Impact of Toxicity Grade and Scoring System on the Relationship Between Mean Lung Dose and Risk of Radiation Pneumonitis in a Large Cohort of Patients With Non–Small Cell Lung Cancer

Decreased risk of radiation pneumonitis with concurrent use of renin-angiotensin system inhibitors in thoracic radiation therapy of lung cancer

Background

Radiation pneumonitis (RP) is the primary dose-limiting toxicity associated with radiotherapy. This study aimed to observe the effects of renin-angiotensin system inhibitors in Chinese patients with lung cancer who received thoracic radiation.

Methods

Patients with lung cancer who received thoracic radiation at a total dose of ≥45 Gray between October 2017 and December 2022 were enrolled in this study. We retrospectively evaluated the factors influencing grade 2 or higher RP.

Results

A total of 320 patients were enrolled in this study; 62 patients were identified as angiotensin receptor blockers or angiotensin-converting enzyme inhibitor users. Additionally, 99 patients (30.9%) had grade 2 or higher RP, and the incidence in the renin-angiotensin system inhibitor group was 17.7% (11 out of 62 patients). Patients in the renin-angiotensin system inhibitors (RASi) group were older and had a higher percentage of males, lower percentage of ECOG score 0, higher percentage of hypertension, and higher percentage of adenocarcinoma than those in the non-RASi group. ECOG score [hazard ratio (HR) = 1.69, p = 0.009], history of smoking (HR = 1.76, p = 0.049), mean dose (HR = 3.63, p = 0.01), and RASi (HR = 0.3, p = 0.003) were independent predictive factors for RP. All subgroups benefited from RASi.

Conclusion

This study showed that oral RASi administration has the potential to mitigate the incidence of grade 2 or higher RP in patients with lung cancer undergoing thoracic radiotherapy. To validate and further substantiate these findings, additional prospective research is warranted.

Characterizing Pulmonary Function Test Changes for Patients With Lung Cancer Treated on a 2-Institution, 4-Dimensional Computed Tomography-Ventilation Functional Avoidance Prospective Clinical Trial

Purpose

Four-dimensional computed tomography (4DCT)-ventilation-based functional avoidance uses 4DCT images to generate plans that avoid functional regions of the lung with the goal of reducing pulmonary toxic effects. A phase 2, multicenter, prospective study was completed to evaluate 4DCT-ventilation functional avoidance radiation therapy. The purpose of this study was to report the results for pretreatment to posttreatment pulmonary function test (PFT) changes for patients treated with functional avoidance radiation therapy.

Methods and Materials

Patients with locally advanced lung cancer receiving chemoradiation were accrued. Functional avoidance plans based on 4DCT-ventilation images were generated. PFTs were obtained at baseline and 3 months after chemoradiation. Differences for PFT metrics are reported, including diffusing capacity for carbon monoxide (DLCO), forced expiratory volume in 1 second (FEV1), and forced vital capacity (FVC). PFT metrics were compared for patients who did and did not experience grade 2 or higher pneumonitis.

Results

Fifty-six patients enrolled on the study had baseline and posttreatment PFTs evaluable for analysis. The mean change in DLCO, FEV1, and FVC was -11.6% ± 14.2%, -5.6% ± 16.9%, and -9.0% ± 20.1%, respectively. The mean change in DLCO was -15.4% ± 14.4% for patients with grade 2 or higher radiation pneumonitis and -10.8% ± 14.1% for patients with grade <2 radiation pneumonitis (P = .37). The mean change in FEV1 was -14.3% ± 22.1% for patients with grade 2 or higher radiation pneumonitis and -3.9% ± 15.4% for patients with grade <2 radiation pneumonitis (P = .09).

Conclusions

The current work is the first to quantitatively characterize PFT changes for patients with lung cancer treated on a prospective functional avoidance radiation therapy study. In comparison with patients treated with standard thoracic radiation planning, the data qualitatively show that functional avoidance resulted in less of a decline in DLCO and FEV1. The presented data can help elucidate the potential pulmonary function improvement with functional avoidance radiation therapy.

Parameters of the Lyman Model for Calculation of Normal-Tissue Complication Probability: A Systematic Literature Review

PURPOSE

The Lyman model is one of the most used radiobiological models for calculation of normal-tissue complication probability (NTCP). Since its introduction in 1985, many authors have published parameter values for the model based on clinical data of different radiotherapeutic situations. This study attempted to collect the entirety of radiobiological parameter sets published to date and provide an overview of the data basis for different variations of the model. Furthermore, it sought to compare the parameter values and calculated NTCPs for selected endpoints with sufficient data available.

METHODS AND MATERIALS

A systematic literature analysis was performed, searching for publications that provided parameters for the different variations of the Lyman model in the Medline database using PubMed. Parameter sets were grouped into 13 toxicity-related endpoint groups. For 3 selected endpoint groups (≤25% reduction of saliva 12 months after irradiation of the parotid, symptomatic pneumonitis after irradiation of the lung, and bleeding of grade 2 or less after irradiation of the rectum), parameter values were compared and differences in calculated NTCP values were analyzed.

RESULTS

A total of 509 parameter sets from 130 publications were identified. Considerable heterogeneities were detected regarding the number of parameters available for different radio-oncological situations. Furthermore, for the 3 selected endpoints, large differences in published parameter values were found. These translated into great variations of calculated NTCPs, with maximum ranges of 35.2% to 93.4% for the saliva endpoint, of 39.4% to 90.4% for the pneumonitis endpoint, and of 5.4% to 99.3% for the rectal bleeding endpoint.

CONCLUSIONS

The detected heterogeneity of the data as well as the large variations of published radiobiological parameters underline the necessity for careful interpretation when using such parameters for NTCP calculations. Appropriate selection of parameters and validation of values are essential when using the Lyman model.

Results of a Multi-Institutional Phase 2 Clinical Trial for 4DCT-Ventilation Functional Avoidance Thoracic Radiation Therapy

PURPOSE

Radiation pneumonitis remains a major limitation in the radiation therapy treatment of patients with lung cancer. Functional avoidance radiation therapy uses functional imaging to reduce pulmonary toxic effects by designing radiation therapy plans that reduce doses to functional regions of the lung. Lung functional imaging has been developed that uses 4-dimensional computed tomography (4DCT) imaging to calculate 4DCT-based lung ventilation (4DCT-ventilation). A phase 2 multicenter study was initiated to evaluate 4DCT-ventilation functional avoidance radiation therapy. The study hypothesis was that functional avoidance radiation therapy could reduce the rate of grade ≥2 radiation pneumonitis to 12% compared with a 25% historical rate, with the trial being positive if ≤16.4% of patients experienced grade ≥2 pneumonitis.

METHODS AND MATERIALS

Lung cancer patients receiving curative-intent radiation therapy (prescription doses of 45-75 Gy) and chemotherapy were accrued. Patient 4DCT scans were used to generate 4DCT-ventilation images. The 4DCT-ventilation images were used to generate functional avoidance plans that reduced doses to functional portions of the lung while delivering the prescribed tumor dose. Pneumonitis was evaluated by a clinician at 3, 6, and 12 months after radiation therapy.

RESULTS

Sixty-seven evaluable patients were accrued between April 2015 and December 2019. The median prescription dose was 60 Gy (range, 45-66 Gy) delivered in 30 fractions (range, 15-33 fractions). The average reduction in the functional volume of lung receiving ≥20 Gy with functional avoidance was 3.5% (range, 0%-12.8%). The median follow-up was 312 days. The rate of grade ≥2 radiation pneumonitis was 10 of 67 patients (14.9%; 95% upper CI, 24.0%), meeting the phase 2 criteria.

CONCLUSIONS

4DCT-ventilation offers an imaging modality that is convenient and provides functional imaging without an extra procedure necessary. This first report of a multicenter study of 4DCT-ventilation functional avoidance radiation therapy provided data showing that the trial met phase 2 criteria and that evaluation in a phase 3 study is warranted.

Quantitative Analysis of Radiation-Associated Parenchymal Lung Change

We present a novel classification system of the parenchymal features of radiation-induced lung damage (RILD). We developed a deep learning network to automate the delineation of five classes of parenchymal textures. We quantify the volumetric change in classes after radiotherapy in order to allow detailed, quantitative descriptions of the evolution of lung parenchyma up to 24 months after RT, and correlate these with radiotherapy dose and respiratory outcomes. Diagnostic CTs were available pre-RT, and at 3, 6, 12 and 24 months post-RT, for 46 subjects enrolled in a clinical trial of chemoradiotherapy for non-small cell lung cancer. All 230 CT scans were segmented using our network. The five parenchymal classes showed distinct temporal patterns. Moderate correlation was seen between change in tissue class volume and clinical and dosimetric parameters, e.g., the Pearson correlation coefficient was ≤0.49 between V30 and change in Class 2, and was 0.39 between change in Class 1 and decline in FVC. The effect of the local dose on tissue class revealed a strong dose-dependent relationship. Respiratory function measured by spirometry and MRC dyspnoea scores after radiotherapy correlated with the measured radiological RILD. We demonstrate the potential of using our approach to analyse and understand the morphological and functional evolution of RILD in greater detail than previously possible.

Radiographic patterns of symptomatic radiation pneumonitis in lung cancer patients: Imaging predictors for clinical severity and outcome

OBJECTIVE

Investigate the spectrum of radiographic patterns of radiation pneumonitis (RP) in lung cancer patients and identify imaging markers for high-grade RP and RP-related death.

METHODS

Eighty-two patients with lung cancer treated with conventional chest radiotherapy who had symptomatic RP were identified from the radiation oncology database. The imaging features of RP were studied for association with high-grade RP (Grade ≥3) and RP-related death (Grade 5).

RESULTS

RP was Grade 2 in 60 (73%), Grade 3 in 15 (18%), and Grade 5 in 7 patients (9%). Lower performance status (p = 0.04), squamous cell histology (p = 0.03), and FEV1 ≤ 2 (p = 0.009) were associated with high-grade pneumonitis. Older age (p = 0.03) and squamous cell histology (p = 0.03) were associated with RP-related death. The CT findings included ground-glass and reticular opacities in all patients, with traction bronchiectasis in 77 (94%) and consolidation in 74 (90%). The most common radiographic pattern of RP was cryptogenic organizing pneumonia (COP) pattern (n = 54), followed by acute interstitial pneumonia (AIP)/acute respiratory distress syndrome (ARDS) pattern (n = 10). Higher extent of lung involvement, diffuse distribution, and AIP/ARDS pattern were associated with high-grade pneumonitis and RP-related death. AIP/ARDS pattern was a significant factor for high-grade pneumonitis (OR:12.62, p = 0.01) in multivariable analyses adjusting for clinical variables.

CONCLUSION

COP pattern was the most common radiographic pattern for symptomatic RP in lung cancer patients. AIP/ARDS pattern was significantly associated with high-grade RP and RP-related deaths, and was an independent marker for high-grade RP. The recognition of the radiographic patterns of RP can help to effectively contribute to patient management.

Annexin A1-mediated inhibition of inflammatory cytokines may facilitate the resolution of inflammation in acute radiation-induced lung injury

The present study evaluated the role of annexin A1 (ANXA1) in the treatment of acute radiation-induced lung injury (RILI) and investigated the mechanism of its action. The expression of ANXA1, interleukin-6 (IL-6) and myeloperoxidase (MPO) in the plasma of patients with RILI prior to and following hormonotherapy was assessed by enzyme-linked immunosorbent assay. The association of plasma ANXA1 concentration with clinical effect, and the correlation between the expression of ANXA1 and that of IL-6 and MPO were evaluated. ANXA1 was overexpressed or knocked down in a macrophage cell line, and its impact on IL-6 and MPO expression was measured. Following glucocorticoid hormonotherapy, patients with RILI exhibited a higher plasma concentration of ANXA1 compared with that prior to treatment, while IL-6 and MPO levels were lower. The concentration of ANXA1 in plasma was negatively correlated with IL-6 and MPO levels, with a correlation coefficient of -0.492 and -0.437, respectively (P<0.001). The increasing concentration of ANXA1 in plasma following treatment was associated with the clinical effect in patients with RILI (P=0.007). The expression levels of of IL-6 and MPO were inhibited both in the cytoplasm and in the culture solution, when ANXA1 expression was upregulated in a macrophage cell line. In conclusion, ANXA1 inhibited the synthesis and secretion of IL-6 and MPO inflammatory cytokines, indicating that ANXA1 may have therapeutic potential as a treatment target for RILI.

Predictors of pneumonitis-free survival following lung stereotactic body radiation therapy

Background

Radiation pneumonitis is a common toxicity following lung stereotactic body radiation therapy (SBRT). We explored whether motion management technique, in conjunction with patient and treatment characteristics, is a predictor of radiation pneumonitis-free survival (PNFS).

Methods

A single institution multi-center lung SBRT database was retrospectively reviewed. PNFS was defined as time to earliest onset of radiation pneumonitis or last clinical follow-up. Patients were simulated using a 4-dimensional approach, and those with 1 cm or greater tumor motion were selected for respiratory-gated treatment. Real-time Position Management and phase-based gating were employed. Univariate and multivariable Cox proportional hazard models were fit for relevant covariates to determine the impact of free-breathing versus respiratory-gated treatment on PNFS.

Results

The initial treatment courses of 208 patients were included, with a median follow-up length of 23 months. The median age at treatment was 71 years. About 91.8% of patient had early stage (T1-2) non-small cell lung cancer and were treated with common regimens including 10 Gy ×5, 12 Gy ×4 and 18 Gy ×3; 26.4% underwent respiratory-gated SBRT. The overall rate of grade 3 or higher radiation pneumonitis was 10.1%. PNFS was not significantly different between patients treated with respiratory-gated versus free-breathing SBRT (HR =0.88; P=0.707); tumor location and fractionation were predictors of PNFS in the multivariate setting.

Conclusions

The method of motion management does not appear to impact PNFS when the tolerance for tumor displacement is 1 cm or less for free-breathing treatment planning and delivery. This approach may be appropriate when selecting patients for respiratory gating.

Validation of Effective Dose as a Better Predictor of Radiation Pneumonitis Risk Than Mean Lung Dose: Secondary Analysis of a Randomized Trial

PURPOSE

To confirm the superiority of effective dose (D_eff) over mean lung dose (MLD) for predicting risk of radiation pneumonitis (RP), using data from patients on a randomized trial of intensity modulated radiation therapy (IMRT) versus passively scattered proton therapy (PSPT).

METHODS AND MATERIALS

The prescribed target dose for the 203 evaluated patients was 66 to 74 Gy (relative biological effectiveness) in 33 to 37 fractions with concurrent carboplatin/paclitaxel. Time to grade ≥2 RP was computed from the start of radiation therapy, with disease recurrence or death considered censoring events. Generalized Lyman models of censored time to RP were constructed with MLD or D_eff as the dosimetric parameter. Smoking status (current, former, never) was also analyzed.

RESULTS

Of the 203 patients, 46 experienced grade ≥2 RP (crude incidence 23%) at a median 3.7 months (range, 0.6-12.6 months). The volume parameter estimated for the D_eff model was n = 0.5, confirming estimates from earlier studies. Compared with MLD (in which n = 1), the dosimetric parameter D_eff, computed using n = 0.5, resulted in a better fit of the Lyman model to the clinical data (P = .010). Using D_eff, the model describes RP risk for IMRT and PSPT data combined because no further improvement was found from separate fits (P = .558). Based on D_eff, predicted RP risk per patient ranged from 24 percentage points lower to 19 percentage points higher than predictions based on MLD. For patients with similar MLD, D_eff predicted higher risk, on average, for PSPT over IMRT. Current smokers had a lower risk of RP compared with former smokers and nonsmokers (P = .021).

CONCLUSIONS

We used data from a randomized trial to validate our previous finding that D_eff with n = 0.5 (corresponding to root mean squared dose) is a better predictor of RP than is MLD. Differences between D_eff and MLD indicate that delivering higher doses to smaller lung volumes (vs lower doses to larger volumes) increases RP risk. We further corroborated that current smoking is associated with decreased RP risk.

The utility of quantitative CT radiomics features for improved prediction of radiation pneumonitis

PURPOSE

The purpose of this study was to explore gains in predictive model performance for radiation pneumonitis (RP) using pretreatment CT radiomics features extracted from the normal lung volume.

METHODS

A total of 192 patients treated for nonsmall cell lung cancer with definitive radiotherapy were considered in the current study. In addition to clinical and dosimetric data, CT radiomics features were extracted from the total lung volume defined using the treatment planning scan. A total of 6851 features (15 clinical, 298 total lung and heart dosimetric, and 6538 image features) were gathered and considered candidate predictors for modeling of RP grade ≥3. Models were built with the least absolute shrinkage and selection operator (LASSO) logistic regression and applied to the set of candidate predictors with 50 iterations of tenfold nested cross-validation.

RESULTS

In the current cohort, 30 of 192 patients (15.6%) presented with RP grade ≥3. Average cross-validated AUC (CV-AUC) using only the clinical and dosimetric parameters was 0.51. CV-AUC was 0.68 when total lung CT radiomics features were added. Analysis with the entire set of available predictors revealed seven different image features selected in at least 40% of the model fits.

CONCLUSIONS

We have successfully incorporated CT radiomics features into a framework for building predictive RP models via LASSO logistic regression. Addition of normal lung image features produced superior model performance relative to traditional dosimetric and clinical predictors of RP, suggesting that pretreatment CT radiomics features should be considered in the context of RP prediction.

Oral administration of herbal medicines for radiation pneumonitis in lung cancer patients: A systematic review and meta-analysis

BACKGROUND

Radiation pneumonitis is a common and serious complication of radiotherapy. Many published randomized controlled studies (RCTs) reveal a growing trend of using herbal medicines as adjuvant therapy to prevent radiation pneumonitis; however, their efficacy and safety remain unexplored.

OBJECTIVE

The aim of this systematic review is to evaluate the efficacy and safety of herbal medicines as adjunctive therapy for the prevention of radiation pneumonitis in patients with lung cancer who undergo radiotherapy.

METHODS

We searched the following 11 databases: three English medical databases [MEDLINE (PubMed), EMBASE, The Cochrane Central Register of Controlled Trials (CENTRAL)], five Korean medical databases (Korean Studies Information, Research information Service System, KoreaMed, DBPIA, National Digital Science Library), and three Chinese medical databases [the China National Knowledge Database (CNKI), Journal Integration Platform (VIP), and WanFang Database]. The primary outcome was the incidence of radiation pneumonitis. The risk of bias was assessed using the Cochrane risk-of-bias tool.

RESULTS

Twenty-two RCTs involving 1819 participants were included. The methodological quality was poor for most of the studies. Meta-analysis showed that herbal medicines combined with radiotherapy significantly reduced the incidence of radiation pneumonitis (n = 1819; RR 0.53, 95% CI 0.45-0.63, I2 = 8%) and the incidence of severe radiation pneumonitis (n = 903; RR 0.22, 95% CI 0.11-0.41, I2 = 0%). Combined therapy also improved the Karnofsky performance score (n = 420; WMD 4.62, 95% CI 1.05-8.18, I2 = 82%).

CONCLUSION

There is some encouraging evidence that oral administration of herbal medicines combined with radiotherapy may benefit patients with lung cancer by preventing or minimizing radiation pneumonitis. However, due to the poor methodological quality of the identified studies, definitive conclusion could not be drawn. To confirm the merits of this approach, further rigorously designed large scale trials are warranted.

The positive role of vitronectin in radiation induced lung toxicity: the in vitro and in vivo mechanism study

Background

Radiation-induced lung toxicity (RILT) is a severe complication of radiotherapy in patients with thoracic tumors. Through proteomics, we have previously identified vitronectin (VTN) as a potential biomarker for patients with lung toxicity of grade ≥ 2 radiation. Herein, we explored the molecular mechanism of VTN in the process of RILT.

Methods

In this study, lentivirus encoding for VTN and VTN-specific siRNA were constructed and transfected into the cultured fibroblasts and C57BL mice. Real-time PCR, western blot and ELISA were used to examine expression of collagens and several potential proteins involved in lung fibrosis. Hematoxylin–eosin and immunohistochemical staining were used to assess the fibrosis scores of lung tissue from mice received irradiation.

Results

The expression of VTN was up-regulated by irradiation. The change trend of collagens, TGF-β expression and p-ERK, p-AKT, and p-JNK expression levels were positively related with VTN mRNA level. Furthermore, overexpression of VTN significantly increased the expression level of α-SMA, as well as the degree of lung fibrosis in mice at 8 and 12 weeks post-irradiation. By contrast, siRNA VTN induced opposite results both in vitro and in vivo.

Conclusions

VTN played a positive role in the lung fibrosis of RILT, possibly through modulation of fibrosis regulatory pathways and up-regulating the expression levels of fibrosis-related genes. Taken together, all the results suggested that VTN had a novel therapeutic potential for the treatment of RILT.

Electronic supplementary material

The online version of this article (10.1186/s12967-018-1474-y) contains supplementary material, which is available to authorized users.

Reducing dose to the lungs through loosing target dose homogeneity requirement for radiotherapy of non small cell lung cancer

It is important to minimize lung dose during intensity-modulated radiation therapy (IMRT) of nonsmall cell lung cancer (NSCLC). In this study, an approach was proposed to reduce lung dose by relaxing the constraint of target dose homogeneity during treatment planning of IMRT. Ten NSCLC patients with lung tumor on the right side were selected. The total dose for planning target volume (PTV) was 60 Gy (2 Gy/fraction). For each patient, two IMRT plans with six beams were created in Pinnacle treatment planning system. The dose homogeneity of target was controlled by constraints on the maximum and uniform doses of target volume. One IMRT plan was made with homogeneous target dose (the resulting target dose was within 95%-107% of the prescribed dose), while another IMRT plan was made with inhomogeneous target dose (the resulting target dose was more than 95% of the prescribed dose). During plan optimization, the dose of cord and heart in two types of IMRT plans were kept nearly the same. The doses of lungs, PTV and organs at risk (OARs) between two types of IMRT plans were compared and analyzed quantitatively. For all patients, the lung dose was decreased in the IMRT plans with inhomogeneous target dose. On average, the mean dose, V5, V20, and V30 of lung were reduced by 1.4 Gy, 4.8%, 3.7%, and 1.7%, respectively, and the dose to normal tissue was also reduced. These reductions in DVH values were all statistically significant (P < 0.05). There were no significant differences between the two IMRT plans on V25, V30, V40, V50 and mean dose for heart. The maximum doses of cords in two type IMRT plans were nearly the same. IMRT plans with inhomogeneous target dose could protect lungs better and may be considered as a choice for treating NSCLC.

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.

Risk of radiation-induced pneumonitis after helical and static-port tomotherapy in lung cancer patients and experimental rats

Background

Radiotherapy (RT) is one of the major non-operative treatment modalities for treating lung cancer. Tomotherapy is an advanced type of intensity-modulated radiotherapy (IMRT) in which radiation may be delivered in a helical fashion. However, unexpected pneumonitis may occur in patients treated with tomotherapy, especially in combination with chemotherapy, as a result of extensive low-dose radiation of large lung volumes. The aim of our study was to investigate the risk of radiation-induced pneumonitis after helical-mode and static-mode tomotherapy in patients with lung cancer and in an animal model.

Method

A total of 63 patients with primary lung cancer who were treated with static or helical tomotherapy with or without concurrent chemoradiotherapy (CCRT) were analyzed. Additionally, rats with radiation-induced pulmonary toxicity, which was induced by the application of helical or static tomography with or without CCRT, were evaluated.

Results

Helical-mode tomotherapy resulted in a significantly higher rate of late radiation pneumonitis in lung cancer patients than static-mode tomotherapy when evaluated by the Radiation Therapy Oncology Group (RTOG) and National Cancer Institute Common Terminology Criteria for Adverse Events (CTCAE) scoring system. In the animal model, helical tomotherapy alone induced significantly higher expression of interleukin (IL)-1α, IL-1β, IL-6, and transforming growth factor (TGF)-β in lung specimens, especially on the untreated side, compared to static tomotherapy alone. Additionally, rats treated with helical tomotherapy and CCRT demonstrated significantly higher expression of inflammatory cytokines compared to those treated with static tomotherapy and CCRT.

Conclusion

Rat models treated with tomotherapy with or without CCRT could present similar patterns of pulmonary toxicity to those shown in lung cancer patients. The models can be used in further investigations of radiation induced pulmonary toxicity.

Extracting the normal lung dose-response curve from clinical DVH data: a possible role for low dose hyper-radiosensitivity, increased radioresistance

In conventionally fractionated radiation therapy for lung cancer, radiation pneumonitis' (RP) dependence on the normal lung dose-volume histogram (DVH) is not well understood. Complication models alternatively make RP a function of a summary statistic, such as mean lung dose (MLD). This work searches over damage profiles, which quantify sub-volume damage as a function of dose. Profiles that achieve best RP predictive accuracy on a clinical dataset are hypothesized to approximate DVH dependence.Step function damage rate profiles R(D) are generated, having discrete steps at several dose points. A range of profiles is sampled by varying the step heights and dose point locations. Normal lung damage is the integral of R(D) with the cumulative DVH. Each profile is used in conjunction with a damage cutoff to predict grade 2 plus (G2+) RP for DVHs from a University of Michigan clinical trial dataset consisting of 89 CFRT patients, of which 17 were diagnosed with G2+ RP.Optimal profiles achieve a modest increase in predictive accuracy--erroneous RP predictions are reduced from 11 (using MLD) to 8. A novel result is that optimal profiles have a similar distinctive shape: enhanced damage contribution from low doses (<20 Gy), a flat contribution from doses in the range ~20-40 Gy, then a further enhanced contribution from doses above 40 Gy. These features resemble the hyper-radiosensitivity / increased radioresistance (HRS/IRR) observed in some cell survival curves, which can be modeled using Joiner's induced repair model.A novel search strategy is employed, which has the potential to estimate RP dependence on the normal lung DVH. When applied to a clinical dataset, identified profiles share a characteristic shape, which resembles HRS/IRR. This suggests that normal lung may have enhanced sensitivity to low doses, and that this sensitivity can affect RP risk.

Effects of proton pump inhibitors on lung cancer precise radiotherapy-induced radiation pneumonitis

The objective of this study was to explore the effects of proton pump inhibitors (PPIs) on the development and prognosis of lung cancer precise radiotherapy-induced radiation pneumonitis. Clinical materials of 84 lung cancer patients who had radiation pneumonitis after precise radiotherapy were retrospectively analyzed, and the patients were divided into PPI group and control group, according to whether or not PPIs were applied. The development and prognosis of patients and the effects of different doses of PPI on patient condition from two groups were compared. There were 57 PPI cases in PPI group and 27 cases in control group. Basic characteristics of patients were not statistically different between the two groups; however, white blood cell count, oxygenation indexes, blood gas pH, and lung imaging index were significantly different (p < 0.05), indicating that radiation pneumonitis tended to be more severe in PPI group. As regards effects of PPI on prognosis of two groups, remission rate of radiation pneumonia in PPI group was significantly less than that of the control group. Among 57 cases in PPI group, there were 31 patients applied with PPI ≤ 1DDD and 31 patients applied with PPI > 1DDD. In comparison of the various parameters of patients, 7 days after being applied with different doses of PPI, there were no significant differences between the parameters of radiation pneumonitis. PPIs should be cautiously utilized to avoid the effects of lung cancer radiotherapy-induced radiation pneumonia.

Complications from Stereotactic Body Radiotherapy for Lung Cancer

Stereotactic body radiotherapy (SBRT) has become a standard treatment option for early stage, node negative non-small cell lung cancer (NSCLC) in patients who are either medically inoperable or refuse surgical resection. SBRT has high local control rates and a favorable toxicity profile relative to other surgical and non-surgical approaches. Given the excellent tumor control rates and increasing utilization of SBRT, recent efforts have focused on limiting toxicity while expanding treatment to increasingly complex patients. We review toxicities from SBRT for lung cancer, including central airway, esophageal, vascular (e.g., aorta), lung parenchyma (e.g., radiation pneumonitis), and chest wall toxicities, as well as radiation-induced neuropathies (e.g., brachial plexus, vagus nerve and recurrent laryngeal nerve). We summarize patient-related, tumor-related, dosimetric characteristics of these toxicities, review published dose constraints, and propose strategies to reduce such complications.

The mean lung dose (MLD) : predictive criterion for lung damage?

AIM

The purpose of this work was to prove the validity of the mean lung dose (MLD), widely used in clinical practice to estimate the lung toxicity of a treatment plan, by reevaluating experimental data from mini pigs.

MATERIALS AND METHODS

A total of 43 mini pigs were irradiated in one of four dose groups (25, 29, 33, and 37 Gy). Two regimens were applied: homogeneous irradiation of the right lung or partial irradiation of both lungs-including parts with lower dose-but with similar mean lung doses. The animals were treated with five fractions with a linear accelerator applying a CT-based treatment plan. The clinical lung reaction (breathing frequency) and morphological changes in CT scans were examined frequently during the 48 weeks after irradiation.

RESULTS

A clear dose-effect relationship was found for both regimens of the trial. However, a straightforward relationship between the MLD and the relative number of responders with respect to different grades of increased breathing frequency for both regimens was not found. A morphologically based parameter NTCPlung was found to be more suitable for this purpose. The dependence of this parameter on the MLD is markedly different for the two regimens.

CONCLUSION

In clinical practice, the MLD can be used to predict lung toxicity of a treatment plan, except for dose values that could lead to severe side effects. In the latter mentioned case, limitations to the predictive value of the MLD are possible. Such severe developments of a radiation-induced pneumopathy are better predicted by the NTCPlung formalism. The predictive advantage of this parameter compared to the MLD seems to remain in the evaluation and comparison of widely differing dose distributions, like in the investigated trial.

Helical and Static-port Tomotherapy Using the Newly-developed Dynamic Jaws Technology for Lung Cancer

With the newly developed dynamic jaws technology, radiation dose for the cranio-caudal edges of a target can be lowered in the treatment with tomotherapy. We compared dynamic-jaw- and fixed-jaw-mode plans for lung cancer. In 35 patients, four plans using the 2.5-cm dynamic-, 2.5-cm fixed-, 5.0-cm dynamic-, and 5.0-cm fixed-jaw modes were generated. For 10 patients with upper lobe stage I lung cancer, the helical tomotherapy mode was used. Fifty-six Gy in 8 fractions was prescribed as a minimum coverage dose for 95% of the target (D95%). For 25 patients with locally advanced lung cancer, plans using four static ports (TomoDirect® mode) were made. Sixty Gy in 30 daily fractions for the primary tumor and swollen lymph nodes and 51 Gy in 30 fractions for prophylactic lymph node areas were prescribed as median doses. The mean conformity index of the planning target volume were similar among the four plans. The mean V5 Gy of the lung for 2.5-cm dynamic-, 2.5-cm fixed-, 5.0-cm dynamic-, and 5.0-cm fixed-jaw mode plans were 18.5%, 21.8%, 20.1%, and 29.4%, respectively (p < 0.0001), for patients with stage I lung cancer, and 37.3%, 38.7%, 40.4%, and 44.0%, respectively (p < 0.0001), for patients with locally advanced lung cancer. The mean V5 Gy of the whole body was 1,826, 2,143, 1,983, and 2,939 ml, respectively (p < 0.0001), for patients with stage I lung cancer and 4,849, 5,197, 5,220, and 6,154 ml, respectively (p < 0.0001), for patients with locally advanced lung cancer. Treatment time was reduced by 21-39% in 5.0-cm dynamic-jaw plans compared to 2.5-cm plans. Regarding dose distribution, 2.5-cm dynamic-jaw plans were the best, and 5.0-cm dynamic-jaw plans were comparable to 2.5-cm fixed-jaw plans with shorter treatment times. The dynamic-jaw mode should be used instead of the conventional fixed-jaw mode in tomotherapy for lung cancer.

Stereotactic body radiation therapy for post-pulmonary lobectomy isolated lung metastasis of thoracic tumor: survival and side effects

BACKGROUND

Stereotactic body radiation therapy (SBRT) has emerged as an alternative treatment for patients with early stage non-small cell lung cancer (NSCLC) or metastatic pulmonary tumors. However, for isolated lung metastasis (ILM) of thoracic malignances after pulmonary lobectomy, reported outcomes of SBRT have been limited. This study evaluates the role of SBRT in the treatment of such patients.

METHODS

A retrospective search of the SBRT database was conducted in three hospitals. The parameters analyzed in the treated patients were local control, progression-free survival (PFS), overall survival (OS), and the treatment-related side-effects.

RESULTS

In total, 23 patients with single ILM after pulmonary lobectomy treated with SBRT were identified and the median follow-up time was 14 months (range: 6.0-47.0 months). Local recurrences were observed in two patients during follow-up and the 1-year local control rate was 91.3%. Median PFS and OS for the studied cohort were 10.0 months [95% confidence interval (CI) 5.1-14.9 months] and 21.0 months (95% CI 11.4-30.6 months), respectively. Acute radiation pneumonitis (RP) of grade 2 or worse was observed in five (21.7%) and three (13.0%) patients, respectively. Other treatment-related toxicities included chest wall pain in one patient (4.3%) and acute esophagitis in two patients (8.7%). By Pearson correlation analysis, the planning target volume (PTV) volume and the volume of the ipsilateral lung exposed to a minimum dose of 5 Gy (IpV5) were significantly related to the acute RP of grade 2 or worse in present study (p < 0.05). The optimal thresholds of the PTV and IpV5 to predict RP of acute grade 2 or worse RP were 59 cm3 and 51% respectively, according to the receiver-operating characteristics curve analysis, with sensitivity/specificity of 75.0%/80.0% and 62.5%/80.0%.

CONCLUSIONS

SBRT for post-lobectomy ILM was effective and well tolerated. The major reason for disease progression was distant failure but not local recurrence. The PTV and IpV5 are potential predictors of acute RP of grade 2 or higher and should be considered in treatment planning for such patients.

Towards individualized dose constraints: Adjusting the QUANTEC radiation pneumonitis model for clinical risk factors

BACKGROUND

Understanding the dose-response of the lung in order to minimize the risk of radiation pneumonitis (RP) is critical for optimization of lung cancer radiotherapy. We propose a method to combine the dose-response relationship for RP in the landmark QUANTEC paper with known clinical risk factors, in order to enable individual risk prediction. The approach is validated in an independent dataset.

MATERIAL AND METHODS

The prevalence of risk factors in the patient populations underlying the QUANTEC analysis was estimated, and a previously published method to adjust dose-response relationships for clinical risk factors was employed. Effect size estimates (odds ratios) for risk factors were drawn from a recently published meta-analysis. Baseline values for D50 and γ50 were found. The method was tested in an independent dataset (103 patients), comparing the predictive power of the dose-only QUANTEC model and the model including risk factors. Subdistribution cumulative incidence functions were compared for patients with high/low-risk predictions from the two models, and concordance indices (c-indices) for the prediction of RP were calculated.

RESULTS

The reference dose- response relationship for a patient without pulmonary co-morbidities, caudally located tumor, no history of smoking, < 63 years old, and receiving no sequential chemotherapy was estimated as D50(0) = 34.4 Gy (95% CI 30.7, 38.9), γ50(0) = 1.19 (95% CI 1.00, 1.43). Individual patient risk estimates were calculated. The cumulative incidences of RP in the validation dataset were not significantly different in high/low-risk patients when doing risk allocation with the QUANTEC model (p = 0.11), but were significantly different using the individualized model (p = 0.006). C-indices were significantly different between the dose-only and the individualized model.

CONCLUSION

This study presents a method to combine a published dose-response function with known clinical risk factors and demonstrates the increased predictive power of the combined model. The method allows for individualization of dose constraints and individual patient risk estimates.

A clinical score, including biohumoral parameters, is a useful pretest index to discriminate pulmonary infections from radiation damage in chemoradiation-treated lung cancer patients

To obtain an easy and prompt differential diagnosis between lower airways infections and acute radiation pneumonitis in chemoradiation lung cancer patients. From 303 patients treated, only patients with severe pulmonary symptoms were hospitalized. Clinical and radiation scores were calculated evaluating clinical, biohumoral, dosimetric parameters. Out of 36 patients hospitalized, infections and acute radiation pneumonitis were reported in 66.7% and 33.3%, respectively. Patients with clinical score ≥ 2 had an Odds Ratio of 3.4 (1.4-8.3; p = .006) to have infectious pneumonia, while radiation score was not predictive.

Quantification of radiation-induced lung damage with CT scans: the possible benefit for radiogenomics

BACKGROUND

Radiation-induced lung damage (RILD) is an important problem. Although physical parameters such as the mean lung dose are used in clinical practice, they are not suited for individualised radiotherapy. Objective, quantitative measurements of RILD on a continuous instead of on an ordinal, semi-quantitative, semi-subjective scale, are needed.

METHODS

Hounsfield unit (HU) changes before versus three months post-radiotherapy were correlated per voxel with the radiotherapy dose in 95 lung cancer patients. Deformable registration was used to register pre- and post-CT scans and the density increase was quantified for various dose bins. The dose-response curve for increased HU was quantified using the slope of a linear regression (HU/Gy). The end-point for the toxicity analysis was dyspnoea ≥ grade 2.

RESULTS

Radiation dose was linearly correlated with the change in HU (mean R(2) = 0.74 ± 0.28). No differences in HU/Gy between groups treated with stereotactic radiotherapy, conventional radiotherapy alone, sequential or concurrent chemo- radiotherapy were observed. In the whole patient group, 33/95 (34.7%) had dyspnoea ≥ G2. Of the 48 patients with a HU/Gy below the median, 16 (33.3%) developed dyspnoea ≥ G2, while in the 47 patients with a HU/Gy above the median, 17 (36.1%) had dyspnoea ≥ G2 (not significant). Individual patients showed a nearly 21-fold difference in radiosensitivity, with HU/Gy ranging from 0 to 10 HU/Gy.

CONCLUSIONS

HU changes identify objectively the whole range of individual radiosensitivity on a continuous, quantitative scale. CT density changes may allow more robust and accurate radiogenomics studies.

Prediction of radiation pneumonitis in lung cancer patients: a systematic review

PURPOSE

Factors prediction in the development of radiation pneumonitis (RP) remains unclear. A meta-analysis about this was performed.

MATERIALS

Articles were searched in February 2012 from PubMed, EMBASE, Cochrane Library and CNKI (Chinese Journal Full-text Database) using the keywords "lung cancer," "radiation pneumonitis" or "radiation lung injury." The outcome was the RP incidence. We pooled the data using RevMan 5.1 software and tested the statistical heterogeneity.

RESULTS

We included the following factors: age, gender, weight loss, smoking history, complications, performance status, pre-radiation therapy (RT) pulmonary function, TNM, histological type, tumor location, pre-RT surgery, RT combined with chemotherapy (RCT), RT/RCT combined with amifostine, plasma end/pre-RT TGF-β1 ratio and irradiation volume. The significant risk factors for RP ≥ grade 2 were patients with chronic lung disease, tumor located in the middle or lower lobe, without pre-RT surgery, RCT, plasma end/pre-RT TGF-β1 ratio ≥1 and gross tumor volume (GTV). Following factors were identified significant for RP, including tumor located not in the upper lobe, smokers, combined with chronic lung diseases or diabetes mellitus, low pre-RT pulmonary function, RCT, RT/RCT without amifostine and plasma end/pre-RT TGF-β1 ratio ≥1. Dose-volume parameters included the average of mean lung dose (MLD) of disease lung, GTV and V (5), V (10) (≥34 %), V (20) (≥25 %), V (30) (≥18 %) of bilateral lung.

CONCLUSIONS

More attention should be paid to the levels of patients' pulmonary function, plasma TGF-β1 and dose-volume histogram (DVH). Rigorous studies are needed to identify the relationship between the above-mentioned factors and RP ≥grade 1 or 3.

Dose--volume metrics associated with radiation pneumonitis after stereotactic body radiation therapy for lung cancer

PURPOSE

To identify dose-volume factors associated with radiation pneumonitis (RP) after stereotactic body radiation therapy (SBRT) for lung cancer.

METHODS AND MATERIALS

This study analyzed 74 patients who underwent SBRT for primary lung cancer. The prescribed dose for SBRT was uniformly 48 Gy in four fractions at the isocenter. RP was graded according to the Common Terminology Criteria for Adverse Events (CTCAE) v.3. Symptomatic RP was defined as grade 2 or worse. Optimal cut-offs dividing the patient population into two subgroups based on the incidence of symptomatic RP were sought using the following dose-volume metrics: PTV volume (ml), mean lung dose (Gy), and V5, V10, V15, V20, V25, V30, V35, and V40 (%) of both lungs excluding the PTV.

RESULTS

With a median follow-up duration of 31.4 months, symptomatic RP was observed in 15 patients (20.3%), including 1 patient with grade 3. Optimal cut-offs for pulmonary dose-volume metrics were V25 and V20. These two factors were highly correlated with each other, and V25 was more significant. Symptomatic RP was observed in 14.8% of the patients with V25 <4.2%, and the rate was 46.2% in the remainder (p = 0.019). PTV volume was another significant factor. The symptomatic RP rate was significantly lower in the group with PTV <37.7 ml compared with the larger PTV group (11.1% vs. 34.5%, p = 0.020). The patients were divided into three subgroups (patients with PTV <37.7 ml; patients with, PTV ≥37.7 ml and V25 <4.2%; and patients with PTV ≥37.7 ml and V25 ≥4.2%); the incidence of RP grade 2 or worse was 11.1%, 23.5%, and 50.0%, respectively (p = 0.013).

CONCLUSIONS

Lung V25 and PTV volume were significant factors associated with RP after SBRT.