Radiation-induced pulmonary injury: symptomatic versus subclinical endpoints

Anatomy-wise lung ventilation imaging for precise functional lung avoidance radiation therapy

Objective.This study aimed to propose a method for obtaining anatomy-wise lung ventilation image (VIaw) that enables functional assessment of lung parenchyma and tumor-blocked pulmonary segments. The VIawwas used to define multiple functional volumes of the lung and thereby support radiation treatment planning.Approach.A super-voxel-based method was employed for functional assessment of lung parenchyma to generate VIsvd. In the VIsvdof the 11 patients with tumor blockage of the airway, the functional value in tumor-blocked segments was set to 0 to generate the VIaw. The lung was divided into regions of high functional volume (HFV), unrecoverable low functional volume (LFV), and recoverable LFV (rLFV, the region in the tumor-blocked segment with a high function value based on the VIsvd) to design three intensity-modulated photon plans for five patients. These plans were an anatomical-lung-guided plan (aPlan), a functional-lung-guided plan (fPlan), and a recoverable functional-lung-guided plan (rfPlan) where the latter protected both HFV and rLFV.Main results.The LFV in the reference ventilation images and the tumor-blocked segments had a high overlap similarity coefficient value of 0.90 ± 0.07. The mean Spearman correlation between the VIawand reference ventilation images was 0.72 ± 0.05 for the patient with tumor blockage of the airway. TheV20 and mean dose of rLFV in rfPlan were lower than those in aPlan by 12.1 ± 8.4% and 13.0 ± 6.4%, respectively, and lower than those in fPlan by 14.9 ± 9.8% and 15.9 ± 6.5%, respectively.Significance.The VIawcan reach a moderate-strong correlation with reference ventilation images and thus can identify rLFV to support treatment planning to preserve lung function.

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.

Evaluation of the relationship between the range of radiation-induced lung injury on CT images after IMRT for stage I lung cancer and dosimetric parameters

BACKGROUND

This study evaluated the correlation between radiation-induced lung injury (RILI) and dosimetric parameters on computed tomography (CT) images of stage I non-small cell lung cancer (NSCLC) patients undergoing intensity-modulated radiotherapy (IMRT).

MATERIALS AND METHODS

Sixty-three stage I NSLC patients who underwent IMRT were enrolled in the study. The patients underwent CT within 6 months (acute phase) and 1.5 years (late phase) after radiotherapy. These were fused with the planned irradiation CT. The range of RILI was measured from 10% to 100%, with an IC in 10% increments.

RESULTS

The median interval from completion of radiotherapy to acute and late phase CT was 92 and 440 days, respectively. The median RILI ranges of the acute and late phases were in the 80% (20-100%) and 70% dose regions (20-100%), respectively. The significantly narrower range of RILI when lung V20 in the acute phase was less than 19.2% and that of V5 in the late phase was less than 27.6% at the time of treatment planning.

CONCLUSIONS

This study showed that RILI occurred in a localized range in stage I NSCLC patients who underwent IMRT. The range of RILI was correlated with V20 in the acute phase and V5 in the late phase. KEY MESSAGES RILI correlated with V20 in acute and V5 in late phase. The shadow of RILI occurred in 80% dose region in acute and 70% in late phase. No relationship exists between radiographic changes in RILI and PTV volume.

A multichannel feature-based approach for longitudinal lung CT registration in the presence of radiation induced lung damage

Quantifying parenchymal tissue changes in the lungs is imperative in furthering the study of radiation induced lung damage (RILD). Registering lung images from different time-points is a key step of this process. Traditional intensity-based registration approaches fail this task due to the considerable anatomical changes that occur between timepoints. This work proposes a novel method to successfully register longitudinal pre- and post-radiotherapy (RT) lung computed tomography (CT) scans that exhibit large changes due to RILD, by extracting consistent anatomical features from CT (lung boundaries, main airways, vessels) and using these features to optimise the registrations. Pre-RT and 12 month post-RT CT pairs from fifteen lung cancer patients were used for this study, all with varying degrees of RILD, ranging from mild parenchymal change to extensive consolidation and collapse. For each CT, signed distance transforms from segmentations of the lungs and main airways were generated, and the Frangi vesselness map was calculated. These were concatenated into multi-channel images and diffeomorphic multichannel registration was performed for each image pair using NiftyReg. Traditional intensity-based registrations were also performed for comparison purposes. For the evaluation, the pre- and post-registration landmark distance was calculated for all patients, using an average of 44 manually identified landmark pairs per patient. The mean (standard deviation) distance for all datasets decreased from 15.95 (8.09) mm pre-registration to 4.56 (5.70) mm post-registration, compared to 7.90 (8.97) mm for the intensity-based registrations. Qualitative improvements in image alignment were observed for all patient datasets. For four representative subjects, registrations were performed for three additional follow-up timepoints up to 48 months post-RT and similar accuracy was achieved. We have demonstrated that our novel multichannel registration method can successfully align longitudinal scans from RILD patients in the presence of large anatomical changes such as consolidation and atelectasis, outperforming the traditional registration approach both quantitatively and through thorough visual inspection.

A Trans-Agency Workshop on the Pathophysiology of Radiation-Induced Lung Injury

Research and development of medical countermeasures (MCMs) for radiation-induced lung injury relies on the availability of animal models with well-characterized pathophysiology, allowing effective bridging to humans. To develop useful animal models, it is important to understand the clinical condition, advantages and limitations of individual models, and how to properly apply these models to demonstrate MCM efficacy. On March 20, 2019, a meeting sponsored by the Radiation and Nuclear Countermeasures Program (RNCP) within the National Institute of Allergy and Infectious Diseases (NIAID) brought together medical, scientific and regulatory communities, including academic and industry subject matter experts, and government stakeholders from the Food and Drug Administration (FDA) and the Biomedical Advanced Research and Development Authority (BARDA), to identify critical research gaps, discuss current clinical practices for various forms of pulmonary damage, and consider available animal models for radiation-induced lung injury.

High-dose thoracic radiation therapy for non-small cell lung cancer: a novel grading scale of radiation-induced lung injury for symptomatic radiation pneumonitis

Background

Symptomatic radiation pneumonitis (RP) may be a serious complication after thoracic radiation therapy (RT) for non-small cell lung cancer (NSCLC). This prospective observational study sought to evaluate the utility of a novel radiation-induced lung injury (RILI) grading scale (RGS) for the prediction of RP.

Materials and methods

Data of 41 patients with NSCLC treated with thoracic RT of 60–66 Gy were analysed. CT scans were scheduled before RT, one month post-RT, and every three months thereafter for one year. Symptomatic RP was defined as Common Terminology Criteria for Adverse Events grade ≥ 2. RGS grading ranged from 0 to 3. The inter-observer variability of the RGS was assessed by four senior radiologists. CT scans performed 28 ± 10 days after RT were used to analyse the predictive value of the RGS. The change in the RGS severity was correlated to dosimetric parameters.

Results

The CT obtained one month post-RT showed RILI in 36 (88%) of patients (RGS grade 0 [5 patients], 1 [25 patients], 2 [6 patients], and 3 [5 patients]). The inter-observer agreement of the RGS grading was high (Kendall’s W coefficient of concordance = 0.80, p < 0.01). Patients with RGS grades 2–3 had a significantly higher risk for development of RP (relative risk (RR): 2.4, 95% CI 1.6–3.7, p < 0.01) and RP symptoms within 8 weeks after RT (RR: 4.8, 95% CI 1.3–17.6, p < 0.01) compared to RGS grades 0–1. The specificity and sensitivity of the RGS grades 2–3 in predicting symptomatic RP was 100% (95% CI 80.5–100%) and 45.4% (95% CI 24.4–67.8%), respectively. Increase in RGS severity correlated to mean lung dose and the percentage of the total lung volume receiving 5 Gy.

Conclusions

The RGS is a simple radiologic tool associated with symptomatic RP. A validation study is warranted.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13014-021-01857-8.

Phase II Trial of Flaxseed to Prevent Acute Complications After Chemoradiation for Lung Cancer

Background: Thoracic radiotherapy is complicated by acute radiation-induced adverse events such as radiation pneumonitis (RP) and radiation esophagitis (RE). Based on preclinical work and a randomized pilot trial from our laboratory, this single-arm phase II trial investigated administering flaxseed as a radioprotector in patients receiving definitive chemoradiation for nonsmall cell lung cancer (NSCLC). Methods: Between June 2015 and February 2018, 33 patients with locally advanced or metastatic NSCLC with planned definitive chemoradiation were enrolled. Finely-ground Linum usitatissimum L. (Linaceae; flaxseed or linseed) in 40-g packets were provided for daily consumption in any patient-desired formulation 1 week before radiotherapy and throughout radiotherapy as tolerated. The primary outcomes were overall adverse events, with particular focus on Grade ≥3 RP, and flaxseed tolerability. Adverse events were graded according to CTCAE v4.0. Results: Of the 33 patients enrolled, 5 patients (15%) did not receive chemoradiation, 4 (12%) withdrew promptly after enrollment, 4 (12%) did not return a flaxseed consumption log, and 1 patient had irritable bowel syndrome (3%). The remaining 19 patients (57%) had chemoradiation and flaxseed ingestion with a mean completion and standard deviation of the intended flaxseed course of 62% ± 8.3%. Nine (50%) of these 19 patients reported difficulties with flaxseed consumption, citing nausea, constipation, odynophagia, or poor taste or texture. One patient (5%), with unverifiable flaxseed consumption, developed Grade 3 RP. There were no cases of Grade 2 RP. Six patients (32%) developed Grade 2 RE, but no patients developed Grade ≥3 RE. Median overall and progression-free survival were 31 and 12 months, respectively. Conclusions: Despite the low incidence of acute radiation-induced complications reported, significant treatment-related gastrointestinal toxicities and subsequently low flaxseed tolerability inhibit accurate determination of flaxseed effect in patients receiving concurrent thoracic chemoradiation. Thus, further investigations should focus on optimizing flaxseed formulation for improved tolerability and evaluation. CTR #: NCT02475330, https://clinicaltrials.gov/ct2/show/study/NCT02475330.

Investigation of the evolution of radiation-induced lung damage using serial CT imaging and pulmonary function tests

BACKGROUND AND PURPOSE

Radiation-induced lung damage (RILD) is a common consequence of lung cancer radiotherapy (RT) with unclear evolution over time. We quantify radiological RILD longitudinally and correlate it with dosimetry and respiratory morbidity.

MATERIALS AND METHODS

CTs were available pre-RT and at 3, 6, 12 and 24-months post-RT for forty-five subjects enrolled in a phase 1/2 clinical trial of isotoxic, dose-escalated chemoradiotherapy for locally advanced non-small cell lung cancer. Fifteen CT-based measures of parenchymal, pleural and lung volume change, and anatomical distortions, were calculated. Respiratory morbidity was assessed with the Medical Research Council (MRC) dyspnoea score and spirometric pulmonary function tests (PFTs): FVC, FEV1, FEV1/FVC and DLCO.

RESULTS

FEV1, FEV1/FVC and MRC scores progressively declined post-RT; FVC decreased by 6-months before partially recovering. Radiologically, an early phase (3-6 months) of acute inflammation was characterised by reversible parenchymal change and non-progressive anatomical distortion. A phase of chronic scarring followed (6-24 months) with irreversible parenchymal change, progressive volume loss and anatomical distortion. Post-RT increase in contralateral lung volume was common. Normal lung volume shrinkage correlated longitudinally with mean lung dose (r = 0.30-0.40, p = 0.01-0.04). Radiological findings allowed separation of patients with predominant acute versus chronic RILD; subjects with predominantly chronic RILD had poorer pre-RT lung function.

CONCLUSIONS

CT-based measures enable detailed quantification of the longitudinal evolution of RILD. The majority of patients developed progressive lung damage, even when the early phase was absent or mild. Pre-RT lung function and RT dosimetry may allow to identify subjects at increased risk of RILD.

Pulmonary function decreases moderately after accelerated high-dose irradiation for stage III non-small cell lung cancer

Background

Chemoradiotherapy (CRT) is the standard treatment for patients with inoperable stage III non‐small cell lung cancer (NSCLC) stage III. With a median OS beyond 30 months, adequate pulmonary function (PF) is essential to ensure acceptable quality of life after treatment. Forced expiratory volume in 1 second (FEV1) and diffusing capacity of the lung for carbon monoxide (DLCO) are the most widely used parameters to assess lung function. The aim of the current study was to evaluate dose‐volume effects of accelerated high‐dose radiation on PF.

Methods

A total of 72 patients were eligible for the current analysis. After induction chemotherapy, all patients received dose‐differentiated accelerated radiotherapy with intensity‐modulated radiotherapy (IMRT‐DART). PF tests were performed six weeks, three and six months after the end of radiotherapy.

Results

The median total dose to the tumor was 73.8 Gy (1.8 Gy bid) with a size dependent range between 61.2 and 90 Gy. In the whole cohort, 321 pulmonary function tests were performed. At six months, the median FEV1 relative to baseline was 0.95 (range: 0.56–1.36), and the relative median DLCO decreased to 0.98 (range: 0.64–1.50). The correlation between V20_{total lung} and FEV1 decline was statistically significant (P = 0.023). A total of 13 of 34 (38%) COPD patients had a 4%–21% FEV1 decrease.

Conclusion

Patients with a V20_{total lung} < 21% are at a low risk for PF decrease after high dose irradiation treatment. Although overall short term FEV1 and DLCO differ only moderately from baseline these changes may be clinically important, especially in patients with COPD.

Key points

Significant findings:

Pulmonary function after high dose irradiation decreases only moderately.

FEV1 and DLCO decrease depend on V20_{total lung}.

Small differences in lung function may be clinically important for COPD patients.

KPS predicts minimal clinically important differences (MCID).

What this study adds:

This study shows that high‐dose irradiation delivered with intensity‐modulated techniques does not impair short‐term lung function even in patients with compromised respiratory capacity before treatment. This is a pre‐requisite for adequate quality of life after thoraco‐oncological therapy.

Fractional exhaled nitric oxide as a potential biomarker for radiation pneumonitis in patients with non-small cell lung cancer: A pilot study

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Weekly FeNO during radiotherapy can be useful in predicting radiation pneumonitis.

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6 months of clinical follow-up is necessary to detect delayed radiation pneumonitis.

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Pulmonary function tests are not predictable for radiation pneumonitis.

Introduction

The aim of the study was to investigate repetitive fractional exhaled nitric oxide (FeNO) measurements during high-dose radiation therapy (HDRT) and to evaluate the use of FeNO to predict symptomatic radiation pneumonitis (RP) in patients being treated for non-small cell lung cancer (NSCLC).

Materials and methods

A total of 50 patients with NSCLC referred for HDRT were enrolled. FeNO was measured at baseline, weekly during HDRT, one month- and every third month after HDRT for a one-year follow-up period. The mean FeNO_{(visit 0-6)} was calculated using the arithmetic mean of the baseline and weekly measurements during HDRT. Patients with grade ≥ 2 of RP according to the Common Terminology Criteria for Adverse Events (CTCAE) were considered symptomatic.

Results

A total of 42 patients completed HDRT and weekly FeNO measurements. Grade ≥ 2 of RP was diagnosed in 24 (57%) patients. The mean FeNO_{(visit 0-6)} ± standard deviation in patients with and without RP was 15.0 ± 7.1 ppb (95%CI: 12.0–18.0) and 10.3 ± 3.4 ppb (95%CI: 8.6–11.9) respectively with significant differences between the groups (p = 0.0169, 95%CI: 2.3–2.6). The leave-one-out cross-validated cut-off value of the mean FeNO_{(visit 0-6)} ≥ 14.8 ppb was predictive of grade ≥ 2 RP with a specificity of 71% and a positive predictive value of 78%.

Conclusions

The mean FeNO_{(visit 0-6)} in patients with symptomatic RP after HDRT for NSCLC was significantly higher than in patients without RP and may serve as a potential biomarker for RP.

LGM2605 Reduces Space Radiation-Induced NLRP3 Inflammasome Activation and Damage in In Vitro Lung Vascular Networks

Updated measurements of charged particle fluxes during the transit from Earth to Mars as well as on site measurements by Curiosity of Martian surface radiation fluxes identified potential health hazards associated with radiation exposure for human space missions. Designing mitigation strategies of radiation risks to astronauts is critical. We investigated radiation-induced endothelial cell damage and its mitigation by LGM2605, a radioprotector with antioxidant and free radical scavenging properties. We used an in vitro model of lung vascular networks (flow-adapted endothelial cells; FAECs), exposed to gamma rays, low/higher linear energy transfer (LET) protons (3⁻4 or 8⁻10 keV/µm, respectively), and mixed field radiation sources (gamma and protons), given at mission-relevant doses (0.25 gray (Gy)⁻1 Gy). We evaluated endothelial inflammatory phenotype, NLRP3 inflammasome activation, and oxidative cell injury. LGM2605 (100 µM) was added 30 min post radiation exposure and gene expression changes evaluated 24 h later. Radiation induced a robust increase in mRNA levels of antioxidant enzymes post 0.25 Gy and 0.5 Gy gamma radiation, which was significantly decreased by LGM2605. Intercellular cell adhesion molecule-1 (ICAM-1) and NOD-like receptor protein 3 (NLRP3) induction by individual or mixed-field exposures were also significantly blunted by LGM2605. We conclude that LGM2605 is a likely candidate to reduce tissue damage from space-relevant radiation exposure.

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.

Time and dose-related changes in lung perfusion after definitive radiotherapy for NSCLC

BACKGROUND AND PURPOSE

To examine radiation-induced changes in regional lung perfusion per dose level in 58 non-small-cell lung cancer (NSCLC) patients treated with intensity-modulated radiotherapy (IMRT).

MATERIAL AND METHODS

NSCLC patients receiving chemo-radiotherapy (RT) of minimum 60 Gy were included prospectively in the study. Lung perfusion single-photon emission computed tomography (SPECT/CT) was performed before and serially after RT. Changes (relative to baseline, %) in regional lung perfusion were correlated with regional dose. Toxicity outcome was radiation pneumonitis (RP) CTC grades 2-5.

RESULTS

Perfusion changes were associated with dose. Dose-dependent reduction in regional perfusion was observed at 3, 6 and 12 months of follow-up. Relative perfusion loss per dose bin was 4% at 1 month, 14% at 3 months, 13% at 6 months and 21% at 12 months after RT. In patients with RP, perfusion reduction was larger in high dose lung regions, compared to those without RP. Low dose regions, on the contrary, revealed perfusion gain in the patients with RP.

CONCLUSION

Progressive dose dependent perfusion loss is manifested on SPECT up to 12 months following IMRT. These findings suggest that the dynamic change in perfusion may have prognostic value in predicting radiation pneumonitis in NSCLC patients treated with IMRT.

Anatomic, functional and molecular imaging in lung cancer precision radiation therapy: treatment response assessment and radiation therapy personalization

This article reviews key imaging modalities for lung cancer patients treated with radiation therapy (RT) and considers their actual or potential contributions to critical decision-making. An international group of researchers with expertise in imaging in lung cancer patients treated with RT considered the relevant literature on modalities, including computed tomography (CT), magnetic resonance imaging (MRI) and positron emission tomography (PET). These perspectives were coordinated to summarize the current status of imaging in lung cancer and flag developments with future implications. Although there are no useful randomized trials of different imaging modalities in lung cancer, multiple prospective studies indicate that management decisions are frequently impacted by the use of complementary imaging modalities, leading both to more appropriate treatments and better outcomes. This is especially true of ¹⁸F-fluoro-deoxyglucose (FDG)-PET/CT which is widely accepted to be the standard imaging modality for staging of lung cancer patients, for selection for potentially curative RT and for treatment planning. PET is also more accurate than CT for predicting survival after RT. PET imaging during RT is also correlated with survival and makes response-adapted therapies possible. PET tracers other than FDG have potential for imaging important biological process in tumors, including hypoxia and proliferation. MRI has superior accuracy in soft tissue imaging and the MRI Linac is a rapidly developing technology with great potential for online monitoring and modification of treatment. The role of imaging in RT-treated lung cancer patients is evolving rapidly and will allow increasing personalization of therapy according to the biology of both the tumor and dose limiting normal tissues.

Quantitatively Excessive Normal Tissue Toxicity and Poor Target Coverage in Postoperative Lung Cancer Radiotherapy Meta-analysis

BACKGROUND

A previous meta-analysis (MA) found postoperative radiotherapy (PORT) in lung cancer patients to be detrimental in N0/N1 patients and equivocal in the N2 setting. We hypothesized that treatment plans generated using MA protocols had worse dosimetric outcomes compared to modern plans.

PATIENTS AND METHODS

We retrieved plans for 13 patients who received PORT with modern planning. A plan was recreated for each patient using the 8 protocols included in MA. Dosimetric values were then compared between the modern and simulated MA plans.

RESULTS

A total of 104 MA plans were generated. Median prescribed dose was 50.4 (range, 50-60) Gy in the modern plans and 53.2 (30-60) Gy in the MA protocols. Median planning volume coverage was 96% (93%-100%) in the modern plans, versus 58% (0%-100%) in the MA plans (P < .001). Internal target volume coverage was 100% (99%-100%) versus 65% (0%-100%), respectively (P < .001). Organs at risk received the following doses: spinal cord maximum dose, 36.8 (4.6-50.4) Gy versus 46.8 (2.9-74.0) Gy (P < .001); esophageal mean dose, 22.9 (5.5-35) Gy versus 30.5 (11.1-52.5) Gy (P = .003); heart V30 (percentage of volume of an organ receiving at least a dose of 30 Gy), 16% (0%-45%) versus 35% (0%-79%) (P = .047); mean lung dose, 12.4 (3.4-24.3) Gy versus 14.8 (4.1-27.4) Gy (P = .008); and lung V20, 18% (4%-34%) versus 25% (8%-67%) (P = .023).

CONCLUSION

We quantitatively confirm the inferiority of the techniques used in the PORT MA. Our analysis showed a lower therapeutic ratio in the MA plans, which may explain the poor outcomes in the MA. The findings of the MA are not relevant in the era of modern treatment planning.

Pulmonary Function Changes After Radiotherapy for Lung or Esophageal Cancer: A Systematic Review Focusing on Dose-Volume Parameters

BACKGROUND

Despite technical developments in treatment delivery, radiation-induced lung toxicity (RILT) remains a crucial problem in thoracic radiotherapy. Clinically based RILT scores have their limitations, and more objective measures such as pulmonary functions tests (PFTs) might help to improve treatment strategies.

PURPOSE

To summarize the available evidence about the effect of dose to the lung in thoracic radiotherapy on forced expiratory volume in one second (FEV1) and diffusion capacity (DLCO) in patients with lung and esophageal cancer treated with curative intent.

MATERIAL AND METHODS

A systematic review following the PRISMA guidelines was performed, using MEDLINE and including clinical studies using (chemo)radiotherapy (CRT) or stereotactic ablative radiotherapy (SABR) for lung or CRT for esophageal cancer that reported both lung dose-volume histogram (DVH) parameters and changes in PFT results. Search terms included lung and esophageal neoplasms, respiratory function tests, and radiotherapy.

RESULTS

Fifteen studies met the inclusion criteria. Seven out of 13 studies on lung cancer reported significant declines (defined as a p value < .05) in PFT results. Both esophageal studies reported significant DLCO declines. One SABR study found a correlation between low lung-dose parameters and FEV1 decline. Relations between decline of FEV1 (three studies) or decline of DLCO (five studies), respectively, and DVH parameters were found in eight studies analyzing CRT. Furthermore, a heterogeneous range of clinical risk factors for pulmonary function changes were reported in the selected studies.

CONCLUSIONS

There is evidence that pulmonary function declines after RT in a dose-dependent manner, but solid data about lung DVH parameters predicting changes in PFT results are scarce. A major disadvantage was the wide variety of methods used, frequently lacking multivariable analyses. Studies using prospective high-quality data, analyzed with appropriate statistical methods, are needed. The Oncologist 2017;22:1257-1264 IMPLICATIONS FOR PRACTICE: Radiation-induced lung toxicity remains crucial in thoracic radiotherapy. To prevent this toxicity in the future and individualize patient treatment, objective measures of pulmonary toxicity are needed. Pulmonary function tests may provide such objective measures. This systematic review, included all available clinical studies using external beam radiotherapy for lung or esophageal cancer reporting pulmonary function combined with dose-volume histogram parameters. There is preliminary evidence that pulmonary function declines post radiotherapy in a dose-dependent manner. Data quality and analyses were generally limited. Analyses of high-quality data are therefore urgently needed to improve individualization of advanced radiation therapy.

Pulmonary toxicity generated from radiotherapeutic treatment of thoracic malignancies

Radiation-induced lung injury (RILI) remains a major obstacle for thoracic radiotherapy for the treatment of lung cancer, esophageal cancer and lymphoma. It is the principal dose-limiting complication, and can markedly impair the therapeutic ratio as well as a patient's quality of life. The current review presents the relevant concepts associated with RILI, including the pathogenic mechanisms and the potential treatment strategies, so as to achieve a general understanding of this issue. RILI comprises an acute radiation pneumonitis phase and subsequent late lung fibrosis. The established assessment criteria are clinical manifestations, imaging changes and the necessity for medical assistance. Risk factors are also considered in order to optimize treatment planning. Due to the underlying molecular mechanisms of RILI, the present review also discusses several targeted pharmacological approaches for its treatment, as well as corticosteroid therapy.

Gene expression profiles among murine strains segregate with distinct differences in the progression of radiation-induced lung disease

Molecular mechanisms underlying development of acute pneumonitis and/or late fibrosis following thoracic irradiation remain poorly understood. Here, we hypothesize that heterogeneity in disease progression and phenotypic expression of radiation-induced lung disease (RILD) across murine strains presents an opportunity to better elucidate mechanisms driving tissue response toward pneumonitis and/or fibrosis. Distinct differences in disease progression were observed in age- and sex-matched CBA/J, C57L/J and C57BL/6J mice over 1 year after graded doses of whole-thorax lung irradiation (WTLI). Separately, comparison of gene expression profiles in lung tissue 24 h post-exposure demonstrated >5000 genes to be differentially expressed (P<0.01; >twofold change) between strains with early versus late onset of disease. An immediate divergence in early tissue response between radiation-sensitive and -resistant strains was observed. In pneumonitis-prone C57L/J mice, differentially expressed genes were enriched in proinflammatory pathways, whereas in fibrosis-prone C57BL/6J mice, genes were enriched in pathways involved in purine and pyrimidine synthesis, DNA replication and cell division. At 24 h post-WTLI, different patterns of cellular damage were observed at the ultrastructural level among strains but microscopic damage was not yet evident under light microscopy. These data point toward a fundamental difference in patterns of early pulmonary tissue response to WTLI, consistent with the macroscopic expression of injury manifesting weeks to months after exposure. Understanding the mechanisms underlying development of RILD might lead to more rational selection of therapeutic interventions to mitigate healthy tissue damage.

Summary: Rational mouse model selection is crucial for identifying new therapeutic targets and screening medical interventions in acute pneumonitis and/or late fibrosis following thoracic irradiation.

Effects of Definitive Chemoradiotherapy on Respiratory Function Tests and Quality of Life Scores During Treatment of Lung Cancer

BACKGROUND

Chemoradiotherapy is an important treatment modality for lung cancers. The aim of this study was to investigate alterations in, as well as the interrelationship between, lung function and quality of life of patients receiving chemoradiotherapy due to locally advanced non-small cell lung cancer (NSCLC) and small cell lung cancer (SCLC) limited to the thorax.

MATERIALS AND METHODS

The study included patients receiving definitive chemoradiotherapy for lung carcinoma. The respiratory function of the patients was assessed by measuring forced expiratory volume in 1 s per unit (FEV1) and forced expiratory volume in 1s per unit of vital capacity (FEV1/VC) before, in the middle of and after treatment. During the study, EORTC QLQ C30 and LC13 questionnaires developed by the Committee of the European Organization for Research and Treatment of Cancer (EORTC) were employed to evaluate the quality of life on the same day as respiratory function tests (RFT).

FINDINGS

The study included 23 patients in total: 19 (82.6%) diagnosed with NSCLC and 4 (17.4%) with SCLC. The average percentage FEV1 was 55.6±21.8% in the pre-treatment period, 56.2±19.2% in the middle of treatment and 60.4±22% at the end of treatment. The improvement in functional scores, symptom scores and general health scores during treatment was not statistically significant (P=0.568, P=0.734, P=0.680, P=0.757 respectively).

CONCLUSIONS

Although this study showed an improvement in respiratory function and quality of life of patients during treatment with thoracic chemoradiotherapy, no statistically significant results were obtained. While evaluating the effectiveness of treatments for lung carcinoma, the effects of treatment on respiratory function and quality of life should be considered.

Changes in pulmonary function after definitive radiotherapy for NSCLC

INTRODUCTION

The objective of this study was to identify factors associated with early and long-term pulmonary function (PF) changes after definitive radiotherapy for NSCLC patients. PF was measured by spirometry i.e. forced expiratory volume in 1s (FEV1), and forced vital capacity (FVC).

MATERIALS

Early (within the first year) PF change was analyzed in 211 patients with 986 pairs of PF-tests (PFTs). Long-term PF change was analyzed relative to the PF at 12months after radiotherapy in 106 patients (1286 PFTs). To investigate the impact of patient and treatment related factors on PF, they were tested as covariates in multivariable analysis.

RESULTS

Early PF change was quantified at six months after the start of radiotherapy. Smoking status and increasing V60 was associated with a significant decrease in PF, whereas smoking was protective. In addition, neoadjuvant chemotherapy had a negative impact on FVC. Long-term FEV1 and FVC were analyzed using linear regression. Treatment year and V60 had a significant impact on loss of FEV1. V60 had a significant impact on FVC changes.

CONCLUSION

In this study, early PF change reached a plateau at 6months after the start of radiotherapy for NSCLC. Large volume of lung receiving high dose was associated with long-term FEV1 change.

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.

Radiation Pneumonitis After Conventional Radiotherapy For Breast Cancer: A Prospective Study

BACKGROUND

Loco-regional radiotherapy is an important treatment modality in breast cancer and radiation pneumonitis (RP) is one of the early toxicities.

AIM

To study the occurrence, correlation of RP with patient and radiotherapy related factors and the effects on pulmonary function following conventional radiotherapy in breast cancer.

SETTINGS AND DESIGN

Prospective study, from a tertiary hospital in a developing country.

MATERIALS AND METHODS

Prospective analysis of clinical symptoms, pulmonary function and radiologic changes was done prior to and 12 weeks after adjuvant radiotherapy (n=46). Statistical analysis was done using SPSS version 10 software.

RESULTS

Radiological and clinical RP was seen in 45.65% (n=21) and 19.56% (n=9) respectively. RP was significantly higher with age >50 years (OR 4.4), chest wall irradiation with electrons, (electrons 83.3% vs cobalt60 32.4%, p=0.02) and supraclavicular field treatment with 6 MV photons (p= 0.011). There was significant relationship between Inferior Lung Distance (ILD) and RP (p=0.013). The fall in Total Lung Capacity (TLC) was significantly more in those with RP (p=0.02).

CONCLUSION

Clinical RP occurs in almost one-fifth of breast cancer patients treated with conventional radiotherapy. Chest wall irradiation with electrons, supraclavicular field irradiation with 6 MV photons, higher ILD and age >50 years was associated with increased RP. The pulmonary function parameter most affected was TLC. The factors associated with increased RP should be considered when adjuvant radiotherapy is planned to minimize its likelihood and intervene appropriately.

Therapeutic effects of C-28 methyl ester of 2-cyano-3,12-dioxoolean-1,9-dien-28-oic acid (CDDO-Me; bardoxolone methyl) on radiation-induced lung inflammation and fibrosis in mice

The C-28 methyl ester of 2-cyano-3,12-dioxoolean-1,9-dien-28-oic acid (CDDO-Me), one of the synthetic triterpenoids, has been found to have potent anti-inflammatory and anticancer properties in vitro and in vivo. However, its usefulness in mitigating radiation-induced lung injury (RILI), including radiation-induced lung inflammation and fibrosis, has not been tested. The aim of this study was to explore the therapeutic effect of CDDO-Me on RILI in mice and the underlying mechanisms. Herein, we found that administration of CDDO-Me improved the histopathological score, reduced the number of inflammatory cells and concentrations of total protein in bronchoalveolar lavage fluid, suppressed secretion and expression of proinflammatory cytokines, including transforming growth factor-β and interleukin-6, elevated expression of the anti-inflammatory cytokine interleukin-10, and downregulated the mRNA level of profibrotic genes, including for fibronectin, α-smooth muscle actin, and collagen I. CDDO-Me attenuated radiation-induced lung inflammation. CDDO-Me also decreased the Masson's trichrome stain score, hydroxyproline content, and mRNA level of profibrotic genes, and blocked radiation-induced collagen accumulation and fibrosis. Collectively, these findings suggest that CDDO-Me ameliorates radiation-induced lung inflammation and fibrosis, and this synthetic triterpenoid is a promising novel therapeutic agent for RILI. Further mechanistic, efficacy, and safety studies are warranted to elucidate the role of CDDO-Me in the management of RILI.

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.

Dietary flaxseed modulates the miRNA profile in irradiated and non-irradiated murine lungs: a novel mechanism of tissue radioprotection by flaxseed

INTRODUCTION

Dietary flaxseed (FS) displays antioxidant and anti-inflammatory properties in preclinical models of lung disease including radiation-induced pneumonopathy, however the mechanisms of lung radioprotection are incompletely understood. MicroRNAs (miRNAs) are short oligonucleotides that act as important posttranscriptional regulators of diverse networks including inflammatory response networks. Responses of miRNA profiles to diet and radiation exposure have been reported, but the potential contribution of miRNAs to diet-related radioprotection has never been tested.

METHODS

In this exploratory pilot study, mice were fed 10% FS or a 0% FS isocaloric control diet and exposed to a single-fraction 13.5 Gy thoracic X-ray radiation treatment (XRT). Lung RNA was extracted 48 h post-XRT and small RNAs profiled by OpenArray.

RESULTS

FS significantly modulated expression of multiple miRNAs, including 7 with P<0.001. miR-150 was downregulated approximately 2.9-fold in the FS groups and is disproportionately integrated into immune response-related networks. Although few miRNAs were significantly changed by radiation, interaction between diet and radiation was observed. For example, miR-29c was greatly downregulated in the FS/Control group (10- to 50-fold) but slightly upregulated in the FS/radiation group. Compared with FS/control, the FS/radiation group experienced a 50% decrease of the p53-responsive miR-34a, which regulates senescence- and apoptosis-related factors.

CONCLUSIONS

FS induced significant changes in lung miRNA profile suggesting that modulation of small RNA by dietary supplements may represent a novel strategy to prevent adverse side-effects of thoracic radiotherapy. This pilot study provides insight into a potential mechanism of flaxseed's radioprotection and provides a useful model-system to further explore and optimize such small RNA-based therapies.

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.

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.

The effect of CyberKnife therapy on pulmonary function tests used for treating non-small cell lung cancer: a retrospective, observational cohort pilot study

Introduction

The current standard for treating operable early stage non-small cell lung cancer is surgical resection and for inoperable cases it is external beam radiotherapy. Lung functions are adversely affected with both the above treatments. CyberKnife treatment limits radiation damage by tracking targets moving with each breath. The effect of CyberKnife treatment on pulmonary function tests has not been well documented.

Methods

Lung cancer patients who underwent CyberKnife treatment and had pre- and post-treatment pulmonary function tests were included. Paired t-tests were conducted. We also conducted subgroup analysis.

Results

Thirty-seven patients were included. Median age was 73 years. No statistical difference between mean pre- and post-CyberKnife pulmonary function tests was found.

Discussion

We observed that CyberKnife better preserves lung function status compared to current standards of care. It has shown to have very minimal side effects.

A preclinical rodent model of radiation-induced lung injury for medical countermeasure screening in accordance with the FDA animal rule

The purpose of preclinical murine model development is to establish that the pathophysiological outcome of the rodent model of radiation-induced lung injury is sufficiently representative of the anticipated pulmonary response in the human population. This objective is based on concerns that the C57BL/6J strain may not be the most appropriate preclinical model of lethal radiation lung injury in humans. In this study, the authors assessed this issue by evaluating the relationship between morbidity (pulmonary function, histopathologic damage) and mortality among three strains of mice: C57BL/6J, CBA/J, and C57L/J. These different strains display variations in latency and phenotypic expression of radiation-induced lung damage. By comparing the response of each strain to the human pulmonary response, an appropriate animal model(s) of human radiation-induced pulmonary injury was established. Observations in the C57L/J and CBA/J murine models can be extrapolated to the human lung for evaluation of the mechanisms of action of radiation as well as future efficacy testing and approving agents that fall under the "Animal Rule" of the U.S. Food and Drug Administration (FDA) (21 CFR Parts 314 and 601).

Change in diffusing capacity after radiation as an objective measure for grading radiation pneumonitis in patients treated for non-small-cell lung cancer

PURPOSE

Scoring of radiation pneumonitis (RP), a dose-limiting toxicity after thoracic radiochemotherapy, is subjective and thus inconsistent among studies. Here we investigated whether the extent of change in diffusing capacity of the lung for carbon monoxide (DLCO) after radiation therapy (RT) for non-small-cell lung cancer (NSCLC) could be used as an objective means of quantifying RP.

PATIENTS AND METHODS

We analyzed potential correlations between DLCO and RP in 140 patients who received definitive RT (≥ 60 Gy) with or without chemotherapy for primary NSCLC. All underwent DLCO analysis before and after RT. Post-RT DLCO values within 1 week of the RP diagnosis (Grade 0, 1, 2, or 3) were selected and compared with that individual's preradiation values. Percent reductions in DLCO and RP grade were compared by point biserial correlation in the entire patient group and in subgroups stratified according to various clinical factors.

RESULTS

Patients experiencing Grade 0, 1, 2, or 3 RP had median percentage changes in DLCO after RT of 10.7%, 13%, 22.1%, or 35.2%. Percent reduction in DLCO correlated with RP Grade ≤ 1 vs. ≥ 2 (p = 0.0004). This association held for the following subgroups: age ≥ 65 years, advanced stage, smokers, use of chemotherapy, volume of normal lung receiving at least 20 Gy ≥ 30%, and baseline DLCO or forced expiratory volume in 1 second ≥ 60%.

CONCLUSIONS

By correlating percent change in DLCO from pretreatment values at the time of diagnosis of RP with RP grade, we were able to identify categories of RP based on the change in DLCO. These criteria provide a basis for an objective scoring system for RP based on change in DLCO.

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.

Dietary curcumin increases antioxidant defenses in lung, ameliorates radiation-induced pulmonary fibrosis, and improves survival in mice

The effectiveness of lung radiotherapy is limited by radiation tolerance of normal tissues and by the intrinsic radiosensitivity of lung cancer cells. The chemopreventive agent curcumin has known antioxidant and tumor cell radiosensitizing properties. Its usefulness in preventing radiation-induced pneumonopathy has not been tested previously. We evaluated dietary curcumin in radiation-induced pneumonopathy and lung tumor regression in a murine model. Mice were given 1% or 5% (w/w) dietary curcumin or control diet prior to irradiation and for the duration of the experiment. Lungs were evaluated at 3 weeks after irradiation for acute lung injury and inflammation by evaluating bronchoalveolar lavage (BAL) fluid content for proteins, neutrophils and at 4 months for pulmonary fibrosis. In a separate series of experiments, an orthotopic model of lung cancer using intravenously injected Lewis lung carcinoma (LLC) cells was used to exclude possible tumor radioprotection by dietary curcumin. In vitro, curcumin boosted antioxidant defenses by increasing heme oxygenase 1 (HO-1) levels in primary lung endothelial and fibroblast cells and blocked radiation-induced generation of reactive oxygen species (ROS). Dietary curcumin significantly increased HO-1 in lungs as early as after 1 week of feeding, coinciding with a steady-state level of curcumin in plasma. Although both 1% and 5% w/w dietary curcumin exerted physiological changes in lung tissues by significantly decreasing LPS-induced TNF-alpha production in lungs, only 5% dietary curcumin significantly improved survival of mice after irradiation and decreased radiation-induced lung fibrosis. Importantly, dietary curcumin did not protect LLC pulmonary metastases from radiation killing. Thus dietary curcumin ameliorates radiation-induced pulmonary fibrosis and increases mouse survival while not impairing tumor cell killing by radiation.

Dietary flaxseed prevents radiation-induced oxidative lung damage, inflammation and fibrosis in a mouse model of thoracic radiation injury

Flaxseed (FS) has high contents of omega-3 fatty acids and lignans with antioxidant properties. Its use in preventing thoracic X-ray radiation therapy (XRT)-induced pneumonopathy has never been evaluated. We evaluated FS supplementation given to mice given before and post-XRT. FS-derived lignans, known for their direct antioxidant properties, were evaluated in abrogating ROS generation in cultured endothelial cells following gamma radiation exposure. Mice were fed 10% FS or isocaloric control diet for three weeks and given 13.5 Gy thoracic XRT. Lungs were evaluated at 24 hours for markers of radiation-induced injury, three weeks for acute lung damage (lipid peroxidation, lung edema and inflammation), and at four months for late lung damage (inflammation and fibrosis). FS-Lignans blunted ROS generation in vitro, resulting from radiation in a dose-dependent manner. FS-fed mice had reduced expression of lung injury biomarkers (Bax, p21 and TGF-beta1) at 24 hours following XRT and reduced oxidative lung damage as measured by malondialdehyde (MDA) levels at 3 weeks following XRT. In addition, FS-fed mice had decreased lung fibrosis as determined by hydroxyproline content and decreased inflammatory cell influx into lungs at 4 months post XRT. Importantly, when Lewis lung carcinoma cells were injected systemically in mice, FS dietary supplementation did not appear to protect lung tumors from responding to thoracic XRT. Dietary FS is protective against pulmonary fibrosis, inflammation and oxidative lung damage in a murine model. Moreover, in this model, tumor radioprotection was not observed. FS lignans exhibited potent radiation-induced ROS scavenging action. Taken together, these data suggest that dietary flaxseed may be clinically useful as an agent to increase the therapeutic index of thoracic XRT by increasing the radiation tolerance of lung tissues.

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.

Radiological and functional assessment of radiation-induced pulmonary damage following breast irradiation

PURPOSE

The purpose of this study was to compare late radiation-induced radiological abnormalities of the lung with spirometric observations. Radiological abnormalities were also related to theoretical calculations, in order to predict late effects based on dose-volume histograms.

PATIENTS AND METHODS

Sixty-one breast cancer patients who had received postoperative radiotherapy were included. During a follow-up examination 3 years or more after start of radiotherapy, computed tomography (CT) scans and pulmonary function tests were performed. Grading of radiological abnormalities (fibrosis) was performed based on CT images. Based on the dose volume histograms of the lung, effective dose was calculated.

RESULTS

There was a positive correlation between the effective radiation dose and the fraction of patients that developed radiation induced fibrosis. No significant association was found between the normalized forced vital capacity (FVC) and the radiological abnormality score or the effective radiation dose.

CONCLUSION

In this study we found no correlation between local radiation-induced changes in the lung tissue and overall lung function. The effective dose was a better predictive factor for radiation induced fibrosis than for overall lung function.

Small molecular inhibitor of transforming growth factor-beta protects against development of radiation-induced lung injury

PURPOSE

To determine whether an anti-transforming growth factor-beta (TGF-beta) type 1 receptor inhibitor (SM16) can prevent radiation-induced lung injury.

METHODS AND MATERIALS

One fraction of 28 Gy or sham radiotherapy (RT) was administered to the right hemithorax of Sprague-Dawley rats. SM16 was administered in the rat chow (0.07 g/kg or 0.15 g/kg) beginning 7 days before RT. The rats were divided into eight groups: group 1, control chow; group 2, SM16, 0.07 g/kg; group 3, SM16, 0.15 g/kg; group 4, RT plus control chow; group 5, RT plus SM16, 0.07 g/kg; group 6, RT plus SM16, 0.15 g/kg; group 7, RT plus 3 weeks of SM16 0.07 g/kg followed by control chow; and group 8, RT plus 3 weeks of SM16 0.15 g/kg followed by control chow. The breathing frequencies, presence of inflammation/fibrosis, activation of macrophages, and expression/activation of TGF-beta were assessed.

RESULTS

The breathing frequencies in the RT plus SM16 0.15 g/kg were significantly lower than the RT plus control chow from Weeks 10-22 (p <0.05). The breathing frequencies in the RT plus SM16 0.07 g/kg group were significantly lower only at Weeks 10, 14, and 20. At 26 weeks after RT, the RT plus SM16 0.15 g/kg group experienced a significant decrease in lung fibrosis (p = 0.016), inflammatory response (p = 0.006), and TGF-beta1 activity (p = 0.011). No significant reduction was found in these measures of lung injury in the group that received SM16 0.7 g/kg nor for the short-course (3 weeks) SM16 at either dose level.

CONCLUSION

SM16 at a dose of 0.15 g/kg reduced functional lung damage, morphologic changes, inflammatory response, and activation of TGF-beta at 26 weeks after RT. The data suggest a dose response and also suggest the superiority of long-term vs. short-term dosing.

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.

Optimized Dose Coverage of Regional Lymph Nodes in Breast Cancer: The Role of Intensity-Modulated Radiotherapy

PURPOSE

To determine whether the use of intensity-modulated radiotherapy (IMRT) would lead to improved dosimetry for the breast and regional nodes.

METHODS AND MATERIALS

Ten patients with left-sided breast cancer were selected. The clinical target volume included left breast and internal mammillary (IM), supraclavicular (SC), and axillary (AX) nodes. The critical structures included heart, right and left lungs, contralateral breast, esophagus, thyroid, and humeral head. Conventional and a series of IMRT plans were generated for comparison.

RESULTS

The average heart D(3) was reduced from 31.4 +/- 18.9 with three-dimensional conformal radiotherapy (3D-CRT) to 15 +/- 7.2 Gy with 9-field (9-FLD IMRT). The average left lung D(30) was also decreased from 27.9 +/- 11.5 Gy (3D-CRT) to 12.6 +/- 8.2 Gy (9-FLD IMRT). The average contralateral breast D(2) was reduced from 4.4 +/- 5.3 Gy (3D-CRT) to 1.8 +/- 1.2 Gy (4-FLD IMRT). Esophagus D(2) was increased from 9.3 +/- 8.1 Gy (3D-CRT) to 29.4 +/- 5.4 (9-FLD IMRT); thyroid D(50) was increased from 0.9 +/- 0.6 Gy (3D-CRT) to 11.9 +/- 6.6 (9-FLD IMRT); humeral head D(2) was increased from 36.1 +/- 13.1 Gy (3D-CRT) to 39.9 +/- 6.5 (9-FLD IMRT).

CONCLUSIONS

The use of IMRT improves breast and regional node coverage while decreasing doses to the lungs, heart, and contralateral breast when compared with 3D-CRT. Doses to esophagus, thyroid, and humeral head, however, were increased with IMRT.

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.