Prognostic Value of Primary Tumor Volume Changes on kV-CBCT during Definitive Chemoradiotherapy for Stage III Non-Small Cell Lung Cancer

Adaptive Radiation Therapy in the Treatment of Lung Cancer: An Overview of the Current State of the Field

Lung cancer treatment is constantly evolving due to technological advances in the delivery of radiation therapy. Adaptive radiation therapy (ART) allows for modification of a treatment plan with the goal of improving the dose distribution to the patient due to anatomic or physiologic deviations from the initial simulation. The implementation of ART for lung cancer is widely varied with limited consensus on who to adapt, when to adapt, how to adapt, and what the actual benefits of adaptation are. ART for lung cancer presents significant challenges due to the nature of the moving target, tumor shrinkage, and complex dose accumulation because of plan adaptation. This article presents an overview of the current state of the field in ART for lung cancer, specifically, probing topics of: patient selection for the greatest benefit from adaptation, models which predict who and when to adapt plans, best timing for plan adaptation, optimized workflows for implementing ART including alternatives to re-simulation, the best radiation techniques for ART including magnetic resonance guided treatment, algorithms and quality assurance, and challenges and techniques for dose reconstruction. To date, the clinical workflow burden of ART is one of the major reasons limiting its widespread acceptance. However, the growing body of evidence demonstrates overwhelming support for reduced toxicity while improving tumor dose coverage by adapting plans mid-treatment, but this is offset by the limited knowledge about tumor control. Progress made in predictive modeling of on-treatment tumor shrinkage and toxicity, optimizing the timing of adaptation of the plan during the course of treatment, creating optimal workflows to minimize staffing burden, and utilizing deformable image registration represent ways the field is moving toward a more uniform implementation of ART.

Liquid Biopsies for Molecular Biology-Based Radiotherapy

Molecular alterations drive cancer initiation and evolution during development and in response to therapy. Radiotherapy is one of the most commonly employed cancer treatment modalities, but radiobiologic approaches for personalizing therapy based on tumor biology and individual risks remain to be defined. In recent years, analysis of circulating nucleic acids has emerged as a non-invasive approach to leverage tumor molecular abnormalities as biomarkers of prognosis and treatment response. Here, we evaluate the roles of circulating tumor DNA and related analyses as powerful tools for precision radiotherapy. We highlight emerging work advancing liquid biopsies beyond biomarker studies into translational research investigating tumor clonal evolution and acquired resistance.

Challenges in the target volume definition of lung cancer radiotherapy

Radiotherapy, with or without systemic treatment has an important role in the management of lung cancer. In order to deliver the treatment accurately, the clinician must precisely outline the gross tumour volume (GTV), mostly on computed tomography (CT) images. However, due to the limited contrast between tumour and non-malignant changes in the lung tissue, it can be difficult to distinguish the tumour boundaries on CT images leading to large interobserver variation and differences in interpretation. Therefore the definition of the GTV has often been described as the weakest link in radiotherapy with its inaccuracy potentially leading to missing the tumour or unnecessarily irradiating normal tissue. In this article, we review the various techniques that can be used to reduce delineation uncertainties in lung cancer.

Concurrent chemoradiotherapy for stage III non-small-cell lung cancer: recent progress and future perspectives (a narrative review)

Concurrent chemoradiotherapy (CHRT) remains the therapeutic standard for locally advanced inoperable non-small-cell lung cancer (NSCLC). The median overall survival (OS) with this approach is in the range of 20–30 months, with five-year survival of approximately 30%. These outcomes have recently been further improved by supplementing CHRT with maintenance durvalumab, a monoclonal anti-PD-L1 agent. The progress in treatment outcomes of locally advanced NSCLC before the era of immunotherapy has been achieved mainly by virtue of developments in diagnostics and radiotherapy techniques. Routine implementation of endoscopic and endobronchial ultrasonography for mediastinal lymph nodes assessment, positron emission tomography/computed tomography and magnetic resonance imaging of the brain allows for more accurate staging of NSCLC and for optimizing treatment strategy. Thorough staging and respiratory motion control allows for higher conformity of radiotherapy and reduction of radiotherapy related toxicity. Dose escalation with prolonged overall treatment time does not improve treatment outcomes of CHRT. In consequence, 60 Gy in 2 Gy fractions or equivalent biological dose remains the standard dose for definitive CHRT in locally advanced NSCLC. However, owing to increased toxicity of CHRT, this option may not be applicable in a proportion of elderly or frail patients. This article summarizes recent developments in curative CHRT for inoperable stage III NSCLC, and presents perspectives for further improvements of this strategy

A Pilot Study Examining the Prognostic Utility of Tumor Shrinkage on Cone-Beam Computed Tomography (CBCT) for Stage III Locally Advanced Non-Small Cell Lung Cancer Patients Treated with Definitive Chemoradiation

There has been growing interest in utilizing information from cone-beam computed tomography (CBCT) to help guide both treatment delivery and prognosis. In this assessment of locally advanced unresectable stage III non-small cell lung cancer (NSCLC) treated with definitive chemoradiation, we aimed to determine the survival advantage associated with using CBCT to measure tumor regression. Patient, tumor, and treatment characteristics were collected. The serial tumor shrinkage for each patient was determined from tumor volume contours on weekly CBCTs. Survival analysis was performed using the Kaplan–Meier technique and a Cox proportional hazards model. At least two-thirds of patients had a tumor volume reduction of at least 5% after each week of chemoradiation. A weekly reduction in tumor volume of 5% or greater seen on the CBCT images during radiation therapy was significantly associated with improved overall survival, which remained significant when adjusted for age, histology, grade, and T- and N-stages (p = 0.0036). Additionally, the presence of N3 disease was associated with a five-fold increased risk of recurrence (p = 0.0006) and a nearly three-fold increased risk of death (p = 0.053) compared with N0–N2 disease. Tumor volume shrinkage observed in the CBCT images during definitive chemoradiation holds promise as a prognostic indicator of stage III NSCLC, especially given its affordability, availability, and applicability. Further evaluation in a prospective fashion is warranted to validate the tumor volume shrinkage and its clinical utility.

Prognostic potential of mid-treatment nodal response in oropharyngeal squamous cell carcinoma

BACKGROUND

We examine the prognostic implications of mid-course nodal response in oropharyngeal cancer (OPX) to radiation therapy.

METHODS

In 44 patients with node-positive OPX undergoing concurrent chemoradiation, nodal volumes were measured on cone beam CTs from days 1, 10, 20, and 35. Nodal decrease (ND) was based on percent shrinkage from day 1.

RESULTS

At a median follow-up of 17 months, the 2-year disease-free survival (DFS), locoregional control (LRC), distant metastasis-free survival (DMFS), and overall survival (OS) were 87%, 92%, 89%, and 92%, respectively. Patients with ND ≥43% at D20 had improved LRC (100% vs 78.4%, P = .03) compared to D20 ND <43%. On multivariate analysis, D20 ≥43% was independently prognostic for LRC (HR 1.17, P = .05).

CONCLUSION

Patients with low-risk oropharynx cancer with ND of ≥43% by treatment day 20 had significantly improved LRC. The prognostic benefit of ND may assist in identifying candidates for treatment de-escalation.

Prognostic factors for overall survival of stage III non-small cell lung cancer patients on computed tomography: A systematic review and meta-analysis

INTRODUCTION

Prognosis prediction is central in treatment decision making and quality of life for non-small cell lung cancer (NSCLC) patients. However, conventional computed tomography (CT) related prognostic factors may not apply to the challenging stage III NSCLC group. The aim of this systematic review was therefore to identify and evaluate CT-related prognostic factors for overall survival (OS) of stage III NSCLC.

METHODS

The Medline, Embase, and Cochrane electronic databases were searched. After study selection, risk of bias was estimated for the included studies. Meta-analysis of univariate results was performed when sufficient data were available.

RESULTS

1595 of the 11,996 retrieved records were selected for full text review, leading to inclusion of 65 studies that reported data of 144,513 stage III NSCLC patients andcompromising 26 unique CT-related prognostic factors. Relevance and validity varied substantially, few studies had low relevance and validity. Only four studies evaluated the added value of new prognostic factors compared with recognized clinical factors. Included studies suggested gross tumor volume (meta-analysis: HR = 1.22, 95%CI: 1.05-1.42), tumor diameter, nodal volume, and pleural effusion, are prognostic in patients treated with chemoradiation. Clinical T-stage and location (right/left) were likely not prognostic within stage III NSCLC. Inconclusive are several radiomic features, tumor volume, atelectasis, location (pulmonary lobes, central/peripheral), interstitial lung abnormalities, great vessel invasion, pit-fall sign, and cavitation.

CONCLUSIONS

Tumor-size and nodal size-related factors are prognostic for OS in stage III NSCLC. Future studies should carefully report study characteristics and contrast factors with guideline recognized factors to improve evidence evaluation and validation.

Tumor volume reduction evaluated by cone beam computed tomography during stereotactic body radiotherapy for early stage non-small cell lung cancer

Background

We hypothesized that significant tumor volume reduction (TVR) occurs over the course of stereotactic body radiotherapy (SBRT) for early stage non-small cell lung cancer (NSCLC), and that TVR correlates with clinical outcomes.

Methods

We conducted a retrospective review of patients treated with SBRT for early stage NSCLC across two academic centers. For each patient, we contoured the tumor volume (TV) on cone beam computed tomography (CBCT) images obtained before each treatment fraction. We then calculated TVR based on the TV from the first and last days of treatment. We used log-rank tests to quantify differences in overall survival (OS), progression-free survival (PFS) and recurrence based on TVR.

Results

Data from 69 patients and a total of 73 treated tumors were analyzed. The median follow-up for survivors was 51.8 months (range, 6.9 to 80.0 months). The median TVR for the cohort was 10.1% (range, −5.7% to 43.5%). There was no significant difference in either OS (median 33.4 vs. 29.1 months, P=0.79) or PFS (median 26.3 vs. 12.3 months, P=0.43) for those with high TVRs (≥10.1%) vs. low TVRs (<10.1%), respectively. There was a trend toward superior 2-year PFS in the high TVR group (52.2% vs. 36.7%, P=0.062), but this effect diminished on longer follow-up (4-year PFS 31.9% vs. 26.7%, P=0.15). No associations were observed between TVR and local, regional or distant recurrence.

Conclusions

We were not able to demonstrate that TVR is a reliable predictive imaging marker for stage I/II NSCLC treated with SBRT. Future studies with larger sample sizes are needed to clarify a potential relationship between TVR and early outcomes.

Cone-beam CT radiomics features might improve the prediction of lung toxicity after SBRT in stage I NSCLC patients

Background

Stereotactic body radiotherapy (SBRT) is the standard care for inoperable early stage non‐small cell lung cancer (NSCLC). The purpose of our study was to investigate whether a prediction model based on cone‐beam CT (CBCT) plus pretreatment CT radiomics features could improve the prediction of tumor control and lung toxicity after SBRT in comparison to a model based on pretreatment CT radiomics features alone.

Methods

A total of 34 cases of stage I NSCLC patients who received SBRT were included in the study. The pretreatment planning CT and serial CBCT radiomics features were analyzed using the imaging biomarker explorer (IBEX) software platform. Multivariate logistic regression was conducted for the association between progression‐free survival (PFS), lung toxicity and features. The predictive capabilities of the models based on CBCT and CT features were compared using receiver operating characteristic (ROC) curves.

Results

Five CBCT features and two planning CT features were correlated with disease progression. Six CBCT features and two planning CT features were related to lung injury. The ROC curves indicated that the model based on the CBCT plus planning CT features might be better than the model based on the planning CT features in predicting lung injury. The other ROC curves indicated that the model based on the planning CT features was similar to the model based on the CBCT plus planning CT features in predicting disease progression.

Conclusions

Both pretreatment CT and CBCT radiomics features could predict disease progression and lung injury. A model with CBCT plus pretreatment CT radiomics features might improve the prediction of lung toxicity in comparison with a model with pretreatment CT features alone.

Key points

Significant findings of the study: A model with cone‐beam CT radiomics features plus pre‐treatment CT radiomics features might improve the prediction of lung toxicity after SBRT in stage I NSCLC patients.

What this study adds: In the prediction of PFS and lung toxicity in early‐stage NSCLC patients treated with SBRT, CBCT radiomics could be another effective method.

Early Tumor and Nodal Response in Patients with Locally Advanced Non-Small Cell Lung Carcinoma Predict for Oncologic Outcomes in Patients Treated with Concurrent Proton Therapy and Chemotherapy

PURPOSE

There are no established imaging biomarkers that predict response during chemoradiation for patients with locally advanced non-small cell lung carcinoma. At our institution, proton therapy (PT) patients undergo repeat computed tomography (CT) simulations twice during radiation. We hypothesized that tumor regression measured on these scans would separate early and late responders and that early response would translate into better outcomes.

METHODS AND MATERIALS

Patients underwent CT simulations before starting PT (CT0) and between weeks 1 to 3 (CT1) and weeks 4 to 7 (CT2) of PT. Primary tumor volume (TVR) and nodal volume (NVR) reduction were calculated at CT1 and CT2. Based on recursive partitioning analysis, early response at CT1 and CT2 was defined as ≥20% and ≥40%, respectively. Locoregional and overall progression-free survival (PFS), distant metastasis-free survival, and overall survival by response status were measured using Kaplan-Meier analysis.

RESULTS

Ninety-seven patients with locally advanced non-small cell lung carcinoma underwent definitive PT to a median dose of 66.6 Gy with concurrent chemotherapy. Median TVR and NVR at CT1 were 19% (0-79%) and 19% (0-75%), respectively. At CT2, they were 33% (2-98%) and 35% (0-89%), respectively. With a median follow-up of 25 months, the median overall survival and PFS for the entire cohort was 24.9 and 13.2 months, respectively. Compared with patients with TVR and NVR <20% at T1 and <40% at T2, patients with TVR and NVR ≥20% at CT1 and ≥40% at CT2 had improved median locoregional PFS (27.15 vs 12.97 months for TVR ≥40% vs <40%, P < .01, and 25.67 vs 12.09 months for NVR ≥40% vs <40%, P < .01) and median PFS (22.7 vs 9.2 months, P < .01, and 20.3 vs 7.9 months, P < .01), confirmed on multivariate Cox regression analysis.

CONCLUSIONS

Significantly improved outcomes in patients with early responses to therapy, as measured by TVR and NVR, were seen. Further study is warranted to determine whether treatment intensification will improve outcomes in slow-responding patients.

Tumor regression during radiotherapy for non-small cell lung cancer patients using cone-beam computed tomography images

PURPOSE

Previous literature has reported contradicting results regarding the relationship between tumor volume changes during radiotherapy treatment for non-small cell lung cancer (NSCLC) patients and locoregional recurrence-free rate or overall survival. The aim of this study is to validate the results from a previous study by using a different volume extraction procedure and evaluating an external validation dataset.

METHODS

For two datasets of 94 and 141 NSCLC patients, gross tumor volumes were determined manually to investigate the relationship between tumor volume regression and locoregional control using Kaplan-Meier curves. For both datasets, different subgroups of patients based on histology and chemotherapy regimens were also investigated. For the first dataset (n = 94), automatically determined tumor volumes were available from a previously published study to further compare their correlation with updated clinical data.

RESULTS

A total of 70 out of 94 patients were classified into the same group as in the previous publication, splitting the dataset based on median tumor regression calculated by the two volume extraction methods. Non-adenocarcinoma patients receiving concurrent chemotherapy with large tumor regression show reduced locoregional recurrence-free rates in both datasets (p < 0.05 in dataset 2). For dataset 2, the opposite behavior is observed for patients not receiving chemotherapy, which was significant for overall survival (p = 0.01) but non-significant for locoregional recurrence-free rate (p = 0.13).

CONCLUSION

The tumor regression pattern observed during radiotherapy is not only influenced by irradiation but depends largely on the delivered chemotherapy schedule, so it follows that the relationship between patient outcome and the degree of tumor regression is also largely determined by the chemotherapy schedule. This analysis shows that the relationship between tumor regression and outcome is complex, and indicates factors that could explain previously reported contradicting findings. This, in turn, will help guide future studies to fully understand the relationship between tumor regression and outcome.

A retrospective study evaluating the pretreatment tumor volume (PTV) in non-small cell lung cancer (NSCLC) as a predictor of response to program death-1 (PD-1) inhibitors

Introduction of hypothesis

Little information is available regarding the imaging characteristics that assist in differentiating responders from non-responders. We hypothesized that patients with higher pretreatment tumor volume (PTV) would have lower response rates and shorter overall survival (OS).

Methods

Data from patients who received at least one dose of program death-1 (PD-1) inhibitors before August 31, 2016 were captured from our institution’s pharmacy database. The primary objective was to determine the association of PTV with best response, evaluated utilizing RECIST v1.1 criteria. Secondary objectives were estimation of progression-free survival (PFS) and OS. PTV was measured using the Philips Intellispace Multi-Modality Tumor Tracking application.

Results

116 non-small cell lung cancer (NSCLC) patients were evaluated. 66% patients had adenocarcinoma, 28% had squamous cell carcinoma and 5% had poorly differentiated NSCLC. Median PTV was 53.7 cm³ (95% CI: 13.3–107.9). Only one individual had no metastases and the remainder had M1 disease; 38% M1a, 10% M1b, 51% M1c. Most (79%) were previously treated. There were no complete responses; among those followed for at least 6 weeks, 26% had a partial response, 39% stable disease and 34% PD; 4% had no recorded response. There were no strong associations of PTV with any of the demographic or clinical characteristics. There was no association between PTV and OS (HR 1.2, P=0.26) or PFS (HR 1.1, P=0.47). Liver metastasis was associated with shorter survival (HR=2.8, P=0.05).

Conclusion

PTV in NSCLC did not prove to be a predictor of response to PD-1 inhibitors but having liver metastasis was associated with significantly shorter survival.

Anatomical Adaptation-Early Clinical Evidence of Benefit and Future Needs in Lung Cancer

Definitive treatment of locally advanced non-small-cell lung cancer with radiation is challenging. During the course of treatment, anatomical changes such as tumor regression, tumor displacement/deformation, pleural effusion, and/or atelectasis can result in a deviation of the administered radiation dose from the intended prescribed treatment and thereby worsen local control and toxicity. Adaptive radiotherapy can help correct for these changes and can be generally categorized into 3 philosophical paradigms: (1) maintenance of prescribed dose to the initially defined target volume; (2) dose reduction to healthy organs while maintaining initial prescribed dose to a regressing tumor volume; or (3) dose escalation to a regressing tumor volume with isotoxicity to healthy organs. Numerous single institution studies have investigated these methods, and results from large prospective clinical trials will hopefully provide consensus on the method, utility, and efficacy of implementing adaptive radiation therapy (ART) in a clinical setting. Additional development into standardization and automation of the ART workflow, specifically in identifying when ART is warranted and in reducing the manual clinical effort needed to produce an adaptive plan, will be paramount to making ART feasible for the broader radiation therapy community.

Clinical significance of pretreatment tumor growth rate for locally advanced non-small cell lung cancer

Background

Locally advanced non-small cell lung cancer (NSCLC) may exhibit significant tumor growth before the initiation of definitive chemoradiation therapy (CRT). We thus investigated the prognostic value of pretreatment tumor growth rate as measured by specific growth rate (SGR).

Methods

We conducted a retrospective review of 42 patients with locally advanced NSCLC treated with definitive concurrent CRT. For each patient, we contoured the primary gross tumor volume (GTV) on the pretreatment diagnostic chest computed tomography (CT) scan and the radiation therapy (RT) planning CT scan. We then calculated SGR based on the primary GTV from each scan and the time interval between scans. We used log-rank tests and univariate Cox regression models to quantify differences in progression-free survival (PFS), overall survival (OS) and recurrence based on SGR.

Results

We divided patients into two groups for analysis: those with an SGR greater than or equal to the upper tercile value of 0.94%/day (high SGR) and those with SGR less than 0.94%/day (low SGR). Patients with high SGRs versus low SGRs experienced inferior PFS (median, 5.6 vs. 13.6 months, P=0.016), without a significant difference in OS. The inferior PFS in the high SGR group persisted on multivariate analysis [adjusted hazard ratio (HR) 2.37, 95% confidence interval (CI): 1.07-5.25, P=0.034]. The risk of distant recurrence was higher in the high SGR group (HR 2.62, 95% CI: 1.08-6.38, P=0.033), but there was no difference in the risk of locoregional recurrence between groups.

Conclusions

Pretreatment SGR was associated with inferior PFS and distant control among patients with locally advanced NSCLC treated with concurrent CRT. Further studies in larger populations may aid in elucidating optimal SGR cut-off points for risk stratification.

The Practicality of ICRU and Considerations for Future ICRU Definitions

The International Commission on Radiation Units and Measurements (ICRU) volumes are standardized volume definitions used in radiation oncology practice that have evolved over time to account for advancements in technology and radiation planning. The current definitions have strengths but also practical limitations. The main limitation is related to the process of accounting for tumor motion during treatment. As radiotherapeutic techniques become more precise, motion interplay effects and anatomical changes during treatment must be taken into account to ensure accurate and safe delivery of treatment. Adaptive replanning can help to mitigate the effect of these uncertainties and widen the therapeutic ratio by maximizing dose to the tumor and protecting critical normal structures. As adaptive replanning becomes more common, standardization of how adaptive therapy is implemented and reported will become necessary.