A comparison of two stereotactic body radiation fractionation schedules for medically inoperable stage I non-small cell lung cancer: the Cleveland Clinic experience. J Thorac Oncol. 2009;4:976-982. [PMID: 19633473 DOI: 10.1097/jto.0b013e3181adf509]

Realistic closed-form TCP model including cell sensitivity dependence

Objective.To develop a mechanistic extension of the Poisonnian linear quadratic (LQ) tumor control probability (TCP) formulation by incorporating tumor volume and cell sensitivity inter-patient variations which can be applied to a cohort of patients.Approach.A novel closed-form expression for TCP was derived from first principles, incorporating inter-individual variations in tumor volume and cell sensitivity within the LQ model of tumor control. Furthermore, an exponential time dependence of local control (LC) in terms of TCP was introduced. The proposed model was fitted to 22 datasets of early-stage non-small cell lung cancer (NSCLC), encompassing various dose regimes, tumor volumes, treatment duration and outcome values over different follow-up periods. A log-likelihood algorithm was employed for the fitting process.Main results.The fit of the population TCP model, which adopts tumor volume and cell radiosensitivities uniformly distributed, resulted in a cell sensitivity value ofα¯U=0.37 [0.13-0.47]Gy-1, its corresponding bandwidthΔα= 0.37 [0.04-0.42] Gy-1,β =0. 015 [0.009-0.039] Gy-2, the characteristic time at which LC reaches TCP,t1/2= 19.6 [7.3-90.8] months, and the cell population doubling timeTd= 2.0 [0.2 4.9] days. The parametersα¯U,Δα andβwere found to be significant (p< 0.05), whilet1/2andTdproved non-statistically significant for the model under Wald test. This model describes data from 1675 lesions and offers a better fit compared to alternative approaches incorporating Gaussian or log-normal radiosensitivity distributions.Significance.A closed form of TCP population model was derived by including cell sensitivity and tumor size heterogeneities. A relation between TCP and LC was established by modeling LC as an exponential function of follow-up time. The derived TCP population model facilitates direct application to clinical datasets and was tested against NSCLC clinical data. Individual TCP can be estimated from the radiobiological parameters of the population.

Systematic Review of Stereotactic Ablative Radiotherapy (SABR)/Stereotactic Body Radiation Therapy (SBRT) for Treatment of High-Risk Patients with Stage I Non-Small Cell Lung Cancer

Stereotactic ablative radiotherapy (SABR) has emerged as an alternative, non-surgical treatment for high-risk patients with stage I non-small cell lung cancer (NSCLC) with increased use over time. The American Association for Thoracic Surgery (AATS) Clinical Practice Standards Committee (CPSC) assembled an expert panel and conducted a systematic review of the literature evaluating the results of SABR, which is also referred to as stereotactic body radiation therapy (SBRT) or stereotactic radiosurgery (SRS), prior to developing treatment recommendations for high-risk patients with stage I NSCLC based on expert consensus. Publications detailing the findings of 16 prospective studies of SABR and 14 retrospective studies of SABR for the management of early-stage lung cancer in 54,697 patients were identified by systematic review of the literature with further review by members of our expert panel. Medical inoperability (93-95%) was the primary reason for utilizing SABR. The median rate of histologically confirmed cancer in treated patients was 67% (range 57-86%). In retrospective studies and prospective studies, the most common dosing regimens were 48-54Gy in 3-5 fractions and 44-66Gy in 3-5 fractions respectively. The median follow-up after SABR was 30 months (range 15-50). The complications, oncological results and quality of life after SABR in high-risk patients with early-stage NSCLC are summarized in this Expert Review article. Further prospective randomized trials are needed and are currently underway to compare outcomes after SABR with outcomes after sublobar resection to fully evaluate treatment options applicable this high-risk group of patients.

Pathophysiology and Management of Chest Wall Pain after Surgical and Non-Surgical Local Therapies for Lung Cancer

Chest wall pain syndromes can emerge following local therapies for lung cancer and can adversely affect patients' quality-of-life. This can occur after lung surgery, radiation therapy, or percutaneous image-guided thermal ablation. This review describes the multifactorial pathophysiology of chest wall pain syndromes that develop following surgical and non-surgical local therapies for lung cancer and summarizes evidence-based management strategies for inflammatory, neuropathic, myofascial, and osseous pain. It discusses a step-wise approach to treating chest wall pain that begins with non-opioid oral analgesics and includes additional pharmacologic treatments as clinically indicated, such as anticonvulsants, serotonin and norepinephrine reuptake inhibitors, tricyclic antidepressants, and various topical treatments. For myofascial pain, physical medicine techniques, such as acupuncture, trigger point injections, deep tissue massage, and intercostal myofascial release can also offer pain relief. For severe or refractory cases, opioid analgesics, intercostal nerve blocks, or intercostal nerve ablations may be indicated. Fortunately, palliation of treatment-related chest wall pain syndromes can be managed by most clinical providers, regardless of the type of local therapy utilized for a patient's lung cancer treatment. In cases where a patient's pain fails to respond to initial medical management, clinicians can consider referring to a pain specialist who can tailor a more specific pharmacologic approach or perform a procedural intervention to relieve pain.

Outcomes for Elective Open and Thoracoscopic Surgical Lung Biopsies in the United States and Temporal Trends

Objective

To elucidate the outcomes of surgical lung biopsies (SLBs) performed for indications other than interstitial lung disease (ILD) and stratify outcomes according to procedural approach (open vs thoracoscopic).

Patients and Methods

Using the Nationwide Inpatient Sample database (January 1, 2008, through December 31, 2014), we identified elective hospitalizations with International Classification of Diseases, Ninth Revision, Clinical Modification codes for open (33.28) and thoracoscopic (33.20) SLB. We stratified cases by the presence/absence of ILD. Our primary outcome was in-hospital mortality.

Results

There were 47,469 hospitalizations for elective SLB (26,540 [55.9%] thoracoscopic) during the study period; 23,930 patients (50.5%) were women, 17,019 (35.9%) had ILD, and the mean ± SD age was 62.6±13.0 years. Over the study period, thoracoscopic increasingly replaced open SLB, and in-hospital mortality declined (3.5% [308 of 8678] in 2008 vs 2.5% [130 of 5215] in 2014; P<.001). Mortality following thoracoscopic SLB was 2.1% (550 of 26,519; 1.9% [214 of 11,513] in ILD and 2.2% [336 of 15,006] in non-ILD), and mean ± SD length of stay was 5.1±6.9 days. Open SLBs had worse outcomes; mortality was 3.7% (782 of 20,914; 3.9% [214 of 5487] in ILD and 3.7% [568 of 15,427] in non-ILD), and mean ± SD length of stay was 8.2±12 days. On multivariable analysis, male sex, advanced age, ILD, and higher comorbidity index correlated with higher mortality. Conversely, lower mortality was observed among individuals with obesity (odds ratio, 0.73; 95% CI, 0.60-0.88) and those who had their thoracoscopic SLBs performed at high-volume centers (top quartile) (odds ratio, 0.73; 95% CI, 0.57-0.94).

Conclusion

Surgical lung biopsy is more often performed for non-ILD indications. Interstitial lung disease was an independent predictor of poor outcomes, but the unadjusted outcomes were worse in the non-ILD cohort due to differences in patient characteristics. Thoracoscopic SLBs performed at high-volume centers had superior outcomes.

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.

Proton stereotactic body radiation therapy for liver metastases-results of 5-year experience for 81 hepatic lesions

Background

To report on our institutional experience using Proton stereotactic body radiation therapy (SBRT) for patients with liver metastases.

Methods

All patients with liver metastases treated with Proton SBRT between September 2012 and December 2017 were retrospectively analyzed. Local control (LC) and overall survival (OS) were estimated using the Kaplan-Meier method calculated from the time of completion of Proton SBRT. LC was defined according to Response Evaluation Criteria in Solid Tumors (RECIST) guidelines (version 1.1). Toxicity was graded according to Common Terminology Criteria for Adverse Events (CTCAE) version 4.0.

Results

Forty-six patients with 81 lesions were treated with Proton SBRT. The median age was 65.5 years old (range, 33-86 years) and the median follow up was 15 months (range, 1-54 months). The median size of the gross tumor volume (GTV) was 2.5 cm (range, 0.7-8.9 cm). Two or more lesions were treated in 56.5% of patients, with one patient receiving treatment to a total of five lesions. There were 37 lesions treated with a biologically effective dose (BED) ≤60, 9 lesions with a BED of 61-80, 22 lesions with a BED of 81-100, and 13 lesions with a BED >100. The 1-year and 2-year LC for all lesions was 92.5% (95% CI, 82.7% to 96.8%). The grade 1 and grade 2 toxicity rates were 37% and 6.5%, respectively. There were no grade 3 or higher toxicities and no cases of radiation-induced liver disease (RILD).

Conclusions

Proton SBRT for the treatment of liver metastases has promising LC rates with the ability to safely treat multiple liver metastases. Accrual continues for our phase II trial treating liver metastases with Proton SBRT to 60 GyE (Gray equivalent) in 3 fractions.

To biopsy or not to biopsy? Outcomes following stereotactic body radiotherapy (SBRT) for biopsy-confirmed versus radiologically-diagnosed primary lung cancer in a single Australian institution

INTRODUCTION

Obtaining tissue diagnosis for lung cancer can sometimes be difficult and unsafe. We evaluated outcomes of biopsy-confirmed versus radiologically-diagnosed lung cancer treated with stereotactic body radiotherapy (SBRT).

METHODS

A single-institutional retrospective cohort of lung cancer patients treated with SBRT between February 2014 and October 2018. Outcomes of interest were: local failure (LF), distant failure (DF), and overall survival (OS). Probability of LF, DF, and OS were estimated using the Kaplan-Meier method. Differences in outcomes between biopsy-confirmed versus radiologically-diagnosed lung cancer were evaluated using the log-rank test.

RESULTS

Sixty-five lung lesions in 61 patients were treated with SBRT. Mean age was 75.6 years. Twenty-seven patients (44.3%) were ECOG 2-3. Thirty-nine patients (64%) were radiologically-diagnosed. There were five cases of LF observed at median of 12.8 months post-SBRT and 12-month LF-free survival was 96% (95% CI, 86-99%), with no differences between groups (p = 0.1). Sixteen patients developed DF, with 12-month DF-free survival of 84% (95% CI, 71-91%), and no difference between groups (p = 0.06). Sixteen deaths were reported at a median of 12.5 months post-SBRT, with 12-month OS of 85% (95% CI, 73-92%), and no differences between study groups (p = 0.5). No grade 3 toxicities were reported.

CONCLUSION

The oncological outcomes were similar in patients with early lung cancer treated with SBRT with or without biopsy-confirmation. In situations where tissue diagnosis is not feasible or unsafe, it is not unreasonable to offer SBRT based on clinical and radiological suspicion following multidisciplinary discussions.

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.

The development and external validation of an overall survival nomogram in medically inoperable centrally located early-stage non-small cell lung carcinoma

BACKGROUND AND PURPOSE

Current nomograms predicting survival prognosis after stereotactic body radiation therapy (SBRT) in non-small cell lung cancer (NSCLC) are based on peripherally located tumors. However, patients with a central lung tumor tend to be older, the tumor is often larger and fraction-schedules are risk-adapted. Therefore, we developed and externally validated a nomogram to predict overall survival (OS) in patients having centrally located early-stage NSCLC treated with SBRT.

MATERIALS AND METHODS

Patients who underwent SBRT for centrally located NSCLC were identified and baseline characteristics were obtained. A nomogram was built to predict 6-month, 1-, 2- and 3-year OS using Cox proportional hazards model. The model building procedure was validated using bootstrap sampling. To determine generalizability, external validation was performed on a cohort of patients with central NSCLC treated with SBRT from another center. Discriminatory ability was measured with the concordance index (C-index) and calibration plots were used to compare Kaplan-Meier-estimated and nomogram-predicted OS.

RESULTS

The nomogram was built on data of 220 patients and consisted of the following variables: PTV, age, WHO performance status, tumor lobe location and ultracentral location. The C-index of the nomogram (corrected for optimism) was moderate at 0.64 (95% confidence interval (CI) 0.59-0.69). Calibration plots showed favorable predictive accuracy. The external validation showed acceptable validity with a C-index of 0.62 (95% CI 0.61-0.64).

DISCUSSION

We developed and externally validated the first nomogram to estimate the OS-probability in patients with centrally located NSCLC treated with SBRT. This nomogram is based on 5 patient and tumor characteristics and gives an individualized survival prediction.

Chest wall toxicity after stereotactic radiation in early lung cancer: a systematic review

Background

Radiation-induced chest wall pain (cwp) and rib fracture (rf) are late adverse effects after stereotactic body radiation therapy (sbrt) for stage i non-small-cell lung cancer (nsclc); however, the literature about their incidence and risk factors shows variability. We performed a systematic review to determine the pooled incidence of cwp and rf in the relevant population.

Methods

A literature search using the prisma (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) guidelines considered English publications in medline and embase from January 1996 to August 2017. Abstracts were screened, followed by full-text review and data extraction.

Results

The database searches identified 547 records. Twenty-eight publications comprising 3892 patients met the inclusion criteria. Median reported ages and follow-up durations fell into the ranges 67-82 years and 12-84 months. Prescriptions fell into the range of 40-70 Gy in 3-10 fractions. Despite study heterogeneity, the pooled incidences of cwp and rf were estimated to be 8.94% and 5.27% respectively. Nineteen studies reported cwp grade: 58 of 308 patients (18.8%) experienced grades 3-4 cwp (no grade 5 events reported). Thirteen studies reported rf grade: grades 3-4 rf were observed in 9 of 113 patients (7.96%). A high chest wall V30 was an important predictor of cwp and rf.

Conclusions

In patients with stage i nsclc, rates of cwp and rf after sbrt are low; however, tumour location, accurate toxicity reporting, and dose-fractionation schemes might alter those rates. Prospective correlation with dosimetry and quality of life assessment will further improve the understanding of cwp and rf after sbrt.

Outpatient Anesthesia Facilitates Stereotactic Body Radiation Therapy for Early Stage Lung Cancer Patients With Advanced Cognitive Impairments

Purpose

To report on the use of outpatient anesthesia (OPA) facilitating delivery of stereotactic body radiation therapy (SBRT) in patients with severe cognitive impairments (CI) diagnosed with inoperable early stage lung cancer.

Methods and Materials

We surveyed our institutional review board-approved prospective lung SBRT data registry to document the feasibility of using anesthesia in CI patients and to determine their SBRT outcomes.

Results

From 2004 to 2018, 8 from a total 2084 patients were identified for this analysis. The median age at treatment was 68 years (range, 44-78). Most patients were female (62.5%). CI diagnoses included Alzheimer-related dementia (3 patients), chronic schizophrenia (3 patients), severe anxiety disorder (1 patient), and severe developmental disability (1 patient). The median tumor size was 3.4 cm (range, 1.1-10.5), and 7 patients (87.5 %) had central lesions. The median follow-up time was 22.5 months. The most common (50%) SBRT schedule used was 50 Gy in 5 fractions. Intravenous propofol (10 mg/mL) was used for OPA in all cases at the time of simulation and with daily treatments. OPA was well tolerated and all patients completed SBRT as prescribed. There was one grade 5 but no other grade 3 or higher SBRT-related toxicities. One patient died with local failure and one of distant failure.

Conclusions

OPA made lung SBRT feasible for patients with CIs. SBRT outcomes were in keeping with those reported in the literature. CI should not be considered a contraindication per se to SBRT delivery in patients otherwise appropriate for this modality.

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.

Generalized Multi-Hit Model of Radiation-Induced Cell Survival with a Closed-Form Solution: An Alternative Method for Determining Isoeffect Doses in Practical Radiotherapy

The standard linear-quadratic (LQ) model is currently the preferred model for describing the ionizing radiation-induced cell survival curves and tissue responses. And the LQ model is also widely used to calculate isoeffect doses for comparing different fractionated schemes in clinical radiotherapy. Despite its ubiquity, because the actual dose-response curve may appear linear at high doses in the semilogarithmic plot, the application of the LQ model is greatly challenged in the high-dose region, while the dose employed in stereotactic body radiotherapy (SBRT) is often in this area. Alternatively, the biophysical models of radiation-induced effects with a linear-quadratic-linear (LQL) characteristic can well fit the dose-survival curve of cells in vitro. However, most of these LQL models are phenomenological and have not fully considered the biophysical mechanism of radiation-induced damage and repair, and the fitting quality decreases in some high-dose ranges. In this work, to provide an alternative model to describe the cell survival curves in high-dose ranges and predict the biologically effective dose (BED) for SBRT, we propose a novel generalized multi-hit model with a closed-form solution by considering an upper bound on the number of lethal damages induced by radiation that can be repaired in a cell. This model has a clear biophysical basis and a simple expression, and also has the LQL characteristic under low- and high-dose approximate conditions. The experimental data fitting indicated that compared to the standard LQ model and our previously generalized target model, the current model can better fit the radiation-induced cell survival curves in the high-dose ranges (P < 0.05). The current model parameters and parameter ratios were determined from the fits in different kinds of cell lines irradiated with various dose rates and linear energy transfer (LET), which indicates that the model parameters significantly depend on the dose rate and LET. Based on the current model, we derived two equivalence formulae for the BED calculations in the low- and high-dose ranges, and then calculated the BED for the clinical data of SBRT from 17 selected studies. The correlation analysis showed that there were significant linear correlations between the BED at isocenter and planning target volume (PTV) edge calculated by this model and the LQ model (R > 0.86, P < 0.001). In conclusion, the generalized multi-hit model proposed in this work can be used as an alternative tool to handle in vitro radiation-induced cell survival curves in high-dose ranges, and calculate the in vivo BED for comparing the dose fractionation schemes in clinical 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.

Stereotactic body radiation therapy with higher biologically effective dose is associated with improved survival in stage II non-small cell lung cancer

OBJECTIVES

The role of stereotactic body radiation therapy (SBRT) in treating stage II non-small cell lung cancer (NSCLC) remains unclear. This study evaluates SBRT dose prescription patterns and survival outcomes in Stage II NSCLC using the National Cancer Database (NCDB).

MATERIALS AND METHODS

Patients diagnosed with Stage II NSCLC and treated with SBRT between 2004-2013 were identified in NCDB. The biologically effective dose with α/β = 10 Gy (BED₁₀) was calculated. Overall survival (OS) was analyzed using the Kaplan-Meier method and Cox regression models.

RESULTS

Of 56,543 patients with Stage II NSCLC, 451 (0.8%) received SBRT. There were 360 patients (79.8%) with node-negative and 91 patients (20.2%) with node-positive disease. The most common prescriptions were 10 Gy x 5 (35.9%) and 12 Gy x 4 (19.3%). The mean and median BED₁₀ were 114.9 Gy and 105.6 Gy, respectively. With median follow-up of 19.3 months, overall median survival was 23.7 months. Median survival was 22.4 months for those treated with BED₁₀ < 114.9 Gy versus 31.5 months for BED₁₀ ≥ 114.9 Gy (p = 0.036). On multivariate analysis, BED₁₀ as a continuous variable (hazard ratio [HR] 0.991, p = 0.009) and ≥ 114.9 Gy (HR 0.63, p = 0.015) were associated with improved survival in node-negative patients. BED₁₀ as a continuous variable (HR 0.997, p = 0.465) and ≥ 114.9 Gy (HR 0.81, p = 0.546) were not significant factors for predicting survival in node-positive patients.

CONCLUSION

SBRT is infrequently utilized to treat Stage II NSCLC in the United States. Treatment with higher BED₁₀ was associated with improved survival, and the benefit was limited to patients with node-negative disease.

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.

Effect of Tumor Location and Dosimetric Predictors for Chest Wall Toxicity in Single-Fraction Stereotactic Body Radiation Therapy for Stage I Non-Small Cell Lung Cancer

PURPOSE

Dosimetric parameters to limit chest wall toxicity (CWT) are not well defined in single-fraction (SF) stereotactic body radiation therapy (SBRT) phase 2 trials. We sought to determine the relationship of tumor location and dosimetric parameters with CWT for SF-SBRT.

METHODS AND MATERIALS

From a prospective registry of 1462 patients, we identified patients treated with 30 Gy or 34 Gy. Gross tumor volume was measured as abutting, ≤1 cm, 1 to 2 cm, or >2 cm from the chest wall. CWT was prospectively graded according to Common Terminology Criteria for Adverse Events version 3.0, with grade 2 requiring medical therapy, grade 3 requiring procedural intervention, and grade 4 being disabling pain. Grade 1 CWT or radiographic rib fracture was not included. Logistic regression analysis was used to identify the parameters associated with CWT and calculate the probability of CWT with dose.

RESULTS

This study included 146 lesions. The median follow-up time was 23.8 months. The 5-year local control, distant metastasis, and overall survival rates were 91.8%, 19.2%, and 28.7%, respectively. Grade 2 to 4 CWT was 30.6% for lesions abutting the chest wall, 8.2% for ≤1 cm from the chest wall, 3.8% for 1 to 2 cm from the chest wall, and 5.7% for >2 cm from the chest wall. Grade ≥3 CWT was 1.4%. Tumor abutment (odds ratio [OR]: 6.5; P = .0005), body mass index (OR: 1.1; P = .02), rib D1cc (OR: 1.01/Gy; P = .03), chest wall D1cc (OR: 1.08/Gy; P = .03), and chest wall D5cc (OR: 1.10/Gy; P = .01) were significant predictors for CWT on univariate analysis. Tumor abutment was significant for CWT (OR: 7.5; P = .007) on multivariate analysis. The probability of CWT was 15% with chest wall D5cc at 27.2 Gy and rib D1cc at 30.2 Gy.

CONCLUSIONS

The rate of CWT with SF-SBRT is similar to the rates published for fractionated SBRT, with most CWT being low grade. Tumor location relative to the chest wall is not a contraindication to SF-SBRT, but the rates increase significantly with abutment. Rib D1cc and chest wall D1cc and D5cc may be used as predictors of CWT.

Chest Wall Toxicity After Stereotactic Body Radiation Therapy: A Pooled Analysis of 57 Studies

PURPOSE

The significance of clinical and dosimetric risk factors in relation to chest wall (CW) injury after stereotactic body radiation therapy (SBRT) for lung tumors were analyzed through a meta-analysis of 57 published studies.

METHODS AND MATERIALS

Studies related to CW injury after lung SBRT were obtained through searching PubMed, Embase, and Cochrane electronic databases. An estimate of the incidence of CW pain (CWP) or rib fracture (RF) was derived using a Bayesian hierarchical model. Linear regression analysis was performed to assess the relationship between CWP or RF and clinical or dosimetric factors.

RESULTS

A total of 57 studies incorporating 5985 cases reporting clinical data on CW injury after SBRT were analyzed. The overall CWP and RF rates by Bayesian hierarchical modeling were 11.0% (95% confidence interval [CI], 8.0-14.4) and 6.3% (95% CI, 3.7-9.7), respectively. The rates of grade ≥2 and grade ≥3 CWP were 6.2% (95% CI, 3.88-8.93) and 1.2% (95% CI, 0.48-2.12), respectively. Sex was significantly correlated with RF (P < .001), with female patients having a greater risk of RF than male patients (hazard ratio = 0.59; 95% CI, 0.46-0.76). No correlation was found between RF, grade ≥2 CWP, or grade ≥3 CWP, with the clinical and dosimetric factors of age, tumor size, origin of lung tumor, gross tumor volume, planning target volume, fractional dose, number of fractions, or biologically effective dose. However, tumor to CW distance (<16-25 mm), body mass index, maximum dose (Dmax) of 0.5 to 5 cm³, and the volume of CW or ribs receiving >30 Gy were significantly associated with CWP and RF.

CONCLUSIONS

The overall rates of RF and grade ≥2 CWP after thoracic SBRT are relatively low. Sex, tumor to CW distance, maximum dose, and the radiation exposure of the CW or ribs are factors associated with the risk of CW toxicity after SBRT.

Clinical outcomes following advanced respiratory motion management (respiratory gating or dynamic tumor tracking) with stereotactic body radiation therapy for stage I non-small-cell lung cancer

Purpose

To report the outcomes of stereotactic body radiation therapy (SBRT) for stage I non-small-cell lung cancer (NSCLC) according to respiratory motion management method.

Methods

Patients with stage I NSCLC who received SBRT from 2007 to 2015 were reviewed. Computed tomography (CT) simulation with four-dimensional CT was performed for respiratory motion assessment. Tumor motion >1 cm in the craniocaudal direction was selectively treated with advanced respiratory management: either respiratory gating to a pre-specified portion of the respiratory cycle or dynamic tracking of an implanted fiducial marker. Comparisons were made with internal target volume approach, which treated all phases of respiratory motion.

Results

Of 297 patients treated with SBRT at our institution, 51 underwent advanced respiratory management (48 with respiratory gating and three with tumor tracking) and 246 underwent all-phase treatment. Groups were similarly balanced with regard to mean age (P=0.242), tumor size (P=0.315), and histology (P=0.715). Tumor location in the lower lung lobes, as compared to middle or upper lobes, was more common in those treated with advanced respiratory management (78.4%) compared to all-phase treatment (25.6%, P<.0001). There were 17 local recurrences in the treated lesions. Kaplan-Meier analyses showed that there were no differences with regard to mean time to local failure (91.5 vs 98.8 months, P=0.56), mean time to any failure (73.2 vs 78.7 months, P=0.73), or median overall survival (43.3 vs 45.5 months, P=0.56) between patients who underwent advanced respiratory motion management and all-phase treatment.

Conclusion

SBRT with advanced respiratory management (the majority with respiratory gating) showed similar efficacy to all-phase treatment approach for stage I NSCLC.

[Radiation-induced lung toxicity predictors after stereotactic radiation therapy for non-small cell lung carcinoma stage I]

In case of refusal or contraindication for surgical management of a stage I non-small cell lung carcinoma, the validated alternative therapy is stereotactic irradiation. This technique reaches an equivalent tumour control rate than surgery and significantly higher than conventional radiotherapy. One of the dreaded complications is radiation induced lung toxicity (radiation pneumonitis and lung fibrosis), especially when it is symptomatic, occurring in about 10 % of cases. This article is a literature review of this complication's predictive factors.

Stereotactic Ablative Body Radiotherapy for Primary Non-Small-Cell Lung Cancer: Achieving Local Control with a Lower Biologically Effective Dose

We conducted a retrospective study of stereotactic ablative radiotherapy (SABR) for 94 patients with non-small-cell lung cancer at our institution. The patients were treated with either 50 Gy in five treatments or 48 Gy in four treatments, corresponding to biologically effective doses (BED) of 100 Gy or 105.6 Gy, respectively. The results demonstrate that, with relatively low BEDs, we can achieve excellent local control with minimal toxicity.

Evolution of Stereotactic Ablative Radiotherapy in Lung Cancer and Birmingham's (UK) Experience

Stereotactic ablative radiotherapy (SABR) has taken a pivotal role in early lung cancer management particularly in the medically inoperable patients. Retrospective studies have shown this to be well tolerated with comparable results to surgery and no significant increase in toxicity. Paucity of randomized evidence has dictated initiation of several trials to provide good quality evidence to steer future practice. This review summaries salient developments in lung SABR, comparisons to surgery and other platforms and our local experience at University Hospitals Birmingham, UK of lung SABR since its initiation in June 2013.

Three- Versus Five-Fraction Regimens of Stereotactic Body Radiotherapy for Peripheral Early-Stage Non-Small-Cell Lung Cancer: A Two-Institution Propensity Score-Matched Analysis

PURPOSE

To evaluate differences in outcomes of early-stage peripheral non-small-cell lung cancer (NSCLC) treated with either 3- or 5-fraction stereotactic body radiotherapy (SBRT) at 2 institutions.

PATIENTS AND METHODS

Patients diagnosed with peripherally located early-stage NSCLC who received either a median dose of 60 Gy (interquartile range [IQR], 60-60, biologically effective dose, 151-151) in 3 fractions or a median dose of 50 Gy (IQR, 50-50, biologically effective dose, 94-94) in 5 fractions were included in this study. All data were retrospectively collected and reviewed in an institutional review board-approved database.

RESULTS

A total of 192 lesions in 192 patients were identified: 94 received 3-fraction SBRT and 98 received 5-fraction SBRT. Patients in the 5-fraction cohort had significantly smaller tumors (P = .0021). Larger tumor size was associated with worse overall survival (hazard ratio, 1.40, P = .0013) for all patients. A single grade 3 toxicity was reported in each cohort. A propensity score-matched cohort of 94 patients was constructed with a median follow-up of 29.3 months (IQR, 17.3-44.6) for the 3-fraction cohort and 31.0 months (IQR, 17.0-48.5) for the 5-fraction cohort (P = .84). There were no statistically significant differences between these 2 cohorts in overall survival (P = .33), progression-free survival (P = .40), local failure (P = .86), and nodal or distant failure (P = .57) at 2 years.

CONCLUSION

The 3- and 5-fraction SBRT regimens for early-stage peripheral NSCLC had comparable clinical outcomes. Both regimens were well tolerated. A large tumor size was an adverse prognostic factor for worse survival.

Comparison of Single- and Three-fraction Schedules of Stereotactic Body Radiation Therapy for Peripheral Early-stage Non-Small-cell Lung Cancer

BACKGROUND

To compare the clinical outcomes of patients with early-stage non-small-cell lung cancer (NSCLC) who had undergone either single-fraction (SF) or three-fraction (TF) stereotactic body radiation therapy (SBRT) at a single institution during over 8-year period.

PATIENTS AND METHODS

Patients with peripherally located early-stage NSCLC who had undergone SBRT from February 2007 to November 2015 were included in the present study. SBRT was delivered without heterogeneity correction. Data were retrospectively reviewed and collected in an institutional review board-approved database. R software (version 3.3.2) was used for statistical analysis.

RESULTS

Of 159 total lung tumors, 65 lesions received 30 Gy (median, 30 Gy) in 1 fraction, and 94 lesions received 48 to 60 Gy (median, 60 Gy) in 3 fractions. Patients with a Karnofsky performance status < 80 were more common in the SF-SBRT cohort (P = .050). After a median follow-up of 22.2 and 26.2 months for the SF-SBRT and TF-SBRT cohorts, respectively (P = .29), no statistically significant difference was found in overall survival (P = .86), progression-free survival (P = .95), local failure (P = .95), nodal failure (P = .91), and distant failure (P = .49) at 24 months. At 1 and 2 years, the overall survival rates were 86.1% and 63.2% for the SF-SBRT cohort and 80.8% and 61.6% for the TF-SBRT cohort, respectively. At 1 and 2 years, the local control rates were 95.1% and 87.8% for the SF-SBRT cohort and 92.7% and 86.2% for the TF-SBRT cohort, respectively. Both regimens were well tolerated.

CONCLUSION

Despite more patients with poor performance status in the SF-SBRT cohort, the SF- and TF-SBRT regimens showed no differences in clinical outcomes. SF-SBRT is now our standard approach.

Dosimetric differences between local failure and local controlled non-small cell lung cancer patients treated with stereotactic body radiotherapy: A matched-pair study

INTRODUCTION

Concerns were raised about the accuracy of pencil beam (PB) calculation and potential underdosing of medically inoperable non-small cell lung cancer (NSCLC) treated with stereotactic body radiation therapy (SBRT). From our institutional series, we designed a matched-pair study where each local failure and controlled patient was matched based upon several clinical factors, to investigate the dose difference between the matched-pair.

METHODS

Eighteen pairs of NSCLC patients, treated with 50 Gy in five fractions, were selected. These patients were matched based on treatment intent, tumour size, histology and clinical follow-up. All PB calculated clinical plans were retrospectively recalculated with a MC algorithm. The D₉₉ and D_Mean of the gross tumour volume (GTV) and D₉₅ and D_Mean of the planning tumour volume (PTV) from PB and Monte Carlo (MC) calculation were compared between local failures and controls using the Mann-Whitney test.

RESULTS

The mean PB calculated D95 of PTV was 50.4 Gy for both failures and controls (P = 0.85), indicating no planning differences between the groups. From MC calculations, the mean (±SD) of GTV D₉₉ , GTV D_Mean , PTV D₉₅ , PTV D_Mean were 47.6 ± 2.6/46.3 ± 2.4, 50.4 ± 2.1/49.8 ± 1.6, 44.4 ± 2.7/43.6 ± 3.1, 48.7 ± 2.4/48.2 ± 2.4 Gy for failure/controlled groups, respectively, and there was no significant difference between two groups (all P > 0.1). The dose differences between MC and PB calculations were in agreement with other literatures and there was no significant difference between two groups.

CONCLUSIONS

While PB algorithms may overestimate tumour doses relative to MC algorithms, our matched-pair study did not find dose differences between local failure and local controlled cases.

Stereotactic Body Radiotherapy for Medically Inoperable Stage I-II Non-Small Cell Lung Cancer: The Mayo Clinic Experience

Objective

To examine disease control and survival after stereotactic body radiotherapy (SBRT) for medically inoperable, early-stage non-small cell lung cancer (NSCLC) and determine associations of pretreatment ¹⁸F-fluorodeoxyglucose-positron emission tomography (FDG-PET) maximum standardized uptake values (SUVmax), biologically effective dose, and mediastinal staging with disease control and survival outcomes.

Patients and Methods

We retrospectively reviewed the cases of consecutive patients with FDG-PET-staged, medically inoperable NSCLC treated with SBRT at our institution between January 1, 2008, and August 4, 2014. Cumulative incidences of recurrence were estimated, accounting for the competing risk of death. Associations of SUVmax, biologically effective dose, and mediastinal staging with outcomes were evaluated using Cox proportional hazards regression models.

Results

Among 282 patients, 2-year cumulative incidences of recurrence were 4.9% (95% CI, 2.6%-8.3%) for local, 9.8% (95% CI, 6.3%-14.2%) for nodal, 10.8% (95% CI, 7.0%-15.5%) for ipsilateral lung, 6.0% (3.3%-9.8%) for contralateral lung, 9.7% (95% CI, 6.3%-14.0%) for distant recurrence, and 26.1% (95% CI, 20.4%-32.0%) for any recurrence. The 2-year overall survival was 70.4% (95% CI, 64.5%-76.8%), and the 2-year disease-free survival was 51.2% (95% CI, 44.9%-58.5%). Risk of any recurrence was significantly higher for patients with higher SUVmax (hazard ratio [per each doubling], 1.29 [95% CI, 1.05-1.59]; P=.02). A similar association with SUVmax was observed when considering the composite outcome of any recurrence or death (hazard ratio, 1.23 [95% CI, 1.05-1.44]; P=.01). The SUVmax was not significantly associated with other outcomes (P≥0.69). Two-year cumulative incidences of local recurrence for patients receiving 48 Gy in 4 fractions, 54 Gy in 3 fractions, or 50 Gy in 5 fractions were 1.7% (95% CI, 0.3%-5.6%), 3.7% (95% CI, 0.7%-11.4%), and 15.3% (95% CI, 5.9%-28.9%), respectively (P=.02); this difference was independent of lesion size (P=.02).

Conclusion

Disease control was excellent for patients who received SBRT for early-stage NSCLC, and this series represents the largest single-institution experience from the United States on SBRT for early-stage inoperable NSCLC. Higher pretreatment FDG-PET SUVmax was associated with increased risk of any recurrence, and the 50 Gy in 5 fractions dose prescription was associated with increased risk of local recurrence.

Tumor Control and Toxicity for Common Stereotactic Body Radiation Therapy Dose-Fractionation Regimens in Stage I Non-Small Cell Lung Cancer

PURPOSE

To examine the impact of stereotactic body radiation therapy (SBRT) dose on outcomes in early-stage non-small cell lung cancer in a large single-institution series.

METHODS AND MATERIALS

We reviewed 600 patients treated from 2003 to 2012 for early-stage non-small cell lung cancer. The SBRT dose was at physician discretion on the basis of tumor size and location. Peripheral tumors were treated to 60 Gy in 3 fractions (homogeneous planning), 48-50 Gy in 4-5 fractions, or 30-34 Gy in 1 fraction. Central tumors were treated to 50 Gy in 5 fractions, 60 Gy in 8 fractions, or 50 Gy in 10 fractions. Patient, tumor, and treatment factors were assessed for their impact on patterns of failure, toxicity, and survival.

RESULTS

An SBRT dose of 54-60 Gy in 3 fractions was associated with a statistically significant lower rate of local failure (LF) (4.3% at 2 years) compared with 30-34 Gy in 1 fraction (21%), 48-50 Gy in 4-5 fractions (15.5%), and 50-60 Gy in 8-10 fractions (13.3%). Lower pre-SBRT hemoglobin and higher positron emission tomography standardized uptake value were also associated with LF. Nodal failure, distant failure, and overall survival were similar between fractionation groups. Pulmonary toxicity (crude rate, any grade) was slightly higher for 3 fractions (5.0%) compared with 1 (3.2%) or 4-5 fractions (3.8%). Chest wall toxicity was also higher for 3 (23.7%) compared with 1 (8.6%) or 4-5 (7.7%) fraction regimens.

CONCLUSIONS

Although higher biologically equivalent dose SBRT (150-180 Gy₁₀) may be associated with slightly lower LF, it was also associated with mildly increased toxicity and no difference in other patterns of failure or overall survival.

Comparison of single- and five-fraction schedules of stereotactic body radiation therapy for central lung tumours: a single institution experience

BACKGROUND

Stereotactic body radiation therapy (SBRT) is a treatment option for patients with early-stage non-small cell lung cancer who are medically inoperable or decline surgery. Here we compare the outcome of patients with centrally located lung tumours who underwent either single fraction (SF)- or five-fraction (FF-) SBRT at a single institution over 5 years.

METHODS

Between January 2009 and October 2014, patients with centrally located lung tumours who underwent SBRT were included in this study. Data were retrospectively collected using an institutional review board-approved database. For analysis, the Kaplan-Meier method and competing risks method were used.

RESULTS

In total, 11 patients received 26-30 Gy in 1 fraction, whereas 31 patients received 50-60 Gy (median 55 Gy) in 5 fractions. After a median follow-up of 12 months for SF-SBRT and 17 months for FF-SBRT groups (p = 0.64), 1-year overall survival rates were 82 and 87%, respectively. SF- and FF-SBRT groups showed no significant difference in grade 3+ toxicity (p = 0·28). The only grade 4 toxicity (n = 1) was reported in the SF-SBRT group. All toxicities occurred >12 months after the SBRT.

CONCLUSIONS

SF- and FF-SBRT have comparable overall survival. SF-SBRT may have some utility for patients unable to have multi-fraction SBRT.

Clinical Outcomes of 130 Patients with Primary and Secondary Lung Tumors treated with Cyberknife Robotic Stereotactic Body Radiotherapy

Background

Authors report clinical outcomes of patients treated with robotic stereotactic body radiotherapy (SBRT) for primary, recurrent and metastatic lung lesions.

Patients and methods

130 patients with 160 lesions were treated with Cyberknife SBRT, including T1-3 primary lung cancers (54%), recurrent tumors (22%) and pulmonary metastases (24%). The mean biologically equivalent dose (BED_10Gy) was 151 Gy (72–180 Gy). Median prescribed dose for peripheral and central lesions was 3×20 Gy and 3×15 Gy, respectively. Local control (LC), overall survival (OS), and cause-specific survival (CSS) rates, early and late toxicities are reported. Statistical analysis was performed to identify factors influencing local tumor control.

Results

Median follow-up time was 21 months. In univariate analysis, higher dose was associated with better LC and a cut-off value was detected at BED_10Gy ≤ 112.5 Gy, resulting in 1-, 2-, and 3-year actuarial LC rates of 93%, vs 73%, 80% vs 61%, and 63% vs 54%, for the high and low dose groups, respectively (p = 0.0061, HR = 0.384). In multivariate analysis, metastatic origin, histological confirmation and larger Planning Target Volume (PTV) were associated with higher risk of local failure. Actuarial OS and CSS rates at 1, 2, and 3 years were 85%, 74% and 62%, and 93%, 89% and 80%, respectively. Acute and late toxicities ≥ Gr 3 were observed in 3 (2%) and 6 patients (5%), respectively.

Conclusions

Our favorable LC and survival rates after robotic SBRT, with low rates of severe toxicities, are coherent with the literature data in this mixed, non-selected study population.

Radiobiology of stereotactic body radiation therapy (SBRT)

Recent advances in the technology of radiotherapy have enabled the development of new therapeutic modalities that deliver radiation with very high accuracy, reduced margins and high dose conformation, allowing the reduction of healthy tissue irradiated and therefore minimizing the risk of toxicity. The next step was to increase the total tumor dose using conventional fractionation (which remains the best way to relatively radioprotect healthy tissues when large volumes are treated) or to use new fractionation schemes with greater biological effectiveness. Based on the experience gained in radiosurgery, the latter way was chosen for small and well-defined tumors in the body. Stereotactic body radiotherapy delivers high doses of radiation to small and well-defined targets in an extreme hypofractionated (and accelerated) scheme with a very high biological effectiveness obtaining very good initial clinical results in terms of local tumor control and acceptable rate of late complications. In fact, we realize a posteriori that it was not feasible to administer such biologically equivalent dose in a conventional fractionation because the treatment could last several months. So far, these new therapeutic modalities have been developed due to technologic advances in image guidance and treatment delivery but without a solid biological basis. It is the role of traditional radiobiology (and molecular radiobiology) to explain the effects of high doses of ionizing radiation on tumor and normal tissues. Only through a better understanding of how high doses of ionizing radiation act, clinicians will know exactly what we do, allowing us in the future to refine our treatments. This article attempts to describe through simple and understandable concepts the known aspects of the biological action of high doses of radiation on tumor and normal tissues, but it is clear that we need much more basic research to better understand the biology of high doses of radiation.

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.

Clinical outcomes of CyberKnife stereotactic radiosurgery for elderly patients with presumed primary stage I lung cancer

BACKGROUND

In certain situations, especially in the elderly patient population, a tissue diagnosis of a suspected pulmonary neoplasm is not feasible. Often, a definitive treatment such as stereotactic body radiosurgery is recommended, rather than active surveillance. The aim of this study is to evaluate the efficacy and tolerability of stereotactic body radiotherapy (SBRT) for elderly patients with presumed primary stage I lung cancer without pathological tissue confirmation.

METHODS

We performed a retrospective analysis of 25 elderly patients (≥75 years) with presumed primary stage I lung cancer treated with SBRT from 2009-2015. The primary end point was local control (LC); secondary end points were survival and toxicity.

RESULTS

The median follow-up (FU) was 36.0 months (range, 4 to 84 months). The 1-year LC rate was 100%, 3-year LC rate was 78.8%, and 5-year LC rate was 65.7%. The median progression-free survival (PFS) time was 48.0 months (95% CI: 31.2-64.8). The 1-, 3-, and 5-year overall survival (OS) rates were 96.0%, 70.2%, and 50.7%, respectively. The 1-, 3-, and 5-year cancer-specific survival (CSS) rates were 100%, 81.3%, and 67.0%, respectively. No grade 4 or higher toxicity was encountered.

CONCLUSIONS

SBRT is safe and effective treatment for patients with presumed primary stage I lung cancer where obtaining pathological confirmation of malignancy is challenging.

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

Stereotactic body radiation therapy (SBRT) has had a profound impact on the treatment paradigm for medically inoperable patients with stage I non-small cell lung cancer. Local control and survival outcomes from prospective collaborative trials using SBRT have been highly favorable in this challenging patient population. Further study in medically operable patients is ongoing; however, randomized trials to help answer this question have terminated early because of poor accrual. Available prospective and retrospective data are discussed for the use of SBRT with regard to the medically inoperable and operable patient populations, as well as considerations for fractionation, dose, and toxicity.

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.

The Effect of Biologically Effective Dose and Radiation Treatment Schedule on Overall Survival in Stage I Non-Small Cell Lung Cancer Patients Treated With Stereotactic Body Radiation Therapy

PURPOSE

To determine the effect of biologically effective dose (BED₁₀) and radiation treatment schedule on overall survival (OS) in patients with early-stage non-small cell lung cancer (NSCLC) undergoing stereotactic body radiation therapy (SBRT).

METHODS AND MATERIALS

Using data from 65 treatment centers in the United States, we retrospectively reviewed the records of T1-2 N0 NSCLC patients undergoing SBRT alone from 2006 to 2014. Biologically relevant covariates, including dose per fraction, number of fractions, and time between fractions, were used to quantify BED₁₀ and radiation treatment schedule. The linear-quadratic equation was used to calculate BED₁₀ and to generate a dichotomous dose variable of <105 Gy versus ≥105 Gy BED₁₀. The primary outcome was OS. We used the Kaplan-Meier method, the log-rank test, and Cox proportional hazards regression with propensity score matching to determine whether prescription BED₁₀ was associated with OS.

RESULTS

We identified 747 patients who met inclusion criteria. The median BED₁₀ was 132 Gy, and 59 (7.7%) had consecutive-day fractions. Median follow-up was 41 months, and 452 patients (60.5%) had died by the conclusion of the study. The 581 patients receiving ≥105 Gy BED₁₀ had a median survival of 28 months, whereas the 166 patients receiving <105 Gy BED₁₀ had a median survival of 22 months (log-rank, P=.01). Radiation treatment schedule was not a significant predictor of OS on univariable analysis. After adjusting for T stage, sex, tumor histology, and Eastern Cooperative Oncology Group performance status, BED₁₀ ≥105 Gy versus <105 Gy remained significantly associated with improved OS (hazard ratio 0.78, 95% confidence interval 0.62-0.98, P=.03). Propensity score matching on imbalanced variables within high- and low-dose cohorts confirmed a survival benefit with higher prescription dose.

CONCLUSIONS

We found that dose escalation to 105 Gy BED₁₀ and beyond may improve survival in NSCLC patients treated with SBRT.

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.

Radiobiological modeling of two stereotactic body radiotherapy schedules in patients with stage I peripheral non-small cell lung cancer

This study aims to compare the radiobiological response of two stereotactic body radiotherapy (SBRT) schedules for patients with stage I peripheral non-small cell lung cancer (NSCLC) using radiobiological modeling methods. Volumetric modulated arc therapy (VMAT)-based SBRT plans were designed using two dose schedules of 1 × 34 Gy (34 Gy in 1 fraction) and 4 × 12 Gy (48 Gy in 4 fractions) for 19 patients diagnosed with primary stage I NSCLC. Dose to the gross target volume (GTV), planning target volume (PTV), lung and chest wall (CW) were converted to biologically equivalent dose in 2 Gy fraction (EQD2) for comparison. Five different radiobiological models were employed to predict the tumor control probability (TCP) value. Three additional models were utilized to estimate the normal tissue complication probability (NTCP) value for the lung and the modified equivalent uniform dose (mEUD) value to the CW. Our result indicates that the 1 × 34 Gy dose schedule provided a higher EQD2 dose to the tumor, lung and CW. Radiobiological modeling revealed that the TCP value for the tumor, NTCP value for the lung and mEUD value for the CW were 7.4% (in absolute value), 7.2% (in absolute value) and 71.8% (in relative value) higher on average, respectively, using the 1 × 34 Gy dose schedule.

Incidence and predictors of chest wall toxicity after high-dose radiation therapy in 15 fractions

PURPOSE

Fifteen fraction treatment schedules are increasingly used to deliver high doses of radiation therapy (RT) to both lung and hepatobiliary malignancies. The purpose of our study was to examine the incidence and predictors of chest wall (CW) toxicity in patients treated with this regimen.

METHODS AND MATERIALS

We evaluated 135 patients treated with RT to doses ≥52.5 Gy in 15 fractions for thoracic and hepatobiliary malignancies between January 2009 and December 2012. We documented patient characteristics and CW dosimetric parameters for each case. Toxicity was scored using the Common Terminology Criteria for Adverse Events, version 4.0, criteria for radiation dermatitis and CW pain. Patient characteristics and CW dosimetric parameters were evaluated for their association with CW toxicity using proportional hazards regression.

RESULTS

Median follow-up was 9 months from the start of RT. Forty-eight patients (36%) developed dermatitis at a median time of 18 days. In multivariable analysis, the absolute volume of CW (in cm³) receiving 40 Gy (V40) ≥120 cm³ was associated with the occurrence of dermatitis (hazard ratio, 3.12; 95% confidence interval, 1.74-5.60; P < .001). Twenty-one patients (16%) developed CW pain (20 grade 1, 1 grade 2) at a median time of 3 months. In multivariable analysis, CW V40 ≥150 cm³ was associated with the occurrence of CW pain (hazard ratio, 2.65; 95% confidence interval, 1.12-6.24; P = .03). The absolute rate of CW pain in patients with V40 <150 cm³ was 11% versus 26% in patients with V40 ≥150 cm³ (P = .03).

CONCLUSIONS

Hypofractionated RT with 15 fraction regimens results in an acceptable incidence of CW toxicity, specifically CW pain. We recommend a dose constraint of V40 <150 cm³ to minimize this adverse event.

Challenges in radiobiological modeling: can we decide between LQ and LQ-L models based on reviewed clinical NSCLC treatment outcome data?

Aim

To study the dose-response of stage I non-small-cell lung cancer (NSCLC) in terms of long-term local tumor control (LC) after conventional and hypofractionated photon radiotherapy, modeled with the linear-quadratic (LQ) and linear-quadratic-linear (LQ-L) approaches and to estimate the clinical α/β ratio within the LQ frame.

Material and methods

We identified studies of curative radiotherapy as single treatment through MedLine search reporting 3-year LC as primary outcome of interest. Logistic models coupled with the biologically effective dose (BED) at isocenter and PTV edge according to both the LQ and LQ-L models with α/β = 10 Gy were fitted. Additionally, α/β was estimated from direct LQ fits.

Results

Thirty one studies were included reporting outcome of 2319 patients. The LQ-L fit yielded a significant value of 11.0 ± 5.2 Gy for the dose threshold (D_t) for BED₁₀ at the isocenter. The LQ and LQ-L fits did not differ substantially. Concerning the estimation of α/β, the value obtained from the direct LQ fit for the complete fractionation range was 3.9 [68 % CI: 2.2–9.0] Gy (p > 0.05).

Conclusion

Both LQ and LQ-L fits can model local tumor control after conventionally and hypofractionated irradiation and are robust methods for predicting clinical effects. The observed dose-effect for local control in NSCLC is weaker at high doses due to data dispersion. For BED₁₀ values of 100–150 Gy in ≥3 fractions, the differences in isoeffects predicted by both models can be neglected.

Electronic supplementary material

The online version of this article (doi:10.1186/s13014-016-0643-5) contains supplementary material, which is available to authorized users.

Radiobiological modeling analysis of the optimal fraction scheme in patients with peripheral non-small cell lung cancer undergoing stereotactic body radiotherapy

This study aimed to determine the optimal fraction scheme (FS) in patients with small peripheral non-small cell lung cancer (NSCLC) undergoing stereotactic body radiotherapy (SBRT) with the 4 × 12 Gy scheme as the reference. CT simulation data for sixteen patients diagnosed with primary NSCLC or metastatic tumor with a single peripheral lesion ≤3 cm were used in this study. Volumetric modulated arc therapy (VMAT) plans were designed based on ten different FS of 1 × 25 Gy, 1 × 30 Gy, 1 × 34 Gy, 3 × 15 Gy, 3 × 18 Gy, 3 × 20 Gy, 4 × 12 Gy, 5 × 12 Gy, 6 × 10 Gy and 10 × 7 Gy. Five different radiobiological models were employed to predict the tumor control probability (TCP) value. Three other models were utilized to estimate the normal tissue complication probability (NTCP) value to the lung and the modified equivalent uniform dose (mEUD) value to the chest wall (CW). The 1 × 30 Gy regimen is recommended to achieve 4.2% higher TCP and slightly higher NTCP and mEUD values to the lung and CW compared with the 4 × 12 Gy schedule, respectively. This regimen also greatly shortens the treatment duration. However, the 3 × 15 Gy schedule is suggested in patients where the lung-to-tumor volume ratio is small or where the tumor is adjacent to the CW.

Clinical utility of RapidArc™ radiotherapy technology

RapidArc™ is a radiation technique that delivers highly conformal dose distributions through the complete rotation (360°) and speed variation of the linear accelerator gantry. This technique, called volumetric modulated arc therapy (VMAT), compared with conventional radiotherapy techniques, can achieve high-target volume coverage and sparing damage to normal tissues. RapidArc delivers precise dose distribution and conformity similar to or greater than intensity-modulated radiation therapy in a short time, generally a few minutes, to which image-guided radiation therapy is added. RapidArc has become a currently used technology in many centers, which use RapidArc technology to treat a large number of patients. Large and small hospitals use it to treat the most challenging cases, but more and more frequently for the most common cancers. The clinical use of RapidArc and VMAT technology is constantly growing. At present, a limited number of clinical data are published, mostly concerning planning and feasibility studies. Clinical outcome data are increasing for a few tumor sites, even if only a little. The purpose of this work is to discuss the current status of VMAT techniques in clinical use through a review of the published data of planning systems and clinical outcomes in several tumor sites. The study consisted of a systematic review based on analysis of manuscripts retrieved from the PubMed, BioMed Central, and Scopus databases by searching for the keywords “RapidArc”, “Volumetric modulated arc radiotherapy”, and “Intensity-modulated radiotherapy”.