Carbon-ion Radiotherapy for Colorectal Cancer

Chronic Encapsulated Intracerebral Hematoma after Carbon Ion Therapy for Chordoma Mimicking Malignant Glioma: A Case Report

Chronic encapsulated intracerebral hematoma is a rare type of intracerebral hemorrhage. Reportedly, it is associated with vascular malformations, including arteriovenous malformations, cavernous hemangiomas, microaneurysms, and venous malformations. Recently, an association between chronic encapsulated intracerebral hematoma and stereotactic radiosurgery for arteriovenous malformations has been reported. In general, as the hematoma enlarges, symptoms progress slowly. In this report, we present a case of a 50-year-old woman who had undergone clivus chordoma resection and carbon ion therapy for the clivus respectively 27 and 20 years before developing chronic encapsulated intracerebral hematoma with rapidly progressing disturbance of consciousness. She was referred to our hospital because of difficulty walking due to left hemiparesis. Head computed tomography and magnetic resonance imaging showed a cystic lesion in the right temporal lobe with perifocal edema. On the second day of hospitalization, the patient's consciousness worsened. We suspected a malignant glioma and performed an emergency craniotomy; however, the pathological diagnosis was chronic encapsulated intracerebral hematoma. After the rehabilitation therapy, the patient became ambulatory and was discharged. To the date of reporting, the patient remained recurrence-free. Chronic encapsulated intracerebral hematoma may be due to invasive craniotomy or carbon ion therapy. It usually progresses slowly; however, in some cases, such as this one, it may cause rapid deterioration of consciousness.

Anti-tumor Effect of High Doses of Carbon Ions and X-Rays during Irradiation of Ehrlich Ascites Carcinoma Cells Ex Vivo

The effect of carbon ions (12C) with the energy of 400 MeV/nucleon on the dynamics of induction and growth rate of solid tumors in mice under irradiation of Ehrlich ascites carcinoma cells (EAC) ex vivo at doses of 5-30 Gy relative to the action of equally effective doses of X-ray radiation was studied. The dynamics of tumor induction under the action of 12C and X-rays had a similar character and depended on the dose during 3 months of observation. The value of the latent period, both when irradiating cells with 12C and X-ray, increased with increasing dose, and the interval for tumor induction decreased. The rate of tumor growth after ex vivo irradiation of EAC cells was independent of either dose or type of radiation. The dose at which EAC tumors are not induced within 90 days was 30 Gy for carbon ions and 60 Gy for X-rays. The value of the relative biological effectiveness of carbon ions, calculated from an equally effective dose of 50% probability of tumors, was 2.59.

Planning Strategy to Optimize the Dose-Averaged LET Distribution in Large Pelvic Sarcomas/Chordomas Treated with Carbon-Ion Radiotherapy

To improve outcomes in large sarcomas/chordomas treated with CIRT, there has been recent interest in LET optimization. We evaluated 22 pelvic sarcoma/chordoma patients treated with CIRT [large: HD-CTV ≥ 250 cm3 (n = 9), small: HD-CTV < 250 cm3 (n = 13)], DRBE|LEM-I = 73.6 (70.4-73.6) Gy (RBE)/16 fractions, using the local effect model-I (LEM-I) optimization and modified-microdosimetric kinetic model (mMKM) recomputation. We observed that to improve high-LETd distribution in large tumors, at least 27 cm3 (low-LETd region) of HD-CTV should receive LETd of ≥33 keV/µm (p < 0.05). Hence, LETd optimization using 'distal patching' was explored in a treatment planning setting (not implemented clinically yet). Distal-patching structures were created to stop beams 1-2 cm beyond the HD-PTV-midplane. These plans were reoptimized and DRBE|LEM-I, DRBE|mMKM, and LETd were recomputed. Distal patching increased (a) LETd50% in HD-CTV (from 38 ± 3.4 keV/µm to 47 ± 8.1 keV/µm), (b) LETdmin in low-LETd regions of the HD-CTV (from 32 ± 2.3 keV/µm to 36.2 ± 3.6 keV/µm), (c) the GTV fraction receiving LETd of ≥50 keV/µm, (from <10% to >50%) and (d) the high-LETd component in the central region of the GTV, without significant compromise in DRBE distribution. However, distal patching is sensitive to setup/range uncertainties, and efforts to ascertain robustness are underway, before routine clinical implementation.

Analysis of the relationship between LET, γH2AX foci volume and cell killing effect of carbon ions using high-resolution imaging technology

The strong cell killing effect of high linear energy transfer (LET) carbon ions is dependent on lethal DNA damage. Our recent studies suggest that induction of clusters of double-strand breaks (DSBs) in close proximity is one of the potential mechanisms. However, the relationship between LET, the degree of DSB clustering and the cell killing effect of carbon ions remains unclear. Here, we used high-resolution imaging technology to analyze the volume of γH2AX foci induced by monoenergetic carbon ions with a clinically-relevant range of LET (13-100 keV/μm). We obtained data from 3317 γH2AX foci and used a gaussian function to approximate the probability (p) that 1 Gy-carbon ions induce γH2AX foci of a given volume (vth) or greater per nucleus. Cell killing effects were assessed in clonogenic assays. The cell killing effect showed high concordance with p at vth = 0.7 μm3 across various LET values; the difference between the two was 4.7% ± 2.2%. This relationship was also true for clinical carbon ion beams harboring a mixed LET profile throughout a spread-out Bragg peak width (30-120 mm), with the difference at vth = 0.7 μm3 being 1.6% ± 1.2% when a Monte Carlo simulation-derived dose-averaged LET was used to calculate p. These data indicate that the cell killing effect of carbon ions is predictable by the ability of carbon ions to induce γH2AX foci containing clustered DSBs, which is linked to LET, providing the biological basis for LET modulation in the planning of carbon ion radiotherapy.

L. reuteri JMR-01 adjuvant 12C6+ irradiation exerts anti-colon carcinoma effects by modulating the gut microbiota in mice

BACKGROUND

Probiotics such as Lactobacillus could modulate the intestinal microbiota and have been considered as an effective strategy for ameliorating colon carcinoma. Nevertheless, its efficiency remains the biggest challenge.

METHODS

We investigated the therapeutic efficacy of Lactobacillus reuteri JMR-01 adjuvant ¹²C⁶⁺ irradiation on CT-26 syngeneic mouse models. Meanwhile, intestinal flora and innate immunity were examined to outline mechanisms.

RESULTS

Anti-proliferation effect of live probiotic combined with inactivated probiotic JMR-01 (LP + IP) on CT-26 reached a maximum of 39.55% among other experiment groups at 24 h when the ratio of cell to CFU was 1:1 in vitro. These activities have been fully validated in vivo, tumor-bearing mice treated by ¹²C⁶⁺ irradiation combining with living and inactivated probiotics JMR-01 (IR + LP + IP) for 50-day held the highest survival rate (71.4%) and complete remission rate (14.3%). We also demonstrated significant fluctuation in gut microbiota, including the decreased abundance of Bacteroides fragilis and Clostridium perfringens related to tumorigenesis and development, and the increased abundance of Lactobacillus and Bifidobacterium closely associated with health restoration in fecal of mice treated with JMR-01 LP + IP adjuvant ¹²C⁶⁺ irradiation (IR + LP + IP). Similarly, the decreasing nitroreductase activities and increasing short chain fatty acids (SCFAs) concentrations were observed in IR + LP + IP group compared with tumor control group, which further confirmed the changes of gut microbiota. Additionally, we found that the strongest stimulation index of splenocyte (2.47) and the phagocytosis index peritoneal macrophage (3.68) were achieved by LP + IP compared with single live JMR-01 (LP) and inactivated JMR-01 (IP).

CONCLUSIONS

JMR-01 LP + IP adjuvant ¹²C⁶⁺ irradiation could mitigate cancer progression by modulating innate immunity as well as intestinal flora.

64Cu-ATSM Predicts Efficacy of Carbon Ion Radiotherapy Associated with Cellular Antioxidant Capacity

Simple Summary

Carbon ion radiotherapy is an emerging cancer treatment modality that has a greater therapeutic window than conventional photon radiotherapy. To maximize the efficacy of this extremely scarce medical resource, it is important to identify predictive biomarkers of higher carbon ion relative biological effectiveness (RBE) over photons. Here we show that the carbon ion RBE in human cancer cells correlates with the cellular uptake of ⁶⁴Cu(II)-diacetyl-bis(N4-methylthiosemicarbazone) (⁶⁴Cu-ATSM), a potential radioligand that reflects an over-reduced intracellular environment. High RBE/⁶⁴Cu-ATSM cells show greater steady-state levels of antioxidant proteins and increased capacity to scavenge reactive oxygen species in response to X-rays than low RBE/⁶⁴Cu-ATSM counterparts. These data suggest that the cellular antioxidant activity is a possible determinant of carbon ion RBE predictable by ⁶⁴Cu-ATSM uptake.

Abstract

Carbon ion radiotherapy is an emerging cancer treatment modality that has a greater therapeutic window than conventional photon radiotherapy. To maximize the efficacy of this extremely scarce medical resource, it is important to identify predictive biomarkers of higher carbon ion relative biological effectiveness (RBE) over photons. We addressed this issue by focusing on cellular antioxidant capacity and investigated ⁶⁴Cu(II)-diacetyl-bis(N4-methylthiosemicarbazone) (⁶⁴Cu-ATSM), a potential radioligand that reflects an over-reduced intracellular environment. We found that the carbon ion RBE correlated with ⁶⁴Cu-ATSM uptake both in vitro and in vivo. High RBE/⁶⁴Cu-ATSM cells showed greater steady-state levels of antioxidant proteins and increased capacity to scavenge reactive oxygen species in response to X-rays than low RBE/⁶⁴Cu-ATSM counterparts; this upregulation of antioxidant systems was associated with downregulation of TCA cycle intermediates. Furthermore, inhibition of nuclear factor erythroid 2-related factor 2 (Nrf2) sensitized high RBE/⁶⁴Cu-ATSM cells to X-rays, thereby reducing RBE values to levels comparable to those in low RBE/⁶⁴Cu-ATSM cells. These data suggest that the cellular activity of Nrf2-driven antioxidant systems is a possible determinant of carbon ion RBE predictable by ⁶⁴Cu-ATSM uptake. These new findings highlight the potential clinical utility of ⁶⁴Cu-ATSM imaging to identify high RBE tumors that will benefit from carbon ion radiotherapy.

Role of Mitochondria in Radiation Responses: Epigenetic, Metabolic, and Signaling Impacts

Until recently, radiation effects have been considered to be mainly due to nuclear DNA damage and their management by repair mechanisms. However, molecular biology studies reveal that the outcomes of exposures to ionizing radiation (IR) highly depend on activation and regulation through other molecular components of organelles that determine cell survival and proliferation capacities. As typical epigenetic-regulated organelles and central power stations of cells, mitochondria play an important pivotal role in those responses. They direct cellular metabolism, energy supply and homeostasis as well as radiation-induced signaling, cell death, and immunological responses. This review is focused on how energy, dose and quality of IR affect mitochondria-dependent epigenetic and functional control at the cellular and tissue level. Low-dose radiation effects on mitochondria appear to be associated with epigenetic and non-targeted effects involved in genomic instability and adaptive responses, whereas high-dose radiation effects (>1 Gy) concern therapeutic effects of radiation and long-term outcomes involving mitochondria-mediated innate and adaptive immune responses. Both effects depend on radiation quality. For example, the increased efficacy of high linear energy transfer particle radiotherapy, e.g., C-ion radiotherapy, relies on the reduction of anastasis, enhanced mitochondria-mediated apoptosis and immunogenic (antitumor) responses.