Application of polyimide films as a nuclear track detector (1): A systematic study of track registration sensitivity

This paper reports the variation of track registration sensitivity as a function of the stopping power of heavy ions in UPILEX-S® films, which is known as the most radiation tolerant polyimide (PI). The detection thresholds in the stopping power for etch pit formation are determined as 4,000, 4,100, 4,800, and 5600 keV/μm for 40Ar, 84Kr, 132Xe and 238U ions, respectively. Furthermore, we investigate the latent track structure in two kinds of PI films (UPILEX-S® and Kapton) by means of FT-IR spectroscopy. At the similar stopping power value, the radiation chemical yields (G value) for heavier ions are lower than those of lighter ions. This is due to the difference of the radial dose distribution for low and high velocity ions.

Application of polyimide films as a nuclear track detector (2): A latent track structure study with Fourier transform infrared spectroscopy

This paper reports the relation between latent track structure and the detection threshold of etch pits formation in UPILEX-S® and Kapton. At the similar stopping power value, effective track core radii and G values for heavier ions are lower than those of lighter ions. These results would be due to the difference of the radial dose distribution for low- and high-velocity ions. The G value starts more rapidly rising above 600 and 1000 keV/μm for Kapton and UPILEX-S®, respectively. The detection threshold of UPILEX-S is 4000 keV/μm for Ar ions, at which effective track core radii of all functional groups are larger than 2 nm. Since the length of a molecule unit of UPILEX-S® is about 1.4 nm, at least more than two molecule units have to be damaged for the etch pit formation. A similar discussion is applicable to Kapton, whose detection threshold is significantly lower than UPILEX-S®.

Proton and carbon ion beam treatment with active raster scanning method in 147 patients with skull base chordoma at the Heidelberg Ion Beam Therapy Center-a single-center experience

BACKGROUND

This study aimed to compare the results of irradiation with protons versus irradiation with carbon ions in a raster scan technique in patients with skull base chordomas and to identify risk factors that may compromise treatment results.

METHODS

A total of 147 patients (85 men, 62 women) were irradiated with carbon ions (111 patients) or protons (36 patients) with a median dose of 66 Gy (RBE (Relative biological effectiveness); carbon ions) in 4 weeks or 74 Gy (RBE; protons) in 7 weeks at the Heidelberg Ion Beam Therapy Center (HIT) in Heidelberg, Germany. The median follow-up time was 49.3 months. All patients had gross residual disease at the beginning of RT. Compression of the brainstem was present in 38%, contact without compression in 18%, and no contact but less than 3 mm distance in 16%. Local control and overall survival were evaluated using the Kaplan-Meier Method based on scheduled treatment (protons vs. carbon ions) and compared via the log rank test. Subgroup analyses were performed to identify possible prognostic factors.

RESULTS

During the follow-up, 41 patients (27.9%) developed a local recurrence. The median follow-up time was 49.3 months (95% CI: 40.8-53.8; reverse Kaplan-Meier median follow-up time 56.3 months, 95% CI: 51.9-60.7). No significant differences between protons and carbon ions were observed regarding LC, OS, or overall toxicity. The 1‑year, 3‑year, and 5‑year LC rates were 97%, 80%, and 61% (protons) and 96%, 80%, and 65% (carbon ions), respectively. The corresponding OS rates were 100%, 92%, and 92% (protons) and 99%, 91%, and 83% (carbon ions). No significant prognostic factors for LC or OS could be determined regarding the whole cohort; however, a significantly improved LC could be observed if the tumor was > 3 mm distant from the brainstem in patients presenting in a primary situation.

CONCLUSION

Outcomes of proton and carbon ion treatment of skull base chordomas seem similar regarding tumor control, survival, and toxicity. Close proximity to the brainstem might be a negative prognostic factor, at least in patients presenting in a primary situation.

Carbon ion radiotherapy for skull base chordomas and chondrosarcomas: a systematic review and meta-analysis of local control, survival, and toxicity outcomes

BACKGROUND

Carbon ion radiotherapy (CIRT) is an emerging radiation therapy to treat skull base chordomas and chondrosarcomas. To date, its use is limited to a few centers around the world, and there has been no attempt to systematically evaluate survival and toxicity outcomes reported in the literature. Correspondingly, the aim of this study was to qualitatively and quantitatively assess these outcomes.

METHODS

A systematic search of seven electronic databases from inception to November 2019 was conducted following PRISMA guidelines. Articles were screened against pre-specified criteria. Outcomes were then pooled by random-effects meta-analyses of proportions.

RESULTS

A total of nine studies provided unique metadata for assessment, with six originating from Heidelberg, Germany. The surveyed cohort size was 632 patients, with 389 (62%) chordomas and 243 (38%) chondrosarcomas of the skull base. Across all studies, median cohort age at therapy and female proportion were 46 years and 51% respectively. Estimates of local control incidence at 1-, 5-, and 10-years in chordoma-only studies were 99%, 80%, and 56%, and in chondrosarcoma-only studies were 99%, 89%, and 88%. Estimates of overall survival probability at 1-, 5-, and 10-years in chordoma-only studies were 100%, 94%, and 78%, and in chondrosarcoma-only studies were 99%, 95%, and 79%. The incidence of early and late toxicity (Grade ≥ 3) ranged from 0 to 4% across all study groups.

CONCLUSIONS

The emerging use of CIRT to treat skull base chordomas and chondrosarcomas appear promising with regard to tumor control, overall survival, and risk profile of early and late toxicity. The current literature suffers from the fact only a few centers in the world currently employ this technology.

Simulated space radiation: Investigating ionizing radiation effects on the stability of amlodipine besylate API and tablets

Efficacious pharmaceuticals with the adequate shelf life are essential for the well-being of the space explorers and successful completion of a space mission. Space is brimming with different types of radiations, which penetrate inside the spacecraft despite the shielding material. Such radiations can alter the stability of the pharmaceuticals during long duration space missions. The literature reporting the space radiation effects on the pharmaceuticals is scarce in a public domain. Ground-based simulation studies can be useful to predict the influence of the space radiations on the stability of the pharmaceuticals. Based upon these facts, the main objective of the present preliminary work was to investigate the effect of different types of ionizing radiations on the stability of amlodipine besylate API and tablets. Amlodipine besylate samples were irradiated by protons, neutrons (thermal and fast), gamma and heavy ion (⁵⁶Fe) radiations with their different doses. The samples were also irradiated with UV-visible radiation to compare the effect of selected ionizing radiations with photodegradation. The physical stability was examined through organoleptic evaluation and the chemical stability was evaluated by FTIR and HPLC. The results of the organoleptic evaluation showed colour changes from colourless to yellow in proton irradiated solid API and gamma irradiated API aqueous solution. The FTIR spectrum of proton irradiated API showed one additional absorption band at 1728 cm^-1 due to degradation products. HPLC analysis revealed that amlodipine degraded up to 10% and 21% after the highest doses of proton and gamma irradiation, respectively. No physical or chemical changes were observed after neutron and ⁵⁶Fe irradiation. The structures of major radiolytic products were elucidated using LC-MS/MS. Two new impurities were found in the API aqueous solution as a result of gamma irradiation. The drug degradation pathways were postulated by proposing the plausible mechanism of formation.

Late sacral recurrence of rectal cancer treated by heavy ion radiotherapy: a case report

Background

The need for surveillance of rare late recurrence of rectal cancer has not yet been established. Local control of unresectable skeletal metastasis is important for palliation of symptoms and support for systemic chemotherapy.

Case presentation

A Japanese man underwent preoperative pelvic irradiation (50.4 Gy/28 Fr) and low anterior resection at the age of 57 years. The pathological stage was II (T3N0M0). Nine years after the surgery, his carcinoembryonic antigen (CEA) level showed rapid elevation, although he had no symptoms. A computed tomography (CT) scan showed no evidence of recurrent lesions, but positron emission tomography (PET)-CT revealed abnormally high 2-[¹⁸F]-fluoro-2-deoxy-d-glucose accumulation in the sacrum. A CT-guided needle biopsy confirmed the diagnosis of metastatic adenocarcinoma from the previous rectal cancer. The sacral metastasis reached the S1/S2 level and was considered inoperable. Conventional radiotherapy was also excluded due to the previous history of pelvic irradiation. Finally, heavy ion radiotherapy with carbon ions was performed as radical local therapy (70.4 GyE/16 Fr). The patient did not consent to systemic chemotherapy immediately after the irradiation. Five months after radiotherapy, multiple lung metastases were noted on CT, followed by mediastinal and hilar lymph node metastases. Systemic chemotherapy was started 9 months after the irradiation. During this time, the patient experienced some degree of pain and loss in muscle strength of the left lower limb, and a second heavy ion irradiation (60.0 GyE/12 Fr) was performed 11 months after the previous irradiation. After that, the sacral lesion has been stable and his symptoms have not worsened. Two years after the heavy ion therapy, the patient steadily continues outpatient chemotherapy and his quality of life is relatively maintained.

Conclusion

In case the risk of late recurrence is relatively high after rectal cancer surgery, clinicians should consider individual follow-up evaluations, including CEA measurements to allow for timely diagnosis and intervention. Heavy ion radiotherapy is effective for local control of sacral metastasis.

Nitric oxide-mediated bystander signal transduction induced by heavy-ion microbeam irradiation

In general, a radiation-induced bystander response is known to be a cellular response induced in non-irradiated cells after receiving bystander signaling factors released from directly irradiated cells within a cell population. Bystander responses induced by high-linear energy transfer (LET) heavy ions at low fluence are an important health problem for astronauts in space. Bystander responses are mediated via physical cell-cell contact, such as gap-junction intercellular communication (GJIC) and/or diffusive factors released into the medium in cell culture conditions. Nitric oxide (NO) is a well-known major initiator/mediator of intercellular signaling within culture medium during bystander responses. In this study, we investigated the NO-mediated bystander signal transduction induced by high-LET argon (Ar)-ion microbeam irradiation of normal human fibroblasts. Foci formation by DNA double-strand break repair proteins was induced in non-irradiated cells, which were co-cultured with those irradiated by high-LET Ar-ion microbeams in the same culture plate. Foci formation was suppressed significantly by pretreatment with an NO scavenger. Furthermore, NO-mediated reproductive cell death was also induced in bystander cells. Phosphorylation of NF-κB and Akt were induced during NO-mediated bystander signaling in the irradiated and bystander cells. However, the activation of these proteins depended on the incubation time after irradiation. The accumulation of cyclooxygenase-2 (COX-2), a downstream target of NO and NF-κB, was observed in the bystander cells 6 h after irradiation but not in the directly irradiated cells. Our findings suggest that Akt- and NF-κB-dependent signaling pathways involving COX-2 play important roles in NO-mediated high-LET heavy-ion-induced bystander responses. In addition, COX-2 may be used as a molecular marker of high-LET heavy-ion-induced bystander cells to distinguish them from directly irradiated cells, although this may depend on the time after irradiation.

The effect of low dose ionizing radiation on homeostasis and functional integrity in an organotypic human skin model

Outside the protection of Earth's atmosphere, astronauts are exposed to low doses of high linear energy transfer (LET) radiation. Future NASA plans for deep space missions or a permanent settlement on the moon are limited by the health risks associated with space radiation exposures. There is a paucity of direct epidemiological data for low dose exposures to space radiation-relevant high LET ions. Health risk models are used to estimate the risk for such exposures, though these models are based on high dose experiments. There is increasing evidence, however, that low and high dose exposures result in different signaling events at the molecular level, and may involve different response mechanisms. Further, despite their low abundance, high LET particles have been identified as the major contributor to health risk during manned space flight. The human skin is exposed in every external radiation scenario, making it an ideal epithelial tissue model in which to study radiation induced effects. Here, we exposed an in vitro three dimensional (3-D) human organotypic skin tissue model to low doses of high LET oxygen (O), silicon (Si) and iron (Fe) ions. We measured proliferation and differentiation profiles in the skin tissue and examined the integrity of the skin's barrier function. We discuss the role of secondary particles in changing the proportion of cells receiving a radiation dose, emphasizing the possible impact on radiation-induced health issues in astronauts.