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

Advances in Non-Small Cell Lung Cancer: Current Insights and Future Directions

The leading cause of cancer deaths worldwide is attributed to non-small cell lung cancer (NSCLC), necessitating a continual focus on improving the diagnosis and treatment of this disease. In this review, the latest breakthroughs and emerging trends in managing NSCLC are highlighted. Major advancements in diagnostic methods, including better imaging technologies and the utilization of molecular biomarkers, are discussed. These advancements have greatly enhanced early detection and personalized treatment plans. Significant improvements in patient outcomes have been achieved by new targeted therapies and immunotherapies, providing new hope for individuals with advanced NSCLC. This review discusses the persistent challenges in accessing advanced treatments and their associated costs despite recent progress. Promising research into new therapies, such as CAR-T cell therapy and oncolytic viruses, which could further revolutionize NSCLC treatment, is also highlighted. This review aims to inform and inspire continued efforts to improve outcomes for NSCLC patients globally, by offering a comprehensive overview of the current state of NSCLC treatment and future possibilities.

Factors that Influence the Need to Start Adaptive Radiotherapy

Introduction

Adaptive radiotherapy (ART) is an essential approach to account for anatomical and biological uncertainties. Adaptive radiotherapy is, however, time-consuming, and it is unclear which patients are eligible or when is the best time to start ART.

Methods

This prospective study was conducted at Kasr El-Aini Center of Clinical Oncology and Nuclear Medicine, Cairo, Egypt from January 2019 to December 2020. Thirty patients with pathologically proven, limited-stage small cell or stage I-II non-small cell lung cancer who were either not fit for or refused surgery or had stage III disease were recruited and underwent treatment planning to receive 60 Gy on a conventional 3D conformal radiation schedule with platinum-based chemotherapy. All patients underwent computed tomography (CT) planning within 2 and 4 weeks of starting radiation therapy to assess the need for adaptation. Pulmonary function test and echocardiography findings were assessed at the end of treatment and at 3 and 6 months after treatment, and were compared to the baseline.

Results

We found a significant reduction in mean value of the planning target volume (PTV) in the CT scans at the second (331 cm3) and fourth (257 cm3) weeks of treatment as compared to baseline (342 cm3) (p-value < 0.0001). Adaptation decreased the dose to the organ at risk with statistical significance and with improvement of the target coverage. At week 2 of radiotherapy, the need for adaptation was correlated to the conformity index (p = 0.0473), esophageal V35 (p = 0.0488), esophageal V50 (p = 0.0295), and its mean dose (p = 0.0087). At week 4 it was correlated to forced expiratory volume in 1 second (FEV1) (p = 0.0303), ratio between the forced expiratory volume in 1 second and the forced vital capacity (FEV1/FVC) (p = 0.0024), and echocardiography (p = 0.0183).

Conclusions

Conformity index and esophageal dose constraints can predict the need for adaptation at week 2, whereas baseline pulmonary function parameters and echocardiography can predict the need for adaptation at week 4 of radiotherapy.

Adaptive Lung Radiation Therapy in the Era of Immunotherapy: A Single-Center Retrospective Study

Purpose

Treatment for locally advanced non-small cell lung cancer consists of concurrent chemoradiation followed by immunotherapy. Though this combination has been shown to have a benefit in both progression-free survival and overall survival, treatment is often limited by the development of pneumonitis. One way to mitigate toxicity is through adaptive radiation therapy, which does not currently have a standardized implementation in clinical practice.

Methods and Materials

A single-center retrospective review of patients with locally advanced stage III or oligometastatic stage IV non-small cell lung cancer who were treated with chemoradiation with concurrent or subsequent immunotherapy from 2015 to 2020 was performed. Patients were stratified based on having 1 or more offline adapted plan. The aim of this study was to evaluate the association between dose-volume histogram values and common toxicities experienced during this treatment, including pneumonitis and esophagitis.

Results

Twenty-five patients were included in the final analysis: 10 with adapted plans (AP), and 15 with nonadapted plans (NAP). Mean age at onset was 74 years. The most common histology was adenocarcinoma (N = 13). Five patients experienced pneumonitis: 2 in AP and 3 in NAP. Mann-Whitney U test of gross tumor volume sizes between AP (346.2 ± 269.7 cm3) and NAP (153.1 ± 99.6 cm3) was significant (P = .019). Multiple linear regression analysis with adjustment for covariates of pneumonitis versus plan adaptation (P = .106) and esophagitis versus plan adaptation (P = .59) did not demonstrate a significant difference in toxicity between the adapted and nonadaptive patients.

Conclusions

Despite similar toxicities in both groups, the gross tumor volume size in the AP was more than double compared with NAP, suggesting that adaptive techniques provide a method for patients with larger target volumes to be treated without an observed difference in pneumonitis rates. These results suggest adaptive radiation therapy may have a role in mitigating toxicity experience from chemoradiation and immunotherapy and warrants further investigation.

Patient-specific quality assurance for deformable IMRT/IMPT dose accumulation: Proposition and validation of energy conservation based validation criterion

BACKGROUND

Deformable image registration (DIR)-based dose accumulation (DDA) is regularly used in adaptive radiotherapy research. However, the applicability and reliability of DDA for direct clinical usage are still being debated. One primary concern is the validity of DDA, particularly for scenarios with substantial anatomical changes, for which energy-conservation problems were observed in conceptual studies.

PURPOSE

We present and validate an energy-conservation (EC)-based DDA validation workflow and further investigate its usefulness for actual patient data, specifically for lung cancer cases.

METHODS

For five non-small cell lung cancer (NSCLC) patients, DDA based on five selective DIR methods were calculated for five different treatment plans, which include one intensity-modulated photon therapy (IMRT), two intensity-modulated proton therapy (IMPT), and two combined proton-photon therapy (CPPT) plans. All plans were optimized on the planning CT (planCT) acquired in deep inspiration breath-hold (DIBH) and were re-optimized on the repeated DIBH CTs of three later fractions. The resulting fractional doses were warped back to the planCT using each DIR. An EC-based validation of the accumulation process was implemented and applied to all DDA results. Correlations between relative organ mass/volume variations and the extent of EC violation were then studied using Bayesian linear regression (BLR).

RESULTS

For most OARs, EC violation within 10% is observed. However, for the PTVs and GTVs with substantial regression, severe overestimation of the fractional energy was found regardless of treatment type and applied DIR method. BLR results show that EC violation is linearly correlated to the relative mass variation (R^2 > 0.95) and volume variation (R^2 > 0.60).

CONCLUSION

DDA results should be used with caution in regions with high mass/volume variation for intensity-based DIRs. EC-based validation is a useful approach to provide patient-specific quality assurance of the validity of DDA in radiotherapy.

Unanticipated Radiation Replanning for Stage III Non-small Cell Lung Cancer

Purpose

The purpose of this study was to identify factors associated with unanticipated radiation therapy (RT) replanning in stage III non-small cell lung cancer (NSCLC).

Methods and Materials

Patients from a single institution with newly diagnosed stage III NSCLC treated with radical RT from January 1, 2016, to December 31, 2019, were retrospectively analyzed. The frequency and reasons for replanning were determined. Logistic regression analysis was used to identify factors associated with replanning.

Results

Of 144 patients included in this study, 11% (n = 16) required replanning after the start of RT. The reason for replanning in these 16 patients was changes in the target detected by cone beam computed tomography (shift in 10 patients, shrinkage in 5 patients, and growth in 1 patient). Larger planning target volume (primary and nodal) was statistically predictive of replanning (odds ratio, 2.5; 95% CI, 1.2-5.4; P = .02). The actuarial median overall survival was 33.3 months (95% CI, 10.3-43.9) for the 16 patients who were replanned and 36.3 months (95% CI, 27.4-66.5) for the remaining 128 patients (P = .96). The median time to local recurrence was 25.0 months (95% CI, 10.3-41.3) for those patients who underwent replanning, which was similar to those patients who did not undergo replanning (19.5 months; 95% CI, 11.8-23.2; P = .28).

Conclusions

In this study, 11% of patients treated with radical RT for NSCLC required replanning due to changes in the target detected by cone beam computed tomography. A larger planning target volume predicts a higher likelihood of requiring adaptive RT. Overall survival and local control were similar between patients who were replanned compared with those who were not replanned.

Evaluating the Necessity of Adaptive RT and the Role of Deformable Image Registration in Lung Cancer with Different Pathologic Classifications

BACKGROUND

This study aimed to analyze differential radiotherapy (RT) responses according to the pathological type of lung cancer to see the possibility of applying adaptive radiotherapy (ART).

METHODS

ART planning with resampled-computed tomography was conducted for a total of 30 patients (20 non-small-cell lung cancer patients and 10 small-cell lung cancer patients) using a deformable image registration technique to reveal gross tumor volume (GTV) changes according to the duration of RT.

RESULTS

The small-cell lung cancer group demonstrated an average GTV reduction of 20.95% after the first week of initial treatment (p = 0.001), whereas the adenocarcinoma and squamous cell carcinoma groups showed an average volume reduction of 20.47% (p = 0.015) and 12.68% in the second week. The application of ART according to the timing of GTV reduction has been shown to affect changes in radiation dose irradiated to normal tissues. This suggests that ART applications may have to be different depending on pathological differences in lung cancer.

CONCLUSION

Through these results, the present study proposes the possibility of personalized treatment options for individual patients by individualizing ART based on specific radiation responses by pathologic types of lung cancer.

ScatterNet for projection-based 4D cone-beam computed tomography intensity correction of lung cancer patients

Background and purpose: In radiotherapy, dose calculations based on 4D cone beam CTs (4DCBCTs) require image intensity corrections. This retrospective study compared the dose calculation accuracy of a deep learning, projection-based scatter correction workflow (ScatterNet), to slower workflows: conventional 4D projection-based scatter correction (CBCTcor) and a deformable image registration (DIR)-based method (4DvCT). Materials and methods: For 26 lung cancer patients, planning CTs (pCTs), 4DCTs and CBCT projections were available. ScatterNet was trained with pairs of raw and corrected CBCT projections. Corrected projections from ScatterNet and the conventional workflow were reconstructed using MA-ROOSTER, yielding 4DCBCTSN and 4DCBCTcor. The 4DvCT was generated by 4DCT to 4DCBCT DIR, as part of the 4DCBCTcor workflow. Robust intensity modulated proton therapy treatment plans were created on free-breathing pCTs. 4DCBCTSN was compared to 4DCBCTcor and the 4DvCT in terms of image quality and dose calculation accuracy (dose-volume-histogram parameters and 3 % /3 mm gamma analysis). Results: 4DCBCTSN resulted in an average mean absolute error of 87 HU and 102 HU when compared to 4DCBCTcor and 4DvCT respectively. High agreement was observed in targets with median dose differences of 0.4 Gy (4DCBCTSN-4DCBCTcor) and 0.3 Gy (4DCBCTSN-4DvCT). The gamma analysis showed high average 3 % /3 mm pass rates of 96 % for both 4DCBCTSN vs. 4DCBCTcor and 4DCBCTSN vs. 4DvCT. Conclusions: Accurate 4D dose calculations are feasible for lung cancer patients using ScatterNet for 4DCBCT correction. Average scatter correction times could be reduced from 10 min (4DCBCTcor) to 3.9 s , showing the clinical suitability of the proposed deep learning-based method.

Accuracy and Feasibility of Synthetic CT for Lung Adaptive Radiotherapy: A Phantom Study

OBJECTIVES

The respiratory variations will lead to inconsistency between the actual delivery dose and the planning dose. How the minor interfractional amplitude changes affect the geometry and dose delivery accuracy remains to be investigated in the context of lung adaptive radiotherapy.

METHODS

Planning 4-dimensional-computed tomography and kV-cone beam computed tomography were scanned based on the Computerized Imaging Reference Systems phantom, which was employed to simulate the minor interfractional amplitude variations. The corresponding synthetic computed tomography for a particular motion pattern can be generated from Velocity program. Then a clinically meaningful synthetic computed tomography was analyzed through the geometrical and dosimetric assessment.

RESULTS

The image quality of synthetic computed tomography was improved obviously compared with cone beam computed tomography. Mean absolute error was minimized when no significant interfractional motion occurs and Velocity can be qualified for dealing with the regular breathing motion patterns. The mean percent hounsfield unit difference of the synthetic hounsfield unit values per organ relative to the planning 4-dimensional-computed tomography image was 22.3%. Under the same conditions, the mean percent hounsfield unit difference of the cone beam computed tomography hounsfield unit values per organ, relative to the planning 4-dimensional-computed tomography image was 83.9%. Overall, the accuracy of hounsfield unit in synthetic computed tomography was improved obviously and the variability of the synthetic image correlates with the planning 4-dimensional-computed tomography image variability. Meanwhile, the dose-volume histograms between planning 4-dimensional-computed tomography and synthetic computed tomography almost coincided each other, which indicates that Velocity program can qualify lung adaptive radiotherapy well when there were no interfractional respiratory variations. However, for cases with obvious interfractional amplitude change, the volume covered at least by 100% of the prescription dose was only 59.6% for that synthetic image.

CONCLUSION

The synthetic computed tomography images generated from Velocity were close to the real images in anatomy and dosimetry, which can make clinical lung adaptive radiotherapy possible based on the actual patient anatomy during treatment.

Salvage LATTICE radiotherapy for a growing tumour despite conventional radio chemotherapy treatment of lung cancer

A 40-year-old patient with cT4cN1M0 squamous cell lung cancer of the upper right lobe received preoperative induction chemotherapy. Systemic induction treatment failed to reverse tumour growth with the addition of conventional radiotherapy (RT). A salvage lattice RT boost of 12 Gy was administered immediately to increase the dose to the tumour. Conventional RT was resumed at the planned dose of 60 Gy. The tumour shrank rapidly, and the patient was surged. The postoperative pathology remained ypT0ypN0 status.

Ultrasound-Stimulated Microbubbles Enhance Radiation-Induced Cell Killing

Recent in vivo studies using ultrasound-stimulated microbubbles as a localized radiosensitizer have had impressive results. While in vitro studies have also obtained similar results using human umbilical vein endothelial cells (HUVEC), studies using other cell lines have had varying results. This study was aimed at investigating any increases in radiation-induced cell killing in vitro using two carcinoma lines not previously investigated before (metastatic follicular thyroid carcinoma cells [FTC-238] and non-small cell lung carcinoma cells [NCI-H727]), in addition to HUVEC. Cells were treated using a combination of 1.6% (v/v) microbubbles, ∼90 s of 2-MHz ultrasound (mechanical index = 0.8) and 0-6 Gy of kilovolt or MV X-rays. Cell viability assays obtained 72 h post-treatment were normalized to untreated controls, and analysis of variance was used to determine statistical significance. All cells treated with combined ultrasound-stimulated microbubbles and radiation exhibited decreased normalized survival, with statistically significant effects observed for the NCI-H727 cells. No statistically significant differences in effects were observed using kV compared with MV radiation. Further studies using increased microbubble concentrations may be required to achieve statistically significant results for the FTC-238 and HUVEC lines.

Optimized Adaptive Radiotherapy with Individualized Plan Library for Muscle-Invasive Bladder Cancer Using Internal Target Volume Generation

Simple Summary

The bladder is a mobile target and is subject to filling variation. This poses a considerable challenge for effective radiotherapy (RT) delivery. We applied an internal target volume to the plan library to resolve intra-fractional errors caused by bladder filling during treatment. Adaptive radiotherapy using ITV is easy to perform and a feasible treatment approach. In this study, image-guided RT-based adaptive RT showed good survival outcomes with a high local control rate.

Abstract

The bladder is subject to filling variation, which poses a challenge to radiotherapy (RT) delivery. We aimed to assess feasibility and clinical outcomes in patients with bladder cancer treated with adaptive RT (ART) using individualized plan libraries. We retrospectively analyzed 19 patients who underwent RT for muscle-invasive bladder cancer (MIBC) in 2015–2021. Four planning computed tomography (CT) scans were acquired at 15-min intervals, and a library of three intensity-modulated RT plans were generated using internal target volumes (ITVs). A post-treatment cone-beam CT (CBCT) scan was acquired daily to assess intra-fraction filling and coverage. All patients completed the treatment, with 408 post-treatment CBCT scans. The bladder was out of the planning target volume (PTV) range in 12 scans. The volumes of the evaluated PTV plans were significantly smaller than those of conventional PTV. The 1-year and 2-year overall survival rates were 88.2% and 63.7%, respectively. Of eight cases that experienced recurrence, only two developed MIBC. There were no grade 3 or higher RT-related adverse events. ART using plan libraries and ITVs demonstrated good survival outcomes with a high local control rate. Irradiated normal tissue volume and treatment margins may be reduced through this approach, potentially resulting in lower toxicity rates.

Prediction of Changes in Tumor Regression during Radiotherapy for Nasopharyngeal Carcinoma by Using the Computed Tomography-Based Radiomics

This work aimed to explore the application value of computed tomography (CT)-based radiomics in predicting changes in tumor regression during radiotherapy for nasopharyngeal carcinoma. In this work, 144 patients with nasopharyngeal carcinoma who underwent concurrent chemoradiotherapy (CCRT) in our hospital from January 2015 to December 2021 were selected. The patients were divided into a radiosensitive group (79 cases) and an insensitive group (65 cases) according to the tumor volume shrinkage during radiotherapy. The 3D Slicer 4.10.2 software was used to delineate the tumor region of interest (ROI), and a total of 1223 radiomics features were extracted using the radiomics module under the software. After between-group and within-group consistency tests, one-way ANOVA, and LASSO dimensionality reduction, three omics features were finally selected for the establishment of predictive models. At the same time, the age, gender, tumor T stage and N stage, hemoglobin, and albumin of the patients were collected to establish a clinical prediction model. The results showed that compared with logistic regression, decision tree, random forest, and AdaBoost models, the SVM model based on CT radiomics features had the best performance in predicting tumor regression changes during tumor radiotherapy (training group area under the receiver operating characteristic curve (AUC): 0.840 (95% confidence interval (CI): 0.764-0.916); validation group: AUC: 0.810 (95% CI: 0.676-0.944)). Compared with the supported vector machine (SVM) prediction model based on clinical features, the SVM model based on radiomics features had better performance in predicting the change of retraction during tumor radiotherapy (training group: omics feature SVM model AUC: 0.84, clinical feature SVM model: 0.78; validation group: omics feature SVM model AUC: 0.8, clinical feature SVM model: 0.58, P = 0.044). Based on the radiomics characteristics and clinical characteristics of patients, a nomo prediction map was established, and the calibration curve shows good consistency, which can be visualized to assist clinical judgment. In this work, the prediction model composed of CT-based radiomic features combined with clinical features can accurately predict withdrawal changes during tumor radiotherapy, ensuring the accuracy of treatment planning, and minimizing the number of CT scans during radiotherapy.

Value of carbon-ion radiotherapy for early stage non-small cell lung cancer

Carbon-ion radiotherapy (CIRT) is an important part of modern radiotherapy. Compared to conventional photon radiotherapy modalities, CIRT brings two major types of advantages to physical and biological aspects respectively. The physical advantages include a substantial dose delivery to the tumoral area and a minimization of dose damage to the surrounding tissue. The biological advantages include an increase in double-strand breaks (DSBs) in DNA structures, an upturn in oxygen enhancement ratio and an improvement of radiosensitivity compared with X-ray radiotherapy. The two advantages of CIRT are that the therapy not only inflicts major cytotoxic lesions on tumor cells, but it also protects the surrounding tissue. According to annual diagnoses, lung cancer is the second most common cancer worldwide, followed by breast cancer. However, lung cancer is the leading cause of cancer death. Patients with stage I non-small cell lung cancer (NSCLC) who are optimally received the treatment of lobectomy. Some patients with comorbidities or combined cardiopulmonary insufficiency have been shown to be unable to tolerate the treatment when combined with surgery. Consequentially, radiotherapy may be the best treatment option for this patient category. Multiple radiotherapy options are available for these cases, such as stereotactic body radiotherapy (SBRT), volumetric modulated arc therapy (VMAT), and intensity-modulated radiotherapy (IMRT). Although these treatments have brought some clinical benefits to some patients, the resulting adverse events (AEs), which include cardiotoxicity and radiation pneumonia, cannot be ignored. The damage and toxicity to normal tissue also limit the increase of tumor dose. Due to the significant physical and biological advantages brought by CIRT, some toxicity induced by radiotherapy may be avoided with CIRT Bragg Peak. CIRT brought clinical benefits to lung cancer patients, especially geriatric patients. This review introduced the clinical efficacy and research results for non-small cell lung cancer (NSCLC) with CIRT.

Utility and limitations of metabolic parameters in head and neck cancer: finding a practical segmentation method

PURPOSE

Although metabolic tumor volume (MTV) and total lesion glycolysis (TLG) have shown good prognostic value in head and neck cancer (HNC), there are still many issues to resolve before their potential application in standard clinical practice. The purpose of this study was to compare the discrimination ability of two relevant segmentation methods in HNC and to evaluate the potential benefit of adding lymph nodes' metabolism (LNM) to the measurements.

METHODS

We retrospectively analyzed a recently published database of 62 patients with HNC treated with chemoradiotherapy. MTV and TLG were measured using an absolute threshold of SUV2.5. Comparison analysis with previously published background-level threshold (BLT) results was done through Concordance index (C-index) in eight prognostic models.

RESULTS

BLT obtained better C-index values in five out of the eight models. The addition of LNM improved C-index values in six of the prognostic models.

CONCLUSION

We found a potential benefit in adding LNM to the main tumor measurements, as well as in using a BLT for MTV segmentation compared to the most commonly used SUV2.5 threshold. Despite its limitations, this study suggests a practical and simple manner to use these parameters in standard clinical practice, aiming to help elaborate a general consensus.