Stereotactic body radiotherapy (SBRT) for non-small cell lung cancer (NSCLC): is FDG-PET a predictor of outcome?

Exploring published and novel pre-treatment CT and PET radiomics to stratify risk of progression among early-stage non-small cell lung cancer patients treated with stereotactic radiation

PURPOSE

Disease progression after definitive stereotactic body radiation therapy (SBRT) for early-stage non-small cell lung cancer (NSCLC) occurs in 20-40% of patients. Here, we explored published and novel pre-treatment CT and PET radiomics features to identify patients at risk of progression.

MATERIALS/METHODS

Published CT and PET features were identified and explored along with 15 other CT and PET features in 408 consecutively treated early-stage NSCLC patients having CT and PET < 3 months pre-SBRT (training/set-aside validation subsets: n = 286/122). Features were associated with progression-free survival (PFS) using bootstrapped Cox regression (Bonferroni-corrected univariate predictor: p ≤ 0.002) and only non-strongly correlated predictors were retained (|Rs|<0.70) in forward-stepwise multivariate analysis.

RESULTS

Tumor diameter and SUVmax were the two most frequently reported features associated with progression/survival (in 6/20 and 10/20 identified studies). These two features and 12 of the 15 additional features (CT: 6; PET: 6) were candidate PFS predictors. A re-fitted model including diameter and SUVmax presented with the best performance (c-index: 0.78; log-rank p-value < 0.0001). A model built with the two best additional features (CTspiculation1 and SUVentropy) had a c-index of 0.75 (log-rank p-value < 0.0001).

CONCLUSIONS

A re-fitted pre-treatment model using the two most frequently published features - tumor diameter and SUVmax - successfully stratified early-stage NSCLC patients by PFS after receiving SBRT.

Pretreatment and Posttreatment Tumor Metabolic Activity Assessed by FDG-PET/CT as Predictors of Tumor Recurrence and Survival Outcomes in Early-Stage Non-Small Cell Lung Cancer Treated With Stereotactic Body Radiation Therapy

Purpose

Stereotactic body radiation therapy (SBRT) is considered the standard of care for medically inoperable early-stage non-small cell lung cancer. There is mixed evidence on the prognostic significance of tumor metabolic activity assessed by positron emission tomography combined with computed tomography (PET/CT) using F-18 fluorodeoxyglucose (FDG). The objectives of this study were to evaluate the maximum standardized uptake value (SUVmax) pretreatment and at 3 and 6 months after SBRT for prediction of tumor control and survival outcomes.

Methods and Materials

Consecutive patients from a single institution with T12N0M0 non-small cell lung cancer receiving primary treatment with SBRT with pretreatment FDG-PET/CT (n = 163) and follow-up FDG-PET/CT at 3 or 6 months (n = 71) were included. Receiver operator characteristic analysis was performed to dichotomize variables for Kaplan-Meier survival analysis. Multivariate analysis was performed with Cox proportional hazards regression.

Results

Median follow-up was 19 months. For the whole cohort, 1-year and 2-year local control, progression-free survival (PFS), and overall survival (OS) were 95.0% and 80.3%, 87.1% and 75.4%, and 67.0% and 49.6% respectively. The following pre-SBRT SUVmax cutoffs were significant: SUV > 4.0 for distant failure-free survival (adjusted hazard ratio [aHR], 3.33, P = .006), >12.3 for PFS (aHR, 2.80, P = .011), and >12.6 for OS (aHR, 3.00, P = .003). SUVmax decreases of at least 45% at 3 months (aHR, 0.15, P = .018), and 53% at 6 months (aHR, 0.12, P = .046) were associated with improved local failure-free survival.

Conclusions

Pre-SBRT SUVmax cutoffs can predict distant failure, PFS, and OS. At both 3 and 6 months after SBRT, cutoffs for percentage change in SUVmax can potentially stratify risk of local recurrence.

Atezolizumab plus stereotactic ablative radiotherapy for medically inoperable patients with early-stage non-small cell lung cancer: a multi-institutional phase I trial

Stereotactic ablative radiotherapy (SABR) is a standard-of-care for medically-inoperable-early-stage non-small cell lung cancer (NSCLC). One third of patients progress and chemotherapy is rarely used in this population. We questioned if addition of the immune-checkpoint-inhibitor (ICI) atezolizumab to standard-of-care SABR can improve outcomes. We initiated a multi-institutional single-arm phase I study (NCT02599454) enrolling twenty patients with the primary endpoint of maximum tolerated dose (MTD); secondary endpoints of safety and efficacy; and exploratory mechanistic correlatives. Treatment is well tolerated and full dose atezolizumab (1200 mg) is the MTD. Efficacy signals include early responses (after 2 cycles of ICI, before initiation of SABR) in 17% of patients. Biomarkers of functional adaptive immunity, including T cell activation in the tumor and response to ex-vivo stimulation by circulating T cells, are highly predictive of benefit. These results require validation and are being tested in a phase III randomized trial.

Metabolic factors associated with the prognosis of oligometastatic patients treated with stereotactic body radiotherapy

Over the past two decades, it has been established that cancer patients with oligometastases, i.e., only a few detectable metastases confined to one or a few organs, may benefit from an aggressive local treatment approach such as the application of high-precision stereotactic body radiotherapy (SBRT). Specifically, some studies have indicated that achieving long-term local tumor control of oligometastases is associated with prolonged overall survival. This motivates investigations into which factors may modify the dose-response relationship of SBRT by making metastases more or less radioresistant. One such factor relates to the uptake of the positron emission tomography tracer 2-deoxy-2-[18F]fluoro-D-glucose (FDG) which reflects the extent of tumor cell glycolysis or the Warburg effect, respectively. Here we review the biological mechanisms how the Warburg effect drives tumor cell radioresistance and metastasis and draw connections to clinical studies reporting associations between high FDG uptake and worse clinical outcomes after SBRT for oligometastases. We further review the evidence for distinct metabolic phenotypes of metastases preferentially seeding to specific organs and their possible translation into distinct radioresistance. Finally, evidence that obesity and hyperglycemia also affect outcomes after SBRT will be presented. While delivered dose is the main determinant of a high local tumor control probability, there might be clinical scenarios when metabolic targeting could make the difference between achieving local control or not, for example when doses have to be compromised in order to spare neighboring high-risk organs, or when tumors are expected to be highly therapy-resistant due to heavy pretreatment such as chemotherapy and/or radiotherapy.

Prediction of Distant Metastases After Stereotactic Body Radiation Therapy for Early Stage NSCLC: Development and External Validation of a Multi-Institutional Model

INTRODUCTION

Distant metastases (DMs) are the primary driver of mortality for patients with early stage NSCLC receiving stereotactic body radiation therapy (SBRT), yet patient-level risk is difficult to predict. We developed and validated a model to predict individualized risk of DM in this population.

METHODS

We used a multi-institutional database of 1280 patients with cT1-3N0M0 NSCLC treated with SBRT from 2006 to 2015 for model development and internal validation. A Fine and Gray (FG) regression model was built to predict 1-year DM risk and compared with a random survival forests model. The higher performing model was evaluated on an external data set of 130 patients from a separate institution. Discriminatory performance was evaluated using the time-dependent area under the curve (AUC). Calibration was assessed graphically and with Brier scores.

RESULTS

The FG model yielded an AUC of 0.71 (95% confidence interval [CI]: 0.57-0.86) compared with the AUC of random survival forest at 0.69 (95% CI: 0.63-0.85) in the internal test set and was selected for further testing. On external validation, the FG model yielded an AUC of 0.70 (95% CI: 0.57-0.83) with good calibration (Brier score: 0.08). The model identified a high-risk patient subgroup with greater 1-year DM rates in the internal test (20.0% [3 of 15] versus 2.9% [7 of 241], p = 0.001) and external validation (21.4% [3 of 15] versus 7.8% [9 of 116], p = 0.095). A model nomogram and online application was made available.

CONCLUSIONS

We developed and externally validated a practical model that predicts DM risk in patients with NSCLC receiving SBRT which may help select patients for systemic therapy.

Prognostic value of node-to-primary tumor maximum standardized uptake value ratio in T1-4N1-3M0 non-small cell lung cancer patients treated with concurrent chemo-radiotherapy

BACKGROUND

This study aimed to identify whether NTR is the independent risk factor for progression-free survival (PFS) and overall survival (OS) in patients treated with concurrent chemo-radiotherapy (cCRT).

METHODS

We retrospectively studied 106 T1-4N1-3M0 non-small cell lung cancer patients treated with cCRT. The maximum standardized uptake value (SUVTumor) of the primary tumor and the metastatic lymph nodes (SUVLN) were measured. The prognostic significance of NTR for predicting PFS and OS was assessed. A multi-adjusted spline regression model was conducted to provide more precise estimates and examine the shape of the associations between NTR and the risk of progression.

RESULTS

From 2012 to 2017, 106 eligible patients were analyzed. The median follow-up time was 15.3 months (3.5-44.6 months). We determined the maximizing area under the time-dependent receiver operating characteristic curve was at an NTR of 0.73 for predicting PFS. The two-year PFS was significantly lower in the high-NTR group (35.7% vs. 55.4%, P = 0.02) and two-year OS (43.4% vs. 61.1%, P = 0.03 was also significantly worse. Multivariable analysis revealed that only NTR was an independent prognostic factor for PFS (hazard ratio [HR]: 10.04, P < 0.001) and OS (HR: 4.19, P = 0.03). The restricted cubic spline regression model showed that NTR had a non-linear relationship with log relative risk for progression.

CONCLUSION

NTR was an independent risk factor for predicting PFS and OS in T1-4N1-3M0 non-small cell lung cancer patients treated with cCRT.

Necrosis on pre-radiotherapy 18F-FDG PET/CT is a predictor for complete metabolic response in patients with non-small cell lung cancer

To investigate necrosis on pre-radiotherapy (RT) 18F-FDG PET/CT (PETNECROSİS) as a predictor of complete metabolic response (CMR) in patients with non-small cell lung cancer (NSCLC).We evaluated patients with inoperable stage I-III NSCLC who underwent pre- and post-radiotherapy 18F-FDG PET/CT. The relationship between CMR and PETNECROSIS, SUVmax, gross tumor volume calculated with 18F-FDG PET/CT (GTVPET-CT), tumor size, histology, metabolic tumor volume (MTV), and RT dose was assessed using logistic regression analysis. To evaluate necrosis on 18F FDG PET/CT, we drew a region of interest (ROI) in the area showing visually very low/or no fluorodeoxyglucose (FDG) uptake on PET images. If the SUVmax was lower than the blood pool SUVmax and showed significantly lower attenuation (10-30 Hounsfield units [HU]) from the surrounding tissue on non-intravenous contrast-enhanced low-dose correlative CT, we defined it as necrotic (PETNECROSİS).Fifty-three patients were included in this study. The mean age was 68.1 ± 9.8 years. Twenty-one patients had adenocarcinoma, and 32 had squamous cell carcinoma. All parameters were independent of histologic status. Multivariate logistic regression analysis showed that SUVmax ≤11.6 vs >11.6, (P = .003; OR, 7.670, 95CI%: 2.013-29.231) and PETNECROSİS absence/presence were independent predictors for CMR (P = .028, OR: 6.704, 95CI% 1.214-30.394).The necrosis on 18F FDG PET/CT and SUVmax > 11.6 could be an imaging marker for the complete metabolic response after definitive chemoradiotherapy or definitive RT alone in patients with NSCLC.

Joint EANM/SNMMI/ESTRO practice recommendations for the use of 2-[18F]FDG PET/CT external beam radiation treatment planning in lung cancer V1.0

Purpose

2-[¹⁸F]FDG PET/CT is of utmost importance for radiation treatment (RT) planning and response monitoring in lung cancer patients, in both non-small and small cell lung cancer (NSCLC and SCLC). This topic has been addressed in guidelines composed by experts within the field of radiation oncology. However, up to present, there is no procedural guideline on this subject, with involvement of the nuclear medicine societies.

Methods

A literature review was performed, followed by a discussion between a multidisciplinary team of experts in the different fields involved in the RT planning of lung cancer, in order to guide clinical management. The project was led by experts of the two nuclear medicine societies (EANM and SNMMI) and radiation oncology (ESTRO).

Results and conclusion

This guideline results from a joint and dynamic collaboration between the relevant disciplines for this topic. It provides a worldwide, state of the art, and multidisciplinary guide to 2-[¹⁸F]FDG PET/CT RT planning in NSCLC and SCLC. These practical recommendations describe applicable updates for existing clinical practices, highlight potential flaws, and provide solutions to overcome these as well. Finally, the recent developments considered for future application are also reviewed.

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.

Prognostic value of positron emission tomography in resected stage IA non-small cell lung cancer

OBJECTIVES

To investigate the role of PET in predicting the prognosis of resected stage IA non-small cell lung cancer (NSCLC) and planning individualized therapeutic strategies.

METHODS

We retrospectively reviewed the data of patients who underwent surgical resection for lung cancer between January 2004 and December 2014. The clinical data, imaging characteristics of nodules, surgical approaches, and outcomes were analyzed.

RESULTS

We evaluated 998 cases; 637 patients with pathological stage I disease were categorized as follows: stage IA1 (251 cases), stage IA2 (250 cases), and stage IA3 (136 cases). The mean follow-up period was 109 months. Significant differences were observed in sex, tumor differentiation, epidermal growth factor receptor mutation, smoking habits, lymphovascular space invasion, tumor size, maximum standard uptake value (SUVmax), and carcinoembryonic antigen level among the groups. Multivariable Cox regression revealed that ground-glass opacity ratio (hazard ratio (HR) = 0.001) and tumor SUVmax independently predicted the postoperative risk of relapse for stage IA3 NSCLC. The HR for SUVmax > 4 was 8.986 (p < 0.001). The 5-year overall survival (OS) rates were 87.2%, 92.9%, and 82.7%, and the 5-year disease-free survival (DFS) rates were 93.2%, 84.2%, and 70.51% for stage IA1, IA2, and IA3 NSCLC, respectively (both p < 0.001). OS and DFS rates were poor in stage IA3 NSCLC patients with an SUVmax uptake > 4 (OS, 71.0% and 92.2%; DFS, 50.2% and 87.3%, for SUVmax > 4 and ≤ 4, respectively; both p = 0.001).

CONCLUSIONS

SUVmax was a prognostic factor for resected stage IA NSCLC. Postoperative treatment may be considered for IA3 NSCLC with SUVmax > 4.

KEY POINTS

• PET helps surgeons to assess patients with early-stage lung cancer. • This retrospective study revealed that PET plays an influential role in predicting the prognosis of resected lung cancer. • Better prognostication aids better planning of therapeutic strategies with diversification.

Multiple Testing, Cut-Point Optimization, and Signs of Publication Bias in Prognostic FDG-PET Imaging Studies of Head and Neck and Lung Cancer: A Review and Meta-Analysis

Positron emission tomography (PET) imaging with 2-deoxy-2-[¹⁸F]-fluorodeoxyglucose (FDG) was proposed as prognostic marker in radiotherapy. Various uptake metrics and cut points were used, potentially leading to inflated effect estimates. Here, we performed a meta-analysis and systematic review of the prognostic value of pretreatment FDG–PET in head and neck squamous cell carcinoma (HNSCC) and non-small cell lung cancer (NSCLC), with tests for publication bias. Hazard ratio (HR) for overall survival (OS), disease free survival (DFS), and local control was extracted or derived from the 57 studies included. Test for publication bias was performed, and the number of statistical tests and cut-point optimizations were registered. Eggers regression related to correlation of SUVmax with OS/DFS yielded p = 0.08/p = 0.02 for HNSCC and p < 0.001/p = 0.014 for NSCLC. No outcomes showed significant correlation with SUVmax, when adjusting for publication bias effect, whereas all four showed a correlation in the conventional meta-analysis. The number of statistical tests and cut points were high with no indication of improvement over time. Our analysis showed significant evidence of publication bias leading to inflated estimates of the prognostic value of SUVmax. We suggest that improved management of these complexities, including predefined statistical analysis plans, are critical for a reliable assessment of FDG–PET.

Radiographic findings after stereotactic body radiation therapy for stage I non-small cell lung carcinomas: retrospective analysis of 90 patients

Aim:

Stereotactic body radiation therapy for lung tumours can expose patients to radiation pneumonitis (RP) (<6 months after irradiation) and lung fibrosis (beyond 6 months). The aim of this study was to describe post-irradiation radiographics appearances.

Materials and methods:

This retrospective study of 90 patients with a stage I non-small cell lung carcinoma reports a detailed description of the computed tomography (CT) or positron emission tomography/CT changes that can be observed after treatment, according to modified Kimura score for RP and Koenig’s classification for fibrosis. This evaluation was realised at 1 month and then every 3–4 months, with a median follow-up of 35 months.

Results:

The most common radiological RP pattern was diffuse consolidation. It appears in a mean time of 4 months and reaches its maximum at 9 months after radiotherapy. Seventy-three per cent of the RP evolved to fibrosis. Most of these findings were encompassed in the 35 Gy isodose.

Findings:

Radiological parenchymal changes are frequent in the treatment region, which renders the tumour response monitoring by tumour size, particularly by response evaluation criteria in solid tumours, unsuitable.

Timing of fluorodeoxyglucose positron emission tomography maximum standardized uptake value for diagnosis of local recurrence of non-small cell lung cancer after stereotactic body radiation therapy

Introduction

After treatment with stereotactic body radiation therapy (SBRT), local recurrence of non‐small cell cancer (NSCLC) can be difficult to differentiate from radiation‐induced changes. Maximum standardized uptake value (SUVmax), measured with 18‐F‐Fluorodeoxyglucose positron emission tomography (FDG‐PET), can have false positives due to acute radiation inflammation. The primary study objective was to determine the utility of SUVmax > 5 to identify local recurrence later than 9 months after SBRT.

Method

A retrospective review was performed of FDG‐PET scans for suspicious CT findings after SBRT treatment of stage 1 NSCLC. SUVmax was measured including surrounding opacification. Outcome measures were local recurrence, progression free survival, and overall survival. Receiver operator curve analysis, sensitivity, specificity, and Kaplan‐Meier analysis were performed.

Results

Of 118 patients treated, 42 patients had eligible FDG‐PET scans. They received SBRT (48‐60Gy in 3‐8 fractions) for 49 NSCLC and had 101 follow‐up PET scans. The median time to first PET scan was 9.3 months, and the median follow‐up period was 22.4 months. Local recurrence was diagnosed in 12 patients, at a median of 16 months. Due to selection bias, the included patients had poorer outcomes than the entire cohort, with progression free survival (PFS) at 1, 2, and 3 years of 82.7%, 57.8%, and 45.8%; and overall survival of 97.9%, 79.9%, and 59.1%, respectively. Thirty FDG‐PET scans were performed within 9 months, of which 17% were false positives. A total of 71 FDG‐PET scans were performed beyond 9 months, and the median SUVmax was significantly higher for patients with local recurrence (7.48 vs. 2.14, P < .0001). SUVmax > 5 has a sensitivity of 91% (95% CI 62%‐99.8%) and 100% (89.1%‐100%).

Conclusion

For local recurrence of NSCLC, SUVmax > 5 on FDG‐PET scan has good sensitivity and specificity after 6 months, but is highest beyond 9 months after SBRT.

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.

Advanced Cancer Imaging Applied in the Comparative Setting

The potential for companion (pet) species with spontaneously arising tumors to act as surrogates for preclinical development of advanced cancer imaging technologies has become more apparent in the last decade. The utility of the companion model specifically centers around issues related to body size (including spatial target/normal anatomic characteristics), physical size and spatial distribution of metastasis, tumor heterogeneity, the presence of an intact syngeneic immune system and a syngeneic tumor microenvironment shaped by the natural evolution of the cancer. Companion species size allows the use of similar equipment, hardware setup, software, and scan protocols which provide the opportunity for standardization and harmonization of imaging operating procedures and quality assurance across imaging protocols, imaging hardware, and the imaged species. Murine models generally do not replicate the size and spatial distribution of human metastatic cancer and these factors strongly influence image resolution and dosimetry. The following review will discuss several aspects of comparative cancer imaging in more detail while providing several illustrative examples of investigational approaches performed or currently under exploration at our institutions. Topics addressed include a discussion on interested consortia; image quality assurance and harmonization; image-based biomarker development and validation; contrast agent and radionuclide tracer development; advanced imaging to assess and predict response to cytotoxic and immunomodulatory anticancer agents; imaging of the tumor microenvironment; development of novel theranostic approaches; cell trafficking assessment via non-invasive imaging; and intraoperative imaging to inform surgical oncology decision making. Taken in totality, these comparative opportunities predict that safety, diagnostic and efficacy data generated in companion species with naturally developing and progressing cancers would better recapitulate the human cancer condition than that of artificial models in small rodent systems and ultimately accelerate the integration of novel imaging technologies into clinical practice. It is our hope that the examples presented should serve to provide those involved in cancer investigations who are unfamiliar with available comparative methodologies an understanding of the potential utility of this approach.

18F-FDG PET/CT in Restaging and Evaluation of Response to Therapy in Lung Cancer: State of the Art

BACKGROUND

Metabolic information provided by 18F-FDG PET/CT are useful for initial staging, therapy planning, response evaluation, and to a lesser extent for the follow-up of non-small cell lung cancer (NSCLC). To date, there are no established clinical guidelines in treatment response and early detection of recurrence.

OBJECTIVE

To provide an overview of 18F-FDG PET/CT in NSCLC and in particular, to discuss its utility in treatment response evaluation and restaging of lung cancer.

METHODS

A comprehensive search was used based on PubMed results. From all studies published in English those that explored the role of 18F-FDG PET/CT in the treatment response scenario were selected.

RESULTS

Several studies have demonstrated that modifications in metabolic activity, expressed by changes in SUV both in the primary tumor as well as in regional lymph nodes, are associated with tumor response and survival. Beside SUV, other metabolic parameters (i.e. MTV, TLG, and percentage changes) are emerging to be helpful for predicting clinical outcomes.

CONCLUSION

18F-FDG parameters appear to be promising factors for evaluating treatment response and for detecting recurrences, although larger prospective trials are needed to confirm these evidences and to determine optimal cut-off values.

Prognostic Role Of Computed Tomography Textural Features In Early-Stage Non-Small Cell Lung Cancer Patients Receiving Stereotactic Body Radiotherapy

Purpose

The imaging features of patients with early-stage non-small cell lung cancer (NSCLC) receiving stereotactic body radiotherapy (SBRT) are crucial for the decision-making process to establish a treatment plan. The purpose of this study was to predict the clinical outcomes of SBRT from the textural features of pretreatment computed tomography (CT) images.

Patients and methods

Forty-one early-stage NSCLC patients who received SBRT were included in this retrospective study. In total, 72 textural features were extracted from the pretreatment contrast-enhanced CT images. Survival analysis was used to identify high-risk groups for progression-free survival (PFS) and disease-specific survival (DSS). Receiver operating characteristic (ROC) curve analysis was utilized to estimate the diagnostic abilities of the textural parameters. Univariable and multivariable Cox regression analyses were performed to evaluate the predictors of PFS and DSS.

Results

Four parameters, including entropy (P=0.003), second angular moment (SAM) (P=0.04), high-intensity long-run emphasis (HILRE) (P=0.046) and long-run emphasis (LRE) (P=0.042), were significant prognostic features for PFS. In addition, contrast (P=0.008), coarseness (P=0.017), low-intensity zone emphasis (LIZE) (P=0.01) and large number emphasis (LNE) (P=0.046) were significant prognostic factors for DSS. In the ROC analysis, the area under the curve (AUC) of coarseness for local recurrence (LR) was 0.722 (0.528–0.916), and the AUC of entropy for lymph node metastasis (LNM) was 0.771 (0.556–0.987). The four highest AUCs for distant metastasis (DM) were 0.885 (0.784–0.985) for LNE, 0.846 (0.733–0.959) for SAM, 0.731 (0.500–0.961) for LRE and 0.731 (0.585–0.876) for contrast. In the multivariable analysis, smoking and entropy were independent prognostic factors for PFS.

Conclusion

This exploratory study reveals that textual features derived from pretreatment CT scans have prognostic value in early-stage NSCLC patients treated with SBRT.

Predicting 5-Year Progression and Survival Outcomes for Early Stage Non-small Cell Lung Cancer Treated with Stereotactic Ablative Radiation Therapy: Development and Validation of Robust Prognostic Nomograms

PURPOSE

Our purpose was to develop predictive nomograms for overall survival (OS), progression-free survival (PFS), and time-to-progression (TTP) at 5 years in patients with early-stage non-small cell lung cancer (ES-NSCLC) treated with stereotactic ablative radiation therapy (SABR).

METHODS AND MATERIALS

The study cohort included 714 ES-NSCLC patients treated with SABR from 2004-2015 with median follow-up of 59 months, divided into training and testing sets (8:2), with the former used for nomogram development. The least absolute shrinkage and selection operator were initially employed to screen for predictors of OS, PFS, and TTP, and identified predictors were subsequently applied toward Cox proportional hazards regression modeling. Significant predictors (P < .05) on multivariable regression were then used to develop nomograms, which were validated via evaluation of concordance indexes (C-index) and calibration plots. Finally, Kaplan-Meier method and Gray's test were employed to compare and confirm differences in outcomes among various groups and explore prognostic factors associated with local versus distant disease progression.

RESULTS

Significant predictors of both OS and PFS at 5 years included age, sex, Charlson comorbidity index, diffusing capacity of carbon monoxide, systemic immune-inflammation index, and tumor size (P ≤ .01 for all). Eastern Cooperative Oncology Group performance status predicted for OS as well (P = .01), and both tumor size (P < .01) and minimum biological equivalent dose to 95% of planning target volume (PTV D95 BED₁₀; P < .01) were predictive of TTP. The C-indexes for the OS, PFS, and TTP nomograms were 0.73, 0.68, and 0.60 in the training data set and 0.72, 0.66, and 0.59 in the testing data set, respectively. Tumor size > 2.45 cm and PTV D95 BED₁₀ < 113 Gy were significantly associated with both local and distant progression.

CONCLUSIONS

These prognostic nomograms can accurately predict for OS, PFS, and TTP at 5 years after SABR for ES-NSCLC and may thus help identify high-risk patients who could benefit from additional systemic therapy.

SUVmax Predicts Disease Progression after Stereotactic Ablative Radiotherapy in Stage I Non-small Cell Lung Cancer

Purpose

Fluorodeoxyglucose positron emission tomography–computed tomography (PET-CT) is gaining evidence as a predictive factor in non-small cell lung cancer (NSCLC). Stereotactic ablative radiotherapy (SABR) is the standard treatment in early-stage NSCLC when a patient is unsuitable for surgery. We performed a study to assess the prognostic clinical significance of PET-CT after SABR in early-stage NSCLC.

Materials and Methods

Seventy-six patients with stage I NSCLC treated with SABR were investigated. Total radiation dose ranged from 36 to 63 Gy in three to eight fractions depending on tumor location and size. Respiratory motion control was implemented at simulation and during treatment. PET-CT prior to SABR was performed in 66 patients (86.8%).

Results

Median follow-up time was 32 months (range, 5 to 142 months). Local control rate at 1, 2, and 5 years were 95.9%, 92.8%, and 86.7%, respectively. Overall survival (OS) at 1, 2, and 5 years were 91.0%, 71.3%, and 52.1% respectively. Cause-specific survival at 1, 2, and 5 years were 98.6%, 93.1%, and 84.3% respectively. Tumor size and pre-SABR maximal standardized uptake value (SUVmax) demonstrated statistical significance in the Kaplan-Meier survival analyses with log-rank test. In multivariate analyses pre-SABR SUVmax remained statistically significant in correlation to OS (p=0.024; hazard ratio [HR], 3.2; 95% confidence interval [CI], 1.2 to 8.8) and with marginal significance in regards to regional progression-free survival (p=0.059; HR, 32.5; 95% CI, 2.6 to 402.5).

Conclusion

Pre-SABR SUVmax demonstrated a predictive power in statistical analyses. Tumors with SUVmax above 6 at diagnosis were associated with inferior outcomes.

Prognostic index score predicts outcome of patients with Stage I non-small cell lung cancer after stereotactic body radiation therapy

OBJECTIVE

Lung cancer is the most common causes of cancer death worldwide and patients with non-small-cell lung cancer (NSCLC) have various prognosis. We conducted this study to identify the prognostic predictors and establish a prognostic index score (PIS) for patients with Stage I NSCLC after stereotactic body radiation therapy (SBRT).

METHODS

A total of 131 consecutive patients with Stage I NSCLC who underwent SBRT in our institute were analyzed retrospectively. The Cox proportional hazards regression model was applied to identify the prognostic predictors. Time-dependent receiver operating characteristic analysis was performed to examine cutoff values for survival. The Kaplan-Meier method with log-rank test was used to compare survival curves.

RESULTS

Univariate analysis indicated that tumor location, maximum standardized uptake value (SUVmax), monocyte counts and platelet-to-lymphocyte ratio (PLR) were prognostic factors of overall survival (OS). SUVmax and PLR remained significant in multivariate analysis. Survival analysis indicated both high-SUVmax and PLR correlated with inferior OS and PFS. A PIS was constructed based on pretreatment SUVmax and PLR and a high PIS was also significantly associated with poor outcome.

CONCLUSION

The pretreatment SUVmax and PLR were independent prognostic factors of OS in patients with Stage I NSCLC after SBRT. PIS provides a convenient and accurate tool for predicting outcome of patients after SBRT.

Maximum standardized uptake value at pre-treatment PET in estimating lung cancer progression after stereotactic body radiotherapy

PURPOSE

This study aimed to identify the feasibility of the maximum standardized uptake value (SUVmax) on baseline 18F-fluorodeoxyglucose positron emission tomography-computed tomography (FDG PET/CT) as a predictive factor for prognosis in early stage primary lung cancer treated with stereotactic body radiotherapy (SBRT).

MATERIALS AND METHODS

Twenty-seven T1-3N0M0 primary lung cancer patients treated with curative SBRT between 2010 and 2018 were retrospectively evaluated. Four patients (14.8%) treated with SBRT to address residual tumor after wedge resection and one patient (3.7%) with local recurrence after resection were included. The SUVmax at baseline PET/CT was assessed to determine its relationship with prognosis after SBRT. Patients were divided into two groups based on maximum SUVmax on pre-treatment FDG PET/CT, estimated by receiver operating characteristic curve.

RESULTS

The median follow-up period was 17.7 months (range, 2.3 to 60.0 months). The actuarial 2-year local control, progressionfree survival (PFS), and overall survival were 80.4%, 66.0%, and 78.2%, respectively. With regard to failure patterns, 5 patients exhibited local failure (in-field failure, 18.5%), 1 (3.7%) experienced regional nodal relapse, and other 2 (7.4%) developed distant failure. SUVmax was significantly correlated with progression (p = 0.08, optimal cut-off point SUVmax > 5.1). PFS was significantly influenced by pretreatment SUVmax (SUVmax > 5.1 vs. SUVmax ≤ 5.1; p = 0.012) and T stage (T1 vs. T2-3; p = 0.012).

CONCLUSION

SUVmax at pre-treatment FDG PET/CT demonstrated a predictive value for PFS after SBRT for lung cancer.

A pilot study using kernelled support tensor machine for distant failure prediction in lung SBRT

We developed a kernelled support tensor machine (KSTM)-based model with tumor tensors derived from pre-treatment PET and CT imaging as input to predict distant failure in early stage non-small cell lung cancer (NSCLC) treated with stereotactic body radiation therapy (SBRT). The patient cohort included 110 early stage NSCLC patients treated with SBRT, 25 of whom experienced failure at distant sites. Three-dimensional tumor tensors were constructed and used as input for the KSTM-based classifier. A KSTM iterative algorithm with a convergent proof was developed to train the weight vectors for every mode of the tensor for the classifier. In contrast to conventional radiomics approaches that rely on handcrafted imaging features, the KSTM-based classifier uses 3D imaging as input, taking full advantage of the imaging information. The KSTM-based classifier preserves the intrinsic 3D geometry structure of the medical images and the correlation in the original images and trains the classification hyper-plane in an adaptive feature tensor space. The KSTM-based predictive algorithm was compared with three conventional machine learning models and three radiomics approaches. For PET and CT, the KSTM-based predictive method achieved the highest prediction results among the seven methods investigated in this study based on 10-fold cross validation and independent testing.

Using max standardized uptake value from positron emission tomography to assess tumor responses after lung stereotactic body radiotherapy for different prescriptions

PURPOSE

To retrospectively investigate tumor responses of lung SBRT patients for different prescriptions. To analyze the relation between optimal biologically equivalent dose (BED) and tumor responses.

METHODS AND MATERIALS

Tumor responses after lung SBRT were compared by examining 48 treatments used four prescriptions. This study used simplified tumor response criteria: (a) Complete Response (CR) - post max SUV (SUVpost ) after SBRT in the treated tumor region was almost the same as the SUVs in the surrounding regions; (b) Partial Response (PR) - SUVpost was smaller than previous max SUV (SUVpre ), but was greater than the SUVs in the surrounding regions; (c) No Response (NR) - SUVpost was the same as or greater than SUVpre . Some SUVpost reported as mild or favorable responses were classified as CR/PR. BED calculated using α/β of 10 Gy were analyzed with assessments of tumor responses for SBRT prescriptions.

RESULTS

For the prescriptions (9 Gy × 5, 10 Gy × 5, 11 Gy × 5, and 12 Gy × 4) historically recommended by RTOG, we observed that higher BED10 and lower tumor volume would achieve a higher complete response rate. The highest complete response rate was observed for smallest tumor volume (PTVave  = 6.8 cc) with higher BED10 (105.6) of 12 Gy × 4 prescription. For 11 Gy × 5 prescription, the BED10 (115.5) was the highest, but its complete response rate (58%) was lower than 79% of 12 Gy × 4 prescription. We observed the PTVave of 11 Gy × 5 prescription was more than double of the PTVave of 12 Gy × 4 prescription. For the same lung SBRT prescription (BED10  > 100) earlier staging tumor had more favorable local control.

CONCLUSION

We demonstrated post max SUV read from PET/CT could efficiently and accurately assess tumor response after lung SBRT. Although SBRT with prescriptions resulting in a BED10  > 100 experienced favorable tumor responses for early staging cancer, escalation of BED10 to higher levels would be beneficial for lung cancer patients with later staging and larger volume tumors.

Metabolic positron emission tomography parameters predict failure patterns in early non-small-cell lung cancer treated with stereotactic body radiation therapy: a single institution experience

Objective

The prognostic value of metabolic parameters using 18F-fluorodeoxyglucose positron emission tomography/computed tomography (FDG PET/CT) has not been established for early non-small cell lung cancer (NSCLC). Accordingly, the authors investigated the prognostic value of metabolic parameters in terms of failure patterns in patients with early NSCLC who underwent stereotactic body radiation therapy (SBRT).

Methods

Data from 35 patients with Stage I NSCLC who underwent SBRT using CyberKnife and received pretreatment FDG PET/CT between 2008 and 2016 were retrospectively reviewed. Maximum standardized uptake value (SUVmax), metabolic tumor volume, and total lesion glycolysis were measured. The significance of these parameters with regard to failure patterns was assessed.

Results

The median follow-up was 23 months for all patients and 34 months for living patients. Ten patients experienced recurrence: three local failures, five regional failures (RF), and eight distant failures (DF). Three-year local, regional and distant control rates were 96.7%, 86.4% and 71.1%, respectively. High SUVmax (<9 vs. ≥9) was an independent predictive factor associated with increased RF (P = 0.027) and DF (P = 0.008). Furthermore, SUVmax was indicative of both progression-free (P = 0.015) and overall (P = 0.034) survival.

Conclusions

High SUVmax was a significant metabolic parameter associated with increased RF and DF in patients with early NSCLC who received SBRT, having a high propensity for dissemination. These results suggest that adjuvant treatment in conjunction with SBRT may be considered in patients with early NSCLC and high SUVmax.

Nomograms for predicting disease progression in patients of Stage I non-small cell lung cancer treated with stereotactic body radiotherapy

Objective

Non-local progression is a major concern in non-small cell lung cancer (NSCLC) treated with stereotactic body radiotherapy (SBRT). Herein we aimed to create a pre-treatment prognostic nomogram for patients with Stage I NSCLC receiving SBRT.

Methods

We retrospectively studied 182 eligible patients. Patients were randomly divided into a model (70%) group and a validation (30%) group. In the model group, thirteen parameters consisting of patient, treatment, and tumor factors were studied and multivariate Cox proportional hazards regression was performed to identify independent predictors for survival outcome, based on which we developed clinical nomogram. The nomogram was externally validated in the validation group.

Results

Multivariate analysis showed that tumor size (P = 0.011) was the only factor correlated with 2-year overall survival, whereas 2-year locoregional control (LRC) was significantly related to tumor size (P = 0.024) and the maximum standardized uptake value (SUVmax) (P = 0.044), so does 2-year progression-free survival (PFS) (tumor size: P = 0.026; SUVmax: P = 0.038). Nomogram for 2-year LRC and 2-year PFS were created based on aforementioned results. The C-indexes for the nomograms to predict 2-year LRC and PFS were 0.816 and 0.804, respectively, in model group, and were 0.729 and 0.731, respectively, in the validation group. Calibration plots also showed that the model performed well.

Conclusions

Tumor of larger size and higher SUVmax predisposed patients to early onset of locoregional and distant progression. The nomogram developed in our study would be helpful in clinical decision-making and selection of patients who may benefit from more rigorous follow-up and aggressive systemic treatment plan.

Response criteria in solid tumors (PERCIST/RECIST) and SUVmax in early-stage non-small cell lung cancer patients treated with stereotactic body radiotherapy

Background

The purpose of this study was to evaluate the prognostic impact of Positron Emission Tomography Response Criteria in Solid Tumors (PERCIST) and Response Evaluation Criteria in Solid Tumors (RECIST) and of pre- and post-treatment maximum Standard Uptake Value (SUV_max) in regards to survival and tumor control for patients treated for early-stage non-small cell lung cancer (ES-NSCLC) with stereotactic body radiotherapy (SBRT).

Methods

This is a retrospective review of patients with ES-NSCLC treated at our institution using SBRT. Lobar, locoregional, and distant failures were evaluated based on PERCIST/RECIST and clinical course. Univariate analysis of the Kaplan-Meier curves for overall survival (OS), progression free survival (PFS), lobar control (LC), locoregional control (LRC), and distant control (DC) was conducted using the log-rank test. Pre- and post-treatment SUV_max were evaluated using cutoffs of < 5 and ≥ 5, < 4 and ≥ 4, and < 3 and ≥ 3. ∆SUV_max was also evaluated at various cutoffs. Cox regression analysis was conducted to evaluate survival outcomes based on age, gender, pre-treatment gross tumor volume (GTV), longest tumor dimension on imaging, and Charlson Comorbidity Index (CCI).

Results

This study included 95 patients (53 female, 42 male), median age 75. Lung SBRT was delivered in 3–5 fractions to a total of 48–60 Gy, with a BED_{α/β = 10Gy} of at least 100 Gy. Median OS and PFS from the end of SBRT was 15.4 and 11.9 months, respectively. On univariate analysis, PERCIST/RECIST response correlated with PFS (p = 0.039), LC (p = 0.007), and LRC (p = 0.015) but not OS (p = 0.21) or DC (p = 0.94). Pre-treatment SUV_max and post-treatment SUV_max with cutoff values of < 5 and ≥ 5, < 4 and ≥ 4, and < 3 and ≥ 3 did not predict for OS, PFS, LC, LRC, or DC. ∆SUV_max did not predict for OS, PFS, LC, LRC, or DC. On multivariate analysis, pre-treatment GTV ≥ 30 cm³ was significantly associated with worse survival outcomes when accounting for other confounding variables.

Conclusions

PERCIST/RECIST response is associated with improved LC and PFS in patients treated for ES-NSCLC with SBRT. In contrast, pre- and post-treatment SUV_max is not predictive of disease control or survival.

Fluorine-18-fluorodeoxyglucose uptake of bone marrow on PET/CT can predict prognosis in patients with colorectal cancer after curative surgical resection

OBJECTIVE

This study investigated the relationship of fluorine-18-fluorodeoxyglucose (F-FDG) uptake of bone marrow (BM) on PET/computed tomography (PET/CT) with clinicopathologic factors and survival in patients with colorectal cancer.

PATIENTS AND METHODS

The study retrospectively included 226 patients with colorectal cancer who underwent F-FDG PET/CT for staging workup and treated with curative surgical resection. The maximum F-FDG uptake of primary cancer (Tmax) and mean F-FDG uptake of BM [BM standardized uptake value (SUV)] were derived from PET/CT images. The relationships between BM SUV and clinicopathologic factors and prognostic value of BM SUV for predicting recurrence-free survival (RFS) were assessed.

RESULTS

Patients with T3-T4 stage and hepatic metastases had significantly higher values of BM SUV than those with T1-T2 stage and no distant metastases (P<0.05). BM SUV showed significant positive correlation with Tmax, tumor size, serum C-reactive protein level, white blood cell count, neutrophil-to-lymphocyte ratio, and platelet-to-lymphocyte ratio (P<0.05). Univariate survival analysis revealed that N stage, M stage, tumor involvement of resection margin, lymphatic invasion, and BM SUV were significant predictors for RFS (P<0.05), whereas Tmax failed to show significance. In multivariate analysis, N stage (P=0.012 for N1 stage and P=0.020 for N2 stage), tumor involvement of resection margin (P=0.009), and BM SUV (P=0.005) were significantly associated with RFS.

CONCLUSION

Increased BM SUV was observed in patients with advanced stage and increased serum inflammatory markers. BM SUV was an independent predictor for RFS in colorectal cancer.

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.

Early PET-CT After Stereotactic Radiotherapy for Stage 1 Non-small Cell Lung Carcinoma Is Predictive of Local Control

BACKGROUND/AIM

Radiological evaluation after stereotactic-body-radiotherapy (SBRT) for non-small-cell lung carcinoma (NSCLC) is often difficult due to lung radiation-induced image modifications on computed tomographic (CT) scan. The aim of this study was to evaluate positron-emission tomography-computed tomography (PET-CT) using fluorodeoxyglucose after SBRT in primary lung cancer.

PATIENTS AND METHODS

Eighteen patients with histologically proven NSCLC were treated with SBRT. All had PET-CT evaluations before treatment, at 2 to 3 months and at 1 year post SBRT during the follow-up.

RESULTS

Early PET-CT in 12/18 patients who did not experience local failure did not show any progression. No conclusion could be drawn in four cases because early PET-CT was disturbed by inflammatory reaction. Early PET-CT was not predictive of late outcome for two patients, as it showed a significant response followed by disease progression on late evaluation.

CONCLUSION

Early PET response appears to correlate with local control at 1 year post SBRT.

Thoracic reirradiation with SBRT for residual/recurrent and new primary NSCLC within or immediately adjacent to a prior high-dose radiation field

PURPOSE

Local failure following concurrent chemoradiation and in-lobe failures following stereotactic body radiation therapy (SBRT) are common. We evaluated our institutional experience using SBRT as salvage in this setting.

METHODS AND MATERIALS

Seventy-two patients were reirradiated with SBRT for residual, locally recurrent, or new primary non-small cell lung cancer within or adjacent to a high-dose external beam radiation therapy or SBRT field. Kaplan-Meier analysis with log-rank test were used to estimate endpoints and differentiate cohorts.

RESULTS

Median follow-up was 17.9 months. Patients had residual or recurrent disease (54.2%); 45.8% had new lung primaries. Median reirradiated T size was 2.5 cm (range, 0.8-7.8 cm). Median pre-retreatment maximum standardized uptake value (SUV_max) was 7.15 (range, 1.2-37.6). The most common SBRT reirradiation regimen was 48 Gy in 4 fractions (range, 17-60 Gy in 1-5 fractions). Median progression-free survival was 15.2 months, and median overall survival was 20.8 months. Two-year local failure was 21.6%. Patients with SUV_max at reirradiation <7.0 had a 2-year local control of 93.1% versus 61.1% above the median (P < .001). The 2-year rate of distant metastases was 10.4% versus 54.1% in patients treated for a new primary versus residual or recurrent disease (P < .001). Median progression-free survival was 31.9 months versus 8.4 months, respectively (P = .037). Median survival of patients treated for new primary was 25.2 months versus 16.2 months with residual or recurrent disease (P = .049), and median survival for patients with reirradiation SUV_max below the median was 42.0 months versus 9.8 months above the median (P < .001). Acute any-grade toxicity was seen in 29.2% of patients, acute grade 3 toxicity in 11.1%, and late grade 3 toxicity in 1.4% with no treatment-related deaths.

CONCLUSIONS

SBRT appears to be a safe and effective means of salvaging recurrent, residual, or new primary NSCLC in or adjacent to a previous high-dose radiation field.

Prognostic Value of 18F-Fluorodeoxyglucose PET/Computed Tomography in Non-Small-Cell Lung Cancer

Non-small cell lung cancer (NSCLC) is a leading cause of cancer-related death with a poor prognosis. Numerous factors contribute to treatment outcome. 18F-fluorodeoxyglucose (FDG) uptake reflects tumor metabolic activity and is an important prognosticator in patients with NSCLC. Volume-based FDG-PET parameters reflect the metabolic status of a malignancy more accurately than maximum standardized uptake value and thus are better prognostic markers in lung cancer. FDG-avid tumor burden parameters may help clinicians to predict treatment outcomes before and during therapy so that treatment can be adjusted to achieve the best possible outcomes while avoiding side effects.

CT imaging features associated with recurrence in non-small cell lung cancer patients after stereotactic body radiotherapy

BACKGROUND

Predicting recurrence after stereotactic body radiotherapy (SBRT) in non-small cell lung cancer (NSCLC) patients is problematic, but critical for the decision of following treatment. This study aims to investigate the association of imaging features derived from the first follow-up computed tomography (CT) on lung cancer patient outcomes following SBRT, and identify patients at high risk of recurrence.

METHODS

Fifty nine biopsy-proven non-small cell lung cancer patients were qualified for this study. The first follow-up CTs were performed about 3 months after SBRT (median time: 91 days). Imaging features included 34 manually scored radiological features (semantics) describing the lesion, lung and thorax and 219 quantitative imaging features (radiomics) extracted automatically after delineation of the lesion. Cox proportional hazard models and Harrel's C-index were used to explore predictors of overall survival (OS), recurrence-free survival (RFS), and loco-regional recurrence-free survival (LR-RFS). Five-fold cross validation was performed on the final prognostic model.

RESULTS

The median follow-up time was 42 months. The model for OS contained Eastern Cooperative Oncology Group (ECOG) performance status (HR = 3.13, 95% CI: 1.17-8.41), vascular involvement (HR = 3.21, 95% CI: 1.29-8.03), lymphadenopathy (HR = 3.59, 95% CI: 1.58-8.16) and the 1st principle component of radiomic features (HR = 1.24, 95% CI: 1.02-1.51). The model for RFS contained vascular involvement (HR = 3.06, 95% CI: 1.40-6.70), vessel attachment (HR = 3.46, 95% CI: 1.65-7.25), pleural retraction (HR = 3.24, 95% CI: 1.41-7.42), lymphadenopathy (HR = 6.41, 95% CI: 2.58-15.90) and relative enhancement (HR = 1.40, 95% CI: 1.00-1.96). The model for LR-RFS contained vascular involvement (HR = 4.96, 95% CI: 2.23-11.03), lymphadenopathy (HR = 2.64, 95% CI: 1.19-5.82), circularity (F13, HR = 1.60, 95% CI: 1.10-2.32) and 3D Laws feature (F92, HR = 1.96, 95% CI: 1.35-2.83). Five-fold cross-validated the areas under the receiver operating characteristic curves (AUC) of these three models were all above 0.8.

CONCLUSIONS

Our analysis reveals disease progression could be prognosticated as early as 3 months after SBRT using CT imaging features, and these features would be helpful in clinical decision-making.

Imaging features from pretreatment CT scans are associated with clinical outcomes in nonsmall-cell lung cancer patients treated with stereotactic body radiotherapy

PURPOSE

To investigate whether imaging features from pretreatment planning CT scans are associated with overall survival (OS), recurrence-free survival (RFS), and loco-regional recurrence-free survival (LR-RFS) after stereotactic body radiotherapy (SBRT) among nonsmall-cell lung cancer (NSCLC) patients.

PATIENTS AND METHODS

A total of 92 patients (median age: 73 yr) with stage I or IIA NSCLC were qualified for this study. A total dose of 50 Gy in five fractions was the standard treatment. Besides clinical characteristics, 24 "semantic" image features were manually scored based on a point scale (up to 5) and 219 computer-derived "radiomic" features were extracted based on whole tumor segmentation. Statistical analysis was performed using Cox proportional hazards model and Harrell's C-index, and the robustness of final prognostic model was assessed using tenfold cross validation by dichotomizing patients according to the survival or recurrence status at 24 months.

RESULTS

Two-year OS, RFS and LR-RFS were 69.95%, 41.3%, and 51.85%, respectively. There was an improvement of Harrell's C-index when adding imaging features to a clinical model. The model for OS contained the Eastern Cooperative Oncology Group (ECOG) performance status [Hazard Ratio (HR) = 2.78, 95% Confidence Interval (CI): 1.37-5.65], pleural retraction (HR = 0.27, 95% CI: 0.08-0.92), F2 (short axis × longest diameter, HR = 1.72, 95% CI: 1.21-2.44) and F186 (Hist-Energy-L1, HR = 1.27, 95% CI: 1.00-1.61); The prognostic model for RFS contained vessel attachment (HR = 2.13, 95% CI: 1.24-3.64) and F2 (HR = 1.69, 95% CI: 1.33-2.15); and the model for LR-RFS contained the ECOG performance status (HR = 2.01, 95% CI: 1.12-3.60) and F2 (HR = 1.67, 95% CI: 1.29-2.18).

CONCLUSIONS

Imaging features derived from planning CT demonstrate prognostic value for recurrence following SBRT treatment, and might be helpful in patient stratification.

Multi-objective radiomics model for predicting distant failure in lung SBRT

Stereotactic body radiation therapy (SBRT) has demonstrated high local control rates in early stage non-small cell lung cancer patients who are not ideal surgical candidates. However, distant failure after SBRT is still common. For patients at high risk of early distant failure after SBRT treatment, additional systemic therapy may reduce the risk of distant relapse and improve overall survival. Therefore, a strategy that can correctly stratify patients at high risk of failure is needed. The field of radiomics holds great potential in predicting treatment outcomes by using high-throughput extraction of quantitative imaging features. The construction of predictive models in radiomics is typically based on a single objective such as overall accuracy or the area under the curve (AUC). However, because of imbalanced positive and negative events in the training datasets, a single objective may not be ideal to guide model construction. To overcome these limitations, we propose a multi-objective radiomics model that simultaneously considers sensitivity and specificity as objective functions. To design a more accurate and reliable model, an iterative multi-objective immune algorithm (IMIA) was proposed to optimize these objective functions. The multi-objective radiomics model is more sensitive than the single-objective model, while maintaining the same levels of specificity and AUC. The IMIA performs better than the traditional immune-inspired multi-objective algorithm.

Maximum standardized uptake value on FDG-PET predicts survival in stage I non-small cell lung cancer following carbon ion radiotherapy

The present study (University Hospital Medical Information Network study no. UMIN000003797) aimed to evaluate whether the maximum standardized uptake value (SUV_max) of pretreatment ¹⁸F-fluorodeoxyglucose-positron emission tomography (FDG-PET) is prognostic factor for stage I non-small cell lung cancer (NSCLC) treated with carbon ion radiotherapy (C-ion RT). Patients treated between June 2010 and June 2013 at Gunma University Heavy Ion Medical Center (Maebashi, Japan) on a prospective protocol were included in the present study. Patients with T1a-b and T2a NSCLC were treated with C-ion RT at a dose of 52.8 Gy [relative biological effectiveness (RBE)] and 60.0 Gy (RBE), respectively, in four fractions. Prior to treatment, all patients underwent FDG-PET, in which the SUV_max of primary tumors was evaluated. Local control, progression-free survival (PFS), and overall survival (OS) were calculated. A total of 45 patients were analyzed and the median follow-up period was 28.9 months. The 2-year local control, PFS and OS rates for all patients were 93, 78 and 89%, respectively. The mean SUV_max of primary tumors was 5.5, and patients were divided into higher (≥5.5) and lower (<5.5) SUV_max groups. The 2-year PFS rates were 61 and 89% for the higher and lower SUV_max groups, respectively (P=0.01), and the 2-year OS rates for the higher and lower SUV_max groups were 76 and 96%, respectively (P=0.01). The higher SUV_max group exhibited a significantly worse PFS and OS compared with the lower SUV_max group; however, the SUV_max was not associated with the local control rate. In total, 2 patients (4%) experienced grade 2 or 3 radiation pneumonitis, with their symptoms improved through conservative treatment. No patients experienced any grade 4 or 5 toxicities. The results of the present study indicate that pretreatment SUV_max is a prognostic indicator for outcomes in patients with stage I NSCLC treated with C-ion RT.

Multi-institutional experience of stereotactic body radiotherapy for large (≥5 centimeters) non-small cell lung tumors

BACKGROUND

Stereotactic body radiotherapy (SBRT) is the standard of care for patients with nonoperative, early-stage non-small cell lung cancer (NSCLC) measuring < 5 cm, but its use among patients with tumors measuring ≥5 cm is considerably less defined, with the existing literature limited to small, single-institution reports. The current multi-institutional study reported outcomes evaluating the largest such population reported to date.

METHODS

Clinical/treatment characteristics, outcomes, toxicities, and patterns of failure were assessed in patients with primary NSCLC measuring ≥5 cm without evidence of distant/lymph node metastasis who underwent SBRT using ≤5 fractions. Statistics included Kaplan-Meier survival analyses and univariate/multivariate Cox proportional hazards models.

RESULTS

A total of 92 patients treated from 2004 through 2016 were analyzed from 12 institutions. The median follow-up was 12 months (15 months in survivors). The median age and tumor size among the patients were 73 years (range, 50-95 years) and 5.4 cm (range, 5.0-7.5 cm), respectively. The median dose/fractionation was 50 Gray/5 fractions. The actuarial local control rates at 1 year and 2 years were 95.7% and 73.2%, respectively. The disease-free survival rate was 72.1% and 53.5%, respectively, at 1 year and 2 years. The 1-year and 2-year disease-specific survival rates were 95.5% and 78.6%, respectively. The median, 1-year, and 2-year overall survival rates were 21.4 months, 76.2%, and 46.4%, respectively. On multivariate analysis, lung cancer history and pre-SBRT positron emission tomography maximum standardized uptake value were found to be associated with overall survival. Posttreatment failures were most commonly distant (33% of all disease recurrences), followed by local (26%) and those occurring elsewhere in the lung (23%). Three patients had isolated local failures. Grade 3 to 4 toxicities included 1 case (1%) and 4 cases (4%) of grade 3 dermatitis and radiation pneumonitis, respectively (toxicities were graded according to the Common Terminology Criteria for Adverse Events [version 4.0]). Grades 2 to 5 radiation pneumonitis occurred in 11% of patients. One patient with a tumor measuring 7.5 cm and a smoking history of 150 pack-years died of radiation pneumonitis.

CONCLUSIONS

The results of the current study, which is the largest study of patients with NSCLC measuring ≥5 cm reported to date, indicate that SBRT is a safe and efficacious option. Cancer 2017;123:688-696. © 2016 American Cancer Society.

The Value of FDG PET/CT in Treatment Response Assessment, Follow-Up, and Surveillance of Lung Cancer

OBJECTIVE

The purpose of this article is to summarize the evidence regarding the role of FDG PET/CT in treatment response assessment and surveillance of lung cancer and to provide suggested best practices.

CONCLUSION

FDG PET/CT is a valuable imaging tool for assessing treatment response for patients with lung cancer, though evidence for its comparative effectiveness with chest CT is still evolving. FDG PET/CT is most useful when there is clinical suspicion or other evidence for disease recurrence or metastases. The sequencing, cost analysis, and comparative effectiveness of FDG PET/CT and conventional imaging modalities in the follow-up setting need to be investigated.

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.

Predictors and Patterns of Regional Recurrence Following Lung SBRT: A Report From the Elekta Lung Research Group

INTRODUCTION

The objective of this study was to determine the predictors and patterns of regional recurrence (RR) following stereotactic body radiotherapy (SBRT) for primary lung cancers.

MATERIAL AND METHODS

Details of patient factors, treatment, and outcome factors were extracted from a multi-institutional (5) database. All events were calculated from the end of radiotherapy. Estimates of local recurrence, RR, and distant metastases (DM) were calculated using the competing risk method. Cause-specific and overall survival were calculated using the Kaplan-Meier method. Details of locations and number of simultaneous RRs were categorized by lymph node anatomic station.

RESULTS

A total of 734 patients were analyzed. The median follow-up was 3.0 years in surviving patients. Four hundred seventy-six (65%) patients had pathologic proof of disease. There were 64 patients with RR. The 2-year local recurrence, RR, and distant metastases rates were 5.6%, 9.0%, and 14.6% respectively. The 2-year cause-specific and overall survival were 89.9% and 63.7%, respectively. There were 136 simultaneous sites of RR. There were 21 recurrences in stations 4R (15.4%), 9 (6.6%) in 4L, 30 (22%) in 7, 19 (13.9%) in 10R, and 14 (10.3%) in 10L. The most common stations for isolated recurrence (n = 19) were station 7 (n = 5; 26.3%) and station 10R (n = 6; 31.6%). The most common RR levels were stations 4 and 7 for right and left upper lobe, stations 5, 7, and 10 for left lower lobe tumors, and stations 7 and 10 for right lower lobe tumors.

CONCLUSION

Stations 4, 7, and 10 were the most common stations for RR. These patterns of recurrence may guide nodal staging procedures prior to SBRT.

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.

Pulmonary imaging after stereotactic radiotherapy-does RECIST still apply?

The use of stereotactic ablative radiotherapy (SABR) for the treatment of primary lung cancer and metastatic disease is rapidly increasing. However, the presence of benign fibrotic changes on CT imaging makes response assessment following SABR a challenge, as these changes develop with an appearance similar to tumour recurrence. Misclassification of benign fibrosis as local recurrence has resulted in unnecessary interventions, including biopsy and surgical resection. Response evaluation criteria in solid tumours (RECIST) are widely used as a universal set of guidelines to assess tumour response following treatment. However, in the context of non-spherical and irregular post-SABR fibrotic changes, the RECIST criteria can have several limitations. Positron emission tomography can also play a role in response assessment following SABR; however, false-positive results in regions of inflammatory lung post-SABR can be a major clinical issue and optimal standardized uptake values to distinguish fibrosis and recurrence have not been determined. Although validated CT high-risk features show a high sensitivity and specificity for predicting recurrence, most recurrences are not detected until more than 1-year post-treatment. Advanced quantitative radiomic analysis on CT imaging has demonstrated promise in distinguishing benign fibrotic changes from local recurrence at earlier time points, and more accurately, than physician assessment. Overall, the use of RECIST alone may prove inferior to novel metrics of assessing response.

Ablative dose proton beam therapy for stage I and recurrent non-small cell lung carcinomas : Ablative dose PBT for NSCLC

PURPOSE

To evaluate the efficacy and safety of ablative dose hypofractionated proton beam therapy (PBT) for patients with stage I and recurrent non-small cell lung carcinoma (NSCLC).

PATIENTS AND METHODS

A total of 55 patients with stage I (n = 42) and recurrent (n = 13) NSCLC underwent hypofractionated PBT and were retrospectively reviewed. A total dose of 50-72 CGE (cobalt gray equivalent) in 5-12 fractions was delivered.

RESULTS

The median follow-up duration was 29 months (range 4-95 months). There were 24 deaths (43.6%) during the follow-up period: 11 died of disease progression and 13 from other causes. Kaplan-Meier overall survival rate (OS) at 3 years was 54.9% and the median OS was 48.6 months (range 4-95 months). Local progression was observed in 7 patients and the median time to local progression was 9.3 months (range 5-14 months). Cumulative actuarial local control rate (LCR), lymph node metastasis-free survival, and distant metastasis-free survival rates at 3 years were 85.4, 78.4, and 76.5%, respectively. Larger tumor diameter was significantly associated with poorer LCR (3-year: 94% for ≤3 cm vs. 65% for >3 cm, p = 0.006) on univariate analysis and also an independent prognostic factor for LCR (HR 6.9, 95% CI = 1.3-37.8, p = 0.026) on multivariate analysis. No grade 3 or 4 treatment-related toxicities developed. One grade 5 treatment-related adverse event occurred in a patient with symptomatic idiopathic pulmonary fibrosis.

CONCLUSIONS

Ablative dose hypofractionated PBT was safe and promising for stage I and recurrent NSCLC.

Predicting distant failure in early stage NSCLC treated with SBRT using clinical parameters

PURPOSE/OBJECTIVE

The aim of this study is to predict early distant failure in early stage non-small cell lung cancer (NSCLC) treated with stereotactic body radiation therapy (SBRT) using clinical parameters by machine learning algorithms.

MATERIALS/METHODS

The dataset used in this work includes 81 early stage NSCLC patients with at least 6months of follow-up who underwent SBRT between 2006 and 2012 at a single institution. The clinical parameters (n=18) for each patient include demographic parameters, tumor characteristics, treatment fraction schemes, and pretreatment medications. Three predictive models were constructed based on different machine learning algorithms: (1) artificial neural network (ANN), (2) logistic regression (LR) and (3) support vector machine (SVM). Furthermore, to select an optimal clinical parameter set for the model construction, three strategies were adopted: (1) clonal selection algorithm (CSA) based selection strategy; (2) sequential forward selection (SFS) method; and (3) statistical analysis (SA) based strategy. 5-cross-validation is used to validate the performance of each predictive model. The accuracy was assessed by area under the receiver operating characteristic (ROC) curve (AUC), sensitivity and specificity of the system was also evaluated.

RESULTS

The AUCs for ANN, LR and SVM were 0.75, 0.73, and 0.80, respectively. The sensitivity values for ANN, LR and SVM were 71.2%, 72.9% and 83.1%, while the specificity values for ANN, LR and SVM were 59.1%, 63.6% and 63.6%, respectively. Meanwhile, the CSA based strategy outperformed SFS and SA in terms of AUC, sensitivity and specificity.

CONCLUSIONS

Based on clinical parameters, the SVM with the CSA optimal parameter set selection strategy achieves better performance than other strategies for predicting distant failure in lung SBRT patients.