Discontinuous stereotactic body radiotherapy schedule increases overall survival in early-stage non-small cell lung cancer

Predictive clinical and dosimetric parameters for risk of relapse in early-stage non-small cell lung cancer treated by SBRT: A large single institution experience

Purpose

To evaluate the impact of dosimetric parameters on efficacy of stereotactic body radiation therapy (SBRT) in early-stage non-small cell lung cancer (ES-NSCLC), using Hypofractionated Treatment Effects in the Clinic (HyTEC) reporting standards.

Methods

From April 2010 to December 2020, 497 patients who received SBRT for ES-NSCLC at the University Hospital of Liège were retrospectively enrolled. A total dose of 40 to 60 Gy in 3-5 fractions (72-180 Gy biologically effective dose with an α/β ratio of 10 (BED10)) was prescribed to the 80 % isodose line of the PTV. Potential clinical and dosimetric predictors of recurrence, overall survival (OS) and disease specific survival (DSS) were evaluated using univariate and multivariate analyses.

Results

After a median follow-up of 32 months (range 3-143 months), the local control and disease-free survival (DFS) rates at 3 years were 91 % (95 % CI: 90 %-93 %) and 75 % (95 % CI: 73 %-77 %), respectively. The median OS was 41.6 months and the median DSS was not reached. On multivariate analysis, a higher gross tumor volume (GTV) Dmax (BED10) (cut-off 198 Gy) and a larger percent of the GTV receiving ≥110 % of the prescribed dose were predictive of a better local control, only GTV volume was correlated with DSS and no parameter was correlated with OS and regional or distant recurrences.

Conclusion

Lung SBRT for ES-NSCLC in 3 to 5 fractions resulted in high local control rates. A higher percent of GTV receiving ≥110 % of the prescribed dose and a higher GTV Dmax (BED10) seem to allow a better local control.

Effect of radiation fractionation on IDO1 via the NF-κB/COX2 axis in non-small cell lung cancer

Radiotherapy (RT) is the mainstay treatment modality for lung cancer. We recently reported that conventionally fractionated radiotherapy (CRT) with daily fractionation of 2Gy significantly increased the activity of indoleamine 2,3-dioxygenase (IDO1), a known immune checkpoint, which predicted poorer long-term survival in patients with non-small cell lung cancer (NSCLC), while stereotactic body radiotherapy (SBRT) using fractionation size of 10Gy did not increase IDO1 activity and had better survival. Here we hypothesized that the hypofractionated SBRT kind of dose fraction stimulates host antitumor immunity via downregulating IDO1 in which CRT could not. We tested this hypothesis in vitro and in vivo using 10Gyx1 and 2Gyx8 fractionations in the laboratory. The results demonstrated that, although there was an initial downregulation after RT, the expression of IDO1 was ultimately upregulated by both fractionation regimens. The 10Gyx1 regimen had minimum upregulation, while the 2Gyx8 regimen significantly increased in IDO1 expression which was positively correlated with the elevated expressions of p-NF-κB and COX2. Pharmacological inhibition of COX2 abolished RT-induced IDO1 expression. Furthermore, the IDO1 inhibitor, D-1-methyl-tryptophan (D-1MT), exerted RT-related tumor-killing effects in the NSCLC cell lines and mouse models. These findings suggest that, in addition to being an immune suppressor, IDO1 may serve as an adaptive resistance factor in RT. Furthermore, an unappreciated mechanism may exist, where a larger fraction size might be superior to conventional sizes in cancer treatment. This study may provide a rationale for future research in using IDO1 as a biomarker to personalize RT dose fractionation and COX2 inhibitor to decrease radiation immune suppression from CRT.

Stereotactic body radiation therapy and thermal ablation for treatment of NSCLC: A systematic literature review and meta-analysis

RATIONALE

Stereotactic body radiation therapy (SBRT) is the standard of care for inoperable early stage non-small cell lung cancer (NSCLC). Use of image guided thermal ablation (IGTA; including microwave ablation [MWA] and radiofrequency ablation [RFA]) has increased in NSCLC, however there are no studies comparing all three.

OBJECTIVE

To compare the efficacy of IGTA (including MWA and RFA) and SBRT for the treatment of NSCLC.

METHODS

Published literature databases were systematically searched for studies assessing MWA, RFA, or SBRT. Local tumor progression (LTP), disease-free survival (DFS), and overall survival (OS) were assessed with single-arm pooled analyses and meta-regressions in NSCLC patients and a stage IA subgroup. Study quality was assessed with a modified methodological index for non-randomized studies (MINORS) tool.

RESULTS

Forty IGTA study-arms (2,691 patients) and 215 SBRT study-arms (54,789 patients) were identified. LTP was lowest after SBRT at one and two years in single-arm pooled analyses (4% and 9% vs. 11% and 18%) and at one year in meta-regressions when compared to IGTA (OR = 0.2, 95%CI = 0.07-0.63). MWA patients had the highest DFS of all treatments in single-arm pooled analyses. In meta-regressions at two and three-years, DFS was significantly lower for RFA compared to MWA (OR = 0.26, 95%CI = 0.12-0.58; OR = 0.33, 95%CI = 0.16-0.66, respectively). OS was similar across modalities, timepoints, and analyses. Older age, male patients, larger tumors, retrospective studies, and non-Asian study region were also predictors of worse clinical outcomes. In high-quality studies (MINORS score ≥ 7), MWA patients had better clinical outcomes than the overall analysis. Stage IA MWA patients had lower LTP, higher OS, and generally lower DFS, compared to the main analysis of all NSCLC patients.

CONCLUSIONS

NSCLC patients had comparable outcomes after SBRT and MWA, which were better than those with RFA.

Relationship between Dose Prescription Methods and Local Control Rate in Stereotactic Body Radiotherapy for Early Stage Non-Small-Cell Lung Cancer: Systematic Review and Meta-Analysis

Variations in dose prescription methods in stereotactic body radiotherapy (SBRT) for early stage non-small-cell lung cancer (ES-NSCLC) make it difficult to properly compare the outcomes of published studies. We conducted a comprehensive search of the published literature to summarize the outcomes by discerning the relationship between local control (LC) and dose prescription sites. We systematically searched PubMed to identify observational studies reporting LC after SBRT for peripheral ES-NSCLC. The correlations between LC and four types of biologically effective doses (BED) were evaluated, which were calculated from nominal, central, and peripheral prescription points and, from those, the average BED. To evaluate information on SBRT for peripheral ES-NSCLC, 188 studies were analyzed. The number of relevant articles increased over time. The use of an inhomogeneity correction was mentioned in less than half of the articles, even among the most recent. To evaluate the relationship between the four BEDs and LC, 33 studies were analyzed. Univariate meta-regression revealed that only the central BED significantly correlated with the 3-year LC of SBRT for ES-NSCLC (p = 0.03). As a limitation, tumor volume, which might affect the results of this study, could not be considered due to a lack of data. In conclusion, the central dose prescription is appropriate for evaluating the correlation between the dose and LC of SBRT for ES-NSCLC. The standardization of SBRT dose prescriptions is desirable.

Stereotactic Body Radiotherapy and Conventional Radiotherapy Induce Cytoskeleton Extension and Enlargement of Cell Morphology in Non-Small Cell Lung Cancer

Stereotactic body radiotherapy (SBRT) is now widely used in cancer therapy. However, the biological effects of SBRT compared with conventional radiotherapy (CRT) are not clear. The cytoskeleton plays an important role in many biological processes and cellular life activities. The effects of SBRT or CRT on the morphology and cytoskeletal structure of non-small cell lung cancer (NSCLC) cells remain unknown. Based on the biologically equivalent dose (BED) formula, we designed SBRT and CRT fractionation regimens with the same BED. The morphology was captured during radiation, and rhodamine-phalloidin immunofluorescence was used to study the cytoskeleton. A lactate dehydrogenase assay kit was used to determine the cell membrane permeability, and western blot was used to detect the cytoskeleton protein expression levels. The morphology and cytoskeleton expanded after SBRT or CRT, with an increase in cell membrane permeability and stable cytoskeleton protein levels. Besides, different dose of SBRT (10,20,30 Gy) induce similar morphology and cytoskeleton enlargement. Our findings indicate that SBRT and CRT can induce cytoskeleton reorganization and the enlargement of cell morphology (at different rates) in NSCLC. The morphology and cytoskeleton enlargement after SBRT are dose independence.