Can we predict radiation-induced changes in pulmonary function based on the sum of predicted regional dysfunction?

Incorporation of Functional Lung Imaging Into Radiation Therapy Planning in Patients With Lung Cancer: A Systematic Review and Meta-Analysis

Our purpose was to provide an understanding of current functional lung imaging (FLI) techniques and their potential to improve dosimetry and outcomes for patients with lung cancer receiving radiation therapy (RT). Excerpta Medica dataBASE (EMBASE), PubMed, and Cochrane Library were searched from 1990 until April 2023. Articles were included if they reported on FLI in one of: techniques, incorporation into RT planning for lung cancer, or quantification of RT-related outcomes for patients with lung cancer. Studies involving all RT modalities, including stereotactic body RT and particle therapy, were included. Meta-analyses were conducted to investigate differences in dose-function parameters between anatomic and functional RT planning techniques, as well as to investigate correlations of dose-function parameters with grade 2+ radiation pneumonitis (RP). One hundred seventy-eight studies were included in the narrative synthesis. We report on FLI modalities, dose-response quantification, functional lung (FL) definitions, FL avoidance techniques, and correlations between FL irradiation and toxicity. Meta-analysis results show that FL avoidance planning gives statistically significant absolute reductions of 3.22% to the fraction of well-ventilated lung receiving 20 Gy or more, 3.52% to the fraction of well-perfused lung receiving 20 Gy or more, 1.3 Gy to the mean dose to the well-ventilated lung, and 2.41 Gy to the mean dose to the well-perfused lung. Increases in the threshold value for defining FL are associated with decreases in functional parameters. For intensity modulated RT and volumetric modulated arc therapy, avoidance planning results in a 13% rate of grade 2+ RP, which is reduced compared with results from conventional planning cohorts. A trend of increased predictive ability for grade 2+ RP was seen in models using FL information but was not statistically significant. FLI shows promise as a method to spare FL during thoracic RT, but interventional trials related to FL avoidance planning are sparse. Such trials are critical to understanding the effect of FL avoidance planning on toxicity reduction and patient outcomes.

Mid-treatment adaptive planning during thoracic radiation using 68 Ventilation-Perfusion Positron emission tomography

Four-Dimensional Gallium 68 Ventilation-Perfusion Positron Emission Tomography (⁶⁸Ga-4D-V/Q PET/CT) allows for dynamic imaging of lung function. To date there has been no assessment of the feasibility of adapting radiation therapy plans to changes in lung function imaged at mid-treatment function using ⁶⁸Ga-4D-V/Q PET/CT. This study assessed the potential reductions of dose to the functional lung when radiation therapy plans were adapted to avoid functional lung at the mid-treatment timepoint using volumetric arc radiotherapy (VMAT).

Methods

A prospective clinical trial (U1111-1138-4421) was performed in patients undergoing conventionally fractionated radiation therapy for non-small cell lung cancer (NSCLC). A ⁶⁸Ga-4D-V/Q PET/CT was acquired at baseline and in the 4th week of treatment. Functional lung target volumes using the ventilated and perfused lung were created. Baseline functional volumes were compared to the week 4 V/Q functional volumes to describe the change in function over time. For each patient, 3 VMAT plans were created and optimised to spare ventilated, perfused or anatomical lung. All key dosimetry metrics were then compared including dose to target volumes, dose to organs at risk and dose to the anatomical and functional sub-units of lung.

Results

25 patients had both baseline and 4 week mid treatment ⁶⁸Ga-4D-V/Q PET/CT imaging. This resulted in a total of 75 adapted VMAT plans. The HPLung volume decreased in 16/25 patients with a mean of the change in volume (cc) -28 ± 515 cc [±SD, range -996 cc to 1496 cc]. The HVLung volume increased in 13/25 patients with mean of the change in volume (cc) + 112 ± 590 cc. [±SD, range -1424 cc to 950 cc]. The functional lung sparing technique was found to be feasible with no significant differences in dose to anatomically defined organs at risk. Most patients did derive a benefit with a reduction in functional volume receiving 20 Gy (fV20) and/or functional mean lung dose (fMLD) in either perfusion and/or ventilation. Patients with the most reduction in fV20 and fMLD were those with stage III NSCLC.

Conclusion

Functional lung volumes change during treatment. Some patients benefit from using ⁶⁸Ga-4D-V/Q PET/CT in the 4th week of radiation therapy to adapt radiation plans. In these patients, the role of mid-treatment adaptation requires further prospective investigation.

Impact of Low-Dose Irradiation of the Lung and Heart on Toxicity and Pulmonary Function Parameters after Thoracic Radiotherapy

Simple Summary

To assess the impact of thoracic (low) dose irradiation on pulmonary function changes after thoracic radiotherapy (RT) data of 62 patients were analyzed. There were several significant correlations between pulmonary function and dose parameters of the lung and heart, most of which remained significant in the multivariate analysis.

Abstract

Objective: To assess the impact of (low) dose irradiation to the lungs and heart on the incidence of pneumonitis and pulmonary function changes after thoracic radiotherapy (RT). Methods/Material: Data of 62 patients treated with curative thoracic radiotherapy were analyzed. Toxicity data and pulmonary function tests (PFTs) were obtained before RT and at 6 weeks, at 12 weeks, and at 6 months after RT. PFTs included ventilation (e.g., vital capacity) and diffusion parameters (e.g., diffusion capacity for carbon monoxide (DL_CO)). Dosimetric data of the lung and heart were extracted to assess the impact of dose on PFT changes and radiation pneumonitis (RP). Results: No statistically significant correlations between dose parameters and changes in ventilation parameters were found. There were statistically significant correlations between DL_CO and low-dose parameters of the lungs (V_5Gy–V_30Gy (%)) and irradiation of the heart during the follow-up up to 6 months after RT, as well as a temporary correlation of the V_60Gy (%) on the blood gas parameters at 12 weeks after RT. On multivariate analysis, both heart and lung parameters had a significant impact on DL_CO. There was no statistically significant influence of any patient or treatment-related (including dose parameters) factors on the incidence of ≥G2 pneumonitis. Conclusion: There seems to be a lasting impact of low dose irradiation to the lung as well as irradiation to the heart on the DL_CO after thoracic radiotherapy. No influence on RP was found in this analysis.

In Silico Ventilation Within the Dose-Volume is Predictive of Lung Function Post-radiation Therapy in Patients with Lung Cancer

Lung cancer is a leading cause of death worldwide. Radiation therapy (RT) is one method to treat this disease. A common side effect of RT for lung cancer is radiation-induced lung damage (RILD) which leads to loss of lung function. RILD often compounds pre-existing smoking-related regional lung function impairment. It is difficult to predict patient outcomes due to large variability in individual response to RT. In this study, the capability of image-based modelling of regional ventilation in lung cancer patients to predict lung function post-RT was investigated. Twenty-five patient-based models were created using CT images to define the airway geometry, size and location of tumour, and distribution of emphysema. Simulated ventilation within the 20 Gy isodose volume showed a statistically significant negative correlation with the change in forced expiratory volume in 1 s 12-months post-RT (p = 0.001, R = - 0.61). Patients with higher simulated ventilation within the 20 Gy isodose volume had a greater loss in lung function post-RT and vice versa. This relationship was only evident with the combined impact of tumour and emphysema, with the location of the emphysema relative to the dose-volume being important. Our results suggest that model-based ventilation measures can be used in the prediction of patient lung function post-RT.

Functional lung imaging in radiation therapy for lung cancer: A systematic review and meta-analysis

RATIONALE

Advanced imaging techniques allow functional information to be derived and integrated into treatment planning.

METHODS

A systematic review was conducted with the primary objective to evaluate the ability of functional lung imaging to predict risk of radiation pneumonitis. Secondary objectives were to evaluate dose-response relationships on post treatment functional imaging and assess the utility in including functional lung information into treatment planning. A structured search for publications was performed following PRISMA guidelines and registered on PROSPERO.

RESULTS

814 articles were screened against review criteria and 114 publications met criteria. Methods of identifying functional lung included using CT, MRI, SPECT and PET to image ventilation or perfusion. Six studies compared differences between functional and anatomical lung imaging at predicting radiation pneumonitis. These found higher predictive values using functional lung imaging. Twenty-one studies identified a dose-response relationship on post-treatment functional lung imaging. Nineteen planning studies demonstrated the ability of functional lung optimised planning techniques to spare regions of functional lung. Meta-analysis of these studies found that mean (95% CI) functional volume receiving 20 Gy was reduced by 4.2% [95% CI: 2.3: 6.0] and mean lung dose by 2.2 Gy [95% CI: 1.2: 3.3] when plans were optimised to spare functional lung. There was significant variation between publications in the definition of functional lung.

CONCLUSION

Functional lung imaging may have potential utility in radiation therapy planning and delivery, although significant heterogeneity was identified in approaches and reporting. Recommendations have been made based on the available evidence for future functional lung trials.

Correlation of Regional Lung Ventilation and Gas Transfer to Red Blood Cells: Implications for Functional-Avoidance Radiation Therapy Planning

PURPOSE

To investigate the degree to which lung ventilation and gas exchange are regionally correlated, using the emerging technology of hyperpolarized (HP)-129Xe magnetic resonance imaging (MRI).

METHODS AND MATERIALS

Hyperpolarized-129Xe MRI studies were performed on 17 institutional review board-approved human subjects, including 13 healthy volunteers, 1 emphysema patient, and 3 non-small cell lung cancer patients imaged before and approximately 11 weeks after radiation therapy (RT). Subjects inhaled 1 L of HP-129Xe mixture, followed by the acquisition of interleaved ventilation and gas exchange images, from which maps were obtained of the relative HP-129Xe distribution in three states: (1) gaseous, in lung airspaces; (2) dissolved interstitially, in alveolar barrier tissue; and (3) transferred to red blood cells (RBCs), in the capillary vasculature. The relative spatial distributions of HP-129Xe in airspaces (regional ventilation) and RBCs (regional gas transfer) were compared. Further, we investigated the degree to which ventilation and RBC transfer images identified similar functional regions of interest (ROIs) suitable for functionally guided RT. For the RT patients, both ventilation and RBC functional images were used to calculate differences in the lung dose-function histogram and functional effective uniform dose.

RESULTS

The correlation of ventilation and RBC transfer was ρ = 0.39 ± 0.15 in healthy volunteers. For the RT patients, this correlation was ρ = 0.53 ± 0.02 before treatment and ρ = 0.39 ± 0.07 after treatment; for the emphysema patient it was ρ = 0.24. Comparing functional ROIs, ventilation and RBC transfer demonstrated poor spatial agreement: Dice similarity coefficient = 0.50 ± 0.07 and 0.26 ± 0.12 for the highest-33%- and highest-10%-function ROIs in healthy volunteers, and in RT patients (before treatment) these were 0.58 ± 0.04 and 0.40 ± 0.04. The average magnitude of the differences between RBC- and ventilation-derived functional effective uniform dose, fV20Gy, fV10Gy, and fV5Gy were 1.5 ± 1.4 Gy, 4.1% ± 3.8%, 5.0% ± 3.8%, and 5.3% ± 3.9%, respectively.

CONCLUSION

Ventilation may not be an effective surrogate for true regional lung function for all patients.

Modeling Patient-Specific Dose-Function Response for Enhanced Characterization of Personalized Functional Damage

PURPOSE

Functional-guided radiation therapy (RT) plans have the potential to limit damage to normal tissue and reduce toxicity. Although functional imaging modalities have continued to improve, a limited understanding of the functional response to radiation and its application to personalized therapy has hindered clinical implementation. The purpose of this study was to retrospectively model the longitudinal, patient-specific dose-function response in non-small cell lung cancer patients treated with RT to better characterize the expected functional damage in future, unknown patients.

METHODS AND MATERIALS

Perfusion single-photon emission computed tomography/computed tomography scans were obtained at baseline (n = 81), midtreatment (n = 74), 3 months post-treatment (n = 51), and 1 year post-treatment (n = 26) and retrospectively analyzed. Patients were treated with conventionally fractionated RT or stereotactic body RT. Normalized perfusion single-photon emission computed tomography voxel intensity was used as a surrogate for local lung function. A patient-specific logistic model was applied to each individual patient's dose-function response to characterize functional reduction at each imaging time point. Patient-specific model parameters were averaged to create a population-level logistic dose-response model.

RESULTS

A significant longitudinal decrease in lung function was observed after RT by analyzing the voxelwise change in normalized perfusion intensity. Generated dose-function response models represent the expected voxelwise reduction in function, and the associated uncertainty, for an unknown patient receiving conventionally fractionated RT or stereotactic body RT. Differential treatment responses based on the functional status of the voxel at baseline suggest that initially higher functioning voxels are damaged at a higher rate than lower functioning voxels.

CONCLUSIONS

This study modeled the patient-specific dose-function response in patients with non-small cell lung cancer during and after radiation treatment. The generated population-level dose-function response models were derived from individual patient assessment and have the potential to inform functional-guided treatment plans regarding the expected functional lung damage. This type of patient-specific modeling approach can be applied broadly to other functional response analyses to better capture intrapatient dependencies and characterize personalized functional damage.

Parenchymal and Functional Lung Changes after Stereotactic Body Radiotherapy for Early-Stage Non-Small Cell Lung Cancer-Experiences from a Single Institution

Introduction

This study aimed to evaluate parenchymal and functional lung changes following stereotactic body radiotherapy (SBRT) for early-stage non-small cell lung cancer (NSCLC) patients and to correlate radiological and functional findings with patient and treatment characteristics as well as survival.

Materials and methods

Seventy patients with early-stage NSCLC treated with SBRT from 2004 to 2015 with more than 1 year of CT follow-up scans were analyzed. Incidence, morphology, severity of acute and late lung abnormalities as well as pulmonary function changes were evaluated and correlated with outcome.

Results

Median follow-up time was 32.2 months with 2-year overall survival (OS) of 83% and local progression-free survival of 88%, respectively. Regarding parenchymal changes, most patients only developed mild to moderate CT abnormalities. Mean ipsilateral lung dose (MLD) in biological effective dose and planning target volume size were significantly associated with maximum severity score of parenchymal changes (p = 0.014, p < 0.001). Furthermore, both maximum severity score and MLD were significantly connected with OS in univariate analysis (p = 0.043, p = 0.025). For functional lung changes, we detected significantly reduced total lung capacity, forced expiratory volume in 1 s, and forced vital capacity (FVC) parameters after SBRT (p ≤ 0.001). Multivariate analyses revealed SBRT with an MLD ≥ 9.72 Gy and FVC reduction ≥0.54 L as independent prognostic factors for inferior OS (p = 0.029, p = 0.004).

Conclusion

SBRT was generally tolerated well with only mild toxicity. For evaluating the possible prognostic impact of MLD and FVC reduction on survival detected in this analysis, larger prospective studies are truly needed.

Imaging Radiation-Induced Normal Tissue Injury to Quantify Regional Dose Response

Noninvasive imaging has and will continue to play a pivotal role in the assessment of radiation-induced normal tissue toxicity. In this review, we will examine key literature regarding the use of anatomic and physiological imaging in relation to radiation-induced normal tissue toxicity. Additionally, this review contains a novel methodology for potentially incorporating dose-response data into treatment planning and normal tissue toxicity modeling.

Pulmonary injury associated with radiation therapy - Assessment, complications and therapeutic targets

Pulmonary injury is more common in patients undergoing radiation therapy for lungs and other thoracic malignancies. Recently with the use of most-advanced technologies powerful doses of radiation can be delivered directly to tumor site with exquisite precision. The awareness of technical and clinical parameters that influence the chance of radiation induced lung injury is important to guide patient selection and toxicity minimization strategies. At the cellular level, radiation activates free radical production, leading to DNA damage, apoptosis, cell cycle changes, and reduced cell survival. Preclinical research shows the potential for therapies targeting transforming growth factor-β (TGF-B), Toll like receptor (TLRs), Tumour necrosis factor-alpha (TNF-alpha), Interferon gamma (IFN-γ) and so on that may restore lung function. At present Amifostine (WR-2721) is the only approved broad spectrum radioprotector in use for patients undergoing radiation therapy. Newer techniques also offer the opportunity to identify new biomarkers and new targets for interventions to prevent or ameliorate these late effects of lung damage.

Changes in pulmonary function and influencing factors after high-dose intrathoracic radio(chemo)therapy

PURPOSE

Using prospectively collected patient-related, dose-related, and pulmonary function test (PFT) data before radiotherapy (RT) and at several follow-up visits after RT, the time course of PFT changes after high-dose radio(chemo)therapy and influencing factors were analyzed.

MATERIALS AND METHODS

From April 2012 to October 2015, 81 patients with non-small-cell lung carcinoma (NSCLC), small cell lung carcinoma (SCLC), or esophageal carcinoma where treated with high-dose radio(chemo)therapy. PFT data were collected before treatment and 6 weeks, 12 weeks, and 6 months after RT. The influence of patient- and treatment-related factors on PFT was analyzed.

RESULTS

Mean forced expiratory volume in 1 s (FEV1) constantly declined during follow-up (p = 0.001). In total, 68% of patients had a reduced FEV1 at 6 months. Mean vital capacity (VC) didn't change during follow-up (p > 0.05). Mean total lung capacity (TLC) showed a constant decline after RT (p = 0.026). At 6 months, 60% of patients showed a decline in VC and 73% in TLC. The mean diffusion capacity for carbon monoxide (DLCO) declined at 6 and 12 weeks, but recovered slightly at 6 months (p < 0.0005). At 6 months, 86% of patients had a reduced DLCO. After treatment, the partial pressure of CO₂ in the blood (pCO₂) was increased and pO₂ was decreased (p > 0.05). Only the pretreatment PFT classification had a significant influence on the post-RT FEV1.

CONCLUSION

DLCO seems to be the most reliable indicator for lung tissue damage after thoracic RT. Ventilation parameters appear to be less reliable. Concerning patient- or treatment-related factors, no reliable conclusion can be drawn regarding which factors may be relevant.

Local and Global Function Model of the Liver

PURPOSE

To develop a local and global function model in the liver based on regional and organ function measurements to support individualized adaptive radiation therapy (RT).

METHODS AND MATERIALS

A local and global model for liver function was developed to include both functional volume and the effect of functional variation of subunits. Adopting the assumption of parallel architecture in the liver, the global function was composed of a sum of local function probabilities of subunits, varying between 0 and 1. The model was fit to 59 datasets of liver regional and organ function measures from 23 patients obtained before, during, and 1 month after RT. The local function probabilities of subunits were modeled by a sigmoid function in relating to MRI-derived portal venous perfusion values. The global function was fitted to a logarithm of an indocyanine green retention rate at 15 minutes (an overall liver function measure). Cross-validation was performed by leave-m-out tests. The model was further evaluated by fitting to the data divided according to whether the patients had hepatocellular carcinoma (HCC) or not.

RESULTS

The liver function model showed that (1) a perfusion value of 68.6 mL/(100 g · min) yielded a local function probability of 0.5; (2) the probability reached 0.9 at a perfusion value of 98 mL/(100 g · min); and (3) at a probability of 0.03 [corresponding perfusion of 38 mL/(100 g · min)] or lower, the contribution to global function was lost. Cross-validations showed that the model parameters were stable. The model fitted to the data from the patients with HCC indicated that the same amount of portal venous perfusion was translated into less local function probability than in the patients with non-HCC tumors.

CONCLUSIONS

The developed liver function model could provide a means to better assess individual and regional dose-responses of hepatic functions, and provide guidance for individualized treatment planning of RT.

Correlation of 68Ga Ventilation-Perfusion PET/CT with Pulmonary Function Test Indices for Assessing Lung Function

Pulmonary function tests (PFTs) are routinely used to assess lung function, but they do not provide information about regional pulmonary dysfunction. We aimed to assess correlation of quantitative ventilation-perfusion (V/Q) PET/CT with PFT indices.

METHODS

Thirty patients underwent V/Q PET/CT and PFT. Respiration-gated images were acquired after inhalation of (68)Ga-carbon nanoparticles and administration of (68)Ga-macroaggregated albumin. Functional volumes were calculated by dividing the volume of normal ventilated and perfused (%NVQ), unmatched and matched defects by the total lung volume. These functional volumes were correlated with forced expiratory volume in 1 s (FEV1), forced vital capacity (FVC), FEV1/FVC, and diffusing capacity for carbon monoxide (DLCO).

RESULTS

All functional volumes were significantly different in patients with chronic obstructive pulmonary disease (P < 0.05). FEV1/FVC and %NVQ had the highest correlation (r = 0.82). FEV1 was also best correlated with %NVQ (r = 0.64). DLCO was best correlated with the volume of unmatched defects (r = -0.55). Considering %NVQ only, a cutoff value of 90% correctly categorized 28 of 30 patients with or without significant pulmonary function impairment.

CONCLUSION

Our study demonstrates strong correlations between V/Q PET/CT functional volumes and PFT parameters. Because V/Q PET/CT is able to assess regional lung function, these data support the feasibility of its use in radiation therapy and preoperative planning and assessing pulmonary dysfunction in a variety of respiratory diseases.

Loss of lung function after chemo-radiotherapy for NSCLC measured by perfusion SPECT/CT: Correlation with radiation dose and clinical morbidity

BACKGROUND

The purpose of the study was to assess dose and time dependence of radiotherapy (RT)-induced changes in regional lung function measured with single photon emission computed tomography (SPECT) of the lung and relate these changes to the symptomatic endpoint of radiation pneumonitis (RP) in patients treated for non-small cell lung cancer (NSCLC).

MATERIAL AND METHODS

NSCLC patients scheduled to receive curative RT of minimum 60 Gy were included prospectively in the study. Lung perfusion SPECT/CT was performed before and three months after RT. Reconstructed SPECT/CT data were registered to treatment planning CT. Dose to the lung was segmented into regions corresponding to 0-5, 6-20, 21-40, 41-60 and > 60 Gy. Changes (%) in regional lung perfusion before and after RT were correlated with regional dose and symptomatic RP (CTC grade 2-5) outcome.

RESULTS

A total of 58 patients were included, of which 45 had three-month follow-up SPECT/CT scans. Analysis showed a statistically significant dose-dependent reduction in regional perfusion at three-month follow-up. The largest population composite perfusion loss was in 41-60 Gy (42.2%) and > 60 Gy (41.7%) dose bins. Lung regions receiving low dose of 0-5 Gy and 6-20 Gy had corresponding perfusion increase (-7.2% and -6.1%, respectively). Regional perfusion reduction was different in patients with and without RP with the largest difference in 21-40 Gy bin (p = 0.02), while for other bins the difference did not reach statistical significance. The risk of symptomatic RP was higher for the patients with perfusion reduction after RT (p = 0.02), with the relative risk estimate of 3.6 (95% CI 1.1-12).

CONCLUSION

Perfusion lung function changes in a dose-dependent manner after RT. The severity of radiation-induced lung symptoms is significantly correlated with SPECT perfusion changes. Perfusion reduction early after RT is associated with a high risk of later development of symptomatic RP.

Dose-mass inverse optimization for minimally moving thoracic lesions

In the past decade, several different radiotherapy treatment plan evaluation and optimization schemes have been proposed as viable approaches, aiming for dose escalation or an increase of healthy tissue sparing. In particular, it has been argued that dose-mass plan evaluation and treatment plan optimization might be viable alternatives to the standard of care, which is realized through dose-volume evaluation and optimization. The purpose of this investigation is to apply dose-mass optimization to a cohort of lung cancer patients and compare the achievable healthy tissue sparing to that one achievable through dose-volume optimization. Fourteen non-small cell lung cancer (NSCLC) patient plans were studied retrospectively. The range of tumor motion was less than 0.5 cm and motion management in the treatment planning process was not considered. For each case, dose-volume (DV)-based and dose-mass (DM)-based optimization was performed. Nine-field step-and-shoot IMRT was used, with all of the optimization parameters kept the same between DV and DM optimizations. Commonly used dosimetric indices (DIs) such as dose to 1% the spinal cord volume, dose to 50% of the esophageal volume, and doses to 20 and 30% of healthy lung volumes were used for cross-comparison. Similarly, mass-based indices (MIs), such as doses to 20 and 30% of healthy lung masses, 1% of spinal cord mass, and 33% of heart mass, were also tallied. Statistical equivalence tests were performed to quantify the findings for the entire patient cohort. Both DV and DM plans for each case were normalized such that 95% of the planning target volume received the prescribed dose. DM optimization resulted in more organs at risk (OAR) sparing than DV optimization. The average sparing of cord, heart, and esophagus was 23, 4, and 6%, respectively. For the majority of the DIs, DM optimization resulted in lower lung doses. On average, the doses to 20 and 30% of healthy lung were lower by approximately 3 and 4%, whereas lung volumes receiving 2000 and 3000 cGy were lower by 3 and 2%, respectively. The behavior of MIs was very similar. The statistical analyses of the results again indicated better healthy anatomical structure sparing with DM optimization. The presented findings indicate that dose-mass-based optimization results in statistically significant OAR sparing as compared to dose-volume-based optimization for NSCLC. However, the sparing is case-dependent and it is not observed for all tallied dosimetric endpoints.

Protective effect of ulinastatin in patients with non-small cell lung cancer after radiation therapy: a randomized, placebo-controlled study

Radiation-induced lung injury (RILI) is a frequent, sometimes life-threatening complication of radiation therapy for the treatment of lung cancer. The anti-inflammatory role of ulinastatin has been well documented, and the potential application of ulinastatin in management of acute lung injury has been suggested in multiple animal studies. In this article, we described a double-blind, randomized, placebo-controlled study in patients with non-small cell lung cancer. A total of 120 patients were randomized into two groups: the trial group was treated with ulinastatin for 3 days prior to and for the first 7 days of radiation therapy and the control group was treated with placebo for 10 days following the same schedule. The results from follow-up studies showed that the incidence and grade of RILI were significantly lower in the trial group than in the control group. Reduction in pulmonary function from baseline was significantly smaller in the trial group than that in the control group. Production of serum TGF-β1, TNF-α and IL-6 decreased significantly in the trial group promptly following radiation therapy. However, no difference in survival or tumour response rate was found between the two groups. The results indicated that ulinastatin exerted a protective effect on radiation-induced lung injury. Treatment with ulinastatin could be an effective management strategy and greatly improve the clinical efficacy of radiation therapy for patients with lung cancer.

Lung

The lungs are particularly sensitive to RT, and are often the primary dose-limiting structure during thoracic therapy.

The alveolar/capillary units and pneumocytes within the alveoli appear to be particularly sensitive to RT.

Hypoxia may be important in the underlying physiology of RT-associated lung injury.

The cytokine transforming growth factor-beta (TGF-β), plays an important role in the development of RT-induced fibrosis.

The histopathological changes observed in the lung after RT are broadly characterized as diffuse alveolar damage.

The interaction between pre-treatment PFTs and the risk of symptomatic lung injury is complex. Similarly, the link between changes in PFTs and the development of symptoms is uncertain.

The incidence of symptomatic lung injury increases with increase in most dosimetric parameters. The mean lung dose (MLD) and V20 have been the most-often considered parameters. MLD might be a preferable metric since it considers the entire 3D dose distribution.

Radiation to the lower lobes appears to be more often associated with clinical symptoms than is radiation to the upper lobes. This might be related to incidental cardiac irradiation. In pre-clinical models, there appears to be a complex interaction between lung and heart irradiation.

TGF-β has been suggested in several studies to predict for RT-induced lung injury, but the data are still somewhat inconsistent.

Oral prednisone (Salinas and Winterbauer 1995), typically 40–60 mg daily for 1–2 weeks with a slow taper, is usually effective in treating pneumonitis. There are no widely accepted treatments for fibrosis.

A number of chemotherapeutic agents have been suggested to be associated with a range of pulmonary toxicities.

Paeoniflorin protects human EA.hy926 endothelial cells against gamma-radiation induced oxidative injury by activating the NF-E2-related factor 2/heme oxygenase-1 pathway

Pulmonary endothelial cells have been demonstrated to have a critical role in the pathogenesis of radiation-induced lung injury. Our preliminary experiments indicated that paeoniflorin protected human EA.hy926 endothelial cells from radiation-induced oxidative injury. This study was designed to confirm the protective effect of paeoniflorin against radiation-induced endothelial cellular damage and to elucidate the underlying mechanisms. Preincubation of EA.hy926 cells with paeoniflorin before γ-radiation resulted in significant inhibition of apoptosis, a decrease in mitochondrial membrane potential and enhanced cell viability. In particular, we showed that paeoniflorin significantly reduced the formation of intracellular reactive oxygen species (ROS), the level of malondialdehyde (MDA) and lactate dehydrogenase (LDH) leakage, and enhanced production of the endogenous antioxidants, glutathione (GSH) and superoxide dismutase (SOD) in EA.hy926 cells. Treatment of these cells with paeoniflorin significantly induced HO-1 expression. Moreover, paeoniflorin promoted the nuclear translocation of nuclear factor erythroid 2 related factor-2 (Nrf-2). The paeoniflorin-induced HO-1 expression was abrogated by Nrf2 siRNA. Furthermore, inhibition of HO-1 with zinc protoporphyrin IX (ZNPP) significantly reversed the protective effect of paeoniflorin against radiation-induced damage in EA.hy926 cells. Our findings confirmed that paeoniflorin protected EA.hy926 cells against radiation-induced injury through the Nrf2/HO-1 pathway.

Analysis of single nucleotide polymorphisms and radiation sensitivity of the lung assessed with an objective radiologic endpoin

BACKGROUND

The primary objective of this study was to evaluate the association between radiation sensitivity of the lungs and candidate single nucleotide polymorphisms (SNP) in genes implicated in radiation-induced toxicity.

METHODS

Patients with lung cancer who received radiation therapy (RT) had pre-RT and serial post-RT single photon emission computed tomography (SPECT) lung perfusion scans. RT-induced changes in regional perfusion were related to regional dose, which generated patient-specific dose-response curves (DRC). The slope of the DRC is independent of total dose and the irradiated volume, and is taken as a reflection of the patient's inherent sensitivity to RT. DNA was extracted from blood samples obtained at baseline. SNPs were determined by using a combination of high-resolution melting, TaqMan assays, and direct sequencing. Genotypes from 33 SNPs in 22 genes were compared against the slope of the DRC by using the Kruskal-Wallis test for ordered alternatives.

RESULTS

Thirty-nine self-reported Caucasian patients with pre-RT and ≥6 month post-RT SPECTs, and blood samples were identified. An association between genotype and increasing slope of the DRC was noted in G(1301) A in XRCC1 (rs25487) (P = .01) and G(3748) A in BRCA1 (rs16942) (P = .03).

CONCLUSIONS

By using an objective radiologic assessment, polymorphisms within genes involved in repair of DNA damage (XRCC1 and BRCA1) were associated with radiation sensitivity of the lungs.

Lack of a dose-effect relationship for pulmonary function changes after stereotactic body radiation therapy for early-stage non-small cell lung cancer

PURPOSE

To evaluate the influence of tumor size, prescription dose, and dose to the lungs on posttreatment pulmonary function test (PFT) changes after stereotactic body radiation therapy (SBRT) for early-stage non-small cell lung cancer (NSCLC).

METHODS AND MATERIALS

The analysis is based on 191 patients treated at 5 international institutions: inclusion criteria were availability of pre- and post-SBRT PFTs and dose-volume histograms of the lung and planning target volume (PTV); patients treated with more than 1 SBRT course were excluded. Correlation between early (1-6 months, median 3 months) and late (7-24 months, median 12 months) PFT changes and tumor size, planning target volume (PTV) dose, and lung doses was assessed using linear regression analysis, receiver operating characteristics analysis, and Lyman's normal tissue complication probability model. The PTV doses were converted to biologically effective doses and lung doses to 2 Gy equivalent doses before correlation analyses.

RESULTS

Up to 6 months after SBRT, forced expiratory volume in 1 second and carbon monoxide diffusion capacity changed by -1.4% (95% confidence interval [CI], -3.4% to 0) and -7.6% (95% CI, -10.2% to -3.4%) compared with pretreatment values, respectively. A modest decrease in PFTs was observed 7-24 months after SBRT, with changes of -8.1% (95% CI, -13.3% to -5.3%) and -12.4% (95% CI, -15.5% to -6.9%), respectively. Using linear regression analysis, receiver operating characteristic analysis, and normal tissue complication probability modeling, all evaluated parameters of tumor size, PTV dose, mean lung dose, and absolute and relative volumes of the lung exposed to minimum doses of 5-70 Gy were not correlated with early and late PFT changes. Subgroup analysis based on pre-SBRT PFTs (greater or equal and less than median) did not identify any dose-effect relationship.

CONCLUSIONS

This study failed to demonstrate a significant dose-effect relationship for changes of pulmonary function after SBRT for early-stage non-small cell lung cancer.

Imaging radiation-induced normal tissue injury

Technological developments in radiation therapy and other cancer therapies have led to a progressive increase in five-year survival rates over the last few decades. Although acute effects have been largely minimized by both technical advances and medical interventions, late effects remain a concern. Indeed, the need to identify those individuals who will develop radiation-induced late effects, and to develop interventions to prevent or ameliorate these late effects is a critical area of radiobiology research. In the last two decades, preclinical studies have clearly established that late radiation injury can be prevented/ameliorated by pharmacological therapies aimed at modulating the cascade of events leading to the clinical expression of radiation-induced late effects. These insights have been accompanied by significant technological advances in imaging that are moving radiation oncology and normal tissue radiobiology from disciplines driven by anatomy and macrostructure to ones in which important quantitative functional, microstructural, and metabolic data can be noninvasively and serially determined. In the current article, we review use of positron emission tomography (PET), single photon emission tomography (SPECT), magnetic resonance (MR) imaging and MR spectroscopy to generate pathophysiological and functional data in the central nervous system, lung, and heart that offer the promise of, (1) identifying individuals who are at risk of developing radiation-induced late effects, and (2) monitoring the efficacy of interventions to prevent/ameliorate them.

Acute left bundle branch block as a complication of brachytherapy for lung cancer

Endoluminal brachytherapy for lung cancer ensures the delivery of a maximal therapeutic radiation dose to the tumor with a minimal effect on normal surrounding tissues. We report on a 62-year-old man, who acutely developed LBBB and heart failure 48 hours after the second course of combined endoluminal and external beam radiation therapy. After administration of angiotensin converting enzyme inhibitors, diuretics, and anti-inflammatory drugs, electrocardiographic changes resolved and patient completely recovered. Radiotherapy was reintroduced after ten days.

Functional dose-volume histograms for predicting radiation pneumonitis in locally advanced non-small cell lung cancer treated with late-course accelerated hyperfractionated radiotherapy

The aim of this study was to determine whether functional dose-volume histograms (FDVHs) are valuable for predicting radiation pneumonitis (RP), and to identify whether FDVHs have advantages over conventional dose-volume histograms (DVHs) for the prediction of RP in patients with locally advanced non-small cell lung cancer (LANSCLC). Fifty-seven patients with LANSCLC undergoing functional image-guided late-course accelerated hyperfractionated radiotherapy were enrolled. The grade of RP was evaluated according to the Common Toxicity Criteria 3.0. To identify predictive factors of RP, the FDVHs, including the volume of the functional lung receiving 5 Gy (FV(5)) through 50 Gy (FV(50)), mean perfusion-weighted lung dose (MPWLD) and functional normal tissue complication probability (FNTCP), were analyzed and compared to their counterparts [total lung receiving 5 Gy (V(5)) through 50 Gy (V(50)), mean lung dose (MLD) and normal tissue complication probability (NTCP)] derived from conventional DVHs. Univariate analysis revealed that V(5)-V(40), MLD, NTCP and FV(5)-FV(50), MPWLD, FNTCP were all statistically significant relative to the development of RP (all p<0.05). Multivariate analysis showed that only MLD and FV(15) were associated with RP (p=0.001 and 0.044, respectively). Receiver operator characteristic curve anaysis indicated that almost all of the FDVHs had larger areas under the curve compared to the DVHs, although no statistically significant difference was observed (p-value ranged from 0.066 to 0.951). FDVHs are valuable for predicting RP with the predictive efficiency equivalent to or slightly advantageous over conventional DVHs. More homogeneous studies involving larger numbers of patients are required to further assess the value of FDVHs for predicting RP.

Radiation-related treatment effects across the age spectrum: differences and similarities or what the old and young can learn from each other

Radiation related effects in children and adults limit the delivery of effective radiation doses and result in long-term morbidity affecting function and quality of life. Improvements in our understanding of the etiology and biology of these effects, including the influence of clinical variables, dosimetric factors, and the underlying biological processes have made treatment safer and more efficacious. However, the approach to studying and understanding these effects differs between children and adults. Using the pulmonary and skeletal organ systems as examples, comparisons are made across the age spectrum for radiation related effects, including pneumonitis, pulmonary fibrosis, osteonecrosis, and fracture. Methods for dosimetric analysis, incorporation of imaging and biology as well a length of follow-up are compared, contrasted, and discussed for both organ systems in children and adults. Better understanding of each age specific approach and how it differs may improve our ability to study late effects of radiation across the ages.

Imaging for assessment of radiation-induced normal tissue effects

Imaging can provide quantitative assessment of radiation-induced normal tissue effects. Identifying an early sign of normal tissue damage with imaging would have the potential to predict organ dysfunction, thereby allowing reoptimization of treatment strategies based on individual patients' risks and benefits. Early detection with noninvasive imaging may enable interventions to mitigate therapy-associated injury before its clinical manifestation. Furthermore, successive imaging may provide an objective assessment of the impact of such mitigation therapies. However, many problems make application of imaging to normal tissue assessment challenging, and further work is required to establish imaging biomarkers as surrogate endpoints of clinical outcome. The performance of clinical trials in which normal tissue injury is a clearly defined endpoint would greatly aid in realization of these goals.

Association between RT-induced changes in lung tissue density and global lung function

PURPOSE

To assess the association between radiotherapy (RT)-induced changes in computed tomography (CT)-defined lung tissue density and pulmonary function tests (PFTs).

METHODS AND MATERIALS

Patients undergoing incidental partial lung RT were prospectively assessed for global (PFTs) and regional (CT and single photon emission CT [SPECT]) lung function before and, serially, after RT. The percent reductions in the PFT and the average changes in lung density were compared (Pearson correlations) in the overall group and subgroups stratified according to various clinical factors. Comparisons were also made between the CT- and SPECT-based computations using the Mann-Whitney U test.

RESULTS

Between 1991 and 2004, 343 patients were enrolled in this study. Of these, 111 patients had a total of 203 concurrent post-RT evaluations of changes in lung density and PFTs available for the analyses, and 81 patients had a total of 141 concurrent post-RT SPECT images. The average increases in lung density were related to the percent reductions in the PFTs, albeit with modest correlation coefficients (range, 0.20-0.43). The analyses also indicated that the association between lung density and PFT changes is essentially equivalent to the corresponding association with SPECT-defined lung perfusion.

CONCLUSION

We found a weak quantitative association between the degree of increase in lung density as defined by CT and the percent reduction in the PFTs.

Lung perfusion imaging can risk stratify lung cancer patients for the development of pulmonary complications after chemoradiation

INTRODUCTION

We investigated the value of lung perfusion imaging in predicting the risk of developing pulmonary complications after chemoradiation (CRT) or radiation therapy (RT) for lung cancer.

METHODS

Fifty patients who underwent lung perfusion imaging before RT for lung cancer were included. Planar and single photon emission computed tomography/computed tomography images of the lungs were obtained. Lung perfusion score (LPS) was developed to visually grade localized perfusion defect per lung on a scale of 0 to 4 and perfusion pattern in the remaining lungs on a scale of 1 to 4. The LPS is the sum of the score for the localized perfusion defect in each lung plus the score for the remaining lungs perfusion. LPSs were correlated with pulmonary function tests and the patients were followed for 8 months after therapy to determine the incidence of grade 2 to 5 symptomatic therapy related pulmonary complications according to the common terminology criteria for adverse events (CTCAE 3.0).

RESULTS

Thirty-four patients underwent CRT and 16 underwent RT. The mean total radiation dose delivered was 56.1 +/- 10.4 Gy. Eighteen patients (36%) suffered from pulmonary complications at a mean interval of 3.4 months after therapy. Nine patients had grade 2, 7 had grade 3, 1 had grade 4, and 1 had grade 5 pulmonary complications. The mean LPS was 4.9 in patients who developed pulmonary complications versus 3.5 in patients who did not (p = 0.01). There were no significant difference between pulmonary function tests in the patients with pulmonary complications and the patient without. In addition, there were no significant differences between the mean lung radiation dose, the volume of lung irradiated or the percentage of lung receiving greater than 20 Gy between the two groups.

CONCLUSIONS

LPS using lung perfusion imaging is useful for predicting possible pulmonary complications after CRT or RT in lung cancer patients.

Protective effects of berberine on radiation-induced lung injury via intercellular adhesion molecular-1 and transforming growth factor-beta-1 in patients with lung cancer

PURPOSE

To investigate the protective effects of berberine on radiation-induced lung injury (RILI) in non-small cell lung cancer (NSCLC) patients treated with radiotherapy.

PATIENTS AND METHODS

In this randomised, double-blind study, 90 patients with NSCLC were divided into two groups. The trial group received radiation therapy plus berberine, and the control group received radiation therapy plus a placebo for 6 weeks. Soluble intercellular adhesion molecular-1 (sICAM-1) and transforming growth factor-beta-1 (TGF-beta1) were measured. RILI and pulmonary function were evaluated at 6 weeks and 6 months after treatment, respectively.

RESULTS

Of the 90 patients enroled, 43 in the control group and 42 in the trial group completed the study. The incidence of RILI was significantly lower in the trial group at 6 weeks and 6 months than that in the control group (45.2% versus 72.1% and 35.7% versus 65.1%, respectively, both P<0.05). sICAM-1 levels in the trial group were significantly lower at weeks 6 and 12 (373.64+/-89.33 versus 459.53+/-123.59 and 447.83+/-111.21 versus 513.91+/-150.46, both P<0.01), and plasma TGF-beta1 levels were lower at week 3 and 6 (5.43+/-1.47 versus 6.22+/-1.78 and 5.93+/-2.39 versus 7.67+/-2.74, P<0.05 and 0.01, respectively) in comparison with the control group. Significant differences were observed in FEV1 (P=0.033) and DLCO (P=0.003) between patients receiving berberine and those receiving placebo. Independent-samples T-test showed reductions from baseline FVC at week 6 (P<0.05), and FEV1 and DLCO at month 6 (P<0.05 and 0.01, respectively) in the trial group were significantly smaller than that in the control group.

CONCLUSION

Berberine significantly reduced the incidence of RILI, improved PF and decreased the levels of sICAM-1 and TGF-beta1. The exact mechanisms remain to be further explored.

Dose mapping: validation in 4D dosimetry with measurements and application in radiotherapy follow-up evaluation

The purpose of this paper is to validate a dose mapping program using optical flow method (OFM), and to demonstrate application of the program in radiotherapy follow-up evaluation. For the purpose of validation, the deformation matrices between four-dimensional (4D) CT data of different simulated respiration phases of a phantom were calculated using OFM. The matrices were then used to map doses of all phases to a single-phase image, and summed in equal time weighting. The calculated dose should closely represent the dose delivered to the moving phantom if the deformation matrices are accurately calculated. The measured point doses agreed with the OFM calculations better than 2% at isocenters, and dose distributions better than 1mm for the 50% isodose line. To demonstrate proof-of-concept for the use of deformable image registration in dose mapping for treatment evaluation, the treatment-planning CT was registered with the post-treatment CT image from the positron emission tomography (PET)/CT resulting in a deformation matrix. The dose distribution from the treatment plan was then mapped onto the restaging PET/CT using the deformation matrix. Two cases in which patients had thoracic malignancies are presented. Each patient had CT-based treatment planning for radiotherapy and restaging fluorodeoxy glucose (FDG)-PET/CT imaging 4-6 weeks after completion of treatments. Areas of pneumonitis and recurrence were identified radiographically on both PET and CT restaging images. Local dose and standard uptake values for pneumonitis and recurrence were studied as a demonstration of this method. By comparing the deformable mapped dose to measurement, the treatment evaluation method which is introduced in this manuscript proved to be accurate. It thus provides a more accurate analysis than other rigid or linear dose-image registration when used in studying treatment outcome versus dose.

Liver function after irradiation based on computed tomographic portal vein perfusion imaging

PURPOSE

To determine whether individual and regional liver sensitivity to radiation could be assessed by measuring liver perfusion during a course of treatment using dynamic contrast-enhanced computed tomography scanning.

METHODS AND MATERIALS

Patients with intrahepatic cancer undergoing conformal radiotherapy underwent dynamic contrast-enhanced computed tomography (to measure perfusion distribution) and an indocyanine extraction study (to measure liver function) before, during, and 1 month after treatment. We hoped to determine whether the residual functioning liver (i.e., those regions showing portal vein perfusion) could be used to predict overall liver function after irradiation.

RESULTS

Radiation doses from 45 to 84 Gy resulted in undetectable regional portal vein perfusion 1 month after treatment. The volume of each liver with undetectable portal vein perfusion ranged from 0 to 39% and depended both on the patient's sensitivity and on dose distribution. There was a significant correlation between indocyanine green clearance and the mean of the estimated portal vein perfusion in the functional liver parenchyma (p < 0.001).

CONCLUSION

This study reveals substantial individual variability in the sensitivity of the liver to irradiation. In addition, these findings suggest that hepatic perfusion imaging may be a marker for liver function and has the potential to be a tool for individualizing therapy.

The prediction of radiation-induced liver dysfunction using a local dose and regional venous perfusion model

We have shown that high dose conformal radiation combined with chemotherapy appears to prolong the survival of patients with unresectable intrahepatic cancers. The ability to safely deliver higher doses is primarily limited by the development of radiation-induced liver disease, characterized by venous occlusion. In this study, we investigated whether portal venous perfusion measured prior to the end of radiation therapy (RT) together with dose could predict liver venous perfusion dysfunction after treatment. Ten patients with unresectable intrahepatic cancer participated in an IRB-approved computer tomography (CT) perfusion study. Hepatic arterial and portal vein perfusion distributions were estimated by using dynamic contrast enhanced CT and the single compartmental model. Scans were obtained at four time points: prior to treatment, after 15 and 30 fractions of 1.5 Gy treatments, and one month following the completion of RT. Multivariant linear regression was used to determine covariances among the first three time point measurements plus dose for prediction of the post RT measurement. The reduction in the regional venous perfusion one month following RT was predicted by the local accumulated dose and the change in the regional venous perfusion after -30 fractions (F=90.6,p <0.000 01). Each Gy produced an approximately 1.2% of reduction in the venous perfusion. This local dose and venous perfusion model has the potential to predict individual sensitivity to radiation. This is the first step toward developing a method to deliver higher and potentially more curative radiation doses to the patients who can safely receive these higher doses.

Normal Tissue Tolerance Dose Metrics for Radiation Therapy of Major Organs

Late organ toxicity from therapeutic radiation is a function of many confounding variables. The total dose delivered to the organ and the volumes of organ exposed to a given dose of radiation are 2 important variables that can be used to predict the risk of late toxicity. Three-dimensional radiation planning enables accurate calculation of the volume of tissue exposed to a given dose of radiation, graphically depicted as a dose-volume histogram. Dose metrics obtained from this 3-dimensional dataset can be used as a quantitative measure to predict late toxicity. This review summarizes the published clinical data on the risk of late toxicity as a function of quantitative dose metrics and attempts to offer suggested dose constraints for radiation treatment planning.

The Role of Functional Imaging in the Diagnosis and Management of Late Normal Tissue Injury

Normal tissue injury after radiation therapy (RT) can be defined based on either clinical symptoms or laboratory/radiologic tests. In the research setting, functional imaging (eg, single-photon emission computed tomography [SPECT], positron-emission tomography [PET], and magnetic resonance imaging [MRI]) is useful because it provides objective quantitative data such as metabolic activity, perfusion, and soft-tissue contrast within tissues and organs. For RT-induced lung, heart, and parotid gland injury, pre- and post-RT SPECT images can be compared with the dose- and volume-dependent nature of regional injury. In the brain, SPECT can detect changes in perfusion and blood flow post-RT, and PET can detect metabolic changes, particularly to regions of the brain that have received doses above 40 to 50 Gy. On MRI, changes in contrast-enhanced images, T(1) and T(2) relaxation times, and pulmonary vascular resistance at different intervals pre- and post-RT show its ability to detect and distinguish different phases of radiation pneumonitis. Similarly, conventional and diffusion-weighted MRI can be used to differentiate between normal tissue edema, necrosis, and tumor in the irradiated brain, and magnetic resonance spectroscopy can measure changes in compounds, indicative of membrane and neuron disruption. The use of functional imaging is a powerful tool for early detection of RT-induced normal tissue injury, which may be related to long-term clinically significant injury.

Prospective assessment of dosimetric/physiologic-based models for predicting radiation pneumonitis

PURPOSE

Clinical and 3D dosimetric parameters are associated with symptomatic radiation pneumonitis rates in retrospective studies. Such parameters include: mean lung dose (MLD), radiation (RT) dose to perfused lung (via SPECT), and pre-RT lung function. Based on prior publications, we defined pre-RT criteria hypothesized to be predictive for later development of pneumonitis. We herein prospectively test the predictive abilities of these dosimetric/functional parameters on 2 cohorts of patients from Duke and The Netherlands Cancer Institute (NKI).

METHODS AND MATERIALS

For the Duke cohort, 55 eligible patients treated between 1999 and 2005 on a prospective IRB-approved study to monitor RT-induced lung injury were analyzed. A similar group of patients treated at the NKI between 1996 and 2002 were identified. Patients believed to be at high and low risk for pneumonitis were defined based on: (1) MLD; (2) OpRP (sum of predicted perfusion reduction based on regional dose-response curve); and (3) pre-RT DLCO. All doses reflected tissue density heterogeneity. The rates of grade > or =2 pneumonitis in the "presumed" high and low risk groups were compared using Fisher's exact test.

RESULTS

In the Duke group, pneumonitis rates in patients prospectively deemed to be at "high" vs. "low" risk are 7 of 20 and 9 of 35, respectively; p = 0.33 one-tailed Fisher's. Similarly, comparable rates for the NKI group are 4 of 21 and 6 of 44, respectively, p = 0.41 one-tailed Fisher's.

CONCLUSION

The prospective model appears unable to accurately segregate patients into high vs. low risk groups. However, considered retrospectively, these data are consistent with prior studies suggesting that dosimetric (e.g., MLD) and functional (e.g., PFTs or SPECT) parameters are predictive for RT-induced pneumonitis. Additional work is needed to better identify, and prospectively assess, predictors of RT-induced lung injury.

NTCP modelling and pulmonary function tests evaluation for the prediction of radiation induced pneumonitis in non-small-cell lung cancer radiotherapy

This work aims to evaluate the predictive strength of the relative seriality, parallel and Lyman-Kutcher-Burman (LKB) normal tissue complication probability (NTCP) models regarding the incidence of radiation pneumonitis (RP), in a group of patients following lung cancer radiotherapy and also to examine their correlation with pulmonary function tests (PFTs). The study was based on 47 patients who received radiation therapy for stage III non-small-cell lung cancer. For each patient, lung dose volume histograms (DVHs) and the clinical treatment outcome were available. Clinical symptoms, radiological findings and pulmonary function tests incorporated in a post-treatment follow-up period of 18 months were used to assess the manifestation of radiation induced complications. Thirteen of the 47 patients were scored as having radiation induced pneumonitis, with RTOG criteria grade 3 and 28 of the 47 with RTOG criteria grade 2. Using this material, different methods of estimating the likelihood of radiation effects were evaluated, by analysing patient data based on their full dose distributions and associating the calculated complication rates with the clinical follow-up records. Lungs were evaluated as a paired organ as well as individual lungs. Of the NTCP models examined in the overall group considering the dose distribution in the ipsilateral lung, all models were able to predict radiation induced pneumonitis only in the case of grade 2 radiation pneumonitis score, with the LKB model giving the best results (chi2-test: probability of agreement between the observed and predicted results Pchi(chi2)=0.524 using the 0.05 significance level). The NTCP modelling considering lungs as a paired organ did not give statistically acceptable results. In the case of lung cancer radiotherapy, the application of different published radiobiological parameters alters the NTCP results, but not excessively as in the case of breast cancer radiotherapy. In this relatively small group of lung cancer patients, no positive statistical correlation could be established between the incidence of radiation pneumonitis as estimated by NTCP models and the pulmonary function test evaluation. However, the use of PFTs as markers or predictors for the incidence or severity of radiation induced pneumonitis must be investigated further.

Does transforming growth factor-beta1 predict for radiation-induced pneumonitis in patients treated for lung cancer?

The purpose of the study was to reassess the utility of transforming growth factor-beta-1 (TGF-beta1) together with dosimetric and tumor parameters as a predictor for radiation pneumonitis (RP). Of the 121 patients studied, 32 (26.4%) developed grade > or =1 RP, and 27 (22.3%) developed grade > or =2 RP. For the endpoint of grade > or =1 RP, those with V30>30% and an end-RT/baseline TGF-beta1 ratio> or =1 had a significantly higher incidence of RP than did those with V30>30% and an end-RT/baseline TGF-beta1 ratio<1. For most other patient groups, there were no clear associations between TGF-beta1 values and rates of RP. These findings suggest that TGF-beta1 is generally not predictive for RP except for the group of patients with a high V30.

Changes in pulmonary function after incidental lung irradiation for breast cancer: A prospective study

PURPOSE

The aim of this study was to analyze changes in pulmonary function after radiation therapy (RT) for breast cancer.

METHODS AND MATERIALS

A total of 39 consecutive eligible women, who underwent postoperative irradiation for breast cancer, were entered in the study. Spirometry consisting of forced vital capacity (FVC) and forced expiratory volume in 1 s (FEV1), carbon monoxide diffusing capacity (DLCO), and gammagraphic (ventilation and perfusion) pulmonary function tests (PFT) were performed before RT and 6, 12, and 36 months afterwards. Dose-volume and perfusion-weighted parameters were obtained from 3D dose planning: Percentage of lung volume receiving more than a threshold dose (Vi) and between 2 dose levels (V(i-j)). The impact of clinical and dosimetric parameters on PFT changes (Delta PFT) after RT was evaluated by Pearson correlation coefficients and stepwise lineal regression analysis.

RESULTS

No significant differences on mean PFT basal values (before RT) with respect to age, smoking, or previous chemotherapy (CT) were found. All the PFT decreased at 6 to 12 months. Furthermore FVC, FEV(1), and ventilation recovered almost to their previous values, whereas DLCO and perfusion continued to decrease until 36 months (-3.3% and -6.6%, respectively). Perfusion-weighted and interval-scaled dose-volume parameters (pV(i-j)) showed better correlation with Delta PFT (only Delta perfusion reached statistically significance at 36 months). Multivariate analysis showed a significant relation between pV(10-20) and Delta perfusion at 3 years, with a multiple correlation coefficient of 0.48. There were no significant differences related to age, previous chemotherapy, concurrent tamoxifen and smoking, although a tendency toward more perfusion reduction in older and nonsmoker patients was seen.

CONCLUSIONS

Changes in FVC, FEV1 and ventilation were reversible, but not the perfusion and DLCO. We have not found a conclusive mathematical predictive model, provided that the best model only explained 48% of the variability. We suggest the use of dose-perfused volume and interval-scaled parameters (i.e., pV(10-20)) for further studies.

Dynamic ventilation imaging from four-dimensional computed tomography

A novel method for dynamic ventilation imaging of the full respiratory cycle from four-dimensional computed tomography (4D CT) acquired without added contrast is presented. Three cases with 4D CT images obtained with respiratory gated acquisition for radiotherapy treatment planning were selected. Each of the 4D CT data sets was acquired during resting tidal breathing. A deformable image registration algorithm mapped each (voxel) corresponding tissue element across the 4D CT data set. From local average CT values, the change in fraction of air per voxel (i.e. local ventilation) was calculated. A 4D ventilation image set was calculated using pairs formed with the maximum expiration image volume, first the exhalation then the inhalation phases representing a complete breath cycle. A preliminary validation using manually determined lung volumes was performed. The calculated total ventilation was compared to the change in contoured lung volumes between the CT pairs (measured volume). A linear regression resulted in a slope of 1.01 and a correlation coefficient of 0.984 for the ventilation images. The spatial distribution of ventilation was found to be case specific and a 30% difference in mass-specific ventilation between the lower and upper lung halves was found. These images may be useful in radiotherapy planning.

Attempts to predict the long-term decrease in lung function due to radiotherapy of non-small cell lung cancer

PURPOSE

To obtain a model which can predict long-term decrease in lung function due to radiation damage from dose-volume data for patients with non-small cell lung cancer.

PATIENTS AND METHODS

27 patients were included, all long-term survivors after radical radiation therapy. For each patient a regression analysis was performed on a post-RT succession of measurements of FEV1 in order to estimate the decrease after 2 years and a standard error (SE) on this regression estimate. The modelling was based on dose-volume histograms (DVH) exported from the treatment planning system, and involved fits of threshold models, a mean lung dose model as well as more complex models based on the relative damaged volume (rdV).

RESULTS

Decreases after 2 years of up to 28% in FEV1 was measured (median 10%), with significant day-to-day variation in FEV1 for the individual patient. The threshold models predicted the long-term decrease in FEV1 well when the SE was interpreted as the uncertainty of the measured decrease. The best threshold value, marginally, was 30 Gy with an R(2) of 0.46. The mean lung dose model did not perform so well. A complex model based on rdV performed better than any of the other models (R(2)=0.52).

CONCLUSION

The long-term decrease in FEV1 could be predicted from a simple dose-volume model when the SE was interpreted as the uncertainty of the measured decrease.

The impact of pre-radiotherapy surgery on radiation-induced lung injury

AIMS

The use of postoperative radiation therapy (PORT) is predicated by an assessment of the potential benefits and risks, including radiation-induced lung injury. In this study, the risk of radiation-induced lung injury is assessed in patients who received PORT, and compared with a group of patients who received radiation without prior surgery, to determine if surgery increases the risk of radiation pneumonitis.

MATERIALS AND METHODS

From 1991 to 2003, 251 patients with lung cancer were enrolled into a prospective study to assess radiation-induced lung injury. All patients received three-dimensional-planned, external-beam radiotherapy. One hundred and seventy-seven patients with over 6-months follow-up were eligible. For the current analysis, 49 patients (28%) had surgical intervention before radiotherapy. The rates of Grade 2 symptomatic pneumonitis in subgroups, based on the type of pre-radiation surgery, were computed and compared using Fisher's Exact Test. To consider the confounding factor of irradiated lung volume, patient subgroups were further defined on the basis of the mean lung dose.

RESULTS

Surgical procedures included pneumonectomy (n=9), lobectomy (n=16), wedge resection (n=8) and exploration without resection (n=16). Radiation-induced lung injury occurred in 33 out of 177 (19%) patients, including 18% of the surgical group and 19% of the non-surgical group. Additionally, no statistically significant difference was found in the rate of radiation-induced lung injury based on the extent of resection.

CONCLUSIONS

The incidence of pneumonitis is similar in the surgical and non-surgical groups. Thus, PORT may be safely given to selected patients after surgical exploration or resection.

Pulmonary toxicity associated with the treatment of non-small cell lung cancer and the effects of cytoprotective strategies

Concurrent chemoradiation regimens for the treatment of non-small cell lung cancer have resulted in improved treatment outcomes. However, they are also more toxic. Acute esophagitis and pneumonitis are experienced by a large number of treated patients. Cytoprotective agents are used to reduce treatment-related toxicity. The cytoprotectant amifostine has been shown to reduce some of the toxicity associated with concurrent chemoradiation. Clinical studies of its role in reducing esophagitis and radiation pneumonitis are discussed. Lung irradiation also leads to a reduction in lung diffusion capacity (DLCO). The magnitude of this reduction is related to the volume of lung irradiated as well as to the use and timing of chemotherapy. Concurrent chemoradiation regimens result in a larger reduction in DLCO than radiation alone. Small changes in DLCO can be detected with sensitive pulmonary function tests, but are subclinical. Larger reductions in DLCO correlate with significant clinical symptoms. Preliminary data show that amifostine can significantly decrease the treatment-related reduction in DLCO associated with concurrent chemoradiation (42% v 24%; P = .004). Additional studies are being designed to verify these results and to further define the evolving role of cytoprotection in cancer care.

Challenges in defining radiation pneumonitis in patients with lung cancer

PURPOSE

To assess the difficulty of assigning a definitive clinical diagnosis of radiation (RT)-induced lung injury in patients irradiated for lung cancer.

METHODS

Between 1991 and 2003, 318 patients were enrolled in a prospective study to evaluate RT-induced lung injury. Only patients with lung cancer who had a longer than 6-month follow-up (251 patients) were considered in the current analysis. Of these, 47 of 251 patients had Grade >/=2 (treated with steroids) increasing shortness of breath after RT, thought possibly consistent with pneumonitis/fibrosis. The treating physician, and one to three additional reviewing physicians, evaluated the patients or their medical records, or both. The presence or absence of confounding clinical factors that made the diagnosis of RT-induced uncertain lung injury were recorded.

RESULTS

Thirty-one of 47 patients (66%) with shortness of breath had "classic" pneumonitis, i.e., they responded to steroids and had a definitive diagnosis of pneumonitis. In 13 of 47 patients (28%), the diagnosis of RT-induced toxicity was confounded by possible infection; exacerbation of preexisting lung disease (chronic obstructive pulmonary disease); tumor regrowth/progression; and cardiac disease in 6, 8, 5, and 1 patients, respectively (some of the patients had multiple confounding factors and were counted more than once). An additional 3 patients (6%) had progressive shortness of breath and an overall clinical course more consistent with fibrosis. All 3 had evidence of bronchial stenosis by bronchoscopy.

CONCLUSIONS

Scoring of radiation pneumonitis was challenging in 28% of patients treated for lung cancer owing to confounding medical conditions. Recognition of this uncertainty is needed and may limit our ability to understand RT-induced lung injury.