Single-Fraction Adjuvant Electronic Brachytherapy after Resection of Conjunctival Carcinoma

Simple Summary

A centralized distribution of specialized oncologic facilities is a widely repeated situation in many latitudes around the globe, limiting the patient’s access options to specialized treatments. Strategies to alleviate the overpassed attention capacities in low- and middle-income countries, such as Peru, have driven the attention of practitioners towards hypofractionated treatments. In order to shorten treatment times and hospital visits, treating ocular conjunctival carcinoma with a single-fraction electronic brachytherapy approach arises as a novel option, which further increases the current therapeutic arsenal against this entity. We aim to report the clinical findings of this treatment modality, in terms of feasibility, oncological outcomes and toxicity profile, while opening a new possibility of diminishing patient- and health care-related financial impact.

Abstract

A retrospective study was performed to assess the outcomes of a single-fraction adjuvant electronic brachytherapy (e-BT) approach for patients with squamous cell conjunctival carcinoma (SCCC). Forty-seven patients with T1–T3 SCCC were included. All patients underwent surgery followed by a single-fraction adjuvant e-BT with a porTable 50-kV device. Depending on margins, e-BT doses ranged between 18 to 22 Gy prescribed at 2 mm depth, resembling equivalent doses in 2 Gy (EQD2) per fraction of 46–66 Gy (α/β ratio of 8–10 Gy and a relative biological effect (RBE) of 1.3). The median age was 69 (29–87) years. Most tumors were T1 (40.4%) or T2 (57.5%) with a median size of 7 mm (1.5–20). Margins were positive in 40.4% of cases. The median time from surgery to e-BT was nine weeks (0–37). After a median follow-up of 24 (17–40) months, recurrence occurred in only two patients (6 and 7 months after e-BT), yielding a median disease-free survival (DFS) of 24 (6–40) months and DFS at two years of 95.7%. Acute grade 2 conjunctivitis occurred in 25.5%. E-BT is a safe and effective for SCCC treatment, with clinical and logistic advantages compared to classical methods. Longer follow-up and prospective assessment are warranted.

Time-resolved laboratory micro-X-ray fluorescence reveals silicon distribution in relation to manganese toxicity in soybean and sunflower

BACKGROUND AND AIMS

Synchrotron- and laboratory-based micro-X-ray fluorescence (µ-XRF) is a powerful technique to quantify the distribution of elements in physically large intact samples, including live plants, at room temperature and atmospheric pressure. However, analysis of light elements with atomic number (Z) less than that of phosphorus is challenging due to the need for a vacuum, which of course is not compatible with live plant material, or the availability of a helium environment.

METHOD

A new laboratory µ-XRF instrument was used to examine the effects of silicon (Si) on the manganese (Mn) status of soybean (Glycine max) and sunflower (Helianthus annuus) grown at elevated Mn in solution. The use of a helium environment allowed for highly sensitive detection of both Si and Mn to determine their distribution.

KEY RESULTS

The µ-XRF analysis revealed that when Si was added to the nutrient solution, the Si also accumulated in the base of the trichomes, being co-located with the Mn and reducing the darkening of the trichomes. The addition of Si did not reduce the concentrations of Mn in accumulations despite seeming to reduce its adverse effects.

CONCLUSIONS

The ability to gain information on the dynamics of the metallome or ionome within living plants or excised hydrated tissues can offer valuable insights into their ecophysiology, and laboratory µ-XRF is likely to become available to more plant scientists for use in their research.

Synchrotron microcrystal native-SAD phasing at a low energy

De novo structural evaluation of native biomolecules from single-wavelength anomalous diffraction (SAD) is a challenge because of the weakness of the anomalous scattering. The anomalous scattering from relevant native elements - primarily sulfur in proteins and phospho-rus in nucleic acids - increases as the X-ray energy decreases toward their K-edge transitions. Thus, measurements at a lowered X-ray energy are promising for making native SAD routine and robust. For microcrystals with sizes less than 10 µm, native-SAD phasing at synchrotron microdiffraction beamlines is even more challenging because of difficulties in sample manipulation, diffraction data collection and data analysis. Native-SAD analysis from microcrystals by using X-ray free-electron lasers has been demonstrated but has required use of thousands of thousands of microcrystals to achieve the necessary accuracy. Here it is shown that by exploitation of anomalous microdiffraction signals obtained at 5 keV, by the use of polyimide wellmounts, and by an iterative crystal and frame-rejection method, microcrystal native-SAD phasing is possible from as few as about 1 200 crystals. Our results show the utility of low-energy native-SAD phasing with microcrystals at synchrotron microdiffraction beamlines.

Sulfur-SAD phasing from microcrystals utilizing low-energy X-rays

A practical approach for obtaining S-SAD data from native protein microcrystals with low-wavelength synchrotron radiation [Guo et al. (2019), IUCrJ, 6, 532-542] is presented in this issue of IUCrJ.

Importance of dosimetry protocol for cell irradiation on a low X-rays facility and consequences for the biological response

PURPOSE

The main objective of radiobiology is to establish links between doses and radiation-induced biological effects. In this context, well-defined dosimetry protocols are crucial to the determination of experimental protocols. This work proposes a new dosimetry protocol for cell irradiation in a SARRP and shows the importance of the modification of some parameters defined in dosimetry protocol for physical dose and biological outcomes.

MATERIALS AND METHODS

Once all parameters of the configuration were defined, dosimetry measurements with ionization chambers and EBT3 films were performed to evaluate the dose rate and the attenuation due to the cell culture medium. To evaluate the influence of changes in cell culture volume and/or additional filtration, 6-well plates containing EBT3 films with water were used to determine the impact on the physical dose at 80 kV. Then, experiments with the same irradiation conditions were performed by replacing EBT3 films by HUVECs. The biological response was assessed using clonogenic assay.

RESULTS

Using a 0.15 mm copper filter lead to a variation of +1% using medium thickness of 0.104 cm to -8% using a medium thickness of 0.936 cm on the physical dose compare to the reference condition (0.313 cm). For the 1 mm aluminum filter, a variation of +8 to -40% for the same medium thickness conditions has been observed. Cells irradiated in the same conditions showed significant differences in survival fraction, corroborating the effects of dosimetric changes on physical dose.

CONCLUSIONS

This work shows the importance of dosimetry in radiobiology studies and the need of an accurate description of the dosimetry protocol used for irradiation.