particularly difficult if performed with a surgical microscope by a plastic surgeon who regularly performs microsurgery. Because the procedure can be performed simply and safely, we believe that reduction clitoroplasty with preservation of the neurovascular bundle is the best overall of the 3 clitoroplasty procedures.

The FGF1/CPP-C chimera protein protects against intestinal adverse effects of C-ion radiotherapy without exacerbating pancreatic carcinoma.

BACKGROUND AND PURPOSE: Carbon ion (C-ion) beams are concentrated to irradiate pancreatic carcinoma in the upper abdomen; however, this radiotherapy potentially causes adverse reactions in the gastrointestinal tract. FGF1 is a candidate radioprotector for radiation-induced intestinal damage, but may promote the malignancy of pancreatic cancer. An FGF1/CPP-C chimeric protein was created to enhance the intracellular signaling mode of FGF1 instead of FGFR signaling. The present study investigated the effects of FGF1/CPP-C on the intestinal adverse reactions of C-ion radiotherapy as well as its influence on the malignancy of pancreatic cancer. MATERIALS AND METHODS: FGF1/CPP-C was administered intraperitoneally to BALB/c mice without heparin 12 h before total body irradiation (TBI) with low-LET C-ion (17 keV/µm) at 6-8 Gy. Several radioprotective effects were examined in the jejunum. The invasion and migration of the human pancreatic carcinoma cell lines MIAPaCa-2 and PANC-1 were assessed using Boyden chambers after cultures with FGF1/CPP-C. RESULTS: The FGF1/CPP-C treatment promoted crypt survival after C-ion irradiation at 7-8 Gy significantly more than the FGF1 treatment. FGF1/CPP-C also inhibited C-ion radiotherapy-induced apoptosis and reduced γH2AX foci in crypt cells more than FGF1. However, FGF1/CPP-C inhibited the downstream signaling pathways of FGFRs and suppressed the activation of cell-cycle regulatory molecules in the intestine until 4 h after TBI. Furthermore, IEC6 cells were arrested in G2M after cultures with FGF1/CPP-C or FGF1, suggesting that DNA repair after irradiation is promoted by FGF1/CPP-C-induced G2M arrest. In contrast, FGF1/CPP-C appeared to be internalized into MIAPaCa-2 and PANC-1 cells more efficiently than FGF1. Therefore, FGF1/CPP-C reduced the in vitro proliferation, invasion, and migration of MIAPaCa-2 and PANC-1 cells significantly more than FGF1 through the cellular internalization of FGF1. CONCLUSION: These results suggest that the intracellular signaling mode of FGF1/CPP-C attenuates the intestinal adverse effects of C-ion radiotherapy without enhancing the malignancy of pancreatic carcinoma.

Closed Fracture Diagnosed by Bedside Ultrasonography During Hemodialysis: A Report of Seven Cases and Relevant Clinical Characteristics.

BACKGROUND: Patients undergoing dialysis have a high incidence of fracture, and early diagnosis is important. We report seven cases of closed rib or upper-limb fractures diagnosed by bedside ultrasonography during maintenance hemodialysis sessions and describe relevant clinical characteristics. CASE PRESENTATION: We identified seven patients who were injured by falls in their homes. No injuries occurred on the day of dialysis. Five of the 7 patients did not visit the emergency room. All patients complained of persistent unexplained pain during a regular hemodialysis session. Ultrasonography (US) was performed during dialysis sessions, without any reports of pain. Before US evaluation, the sensitivity of radiography for diagnosis of fracture was 25%, while the sensitivity of US was 100%. Compared with other patients in our clinic, these patients were significantly older and had lower serum albumin concentrations and lower hemodialysis efficiency as determined by Kt/V. They also had a higher incidence of diabetes and a greater need for vasopressors during dialysis. These findings were consistent with the results of previous studies of the characteristics of fractures in dialysis patients. However, blood levels of creatinine, corrected calcium, phosphate, intact parathyroid hormone, and hemoglobin, as well as bone density and blood pressure, after the previous dialysis session were not different. CONCLUSIONS: To our knowledge, this is the first report of closed fracture of superficial bone diagnosed by bedside ultrasonography during a hemodialysis session. Ultrasonography is especially useful for diagnosis in these cases because it is noninvasive and highly accurate. Doctors should determine the differential diagnosis for closed fracture in patients undergoing dialysis, especially in those who are older, have diabetes, and are malnourished, and in those with recent contusions and persistent pain.

Radiobiologic significance of response of intratumor quiescent cells in vivo to accelerated carbon ion beams compared with gamma-rays and reactor neutron beams.

PURPOSE: To clarify the radiosensitivity of intratumor quiescent cells in vivo to accelerated carbon ion beams and reactor neutron beams. METHODS AND MATERIALS: Squamous cell carcinoma VII tumor-bearing mice were continuously given 5-bromo-2'-deoxyuridine to label all intratumor proliferating cells. Next, they received accelerated carbon ion or gamma-ray high-dose-rate (HDR) or reduced-dose-rate (RDR) irradiation. Other tumor-bearing mice received reactor thermal or epithermal neutrons with RDR irradiation. Immediately after HDR and RDR irradiation or 12 h after HDR irradiation, the response of quiescent cells was assessed in terms of the micronucleus frequency using immunofluorescence staining for 5-bromo-2'-deoxyuridine. The response of the total (proliferating plus quiescent) tumor cells was determined from the 5-bromo-2'-deoxyuridine nontreated tumors. RESULTS: The difference in radiosensitivity between the total and quiescent cell populations after gamma-ray irradiation was markedly reduced with reactor neutron beams or accelerated carbon ion beams, especially with a greater linear energy transfer (LET) value. Clearer repair in quiescent cells than in total cells through delayed assay or a decrease in the dose rate with gamma-ray irradiation was efficiently inhibited with carbon ion beams, especially with a greater LET. With RDR irradiation, the radiosensitivity to accelerated carbon ion beams with a greater LET was almost similar to that to reactor thermal and epithermal neutron beams. CONCLUSION: In terms of tumor cell-killing effect as a whole, including quiescent cells, accelerated carbon ion beams, especially with greater LET values, are very useful for suppressing the dependency on the heterogeneity within solid tumors, as well as depositing the radiation dose precisely.

The radiosensitivity of total and quiescent cell populations in solid tumors to 290 MeV/u carbon ion beam irradiation in vivo.

PURPOSE: To clarify the radiosensitivity of intratumor total and quiescent (Q) cells in vivo to accelerated carbon ion beams compared with gamma-ray irradiation. MATERIALS AND METHODS: SCC VII tumor-bearing mice received a continuous administration of 5-bromo-2'-deoxyuridine (BrdU) to label all intratumor proliferating (P) cells. Then they received 290 MeV/u carbon ions or gamma-rays. Immediately or 12 hours after the irradiation, the radiosensitivity of Q cells was assessed in terms of the micronucleus frequency using immunofluorescence staining for BrdU. That of the total (=P+Q) tumor cells was determined from the BrdU non-treated tumors based on the micronucleus frequency and clonogenic cell survival. RESULTS: The apparent difference in radiosensitivity between total and Q cell populations under gamma-ray irradiation was markedly reduced with carbon ion beam, especially with a higher linear energy transfer (LET) value. Clearer repair in Q cells than total cells through delayed assay under gamma-ray irradiation was efficiently inhibited with carbon ion beams, especially with a higher LET. CONCLUSION: In terms of tumor cell-killing effect as a whole, including intratumor Q cells, carbon ion beams, especially with higher LET values, were very useful for suppressing the dependency on the heterogeneity within solid tumors as well as depositing radiation dose precisely.

Responses of total and quiescent cell populations in solid tumors to carbon ion beam irradiation (290 MeV/u) in vivo.

PURPOSE: The aim of this study was to clarify the radiosensitivity of intratumor total cells and quiescent (Q) cells in vivo to accelerated carbon ion beams compared with gamma-ray irradiation. MATERIALS AND METHODS: Squamous cell carcinoma (SCC) VII tumor-bearing mice received continuous administration of 5-bromo-2'-deoxyuridine (BrdU) to label all intratumor proliferating (P) cells. They then were exposed to carbon ions (290 MeV/u) or gamma-rays. Immediately after and 12 h after irradiation, immunofluorescence staining for BrdU was used to assess the response of Q cells in terms of micronucleus frequency. The response of the total (P + Q) tumor cells was determined from the tumors not treated with BrdU. RESULTS: The apparent difference in radiosensitivity between total and Q cell populations under gamma-ray irradiation was markedly reduced with carbon ion beams, especially with a higher linear energy transfer (LET) value. Clearer recovery in Q cells than in total cells through delayed assay under gamma-ray irradiation was efficiently inhibited by carbon ion beams, especially those with a higher LET. CONCLUSION: In terms of the tumor cell-killing effect as a whole, including intratumor Q cells, carbon ion beams, especially with higher LET values, were extremely useful for suppressing the dependence on the heterogeneity within solid tumors as well as depositing the radiation dose precisely.

Antimetastatic Effects of Carbon-Ion Beams on Malignant Melanomas.

The goal of this work was to clarify the effect of carbon-ion beams on reduction of the metastatic potential of malignant melanoma using in vitro and in vivo techniques. We utilized a 290 MeV/u carbon beam with a 6-cm spread-out Bragg-peak (SOBP), 137Cs γ rays or 200 kVp X rays for irradiation, and in vitro murine melanoma B16/BL6 cells that were implanted into C57BL/6J mice. The metastatic abilities (migration, invasion and adhesion) were suppressed by carbon ion treatment at all doses that were tested, whereas invasion and migration tended to increase after X-ray irradiation at low dose. Biological effects of carbon ions increased with linear energy transfer (LET) for both cell killing and metastatic abilities, although the effects were more pronounced for migration and invasion. mRNA expression of E-cadherin was significantly downregulated with low-dose photon exposures, but increased with dose or LET. Expression of Mel-CAM and L1-CAM was upregulated after low-dose photon exposure, but decreased with dose, especially after carbon-ion treatment. Conversely, these molecules showed a reversal in expression changes, especially after low-dose photon exposure. Cell-cell adhesion may be an important contributor to the antimetastatic effect of carbon ion treatment. The number of lung metastases after local tumor irradiation significantly decreased with increased dose and LET, with carbon ions being more effective than γ rays. Integrating dose-response curves to examine the relationship between cell killing and lung metastasis clearly showed that carbon ions inhibit lung metastasis more efficiently than photons at the iso-effective level of cell killing. Thus, carbon ions were more effective than photon beams, not only at killing tumor cells, but also at inhibiting metastatic spread caused by tumor cells that survived irradiation.

Repair of skin damage during fractionated irradiation with gamma rays and low-LET carbon ions.

In clinical use of carbon-ion beams, a deep-seated tumor is irradiated with a Spread-Out Bragg peak (SOBP) with a high-LET feature, whereas surface skin is irradiated with an entrance plateau, the LET of which is lower than that of the peak. The repair kinetics of murine skin damage caused by an entrance plateau of carbon ions was compared with that caused by photons using a scheme of daily fractionated doses followed by a top-up dose. Right hind legs received local irradiations with either 20 keV/microm carbon ions or gamma rays. The skin reaction of the irradiated legs was scored every other day up to Day 35 using a scoring scale that consisted of 10 steps, ranging from 0.5 to 5.0. An isoeffect dose to produce a skin reaction score of 3.0 was used to obtain a total dose and a top-up dose for each fractionation. Dependence on a preceding dose and on the time interval of a top-up dose was examined using gamma rays. For fractionated gamma rays, the total dose linearly increased while the top-up dose linearly decreased with an increase in the number of fractions. The magnitude of damage repair depended on the size of dose per fraction, and was larger for 5.2 Gy than 12.5 Gy. The total dose of carbon ions with 5.2 Gy per fraction did not change till 2 fractions, but abruptly increased at the 3rd fraction. Factors such as rapid repopulation, induced repair and cell cycle synchronization are possible explanations for the abrupt increase. As an abrupt increase/decrease of normal tissue damage could be caused by changing the number of fractions in carbon-ion radiotherapy, we conclude that, unlike photon therapy, skin damage should be carefully studied when the number of fractions is changed in new clinical trials.

Utility of Ultrasonography of the Median Nerve With a High-Frequency Probe for the Diagnosis of Dialysis-Related Carpal Tunnel Syndrome.

This cross-sectional study aimed to determine the utility of ultrasonography with improved resolution using a high-frequency probe for dialysis-related carpal tunnel syndrome (CTS). This study targeted 125 hemodialysis patients at our hospital. A 12 MHz probe was placed on the carpal tunnel area to identify the median nerve. The compression rate of the nerve was calculated by measuring the smallest diameter of the compressed nerve and largest diameter of the unaffected part. To quantify CTS symptoms, we determined the presence of Tinel's sign, measured pinch strength, and used questionnaires to assess numbness and pain. The association of these clinical data with the compression rate was examined. Mean compression rate was 12.1 ± 1.1%. The compression rate cutoff value for those positive with Tinel's sign was 25%, (sensitivity and specificity were 0.80 and 0.91, respectively), and that for those with a history of CTS surgery was 25% (sensitivity and specificity were 0.67 and 0.89, respectively). Multiple regression analysis identified duration of dialysis, ß2-microglobulin(ß2-Mg) concentration, positivity for Tinel's sign, history of CTS surgery, and pinch strength as independent compression rate determinants. Notably, compression rates were significantly higher in patients with a ≥4-year duration of dialysis and a ß2-Mg level of 20 mg/L or more. The compression rate of the median nerve measured by an improved ultrasound device significantly correlated with clinical symptoms, medical history, and serological features associated with dialysis-related CTS. Because ultrasonography is non-invasive, the examination might be a simple method especially for early diagnosis of dialysis-related CTS.

Early growth of experimental lung metastasis in mouse.

A radiobiological method was developed to measure the initial growth of clonogenic tumor cells metastasizing to the lung. The thoraxes of mice were externally irradiated by g rays after an intravenous transplantation of syngeneic fibrosarcoma cells. The lung colonies which developed 11 days after irradiation were counted and provided surviving fractions. Survival curves moved downward when the time interval between transplantation and radiation was delayed from 1 to 21 hr, but shifted upward at 48 hr or later. Survival ratios at given doses and the extrapolation number of survival curves fitted to multi-target model were calculated, and plotted against time after the intravenous transplantation. Doubling times of 13.3 and 13.1 hr were obtained by use of the survival ratio and of the extrapolation number, respectively. This method is useful to measure the growth dynamics of clonogenic tumor cells at the site of a metastasized organ.

Tumor induction in mice locally irradiated with carbon ions: a retrospective analysis.

Tumor induction in mice legs that were locally irradiated with carbon ions was compared to tumor induction by gamma rays after single and fractionated irradiation. A total of 250 tumors were induced in 1104 mice that received carbon-ion doses of 5 through 65 Gy. A total of 77 tumors were induced in 371 mice that received gamma-ray doses of 45 through 95 Gy. Of 91 carbon-ion induced tumors examined histologically, 97 percent were malignant, and sarcomas such as malignant fibrous histiocytoma (47%) and fibrosarcoma (32%) were most frequently observed. Malignant fibrous histiocytoma was also the most frequently observed tumor (12 out of 20 tumors; 60%) after gamma-ray irradiation, followed by carcinomas (25%) such as adenocarcinoma and squamous cell carcinoma. Neither dose fractionation nor linear energy transfer affected tumor induction for carbon ions and gamma rays. Dose responses were linear for carbon ions and gamma rays, and showed no saturation up to 65 Gy of carbon ions and 95 Gy of gamma rays. The relative biological effectiveness of carbon ions was 2.2 for tumor induction and 1.9 for early skin reaction. We conclude that risk of secondary tumor induction by carbon-ion radiotherapy would not be seriously higher than anticipated.

Biological gain of carbon-ion radiotherapy for the early response of tumor growth delay and against early response of skin reaction in mice.

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.

BACKGROUND AND PURPOSE: Carbon-ion radiotherapy uses spread-out Bragg peaks (SOBP) to produce uniform biological effects within a target volume. The relative biological effectiveness is determined by the in vitro cell kill after a single dose is employed to design the SOBP. A question remains as to whether biological effects for in vivo tissues after fractionated doses are also uniform within the SOBP. MATERIAL AND METHODS: Mouse foot skin was irradiated with fractionated doses of carbon ions at various linear energy transfer (LET) values. A new ridge filter was designed based on alpha and beta values for each LET to cause moderate skin reaction, and was studied concerning its uniformity. RESULTS: The reciprocal total doses of intermediate-LET carbon ions and of reference gamma rays linearly increased with an increase of a dose per fraction in Fe-plots. As the single total dose of higher LET run off linearity, data obtained from 2 to 6 fractions were used to design a new ridge filter. The physical dose distribution of the new ridge filter was almost identical to, and indistinguishable from, the ridge filter designed based on the in vitro cell kill. CONCLUSIONS: The LET dependence of alpha is a principle of the biological factor to be used for designing spread-out Bragg peaks of carbon-ion radiotherapy.

Evaluation of therapeutic gain for fractionated carbon-ion radiotherapy using the tumor growth delay and crypt survival assays.

BACKGROUND AND PURPOSE: The aim of the study was to evaluate the therapeutic gain of carbon ion (C-ion) radiotherapy using a mouse model. MATERIALS AND METHODS: Transplanted fibrosarcoma (NFSa) growing in C3H/He mice and murine small intestine were irradiated with 290 MeV/nucleon C-ion beams (C-ions) in 1-12 fractions separated by 4h. The cell killing efficiencies of C-ions were measured using jejunum crypt survival and tumor growth delay (TGD) assays. RESULTS: The equieffect dose for crypt survival and TGD increased with increasing number of fractions after X-rays and 20 keV/µm C-ions, whereas TGD after 77 keV/µm C-ions rather decreased. Crypts showed stronger LET-dependent increase in α terms than the tumor while ß terms less depended on LET irrespective of tissues. Therapeutic gain factor, i.e., a ratio of tumor RBE over crypt RBE, of 77 keV/µm C-ions was more than unity at any doses while that of 20 keV/µm C-ions increased with an increase in dose per fraction. CONCLUSIONS: These specific data imply that use of large dose per fraction would be suitable for C-ion radiotherapy irrespective of LET from the point of view of therapeutic gain, though small dose per fraction by high-LET radiation decreases total dose for tumor.

Determination of the relative biological effectiveness and oxygen enhancement ratio for micronuclei formation using high-LET radiation in solid tumor cells: An in vitro and in vivo study.

We determined the relative biological effectiveness (RBE) and oxygen enhancement ratio (OER) of micronuclei (MN) formation in clamped (hypoxic) and non-clamped (normoxic) solid tumors in mice legs following exposure to X-rays and heavy ions. Single-cell suspensions (aerobic) of non-irradiated tumors were prepared in parallel and used directly to determine the radiation response for aerobic cells. Squamous cell carcinoma (SCCVII) cells were transplanted into the right hind legs of syngeneic C3H/He male mice. Irradiation doses with either X-rays or heavy ions at a dose-averaged LET (linear energy transfer) of 14-192keV/µm were delivered to 5-mm diameter tumors and aerobic single-cells in sample-tubes. After irradiation, the tumors were excised and trypsinized to observe MN in single-cells. The single-cell suspensions were used for MN formation assays. The RBE values increased with increasing LET. The maximum RBE values for the three different oxygen conditions; hypoxic tumor, normoxic tumor, and aerobic cells, were 8.18, 5.30, and 3.76 at an LET of 192keV/µm, respectively. After X-irradiation, the OERh/n values (hypoxic tumor/normoxic tumor) were lower than the OERh/a (hypoxic tumor/aerobic cells), and were 1.73 and 2.58, respectively. We found that the OER for the in vivo studies were smaller in comparison to that for the in vitro studies. Both of the OER values at 192keV/µm were small in comparison to those of the X-ray irradiated samples. The OERh/n and OERh/a values at 192keV/µm were 1.12 and 1.19, respectively. Our results suggest that high LET radiation has a large biological effect even if a solid tumor includes substantial numbers of hypoxic cells. To conclude, we found that the RBE values under each oxygen state for non-MN fraction increased with increasing LET and that the OER values for both tumors in vivo and cells in vitro decreased with increasing LET.

Radioprotective activities of beer administration for radiation-induced acute toxicity in mice.

BACKGROUND AND PURPOSE: We previously found that drinking beer reduces chromosome aberrations in blood lymphocytes that were collected and irradiated in vitro. In this study, we investigated the radioprotective activities of beer-administration for bone marrow and intestine in mice. METHODS: C3H/He female mice received an oral administration of beer, ethanol or saline at a dose of 1 ml/mouse 30 min before whole body irradiation with 137Cs gamma rays or LET 50 keV/microm carbon ions. Radioprotective activities were estimated using a LD(50/30) (The dose required to kill 50% of the mice within 30 days) and a microcolony technique for intestine. RESULTS: The LD(50/30) for the beer-administered mice was significantly increased in comparison with saline administered mice. The LD(50/30) of gamma-ray was 7.8 Gy (p < 0.05), 7.6 Gy and 7.3 Gy for beer-, ethanol- and saline-administered group, respectively. The LD(50/30) of carbon ions was 6.6 Gy (p < 0.05), 6.2 Gy and 5.9 Gy for the beer-, ethanol- and saline-administered groups, respectively. The crypt survivals that were semi-logarithmically plotted against dose were well fitted to a linear regression line. The dose reduction factor (DRF) (D10) of beer- and ethanol-administered mice for gamma rays was 1.09 and 1.08, respectively. The DRF (D10) of beer- and ethanol-administered mice for carbon ions was 1.08 and 1.07, respectively. CONCLUSIONS: The radioprotection by beer-administration is due to not only OH radical-scavenge action by the ethanol contained in beer.