Hypofractionated Volumetric-Modulated Arc Radiotherapy for Patients With Non-Small-Cell Lung Cancer Not Suitable for Surgery or Conventional Chemoradiotherapy or SBRT

Evidence-based clinical recommendations for hypofractionated radiotherapy: exploring efficacy and safety - Part 2. Lung (non-small cell lung cancer)

Several recent studies have investigated the use of hypofractionated radiotherapy (HFRT) for various cancers. However, HFRT for non-small cell lung cancer (NSCLC) with or without concurrent chemotherapy is not yet widely used because of concerns about serious side effects and the lack of evidence for improved treatment results. Investigations of HFRT with concurrent chemotherapy in NSCLC have usually been performed in single-arm studies and with a small number of patients, so there are not yet sufficient data. Therefore, the Korean Society for Radiation Oncology Practice Guidelines Committee planned this review article to summarize the evidence on HFRT so far and provide it to radiation oncology clinicians. In summary, HFRT has demonstrated promising results, and the reviewed data support its feasibility and comparable efficacy for the treatment of locally advanced NSCLC. The incidence and severity of esophageal toxicity have been identified as major concerns, particularly when treating large fraction sizes. Strategies, such as esophagus-sparing techniques, image guidance, and dose constraints, may help mitigate this problem and improve treatment tolerability. Continued research and clinical trials are essential to refine treatment strategies, identify optimal patient selection criteria, and enhance therapeutic outcomes.

Efficiency of moderately hypofractionated radiotherapy in NSCLC cell model

Background

The current standard of radiotherapy for inoperable locally advanced NSCLCs with single fraction doses of 2.0 Gy, results in poor outcomes. Several fractionation schedules have been explored that developed over the past decades to increasingly more hypofractionated treatments. Moderate hypofractionated radiotherapy, as an alternative treatment, has gained clinical importance due to shorter duration and higher patient convenience. However, clinical trials show controversial results, adding to the need for pre-clinical radiobiological studies of this schedule.

Methods

We examined in comparative analysis the efficiency of moderate hypofractionation and normofractionation in four different NSCLC cell lines and fibroblasts using several molecular-biological approaches. Cells were daily irradiated with 24x2.75 Gy (moderate hypofractionation) or with 30x2 Gy (normofractionation), imitating the clinical situation. Proliferation and growth rate via direct counting of cell numbers, MTT assay and measurements of DNA-synthesizing cells (EdU assay), DNA repair efficiency via immunocytochemical staining of residual γH2AX/53BP1 foci and cell surviving via clonogenic assay (CSA) were experimentally evaluated.

Results

Overall, the four tumor cell lines and fibroblasts showed different sensitivity to both radiation regimes, indicating cell specificity of the effect. The absolute cell numbers and the CSA revealed significant differences between schedules (P < 0.0001 for all employed cell lines and both assays) with a stronger effect of moderate hypofractionation.

Conclusion

Our results provide evidence for the similar effectiveness and toxicity of both regimes, with some favorable evidence towards a moderate hypofractionation. This indicates that increasing the dose per fraction may improve patient survival and therapy outcomes.

Virtual clinical trial based on outcome modeling with iteratively redistributed extrapolation data

Virtual clinical trials (VCTs) can potentially simulate clinical trials on a computer, but their application with a limited number of past clinical cases is challenging due to the biased estimation of the statistical population. In this study, we developed ExMixup, a novel training technique based on machine learning, using iteratively redistributed extrapolated data. Information obtained from 100 patients with prostate cancer and 385 patients with oropharyngeal cancer was used to predict the recurrence after radiotherapy. Model performance was evaluated by developing outcome prediction models based on three types of training methods: training with original data (baseline), interpolation data (Mixup), and interpolation + extrapolation data (ExMixup). Two types of VCTs were conducted to predict the treatment response of patients with distinct characteristics compared to the training data obtained from patient cohorts categorized under risk classification or cancer stage. The prediction models developed with ExMixup yielded concordance indices (95% confidence intervals) of 0.751 (0.719-0.818) and 0.752 (0.734-0.785) for VCTs on the prostate and oropharyngeal cancer datasets, respectively, which significantly outperformed the baseline and Mixup models (P < 0.01). The proposed approach could enhance the ability of VCTs to predict treatment results in patients excluded from past clinical trials.

Near-infrared Nrf2 activator IR-61 dye alleviates radiation-induced lung injury

Oxidative stress injury and subsequent inflammatory response are considered to play critical roles in radiation-induced lung injury (RILI). Nuclear factor erythroid 2-related factor 2 (Nrf2) is a key transcription factor that regulates oxidative stress response and represses inflammation, but its therapeutic value in RILI remains elusive. Our previous studies have shown that the near-infrared (NIR) IR-61 dye evokes intracellular antioxidant defence by enhancing Nrf2 signalling and promoting anti-inflammatory effects. We established a model of RILI in mice exposed to whole-thoracic irradiation. The results showed that IR-61 treatment notably improved pulmonary functions by decreasing lung density and diminishing airway resistance. In addition, IR-61 significantly ameliorated radiation-induced inflammatory cell infiltration and proinflammatory cytokine (IL-1β, IL-6 and TNF-α) release, thereby mitigating inflammatory response. Furthermore, IR-61 mitigated radiation-induced lung fibrosis by decreasing the collagen deposition and the levels of fibrogenesis-related factors (collagen I, collagen III, α-SMA, and fibronectin). More importantly, IR-61 was found to accumulate in the mitochondria of macrophages in irradiated lung tissues. Therefore, the functions of IR-61 in macrophages were further studied in irradiated macrophage cell lines, MH-s and RAW 264.7 in vitro. The results indicated that IR-61 upregulated the expression of Nrf2 and haem oxygenase-1(HO-1) and decreased the levels of reactive oxygen species (ROS) and pro-inflammatory cytokines (IL-1β and IL-6) in macrophages after radiation. In summary, our study suggests that IR-61 effectively mitigates RILI by activating Nrf2 signalling in irradiated lung tissues. In particular, Nrf2-mediated anti-inflammatory and antioxidant effects in irradiated lung tissue macrophages play critical roles in protecting against RILI.

Technological Advancements in External Beam Radiation Therapy (EBRT): An Indispensable Tool for Cancer Treatment

Recent technological advancements have increased the efficacy of radiotherapy, leading to effective management of cancer patients with enhanced patient survival and improved quality of life. Several important developments like multileaf collimator, integration of imaging techniques like positron emission tomography (PET) and computed tomography (CT), involvement of advanced dose calculation algorithms, and delivery techniques have increased tumor dose distribution and decreased normal tissue toxicity. Three-dimensional conformal radiotherapy (3DCRT), intensity-modulated radiotherapy (IMRT), stereotactic radiotherapy, image-guided radiotherapy (IGT), and particle therapy have facilitated the planning procedures, accurate tumor delineation, and dose estimation for effective personalized treatment. In this review, we present the technological advancements in various types of EBRT methods and discuss their clinical utility and associated limitations. We also reveal novel approaches of using biocompatible yttrium oxide scintillator-photosensitizer complex (YSM) that can generate X-ray induced cytotoxic reactive oxygen species, facilitating X-ray activated photodynamic therapy (XPDT (external beam) and/or iXPDT (internal X-ray source)) and azido-derivatives of 2-deoxy-D-glucose (2-DG) as agents for site-specific radiation-induced DNA damage.