A phase II study on stereotactic body radiotherapy for stage I non-small cell lung cancer

Cost-Utility Analysis of Stereotactic Body Radiation Therapy Versus Surgery for Patients With Stage I Non-small Cell Lung Cancer in Japan

PURPOSE

Stereotactic body radiation therapy (SBRT) for patients with operable stage I non-small cell lung cancer (NSCLC) is less invasive than surgery. However, differences in lifetime costs and patient outcomes remain unclear. In this study, a cost-utility analysis of SBRT compared with surgery for Japanese patients with operable stage I NSCLC was conducted.

METHODS AND MATERIALS

A partitioned survival model was constructed using each treatment arm's overall survival (OS) and progression-free survival (PFS) data. The data for the SBRT arm were extracted from the Japanese multicenter cohort study, which enrolled 678 medically operable patients with stage I NSCLC, and patient registry data were used for the surgery arm. The 5-year OS rate was 78.2% for SBRT and 74.8% for surgery from both studies. The 5-year PFS rate was 57.0% for SBRT and 63.4% for surgery. The quality of life values of PFS and progressive disease were obtained from domestic and overseas literature (PFS: 0.74, progressive disease: 0.65). The time horizon was set to 10 years. The expected costs and quality-adjusted life years for each treatment group were calculated. All costs are expressed in Japanese yen converted to US dollars (USD).

RESULTS

SBRT was the dominant strategy, reducing treatment costs by 4,443.8 USD and increasing quality-adjusted life years by 0.131 compared with surgery. According to probabilistic sensitivity analysis, the probability of SBRT being dominant and cost-effective was 50.6% and 72.4%, respectively. Under the budget impact analysis, the total savings for the patients with stage I NSCLC in Japan was 6,252,870.0 USD (n = 1,407).

CONCLUSIONS

SBRT is a more cost-effective option than surgery in patients with medically operable stage I NSCLC in Japan. Large-scale epidemiologic studies that reflect the latest clinical realities, such as OS/PFS, will be needed to validate this study's robustness.

Predictors of pathologic fracture and local recurrence following stereotactic body radiation therapy to 505 non-spine bone metastases

PURPOSE

Stereotactic Body Radiation Therapy (SBRT) is increasingly applied to treat non-spine bone metastases (NSBM) though data remains limited on this approach. In this retrospective study, we report outcomes and predictors of local failure (LF) and pathological fracture (PF) post-SBRT for NSBM using a mature single-institution database.

METHODS

Patients with NSBM treated with SBRT between 2011 and 2021 were identified. The primary objective was to assess the rates of radiographic LF. Secondary objectives were to assess the rates of in-field PF, overall survival (OS), and late grade ≥ 3 toxicity. Competing risks analysis was used to assess rates of LF and PF. Univariable regression and multivariable regression (MVR) were performed to investigate predictors of LF and PF.

RESULTS

A total of 373 patients with 505 NSBM were included in this study. Median follow-up was 26.5 months. The cumulative incidence of LF at 6, 12, and 24 months were 5.7%, 7.9%, and 12.6%, respectively. The cumulative incidence of PF at 6, 12, and 24 months were 3.8%, 6.1%, and 10.9%, respectively. Lytic NSBM (HR = 2.18; p < 0.01), a lower biologically effective dose (HR = 1.11 per 5 Gy10 decrease; p = 0.04), and a PTV ≥ 54 cc (HR = 4.32; p < 0.01) predicted for a higher risk of LF on MVR. Lytic NSBM (HR = 3.43; p < 0.01), mixed (lytic/sclerotic) lesions (HR = 2.70; p = 0.04), and rib metastases (HR = 2.68; p < 0.01) predicted for a higher risk of PF on MVR.

CONCLUSION

SBRT is an effective modality to treat NSBM with high rates of radiographic local control with an acceptable rate of PF. We identify predictors of both LF and PF that can serve to inform practice and trial design.

Application of real-time MRI-guided linear accelerator in stereotactic ablative body radiotherapy for non-small cell lung cancer: one step forward to precise targeting

PURPOSE

Tumor motion is a major challenge in stereotactic ablative body radiotherapy (SABR) for non-small cell lung cancer (NSCLC), causing excessive irradiation to compensate for this motion. Real-time tumor tracking with a magnetic resonance imaging-guided linear accelerator (MR-Linac) could address this problem. This study aimed to assess the effects and advantages of MR-Linac in SABR for the treatment of lung tumors.

METHODS

Overall, 41 patients with NSCLC treated with SABR using MR-Linac between March 2019 and December 2021 were included. For comparison, 40 patients treated with SABR using computed tomography-based modalities were also enrolled. The SABR dose ranged from 48 to 60 Gy in 3-5 fractions. The primary endpoint was a lower radiation volume compared to CT-based SABR. The secondary endpoint was the local control rate of SABR using the MR-Linac.

RESULTS

The median follow-up time was 19 months (range: 3-105 months). There was no significant difference in the gross tumor volume between the MR and CT groups (7.1 ± 9.3 cm³ vs 8.0 ± 6.8 cm³, p = 0.643), but the planning target volume was significantly smaller in the MR group (20.8 ± 18.8 cm³ vs 34.1 ± 22.9 cm³, p = 0.005). The 1-year local control rates for the MR and CT groups were 92.1 and 75.4%, respectively (p = 0.07), and the 1-year overall survival rates were 87.4 and 87.0%, respectively (p = 0.30).

CONCLUSION

Lung SABR with MR-Linac can reduce the radiation field without compromising the local control rate. Further follow-up is needed to assess the long-term effects.

Comparison of stereotactic body radiotherapy and radiofrequency ablation for early-stage non-small cell lung cancer: a systematic review and meta-analysis

Background

Stereotactic body radiation therapy (SBRT) and radiofrequency ablation (RFA) are recommended for patients with inoperable early-stage non-small cell lung cancer (NSCLC), with both offering promising results. However, it is largely unknown which of these two treatment modalities provides superior benefits for patients. Therefore, this systematic review and meta-analysis compared clinical outcomes and safety between SBRT and RFA in patients with inoperable early-stage NSCLC.

Methods

Eligible studies published between 2001 and 2020 were obtained through a comprehensive search of the PubMed, Medline, Embase, and Cochrane Library databases. Original English-language studies on the treatment of early-stage NSCLC with SBRT or RFA were included. Local control (LC) rates, overall survival (OS) rates, and adverse events were obtained by pooled analyses.

Results

Eighty-seven SBRT studies (12,811 patients) and 18 RFA studies (1,535 patients) met the eligibility criteria. For SBRT, the LC rates (with 95% confidence intervals) at 1, 2, 3, and 5 years were 98% (97-98%), 95% (95-96%), 92% (91-93%), and 92% (91-93%), respectively, which were significantly higher than those for RFA [75% (69-82%), 31% (22-39%), 67% (58-76%), and 41% (30-52%), respectively] (P<0.01). There were no significant differences in short-term OS between SBRT and RFA [1-year OS rate: 87% (86-88%) versus 89% (88-91%), P=0.07; 2-year OS rate: 71% (69-72%) versus 69% (64-74%), P=0.42]. Regarding long-term OS, the 3- and 5-year OS rates for SBRT were 58% (56-59%) and 39% (37-40%), respectively, which were significantly (P<0.01) superior to those for RFA [48% (45-51%) and 21% (19-23%), respectively]. The most common complication of SBRT was radiation pneumonitis (grade ≥2), making up 9.1% of patients treated with SBRT, while pneumothorax was the most common complication of RFA, making up 27.2% of patients treated with RFA.

Discussion

Compared with RFA, SBRT has superior LC and long-term OS rates but similar short-term OS rates. Prospective randomized trials with large sample sizes comparing the efficacy of SBRT and RFA are warranted.

Cost-effectiveness of carbon-ion radiotherapy versus stereotactic body radiotherapy for non-small-cell lung cancer

Carbon-ion radiotherapy (CIRT) for clinical stage I non-small-cell lung cancer (NSCLC) is used as an advanced medical treatment regimen in Japan. Carbon-ion radiotherapy reportedly aids in achieving excellent treatment outcomes, despite its high medical cost. We aimed to compare CIRT with stereotactic body radiotherapy (SBRT) in terms of cost-effectiveness for treating clinical stage I NSCLC. Data of patients with clinical stage I NSCLC treated with CIRT or SBRT at Gunma University between 2010 and 2015 were analyzed. The CIRT and SBRT groups included 62 and 27 patients, respectively. After propensity-score matching, both groups comprised 15 patients. Life year (LY) was used as an indicator of outcome. The CIRT technical fee was 3 140 000 JPY. There was no technical fee for the second CIRT carried out on the same organ within 2 years. The incremental cost-effectiveness ratio (ICER) was calculated by dividing the incremental cost by the incremental LY for 5 years after treatment. Sensitivity analysis was applied to evaluate the impact of LY or costs of each group on ICER. The ICERs were 7 491 017 JPY/LY and 3 708 330 JPY/LY for all patients and matched patients, respectively. Hospitalization and examination costs were significantly higher in the CIRT group, and the impact of the CIRT technical costs was smaller than other costs and LY. Carbon-ion radiotherapy is a cost-effective treatment approach. However, our findings suggest that reducing excessive costs by considering the validity and necessity of examinations and hospitalizations would make CIRT a more cost-effective approach.

Using 4DCBCT simulation and guidance to evaluate inter-fractional tumor variance during SABR for lung tumor within the lower lobe

Inter-fractional tumor variance would lead to insufficient dosage or overdose in tumor region during lung cancer radiotherapy. However, previous works have not considered influence of inter-fractional tumor amplitude variance at treatment position due to lack of effective evaluation method during radiotherapy, especially for lung tumor within the lower lobe. Our objective was to investigate inter-fractional tumor baseline shift and amplitude variance due to respiratory motion with 4DCBCT simulation and guidance during stereotactic ablative body radiotherapy (SABR) for lung tumor. Subject included 19 patients with lung tumor within the lower lobe. 4DCBCT-simulated images at treatment position were acquired sequentially to determine internal tumor volume (ITV) and reference tumor motion at simulation process. Compared with reference tumor motion, 95 4DCBCT-guided images were acquired during each treatment to evaluate inter-fractional tumor baseline shift and amplitude variance, which were − 0.0 ± 1.3 mm and − 0.2 ± 1.4 mm in left–right(LR) direction, 0.9 ± 2.3 mm and 0.4 ± 2.9 mm in superior-inferior (SI) direction, 0.1 ± 1.5 mm and − 0.4 ± 2.0 mm in anterior–posterior (AP) direction. ITV margin were 3.5 mm, 7.5 mm and 5.3 mm in LR, SI and AP directions with van Herk’s (Int J Radiat Oncol Biol Phys 52(5):1407–1422, 2002) formula. 4DCBCT simulation and guidance is a reliable method to evaluate inter-fractional tumor variance during SABR for lung tumor within the lower lobe. ITV margin of 3.5 mm, 7.5 mm and 5.3 mm in LR, SI and AP directions would ensure greater tumor coverage during SABR for lung tumor within the lower lobe.

Impact of low iodine density tumor area ratio on the local control of non-small cell lung cancer through stereotactic body radiotherapy

Lung cancer with low average iodine density measured via contrast-enhanced computed tomography (CT) using dual-energy CT technology has shown a reduced local control rate after stereotactic body radiotherapy (SBRT). The current study therefore investigated the relationship between low iodine density tumor area and its ratio and local recurrence after SBRT. Dual-energy CT was performed on the day before SBRT initiation, with a low iodine density tumor area being defined as that with an iodine density of <1.81 mg cm-3. The low iodine density tumor area, the ratio between the low iodine density tumor area and the entire tumor, and the local recurrence rate were then determined. No correlation was observed between the low iodine density tumor area and the local recurrence rate. However, tumors with a large low iodine density tumor area ratio showed an increased local recurrence rate, with the prognostic accuracy almost similar to that in previous studies using average iodine densities. Our results therefore suggest that the low iodine density tumor area ratio was a useful prognostic index after SBRT, with an accuracy comparable with that of the average iodine density.

Local Control After Stereotactic Body Radiation Therapy for Stage I Non-Small Cell Lung Cancer

PURPOSE

Numerous dose and fractionation schedules have been used to treat medically inoperable stage I non-small cell lung cancer (NSCLC) with stereotactic body radiation therapy (SBRT) or stereotactic ablative radiation therapy. We evaluated published experiences with SBRT to determine local control (LC) rates as a function of SBRT dose.

METHODS AND MATERIALS

One hundred sixty published articles reporting LC rates after SBRT for stage I NSCLC were identified. Quality of the series was assessed by evaluating the number of patients in the study, homogeneity of the dose regimen, length of follow-up time, and reporting of LC. Clinical data including 1, 2, 3, and 5-year tumor control probabilities for stages T1, T2, and combined T1 and T2 as a function of the biological effective dose were fitted to the linear quadratic, universal survival curve, and regrowth models.

RESULTS

Forty-six studies met inclusion criteria. As measured by the goodness of fit χ2/ndf, with ndf as the number of degrees of freedom, none of the models were ideal fits for the data. Of the 3 models, the regrowth model provides the best fit to the clinical data. For the regrowth model, the fitting yielded an α-to-β ratio of approximately 25 Gy for T1 tumors, 19 Gy for T2 tumors, and 21 Gy for T1 and T2 combined. To achieve the maximal LC rate, the predicted physical dose schemes when prescribed at the periphery of the planning target volume are 43 ± 1 Gy in 3 fractions, 47 ± 1 Gy in 4 fractions, and 50 ± 1 Gy in 5 fractions for combined T1 and T2 tumors.

CONCLUSIONS

Early-stage NSCLC is radioresponsive when treated with SBRT or stereotactic ablative radiation therapy. A steep dose-response relationship exists with high rates of durable LC when physical doses of 43-50 Gy are delivered in 3 to 5 fractions.

Stereotactic radiotherapy for early stage non-small cell lung cancer: current standards and ongoing research

Stereotactic body radiation therapy (SBRT) allows for the non-invasive and precise delivery of ablative radiation dose. The use and availability of SBRT has increased rapidly over the past decades. SBRT has been proven to be a safe, effective and efficient treatment for early stage non-small cell lung cancer (NSCLC) and is presently considered the standard of care in the treatment of medically or functionally inoperable patients. Evidence from prospective randomized trials on the optimal treatment of patients deemed medically operable remains owing, as three trials comparing SBRT to surgery in this cohort were terminated prematurely due to poor accrual. Yet, SBRT in early stage NSCLC is associated with favorable toxicity profiles and excellent rates of local control, prompting discussion in regard of the treatment of medically operable patients, where the standard of care currently remains surgical resection. Although local control in early stage NSCLC after SBRT is high, distant failure remains an issue, prompting research interest to the combination of SBRT and systemic treatment. Evolving advances in SBRT technology further facilitate the safe treatment of patients with medically or anatomically challenging situations. In this review article, we discuss international guidelines and the current standard of care, ongoing clinical challenges and future directions from the clinical and technical point of view.

Can dosimetry affect local control and survival in patients with early-stage lung cancer treated with Stereotactic Ablative Radiotherapy (SABR)? An analysis of the UK's largest cohort of lung SABR patients

PURPOSE/OBJECTIVES

A recent study has shown that tight conformity of lung Stereotactic Ablative Radiotherapy (SABR) plans might worsen loco-regional control and can predict distant metastases. The study aims to report overall survival (OS), progression-free survival (PFS), local recurrence free survival (LRFS), and dosimetry of early-stage lung cancer patients treated with SABR and to try to explore any dosimetric predictor of outcomes.

MATERIAL AND METHODS

Patients treated in our institute (May 2009-August 2018) were included. Electronic medical records were reviewed for baseline characteristics, treatment details, and outcomes. Dosimetric data were extracted from Xio and Monaco software. Patients were treated according to the United Kingdom (UK) SABR consortium guidelines. Kaplan-Meier's analysis with log-rank test was used for survival analysis. The univariate and multivariable Cox regression model was used for correlating dosimetric variables and outcomes.

RESULTS

We treated 1266 patients with median age of 75 years and 47.4% were male. Median follow up was 56 months. Median OS was 36 months with 1, 2, and 5 years OS of 84.2%, 64.5%, and 31.5%, respectively. Median for PFS and LRFS was not reached. One, 2, and 5 years PFS were 87.4%, 78.4%, and 72.5%, respectively. One, 2, and 5 years LRFS were 98.2%, 95.1%, and 92.5%, respectively. Planning target volume (PTV), dose to 99% volume of PTV (D99), and R50 (volume receiving the 50% dose/volume (PTV)) were significantly associated with OS. PTV, mean lung dose (MLD), V20 (volume of lung minus gross tumour volume (GTV) receiving 20 Gy), V12.5 (volume of lung minus GTV receiving 12.5 Gy), and dose fractionation were significantly associated with PFS. Nothing was associated with LRFS on univariate analysis. R100 of >1.1 was associated with better OS, PFS, and LRFS compared to R100 ≤ 1.1.

CONCLUSION

SABR achieves good clinical outcomes in patients with early-stage lung cancer; even in elderly patients with multiple comorbidities. In the largest UK early lung cancer cohort treated with SABR, we found that dosimetry correlates with clinical outcomes. Further validation of these results is needed to guide future optimisation of SABR delivery.

A long-term survival case following salvage stereotactic radiotherapy for local recurrence after definitive chemoradiotherapy for stage III non-small cell lung cancer

A 56-year-old male with stage IIIA (UICC 7th) non-small cell lung cancer (adenocarcinoma) received radiotherapy with 66 Gy/33 fractions concomitant with CBDCA and PTX. A partial response was achieved after chemoradiotherapy and the tumor continued to shrink over a period of 1 year; however, regrowth of the tumor attached to the aortic arch was observed without any other residual tumor or metastases. We diagnosed recurrence with slightly increased ¹⁸F-FDG uptake (maximum standardized uptake value: 12.2). Stereotactic radiotherapy was performed for the relapsed lesion with 60 Gy/10 fractions. The patient has survived for more than 5 years after stereotactic radiotherapy without recurrence or metastases, although he has been suffering from chest pain that has required treatment with a low dose of oxycodone.

Oncologic Outcomes of Surgery Versus SBRT for Non-Small-Cell Lung Carcinoma: A Systematic Review and Meta-analysis

BACKGROUND

The optimal treatment of stage I non-small-cell lung carcinoma is subject to debate. The aim of this study was to compare overall survival and oncologic outcomes of lobar resection (LR), sublobar resection (SR), and stereotactic body radiotherapy (SBRT).

METHODS

A systematic review and meta-analysis of oncologic outcomes of propensity matched comparative and noncomparative cohort studies was performed. Outcomes of interest were overall survival and disease-free survival. The inverse variance method and the random-effects method for meta-analysis were utilized to assess the pooled estimates.

RESULTS

A total of 100 studies with patients treated for clinical stage I non-small-cell lung carcinoma were included. Long-term overall and disease-free survival after LR was superior over SBRT in all comparisons, and for most comparisons, SR was superior to SBRT. Noncomparative studies showed superior long-term overall and disease-free survival for both LR and SR over SBRT. Although the papers were heterogeneous and of low quality, results remained essentially the same throughout a large number of stratifications and sensitivity analyses.

CONCLUSION

Results of this systematic review and meta-analysis showed that LR has superior outcomes compared to SBRT for cI non-small-cell lung carcinoma. New trials are underway evaluating long-term results of SBRT in potentially operable patients.

Stereotactic body radiotherapy versus percutaneous local tumor ablation for early-stage non-small cell lung cancer

OBJECTIVES

To compare patterns of care and overall survival (OS) between stereotactic body radiotherapy (SBRT) and percutaneous local tumor ablation (LTA) for non-surgically managed early-stage non-small-cell lung cancer (NSCLC).

MATERIALS AND METHODS

The National Cancer Database (NCDB) was queried from 2004 to 2014 for adults with non-metastatic, node-negative invasive adenocarcinoma or squamous cell carcinoma of the lung with primary tumor size ≤5.0 cm who did not undergo surgery or chemotherapy and received SBRT or LTA. Patterns of care were assessed with multivariate logistic regression. After propensity-score weighting with generalized boosted regression, OS was assessed with univariate and doubly-robust multivariate Cox regression.

RESULTS

Of 15,792 patients, 14,651 (93%) received SBRT and 1141 (7%) received LTA. Increasing age (OR 1.01, p = .035), treatment at an academic institution (OR 2.94, p < .001), increasing tumor size (OR 1.05, p < .001), and more recent year of diagnosis (OR 1.43, p < .001) were predictive of treatment with SBRT, whereas comorbidities (OR 0.74, p = .003) and treatment at a high-volume facility (OR 0.05, p < .001) were predictive for LTA. At a median follow-up of 26.2 months, SBRT was associated with improved OS relative to LTA within a propensity-score weighted doubly-robust multivariate analysis (HR 0.71, p < .001). On weighted subgroup analyses, improved OS was observed with SBRT for tumor sizes >2.0 cm (HR 0.72, p < .001) and for those treated at high-volume facilities (HR 0.71, p < .001). No OS difference was found with SBRT or LTA in tumor sizes ≤2.0 cm (HR 0.90, p = .227).

CONCLUSION

Within the NCDB, SBRT was more commonly utilized and was associated with improved OS when compared to percutaneous LTA for patients with non-surgically managed early-stage NSCLC. Patients with small tumor volumes likely represent an appropriate population for future prospective randomized comparisons between SBRT and LTA.

[Lung cancer and elective nodal irradiation: A solved issue?]

Lung cancer treatment is a heavy workload for radiation oncologist and that field showed many evolutions over the last two decades. The issue about target volume was raised when treatment delivery became more precise with the development of three-dimensional conformal radiotherapy. Initially based upon surgical series, numerous retrospective and prospective studies aimed to evaluate the risk of elective nodal failure of involved-field radiotherapy compared to standard large field elective nodal irradiation. In every setting, locally advanced non-small cell lung cancer, localized non-small cell lung cancer, localized small cell lung cancer, exclusive chemoradiation or postoperative radiotherapy, most of the studies showed no significant difference between involved-field radiotherapy or elective nodal irradiation with elective nodal failure rate under 5% at 2 years, provided staging had been done with modern imaging and diagnostic techniques (positron emission tomography scan, endoscopy, etc.). Moreover, if reducing irradiated volumes are safe regarding recurrences, involved-field radiotherapy allowed dose escalation while reducing acute and late oesophageal, cardiac and pulmonary toxicities. Consequently, major clinical trials involving radiotherapy initiated in the last two decades and international clinical guidelines recommended omission of elective nodal irradiation in favour of in-field radiotherapy.

Should stereotactic body radiotherapy doses be adjusted according to tumor size in early-stage non-small-cell lung cancer? A systematic review and meta-analysis

Aim: Treatment schedules of stereotactic body radiotherapy (SBRT) for patients with early-stage non-small-cell lung cancer (NSCLC) are varied. The aim of this study was to clarify the optimal biologically effective dose (BED) for the treatment of stage I NSCLC. Methods: Research findings published after 1990 detailing the effects of SBRT on early-stage NSCLC patients were compiled from the Medline, Embase, Web of Science and Cochrane Library. For comparative analyses, two groups were divided into moderate BED (100-150 Gy) and high BED (BED ≥150 Gy). Results: Two moderate BED studies and four high BED studies were selected for analysis. The results from the analysis of four moderate and high groups suggest that the 2-year local control rate was significantly lower in moderate BED group than that of high BED group (p = 0.04). Subgroup analysis by tumor size was also conducted. For patients with Stage IA disease, no difference in overall survival (OS) was found. No statistically significant difference was achieved in the instance of Stage IB tumor; however, the 2-year OS showed a trend in favor of high BED (p = 0.08). The remaining two studies, comparing 106 Gy (Stage IA) to 120-132 Gy (Stage IB) treatment, indicated a significantly higher 3-year OS in the 106 Gy group than that of 120-132 Gy group (p = 0.009). Conclusion: In patients with early-stage NSCLC treated with SBRT, our analyses suggested that a moderate BED, especially 106 Gy, is sufficient for the treatment of Stage IA tumor; although a high BED conferred no significant benefit to OS for the treatment of Stage IB tumor, a higher local control rate was achieved. Further detailed studies should be performed to explore the optimal BED for the treatment of Stage IB tumor.

Change in Apparent Diffusion Coefficient Is Associated With Local Failure After Stereotactic Body Radiation Therapy for Non-Small Cell Lung Cancer: A Prospective Clinical Trial

PURPOSE

Response assessment with computed tomography after stereotactic body radiation therapy (SBRT) for non-small cell lung cancer (NSCLC) is challenging because myriad anatomic changes can occur after treatment. Diffusion-weighted magnetic resonance imaging (MRI) may provide additional data to guide therapy response. The primary objective was to evaluate the effect of SBRT on the mean apparent diffusion coefficient (ADC).

METHODS AND MATERIALS

This is a prospective clinical study of patients with NSCLC who received SBRT to the primary lung lesion. Patients underwent MRI scans before and at 1 month after completion of SBRT. MRI consisted of T1- and T2-weighted sequences, along with postcontrast, dynamic-contrast, and diffusion-weighted sequences with construction of ADC maps. Two blinded radiologists generated the ADC. SBRT was given over 5 fractions.

RESULTS

A total of 13 patients were enrolled. Twelve patients were eligible for analysis. An average increase of 50% and 46% in mean single-plane ADC was observed after treatment by readers 1 and 2, respectively (P < .01, both reviewers). There was good interobserver agreement of single-plane ADC values between the 2 radiologists (Pearson correlation of 0.85 [baseline] and 0.89 [1-month post-SBRT], P < .001 for both). There was also a significant 18% increase in mean volumetric ADC on the 1-month scan (Wilcoxon P = .02). Two patients developed a local failure after SBRT, 1 at 6 months and the other at 34 months. Using a threshold of volumetric ADC increase of greater than 40%, 2 of 2 patients demonstrated local failure compared with 0 of 10 patients below this limit.

CONCLUSIONS

A statistically significant increase in ADC was observed 1 month after treatment. An ADC increase of 40% at 1 month was associated with a higher rate of local failure. This pilot study provides impetus for studying ADC as a radiomic biomarker in patients receiving lung SBRT for NSCLC.

Lobectomy versus stereotactic ablative radiotherapy for medically operable patients with stage IA non-small cell lung cancer: A virtual randomized phase III trial stratified by age

BACKGROUND

Although the choice between stereotactic ablative radiotherapy (SABR) and lobectomy for early-stage non-small cell lung cancer (NSCLC) has been debated for years, the two procedures have not yet been directly compared in a randomized trial. We conducted a virtual randomized phase III trial stratified by age to compare the effectiveness of lobectomy and SABR for medically operable patients with stage IA (AJCC eighth) NSCLC using the Markov model analysis.

METHODS

A Markov model was developed to simulate a cohort of patients aged 45-85 years with stage IA NSCLC who had undergone either lobectomy or SABR and were followed up for their remaining lifetime. Each virtual patient was randomly assigned to undergo lobectomy or SABR, and 10 000 patients were allocated to each group. All estimates of the variables were obtained by a systematic review of published articles.

RESULTS

The lobectomy group showed a better life expectancy than the SABR group, in patients under 75 years of age. However, no statistically significant difference was seen in patients 75 years or older. The predicted life expectancy was 9.43 and 8.70 years in 75-year-old patients in the lobectomy and SABR groups, respectively. However, the 95%CI for the difference in life expectancy between the two groups was - 0.06-1.50 years (P = 0.0689).

CONCLUSIONS

The Markov model showed no statistically significant difference in the expected overall survival in stage IA NSCLC patients who were older than 75 years and had undergone SABR or lobectomy.

Technical Note: In silico and experimental evaluation of two leaf-fitting algorithms for MLC tracking based on exposure error and plan complexity

PURPOSE

Multileaf collimator (MLC) tracking is being clinically pioneered to continuously compensate for thoracic and pelvic motion during radiotherapy. The purpose of this work was to characterize the performance of two MLC leaf-fitting algorithms, direct optimization and piecewise optimization, for real-time motion compensation with different plan complexity and tumor trajectories.

METHODS

To test the algorithms, both in silico and phantom experiments were performed. The phantom experiments were performed on a Trilogy Varian linac and a HexaMotion programmable motion platform. High and low modulation VMAT plans for lung and prostate cancer cases were used along with eight patient-measured organ-specific trajectories. For both MLC leaf-fitting algorithms, the plans were run with their corresponding patient trajectories. To compare algorithms, the average exposure errors, i.e., the difference in shape between ideal and fitted MLC leaves by the algorithm, plan complexity and system latency of each experiment were calculated.

RESULTS

Comparison of exposure errors for the in silico and phantom experiments showed minor differences between the two algorithms. The average exposure errors for in silico experiments with low/high plan complexity were 0.66/0.88 cm² for direct optimization and 0.66/0.88 cm² for piecewise optimization, respectively. The average exposure errors for the phantom experiments with low/high plan complexity were 0.73/1.02 cm² for direct and 0.73/1.02 cm² for piecewise optimization, respectively. The measured latency for the direct optimization was 226 ± 10 ms and for the piecewise algorithm was 228 ± 10 ms. In silico and phantom exposure errors quantified for each treatment plan demonstrated that the exposure errors from the high plan complexity (0.96 cm² mean, 2.88 cm² 95% percentile) were all significantly different from the low plan complexity (0.70 cm² mean, 2.18 cm² 95% percentile) (P < 0.001, two-tailed, Mann-Whitney statistical test).

CONCLUSIONS

The comparison between the two leaf-fitting algorithms demonstrated no significant differences in exposure errors, neither in silico nor with phantom experiments. This study revealed that plan complexity impacts the overall exposure errors significantly more than the difference between the algorithms.

Survival After Stereotactic Body Radiation Therapy for Clinically Diagnosed or Biopsy-Proven Early-Stage NSCLC: A Systematic Review and Meta-Analysis

INTRODUCTION

Stereotactic body radiation therapy (SBRT) is a promising curative treatment for early-stage NSCLC. It is unclear if survival outcomes for SBRT are influenced by a lack of pathological confirmation of malignancy and staging of disease in these patients. In this systematic review and meta-analysis, we assess survival outcomes after SBRT in studies with patients with clinically diagnosed versus biopsy-proven early-stage NSCLC.

METHODS

The main databases were searched for trials and cohort studies without restrictions to publication status or language. Two independent researchers performed the screening and selection of eligible studies. Outcomes were overall survival, cancer-specific survival, and disease-free survival. The inverse variance method and the random effects method for meta-analysis were used to assess pooled survival estimates.

RESULTS

A total of 11,195 nonduplicate records were identified by the original search strategy. After screening by title and abstract, 1051 potentially eligible records were identified. A total of 43 articles were included. The comparative studies showed lower 3-year overall survival and lower 2-year and 5-year cancer-specific survival for biopsy-proven disease compared to clinical disease. However, 5-year overall survival was the same for both groups. For the pooled estimates, 3-year disease-free survival and 2-year cancer-specific survival were lower for biopsied disease.

CONCLUSIONS

Results of this systematic review and meta-analysis show a discrepancy in oncological outcomes for patients undergoing SBRT for suspected early-stage NSCLC in whom there is pathologic conformation of malignancy and those who there is only a clinical diagnose of NSCLC. These results emphasize the importance of obtaining pathologic proof of malignancy.

Stereotactic body radiation therapy in early-stage NSCLC: historical review, contemporary evidence and future implications

Clinical use of stereotactic body radiation therapy (SBRT) has increased dramatically over the last 2 decades and is the current standard-of-care in cases of inoperable early stage non-small-cell lung cancer. While surgical resection remains the standard-of-care for operable patients, several ongoing clinical trials are investigating the role of SBRT in these operative candidates as well. Taking into consideration the expanding role and utility of SBRT, this paper will: review the historical basis of SBRT; examine landmark trials establishing the framework for the current body of evidence; discuss areas of active and future research; and identify epidemiological trends that are likely to further increase the use of SBRT.

Stereotactic body radiation therapy for non-small cell lung cancer: A review

Stereotactic body radiation therapy (SBRT) is the treatment of choice for medically inoperable patients with early stage non-small cell lung cancer (NSCLC). A literature search primarily based on PubMed electronic databases was completed in July 2018. Inclusion and exclusion criteria were determined prior to the search, and only prospective clinical trials were included. Nineteen trials from 2005 to 2018 met the inclusion criteria, reporting the outcomes of 1434 patients with central and peripheral early stage NSCLC. Patient eligibility, prescription dose and delivery, and follow up duration varied widely. Three-years overall survival ranged from 43% to 95% with loco-regional control of up to 98% at 3 years. Up to 33% of patients failed distantly after SBRT at 3 years. SBRT was generally well tolerated with 10%-30% grade 3-4 toxicities and a few treatment-related deaths. No differences in outcomes were observed between conventionally fractionated radiation therapy and SBRT, central and peripheral lung tumors, or inoperable and operable patients. SBRT remains a reasonable treatment option for medically inoperable and select operable patients with early stage NSCLC. SBRT has shown excellent local and regional control with toxicity rates equivalent to surgery. Decreasing fractionation schedules have been consistently shown to be both safe and effective. Distant failure is common, and chemotherapy may be considered for select patients. However, the survival benefit of additional interventions, such as chemotherapy, for early stage NSCLC treated with SBRT remains unclear.

Treatment-Related Adverse Effects in Lung Cancer Patients after Stereotactic Ablative Radiation Therapy

Introduction

Lung cancer is a disease which, despite the advancements in treatment, still has a very poor 5-year survival rate. Stereotactic ablative radiation therapy (SABR) is a highly advanced, sophisticated, and safe treatment which allows patients with early stage lung cancer to be treated effectively without invasive procedures and with excellent clinical outcomes. Avoiding surgery minimises morbidity and recovery time, bettering patients' quality of life. Furthermore, SABR allows patients unsuitable for surgery to still undergo curative treatment.

Methods

We aimed to review SABR-related normal tissue toxicities reported in the literature. While many studies assess safety, clinical efficacy, and disease control of SABR for lung cancer, the number of comprehensive reviews that analyse SABR-related side-effects is scarce. This integrative review summarises the toxicities reported in literature based on published clinical trials and tumour location (central or peripheral tumours) for available SABR techniques. Given that the majority of the clinical studies did not report on the statistical significance (e.g., p-values and confidence intervals) of the toxicities experienced by patients, statistical analyses cannot be performed. As a result, adverse events are compiled from clinical reports; however, due to various techniques and nonstandard toxicity reports, no meta-analysis is possible at the current stage of reported data.

Results

When comparing lobectomy and SABR in phase III trials, surgery resulted in increased procedure-related morbidity. In phase II trials, very few studies showed high grade toxicities/fatalities as a result of SABR for lung cancer. Gross target volume size was a significant predictor of toxicity. An ipsilateral mean lung dose larger than 9 Gy was significantly associated with radiation pneumonitis.

Conclusions

Based on the studies reviewed SABR is a safe treatment technique for lung cancer; however, further well-designed phase III randomised clinical trials are required to produce timely conclusive results and to enable their comparison and statistical analysis.

Do SABR-related toxicities for lung cancer depend on treatment delivery?

Stereotactic ablative radiation therapy for lung cancer is an advanced technique where tumours are ablated with hypofractionated radiation doses, with a high degree of accuracy. The aim of this paper is to review the available literature and to discuss the SABR-induced toxicities for lung malignancies as a function of radiation delivery technique. A Medline search was conducted to identify the appropriate literature to fulfil the aim of this review and data from all applicable papers were collated and analysed. The most common techniques of SABR delivery employ linear accelerators, CyberKnife robotic radiosurgery system, TomoTherapy and the Novalis beam surgery system. Linear accelerator-based treatments give rise to a variety of toxicities that are strongly dependent on both patient-related factors and planning/dosimetry-related factors. The limited number of studies using CyberKnife reported low grade toxicities. Grade three toxicities mainly include fatigue and chest pain, usually in less than 10% of patients. All treatment techniques presented show efficiency in SABR delivery with various toxicities which, at this stage, cannot render one technique better than the other. For more conclusive results, well-designed phase three randomised clinical trials are required with better patient selection criteria, including dose and fractionation, treatment machine and technique, along with the consistent selection of a common toxicity grading criterion.

Local control and fracture risk following stereotactic body radiation therapy for non-spine bone metastases

AIMS

To report local control and toxicity rates for patients treated with stereotactic body radiotherapy (SBRT) for non-spine bone metastases.

METHODS AND MATERIALS

Eighty-one patients with 106 non-spine bone metastases were treated between 2011 and 2014 and retrospectively reviewed. Indications included: oligometastases (63%), oligoprogression (17.3%), retreatment (2.4%) or other (17.3%). Cumulative incidence function was used to assess local recurrence and fracture probability. Bivariate relationships were investigated based on selected patient, tumour and dose-volume factors.

RESULTS

Mean follow-up was 13 months (range, 0.25-45.6) and the median patient age was 66.4 years (range, 36-86). Most patients were male (60.5%) and the predominant histology prostate cancer (32%). Bone metastases were most commonly located in the pelvis (41.5%) and almost half sclerotic. The most common prescriptions were 30 Gy/5 (30.2%) and 35 Gy/5 (42.5%). The cumulative incidence of local recurrence at 6,18 and 24 months respectively was 4.7%, 8.3% and 13.3% with a mean time to local recurrence of 11.8 months (range, 3.9-23.4). A significant association was found between local recurrence and volume of the PTV (p = 0.02), with larger PTVs having a greater risk of local failure. Fracture was observed radiographically in the treatment volume in 9/106 (8.5%) of treated lesions and the mean time to fracture was 8.4 months (range, 0.7-32.5 months). With respect to predictors, a trend was observed for lytic lesions (p = 0.11) and female gender (p = 0.09).

CONCLUSIONS

The results of this study confirm that SBRT yields high rates of long-term local control for non-spine bone metastases with a low fracture risk.

Significance of stereotactic body radiotherapy in older patients with early stage non-small cell lung cancer

OBJECTIVES

Our aim was to investigate long-term treatment outcomes in older patients with early stage non-small cell lung cancer (NSCLC) and the presence or absence of therapeutic benefits, using the G8 screening tool.

METHODS

We retrospectively studied 43 older patients (median age 78 years, range 65-89 years) with stage I lung tumors (T1 and T2 tumors in 34 and 9 patients, respectively), who underwent stereotactic body radiotherapy (SBRT). This study assessed outcomes in a cohort of patients who received geriatric assessments, performed between 2004 and 2011, before the start of their SBRT regimen. Any questions asked to patients before undergoing treatment were applied to the G8 screening tool.

RESULTS

G8 scores ranged from 8 to 16 (median, 12) in all patients (n = 43), while G8 scores in the T1 and T2 groups ranged from 9 to 16 (median, 13) and 8 to 15 (median, 12), respectively. In patients with G8 scores ≤12, the 2-year and 5-year survival rates were 56.1% and 28% respectively, while the rates were 94.1% and 68.4%, respectively, in patients with G8 scores ≥13 (P = 0.0014). During long-term follow-up, 25.9% of the patients (n = 43) died of the primary disease, NSCLC, and 34.9% of patients died of other diseases or other types of cancer.

CONCLUSION

SBRT may be effective, even in older adults. Regardless of age, SBRT improved the long-term survival of patients only with G8 scores ≥13. The G8 screening tool may aid in determining whether older patients with comorbidities would benefit from SBRT.

The impact of technology on the changing practice of lung SBRT

Stereotactic body radiotherapy (SBRT) for lung tumours has been gaining wide acceptance in lung cancer. Here, we review the technological evolution of SBRT delivery in lung cancer, from the first treatments using the stereotactic body frame in the 1990's to modern developments in image guidance and motion management. Finally, we discuss the impact of current technological approaches on the requirements for quality assurance as well as future technological developments.

Optimizing immobilization, margins, and imaging for lung stereotactic body radiation therapy

The simultaneous advancement of technologies for the delivery of precisely targeted radiation therapy and the paradigm shift to substantial hypofractionation have led to significant improvements in the treatment of early stage non-small cell lung cancer (ES-NSCLC). Stereotactic body radiation therapy (SBRT) has become a well-established option for the treatment of ES-NSCLC and is now becoming widely available within the radiation oncology community. Implementation of this technique, however, requires highly accurate target delineation, thorough evaluation of tumor motion, and improved on-board imaging at the time of treatment for patient alignment, each of which is critical for successful tumor control and mitigation of risks to normal tissues. In this article, we review updates and issues related to immobilization and image guidance for SBRT in the treatment of ES-NSCLC.

Frontiers in planning optimization for lung SBRT

Emerging data are showing the safety and the efficacy of Stereotactic Body Radiation therapy (SBRT) in lung cancer management. In this context, the very high doses delivered to the Planning Target Volume, make the planning phase essential for achieving high dose levels conformed to the shape of the target in order to have a good prognosis for tumor control and to avoid an overdose in relevant healthy adjacent tissue. In this non-systematic review we analyzed the technological and the physics aspects of SBRT planning for lung cancer. In particular, the aims of the study were: (i) to evaluate prescription strategies (homogeneous or inhomogeneous), (ii) to outline possible geometrical solutions by comparing the dosimetric results (iii) to describe the technological possibilities for a safe and effective treatment, (iv) to present the issues concerning radiobiological planning and the automation of the planning process.

The evolution of proton beam therapy: Current and future status

Proton beam therapy (PBT) has been increasingly used in a variety of cancers due to its excellent physical properties and superior dosimetric parameters. PBT may improve patient survival by improving the local tumor treatment rate while reducing injury to normal organs, which may result in fewer radiation-induced adverse effects. However, the significant cost of establishing and maintaining proton facilities cannot be overlooked. In addition, there has been significant controversy regarding routine application of this treatment in certain types of cancer. The challenges of PBT in the future mainly include the lack of basic clinical trials, unclear biological effects, immature imaging technology and miniaturization of imaging guidance. Overcoming these limitations may promote the rapid development of PBT. We herein provide an overview of the existing literature on the efficacy and toxicity of common oncological applications of proton beam therapy.

Dosimetric evaluation of MLC-based dynamic tumor tracking radiotherapy using digital phantom: Desired setup margin for tracking radiotherapy

The purpose of this study is to evaluate the dosimetric impact of the margin on the multileaf collimator-based dynamic tumor tracking plan. Furthermore, an equivalent setup margin (EM) of the tracking plan was determined according to the gated plan. A 4-dimensional extended cardiac-torso was used to create 9 digital phantom datasets of different tumor diameters (TDs) of 1, 3, and 5 cm and motion ranges (MRs) of 1, 2, and 3 cm. For each dataset, respiratory gating (30% to 70% phase) and tumor tracking treatment plans were prepared using 8-field 3-dimensional conformal radiation therapy by 4-dimensional dose calculation. The total lung V20 was calculated to evaluate the dosimetric impact for each case and to estimate the EM with the same impact on lung V20 obtained with the gating plan with a setup margin of 5 mm. The EMs for {TD = 1 cm, MR = 1 cm}, {TD = 1 cm, MR = 2 cm}, and {TD = 1 cm, MR = 3 cm} were estimated as 5.00, 4.16, and 4.24 mm, respectively. The EMs for {TD = 5 cm, MR = 1 cm}, {TD = 5 cm, MR = 2 cm}, and {TD = 5 cm, MR = 3 cm} were estimated as 4.24 mm, 6.35 mm, and 7.49 mm, respectively. This result showed that with a larger MR, the EM was found to be increased. In addition, with a larger TD, the EM became smaller. Our result showing the EMs provided the desired accuracy for multileaf collimator-based dynamic tumor tracking radiotherapy.

Proton beam therapy in non-small cell lung cancer: state of the art

This review summarizes the past and present status of proton beam therapy (PBT) for lung cancer. PBT has a unique characteristic called the Bragg peak that enables a reduction in the dose of normal tissue around the tumor, but is sensitive to the uncertainties of density changes. The heterogeneity in electron density for thoracic lesions, such as those in the lung and mediastinum, and tumor movement according to respiration necessitates respiratory management for PBT to be applied in lung cancer patients. There are two types of PBT - a passively scattered approach and a scanning approach. Typically, a passively scattered approach is more robust for respiratory movement and a scanning approach could result in a more conformal dose distribution even when the tumor shape is complex. Large tumors of centrally located lung cancer may be more suitably irradiated than with intensity-modulated radiotherapy (IMRT) or stereotactic body radiotherapy (SBRT). For a locally advanced lung cancer, PBT can spare the lung and heart more than photon IMRT. However, no randomized controlled trial has reported differences between PBT and IMRT or SBRT for early-stage and locally advanced lung cancers. Therefore, a well-designed controlled trial is warranted.

Comparison of the Effectiveness of Radiofrequency Ablation With Stereotactic Body Radiation Therapy in Inoperable Stage I Non-Small Cell Lung Cancer: A Systemic Review and Pooled Analysis

PURPOSE

To performed a systematic review and pooled analysis to compare clinical outcomes of stereotactic body radiation therapy (SBRT) and radiofrequency ablation (RFA) for the treatment of medically inoperable stage I non-small cell lung cancer.

METHODS AND MATERIALS

A comprehensive literature search for published trials from 2001 to 2012 was undertaken. Pooled analyses were performed to obtain overall survival (OS) and local tumor control rates (LCRs) and adverse events. Regression analysis was conducted considering each study's proportions of stage IA and age.

RESULTS

Thirty-one studies on SBRT (2767 patients) and 13 studies on RFA (328 patients) were eligible. The LCR (95% confidence interval) at 1, 2, 3, and 5 years for RFA was 77% (70%-85%), 48% (37%-58%), 55% (47%-62%), and 42% (30%-54%) respectively, which was significantly lower than that for SBRT: 97% (96%-98%), 92% (91%-94%), 88% (86%-90%), and 86% (85%-88%) (P<.001). These differences remained significant after correcting for stage IA and age (P<.001 at 1 year, 2 years, and 3 years; P=.04 at 5 years). The effect of RFA was not different from that of SBRT on OS (P>.05). The most frequent complication of RFA was pneumothorax, occurring in 31% of patients, whereas that for SBRT (grade ≥3) was radiation pneumonitis, occurring in 2% of patients.

CONCLUSIONS

Compared with RFA, SBRT seems to have a higher LCR but similar OS. More studies with larger sample sizes are warranted to validate such findings.

Comparison of particle beam therapy and stereotactic body radiotherapy for early stage non-small cell lung cancer: A systematic review and hypothesis-generating meta-analysis

PURPOSE

To assess hypo-fractionated particle beam therapy (PBT)'s efficacy relative to that of photon stereotactic body radiotherapy (SBRT) for early stage (ES) non-small cell lung cancer (NSCLC).

METHODS

Eligible studies were identified through extensive searches of the PubMed, Medline, Google-scholar, and Cochrane library databases from 2000 to 2016. Original English publications of ES NSCLC were included. A meta-analysis was performed to compare the survival outcome, toxicity profile, and patterns of failure following each treatment.

RESULTS

72 SBRT studies and 9 hypo-fractionated PBT studies (mostly single-arm) were included. PBT was associated with improved overall survival (OS; p=0.005) and progression-free survival (PFS; p=0.01) in the univariate meta-analysis. The OS benefit did not reach its statistical significance after inclusion of operability into the final multivariate meta-analysis (p=0.11); while the 3-year local control (LC) still favored PBT (p=0.03).

CONCLUSION

Although hypo-fractionated PBT may lead to additional clinical benefit when compared with photon SBRT, no statistically significant survival benefit from PBT over SBRT was observed in the treatment of ES NSCLC in this hypothesis-generating meta-analysis after adjusting for potential confounding variables.

A systematic review of outcomes following stereotactic ablative radiotherapy in the treatment of early-stage primary lung cancer

Stereotactic ablative body radiotherapy (SABR) describes a radiotherapy (RT) technique where high doses of radiation are precisely delivered to an extracranial target within the body, using either a single fraction of RT or using multiple small numbers of fractions. SABR has now become the standard of care treatment for patients with early-stage non-small-cell lung cancer (NSCLC) for whom surgery is not appropriate. This systematic review considers the evidence supporting the use of SABR in early-stage NSCLC, reported toxicity rates, the use of SABR in centrally located NSCLC, the use of SABR as salvage therapy following surgery or RT, and future potential drug combinations with SABR.

Assessing the Need for Adjuvant Chemotherapy After Stereotactic Body Radiation Therapy in Early-stage Non-small Cell Lung Carcinoma

Purpose

Surgery remains the standard treatment for medically operable patients with early-stage non-small cell lung carcinoma (NSCLC). Following surgical resection, adjuvant chemotherapy is recommended for large tumors >4 cm. For unfit patients, stereotactic body radiation therapy (SBRT) has emerged as an excellent alternative to surgery. This study aims to assess patterns of recurrence and discuss the role of chemotherapy after SBRT for NSCLC.

Methods

We reviewed patients treated with SBRT for primary early-stage NSCLC between 2009 and 2015. Total target doses were between 50 and 60 Gy administered in three to eight fractions. All patients had a staging fluorodeoxyglucose (FDG) positron emission tomography (PET) integrated with computed tomography (CT) scan, and histologic confirmation was obtained whenever possible. Mediastinal staging was performed if lymph node involvement was suspected on CT or PET/CT. Survival outcomes were estimated using the Kaplan-Meier method.

Results

Among the 559 early-stage NSCLC patients treated with SBRT, 121 patients were stage T2N0. The one-year and three-year overall survival rates were 88% and 70%, respectively, for patients with T2 disease, compared to 95% and 81%, respectively, for the T1 patients (p<0.05). The one-year and three-year local control rates were equal in both groups (98% and 91%, respectively). In T2 patients, 25 (21%) presented a relapse, among which 21 (84%) were nodal or distant. The median survival of T2N0 patients following a relapse was 11 months.

Conclusion

Lung SBRT provides high local control rates, even for larger tumors. When patients relapse, the majority of them do so at regional or distant sites. These results raise the question as to whether adjuvant treatment should be considered following SBRT for larger tumors. 

Tumor control probability modeling for stereotactic body radiation therapy of early-stage lung cancer using multiple bio-physical models

This work is to analyze pooled clinical data using different radiobiological models and to understand the relationship between biologically effective dose (BED) and tumor control probability (TCP) for stereotactic body radiotherapy (SBRT) of early-stage non-small cell lung cancer (NSCLC). The clinical data of 1-, 2-, 3-, and 5-year actuarial or Kaplan-Meier TCP from 46 selected studies were collected for SBRT of NSCLC in the literature. The TCP data were separated for Stage T1 and T2 tumors if possible, otherwise collected for combined stages. BED was calculated at isocenters using six radiobiological models. For each model, the independent model parameters were determined from a fit to the TCP data using the least chi-square (χ²) method with either one set of parameters regardless of tumor stages or two sets for T1 and T2 tumors separately. The fits to the clinic data yield consistent results of large α/β ratios of about 20Gy for all models investigated. The regrowth model that accounts for the tumor repopulation and heterogeneity leads to a better fit to the data, compared to other 5 models where the fits were indistinguishable between the models. The models based on the fitting parameters predict that the T2 tumors require about additional 1Gy physical dose at isocenters per fraction (⩽5 fractions) to achieve the optimal TCP when compared to the T1 tumors. In conclusion, this systematic analysis of a large set of published clinical data using different radiobiological models shows that local TCP for SBRT of early-stage NSCLC has strong dependence on BED with large α/β ratios of about 20Gy. The six models predict that a BED (calculated with α/β of 20) of 90Gy is sufficient to achieve TCP⩾95%. Among the models considered, the regrowth model leads to a better fit to the clinical data.

Pro-apoptotic Noxa is involved in ablative focal irradiation-induced lung injury

Although lung injury including fibrosis is a well‐documented side effect of lung irradiation, the mechanisms underlying its pathology are poorly understood. X‐rays are known to cause apoptosis in the alveolar epithelial cells of irradiated lungs, which results in fibrosis due to the proliferation and differentiation of fibroblasts and the deposition of collagen. Apoptosis and BH3‐only pro‐apoptotic proteins have been implicated in the pathogenesis of pulmonary fibrosis. Recently, we have established a clinically analogous experimental model that reflects focal high‐dose irradiation of the ipsilateral lung. The goal of this study was to elucidate the mechanism underlying radiation‐induced lung injury based on this model. A radiation dose of 90 Gy was focally delivered to the left lung of C57BL/6 mice for 14 days. About 9 days after irradiation, the mice began to show increased levels of the pro‐apoptotic protein Noxa in the irradiated lung alongside increased apoptosis and fibrosis. Suppression of Noxa expression by small interfering RNA protected cells from radiation‐induced cell death and decreased expression of fibrogenic markers. Furthermore, we showed that reactive oxygen species participate in Noxa‐mediated, radiation‐induced cell death. Taken together, our results show that Noxa is involved in X‐ray‐induced lung injury.

SPACE - A randomized study of SBRT vs conventional fractionated radiotherapy in medically inoperable stage I NSCLC

BACKGROUND

Stereotactic body radiotherapy (SBRT) has been introduced for small lung tumors due to excellent local control and few side effects, even though there are no comparative studies. SPACE (Stereotactic Precision And Conventional radiotherapy Evaluation) is the first randomized phase II trial comparing SBRT and conventional fractionated radiotherapy (3DCRT).

METHODS

Patients with stage I medically inoperable NSCLC were randomized to receive SBRT to 66Gy in 3 fractions (one week) or 3DCRT to 70Gy (7weeks). Patients were followed to assess efficacy, toxicity and HRQL.

FINDINGS

Between 2007 and 2011, 102 patients were randomized. Mean age 74 (57-86), 60% women, the vast majority (92%) had COPD or cardiovascular comorbidity. The SBRT arm included more patients with T2-tumors (p=0.02) and male gender (p=0.35). The median follow-up was 37months with a 1-, 2- and 3-year PFS of: SBRT: 76%, 53%, 42% and 3DCRT: 87%, 54% 42%, HR=0.85 (95% CI 0.52-1.36) with no difference between the groups and no difference in OS (HR=0.75, 95% CI 0.43-1.30). At the end of the study 70% of SBRT patients had not progressed compared to 59% (3DCRT, p=0.26). Toxicity was low with no grade 5 events. Pneumonitis of any grade was observed in 19% (SBRT) and 34% (3DCRT, p=0.26), and esophagitis in 8% and 30% respectively (p=0.006). HRQL was evaluated with the EORTC QLQ 30 and LC14 module and patients treated with 3DCRT experienced worse dyspnea (p=0.01), chest pain (p=0.02) and cough (>10 points difference).

INTERPRETATION

There was no difference in PFS and OS between SBRT and conventionally treated patients despite an imbalance of prognostic factors. We observed a tendency of an improved disease control rate in the SBRT group and they experienced better HRQL and less toxicity. SBRT is convenient for patients and should be considered standard treatment for patients with inoperable stage I NSCLC.

Impact of pretreatment whole-tumor perfusion computed tomography and 18F-fluorodeoxyglucose positron emission tomography/computed tomography measurements on local control of non-small cell lung cancer treated with stereotactic body radiotherapy

This study aimed to investigate the correlation between the average iodine density (AID) detected by dual-energy computed tomography (DE-CT) and the maximum standardized uptake value (SUV_max) yielded by [¹⁸F] fluorodeoxyglucose positron emission tomography (¹⁸F-FDG PET) for non-small cell lung cancer (NSCLC) treated with stereotactic body radiotherapy (SBRT). Seventy-four patients with medically inoperable NSCLC who underwent both DE-CT and ¹⁸F-FDG PET/CT before SBRT (50‒60 Gy in 5‒6 fractions) were followed up after a median interval of 24.5 months. Kaplan-Meier analysis was used to determine associations between local control (LC) and variables, including AID, SUV_max, tumor size, histology, and prescribed dose. The median AID and SUV_max were 18.64 (range, 1.18-45.31) (100 µg/cm³) and 3.2 (range, 0.7-17.6), respectively. No correlation was observed between AID and SUV_max Two-year LC rates were 96.2% vs 75.0% (P = 0.039) and 72.0% vs 96.2% (P = 0.002) for patients classified according to high vs low AID or SUV_max, respectively. Two-year LC rates for patients with adenocarcinoma vs squamous cell carcinoma vs unknown cancer were 96.4% vs 67.1% vs 92.9% (P = 0.008), respectively. Multivariate analysis identified SUV_max as a significant predictor of LC. The 2-year LC rate was only 48.5% in the subgroup of lower AID and higher SUV_max vs >90% (range, 94.4-100%) in other subgroups (P = 0.000). Despite the short follow-up period, a reduction in AID and subsequent increase in SUV_max correlated significantly with local failure in SBRT-treated NSCLC patients. Further studies involving larger populations and longer follow-up periods are needed to confirm these results.

Proton beam therapy in Japan: current and future status

The number of patients treated by proton beam therapy in Japan since 2000 has increased; in 2016, 11 proton facilities were available to treat patients. Notably, proton beam therapy is very useful for pediatric cancer; since the pediatric radiation dose to normal tissues should be reduced as much as possible because of the effect of radiation on growth, intellectual development, endocrine organ function and secondary cancer development. Hepatocellular carcinoma is common in Asia, and most of the studies of proton beam therapy for liver cancer have been reported by Japanese investigators. Proton beam therapy is also a standard treatment for nasal and paranasal lesions and lesions at the base of the skull, because the radiation dose to critical organs such as the eyes, optic nerves and central nervous system can be reduced with proton beam therapy. For prostate cancer, comparative studies that address adverse effects, safety, patient quality of life and socioeconomic issues should be performed to determine the appropriate use of proton beam therapy for prostate cancer. Regarding new proton beam therapy applications, experience with proton beam therapy combined with chemotherapy is limited, although favorable outcomes have been recently reported for locally advanced lung cancer, esophageal cancer and pancreatic cancer. Therefore, 'chemoproton' therapy appears to be a very attractive field for further clinical investigations. In conclusion, there are cost issues and considerations regarding national insurance for the use of proton beam therapy in Japan. Further studies and discussions are needed to address the use of proton beam therapy for several types of cancers, and for maintaining the quality of life of patients while retaining a high cure rate.

Stereotactic Body Radiation Therapy for Stage I Non-Small Cell Lung Cancer: A Retrospective, Single-Center Study of 55 Patients

Purpose/Objective(s): Stereotactic body radiation therapy (SBRT) is an effective treatment for patients with early-stage non-small cell lung cancer (NSCLC) who are not surgical candidates or who refuse surgical management. In this study, we report on our clinical outcomes and toxicity in the treatment of early-stage NSCLC with SBRT.

METHODS AND MATERIALS

Fifty-five patients with 59 T1-2N0M0 NSCLC lesions were treated at our institution between December 2009 and August 2014. The majority of the patients [38 (69%)] were treated with 50 Gy in 5 fractions, 7 patients (13%) with 48 Gy in 4 fractions, 8 patients (14%) with 60 Gy in 3 fractions, 1 patient (2%) with 62.5 Gy in 10 fractions, and 1 patient (2%) with 54 Gy in 3 fractions. Tumor response was evaluated using RECIST 1.1, and toxicity was graded using the CTCAE (Common Terminology Criteria for Adverse Events) version 3.0. The primary endpoints of this retrospective review included rates of overall survival, disease-free and progression-free survival, local failure, regional failure, and distant failure. A secondary endpoint included radiation-related toxicities.

RESULTS

The median follow-up was 23.8 months (range 1.1-57.6). The 3-year local control, progression-free survival, and overall survival rates were 91, 55, and 71%, respectively. The median age at diagnosis was 67.9 years (range 51.4-87.1). There were a total of 54 T1N0 tumors (92%) and 5 T2N0 lesions (8%). Adenocarcinoma was the most common pathology, comprising 54% of the lesions. A total of 16 of the patients (29%) failed. Among these, 5 local (9%), 14 regional (25%), and 4 distant failures (7%) were observed. On follow-up, one patient had grade 2 and another had grade 5 pneumonitis. Three patients experienced grade 2 chest wall tenderness. Two patients had grade 1 rib fractures, one of which could not be discerned from radiation-induced toxicity versus a traumatic fall.

CONCLUSION

The University of Mississippi Medical Center SBRT experience has shown that SBRT provides satisfactory local control and overall survival rates with minimal toxicity in early-stage NSCLC patients.

Clinical outcome of stereotactic body radiotherapy for primary and oligometastatic lung tumors: a single institutional study with almost uniform dose with different five treatment schedules

Background

To evaluate clinical outcomes of stereotactic body radiotherapy (SBRT) for localized primary and oligometastatic lung tumors by assessing efficacy and safety of 5 regimens of varying fraction size and number.

Methods

One-hundred patients with primary lung cancer (n = 69) or oligometastatic lung tumors (n = 31), who underwent SBRT between May 2003 and August 2010, were included. The median age was 75 years (range, 45–88). Of them, 98 were judged to have medically inoperable disease, predominantly due to chronic illness or advanced age. SBRT was performed using 3 coplanar and 3 non-coplanar fixed beams with a standard linear accelerator. Fraction sizes were escalated by 1 Gy, and number of fractions given was decreased by 1 for every 20 included patients. Total target doses were between 50 and 56 Gy, administered as 5–9 fractions. The prescribed dose was defined at the isocenter, and median overall treatment duration was 10 days (range, 5–22).

Results

The median follow-up was 51.1 months for survivors. The 3-year local recurrence rates for primary lung cancer and oligometastasis was 6 % and 3 %, respectively. The 3-year local recurrence rates for tumor sizes ≤3 cm and >3 cm were 3 % and 14 %, respectively (p = 0.124). Additionally, other factors (fraction size, total target dose, and BED₁₀) were not significant predictors of local control. Radiation pneumonia (≥ grade 2) was observed in 2 patients. Radiation-induced rib fractures were observed in 22 patients. Other late adverse events of greater than grade 2 were not observed.

Conclusion

Within this dataset, we did not observe a dose response in BED₁₀ values between 86.4 and 102.6 Gy. SBRT with doses between 50 and 56 Gy, administered over 5–9 fractions achieved acceptable tumor control without severe complications.

Treatment: Radiation Therapy

Radiation therapy (RT) is an integral part of treating all stages of lung cancer. Stereotactic ablative radiation therapy (SABR) has emerged as a standard treatment option for stage I-II patients with medically inoperable disease. Stage IIIA-IIIB disease is typically managed with definitive concurrent chemo-radiotherapy (CRT). Intensity modulated radiation therapy (IMRT) has enabled delivery of more potent RT dose while greatly limiting dose to surrounding normal organs, including lung, esophagus, and heart. SABR may have an expanding role in the treatment of stage IV patients, with new clinical trials exploring its combination with systemic immuotherapies.