MR-LINAC, a New Partner in Radiation Oncology: Current Landscape

Technological advances in radiation oncology are oriented towards improving treatment precision and tumor control. Among these advances, magnetic-resonance-image-guided radiation therapy (MRgRT) stands out, with technological advances to deliver targeted treatments adapted to a tumor's anatomy on the day while minimizing incidental exposure to organs at risk, offering an unprecedented therapeutic advantage compared to X-ray-based IGRT delivery systems. This new technology changes the traditional workflow in radiation oncology and requires an evolution in team coordination to administer more precise treatments. Once implemented, it paves the way for newer indication for radiation therapy to safely deliver higher doses than ever before, with better preservation of healthy tissues to optimize patient outcomes. In this narrative review, we assess the technical aspects of the novel linear accelerators that can deliver MRgRT and summarize the available published experience to date, focusing on oncological results and future challenges.

TLI in pediatric patients

PURPOSE

Hematopoietic progenitor cell transplantation (HSCT) is a procedure used in different hematological diseases as part of the curative treatment, so the investigators propose a system of conditioning of reduced intensity based on total lymphoid irradiation (TLI) as an alternative to the classic total body irradiation (TBI) followed by haploidentical transplantation in patients compatible with a single HLA haplotype, as an alternative to patients who do not have an HLA compatible donor.

MATERIALS AND METHODS

A cohort of 25 patients with hematological disease underwent haploidentical HSCT from February 2015 to May 2018, conditioned with TLI from day - 10 (2-4 days of treatment) followed by thiotepa (5 mg/kg/12 h) and melphalan (70 mg/m²/day) prior to HSCT and prophylaxis with ciclosporin (1.5 mg/kg/12 h). 2 Gy/fraction was administered to complete 8 Gy with IMRT and VMAT technique.

RESULTS

12% rejection of the transplant was obtained with acute GVHD < II (48%) and chronic GVHD 12%. No acute toxicity was recorded in irradiated patients and 56% survival of patients at the end of follow-up.

CONCLUSION

Conditioning the haploidentical transplant with TLI, IMRT, and VMAT techniques compared with TBI and RT3D-C techniques is a feasible technique that helps inducing the necessary immunosuppression in patients with a high risk of graft rejection, minimal adverse effects, low incidence of GVHD, and high survival rate.

Prevention of urinary tract infections in palliative radiation for vertebral metastasis and spinal compression: A pilot study in 71 patients

PURPOSE

To assess the impact of bladder instillations of hyaluronic acid (HA) on the prevalence of urinary tract infection (UTI) in patients receiving emergency radiotherapy for metastatic spinal cord compression.

METHODS AND MATERIALS

Patients were recruited consecutively at one center and assigned to usual care (UC) (n = 34, mean age 62.2 years) or UC with once-weekly HA instillation (UC + HA) (Cystistat: 40 mg in 50 mL phosphate-buffered saline) (n = 37; mean age, 63.1 years). All patients had an indwelling catheter and received radiotherapy. UTI status was assessed at baseline and during hospitalization.

RESULTS

At baseline, patient groups were comparable, except for the prevalence of UTI at baseline, which was 11.8% and 0% in the UC and UC + HA patients, respectively (p = 0.0477). During hospitalization, 76.5% (vs. 11.8% at baseline, p < 0.0001) of the UC patients had a UTI compared with 13.5% (vs. 0% at baseline, p = 0.0541) of the UC + HA patients (p < 0.0001). Both groups were hospitalized for similar periods (19.8 days [UC] vs. 18.5 days, p = 0.4769) and received equivalent radiotherapy sessions (4.6 [UC] vs. 5.8 sessions, p = 0.2368).

CONCLUSIONS

Patients receiving UC + HA had a 5.7-fold decrease in UTI prevalence over the hospitalization period compared to UC patients, suggesting that bladder instillations of HA effectively prevent UTI in patients with indwelling catheters receiving radiotherapy for nerve compression.

Effect of advanced glycosylation end products on the induction of nitric oxide synthase in murine macrophages

We studied the role of advanced glycosylation end products on the induction of nitric oxide synthase in peritoneal mouse macrophages previously exposed to modified BSA. A dose-dependent increment in the nitric oxide production induced by LPS and IFN-gamma was observed when cell cultures were pretreated with modified BSA for 48 hours. In addition, the up regulation of nitric oxide production was also time-dependent, being maximal at 24-48 hours. Experiments carried out in the presence of neutralizing antibodies to IL-1 and TNF-alpha, suggested that up regulation was not due to the capacity of modified BSA to induce both proinflammatory signals. The up regulation of nitric oxide production was paralleled with an increase in iNOS mRNA.

Nitric oxide modulates interleukin-2-induced proliferation in CTLL-2 cells

The role of the L-arginine–nitric oxide metabolic pathway was explored for interleukin-2-induced proliferation in the cytotoxic T lymphocyte clone CTLL-2. Specific inhibition of nitric oxide synthase significantly diminished, in a concentration-dependent manner,3H-thymidine uptake of CTLL-2 cells in response to different concentrations of interleukin 2. Withdrawal of L-arginine from culture medium resulted as potent as the higher inhibition obtained when blocking nitric oxide synthase with L-arginine analogues. Furthermore, intermedial concentrations of Larginine and exogenous nitric oxide donors were found for achieving optimal IL2-induced proliferation of CTLL-2. These findings prompted us to suggest that intra- and/or inter-cellular nitric oxide signalling may contribute to the modulation of the IL2 mitogenic effect upon cytotoxic T lymphocytes.

Nitric oxide modulates interleukin-2-induced proliferation in CTLL-2 cells

The role of the L-arginine-nitric oxide metabolic pathway was explored for interleukin-2-induced proliferation in the cytotoxic T lymphocyte clone CTLL-2. Specific inhibition of nitric oxide synthase significantly diminished, in a concentration-dependent manner, (3)H-thymidine uptake of CTLL-2 cells in response to different concentrations of interleukin 2. Withdrawal of L-arginine from culture medium resulted as potent as the higher inhibition obtained when blocking nitric oxide synthase with L-arginine analogues. Furthermore, intermedial concentrations of Larginine and exogenous nitric oxide donors were found for achieving optimal IL2-induced proliferation of CTLL-2. These findings prompted us to suggest that intra- and/or inter-cellular nitric oxide signalling may contribute to the modulation of the IL2 mitogenic effect upon cytotoxic T lymphocytes.

Lobenzarit disodium inhibits the constitutive NO-cGMP metabolic pathways. Possible involvement as an immunomodulatory drug

Lobenzarit disodtulIl (CCA) is a novel immunomodulatory drug useful in the treatment of chronic inflammations. Its principal mechanism of action seems to be through enhancing the T suppressor/T helper lymphocyte ratio. However, the molecular basis for these actions remains unclear. In this study it was found that CCA inhibits the production of guanosine 3',5'-cyclic monophosphate almost completely when present in concentrations of 1 mM. Further results demonstrated that such inhibition could also be explained by interference in constitutive nitric oxide generation. In addition to previous findings, more insight into the molecular mechanism of action of CCA is provided.

Monocyte chemotactic protein-1 inhibits the induction of nitric oxide synthase in J774 cells

We evaluated the effect of monocyte chemotactic protein-1 (MCP-1) on the induction of nitric oxide synthase activity in J774 cells. MCP-1 was able to inhibit the production of nitric oxide induced by LPS and IFN-gamma in a dose-dependent manner. Moreover, the inhibition was only achieved when the cells were pretreated with MCP-1. No inhibition was observed when MCP-1 was added after stimulation with LPS and IFN-gamma. These results demonstrate that MCP-1 is able to inhibit the induction of nitric oxide synthesis.